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  • 2020.10
    RELEASE 2020.10
    
    RIOT-2020.10 - Release Notes
    ============================
    RIOT is a multi-threading operating system which enables soft real-time
    capabilities and comes with support for a range of devices that are typically
    found in the Internet of Things: 8-bit and 16-bit microcontrollers as well as
    light-weight 32-bit processors.
    
    RIOT is based on the following design principles: energy-efficiency, soft
    real-time capabilities, small memory footprint, modularity, and uniform API
    access, independent of the underlying hardware (with partial POSIX compliance).
    
    RIOT is developed by an international open-source community which is
    independent of specific vendors (e.g. similarly to the Linux community) and is
    licensed with a non-viral copyleft license (LGPLv2.1), which allows indirect
    business models around the free open-source software platform provided by RIOT.
    
    About this release:
    ===================
    
    The 2020.10 release includes:
    
     - Support for PicoLIBC as standard C library implementation
     - A new radio abstraction layer for ieee802.15.4 radios
     - Improvement to the linking of modules
     - An improved algorithm for generating local unique identifiers
     - Pagewise addressing support for MTD devices
     - 23 additional modules supported by Kconfig
     - Initial rework of the clock modelling on stm32 devices
     - 5 new boards, 2 new device drivers, 7 packages updated
    
    482 pull requests, composed of 1355 commits, have been merged since the
    last release, and 84 issues have been solved. 64 people contributed with
    code in 94 days. 2426 files have been touched with 133358 (+) insertions and
    756906 deletions (-).
    
    Notations used below:
    =====================
    
        + means new feature/item
        * means modified feature/item
        - means removed feature/item
    
    New features and changes
    ========================
    
    Core
    ----
    + init: make boot message configurable
    + panic: callback app during panic
    + bitarithm: add bitarithm_test_and_clear()
    * thread: Add THREAD_NAMES make flag
    * kernel_defines.h: Fix container_of()
    * core: Add and use helper functions for internal data
    * treewide: Fix direct access to scheduler internals
    * core/bitarithm: use __builtin_clz() for bitarithm_msb()
    
    System Libraries
    ----------------
    + architecture: New module to access architecture internals
    + Add support for PicoLIBC
    + ztimer: add ztimer_spin()
    + ztimer: add periodic timers API
    * byteorder:
        * Moved to sys
        + Add byteorder_bebuftohll() and inverse
        + add uint32 from/to buffer funcs
    + event: implement waiting on multiple queues
    + evtimer: add mbox support
    + random: add SHA256 mode to SHA1PRNG & tests
    * sys/luid: improve luid_base() algorithm
    * tsrb: Make thread-safe
    * pipe_dynamic: fix possible null pointer dereference
    
    Networking
    ----------
    + ieee802154_submac: add initial support for common MAC sub layer
    + ieee802154/radio_hal: introduce Radio HAL for IEEE802.15.4 compatible radios
    + EUI:
        + luid: add luid_netdev_get_eui48() & luid_netdev_get_eui64()
        + eui64: add eui64_to_eui48()
    + link_layer: implement EUI provider
    * luid: shuffle bytes
    * uhcp: use LOG_xxx functions
    * gcoap: Insert registrations at the front
    * gnrc_ipv6_nib: only multicast probe UNREACHABLE neighbor if 6LR
    * gnrc_ipv6_nib: set NCE stale on incoming ARO
    * gnrc_ipv6_nib: don't add non-link-local to NC without ARSM
    + gnrc_netif_pktq: add packets to optional send queue when device is busy
    * emcute: fix buffer overflow in _willupd_msg()
    * SUIT:
        + Introduction of a payload storage API for SUIT manifest payloads
        * Upgrade to draft-ietf-suit-manifest-09
        * fail fetch if the image size doesn't match expected
    * gnrc:
        - Remove cyclic dependencies
        - Remove deprecated module gnrc_nettest
    - netopt: remove deprecated alias NETOPT_LINK_CONNECTED
    
    Packages
    --------
    + openwsn: add riot based openwsn scheduler
    + openwsn: add shell commands
    * openthread: migrate to event loop
    * nimble/netif: fix deadlock on connection loss
    * wolfssl: bump version to 4.5.0
    * nanopb: bump version to 0.4.3
    * ccn-lite: bump version
    * cn-cbor bump to 1.0.0
    * tinycbor: bump to v0.5.3
    * tinydtls: enforce the selection of a crypto secure PRNG
    * jerryscript: bump to version 2.3.0
    * semtech-loramac: replace xtimer by ztimer
    * lvgl:
        + add logic for managing touch devices
        + introduce screen_dev wrapper
        * bump to v7
    - emb6: remove deprecated package
    
    Boards
    ------
    + nrf52: Enable PWM on the LED pins
    + nucleo-g071rb: add initial support
    + nucleo-g070rb: add board
    + nucleo-g431rb: add initial support
    + Support for YARM board
    + add Adafruit Itsy Bitsy
    * samr21-xpro: fix reading EUI-64 from EDBG on cold boot
    * nucleo-l452re: add i2c config
    * hifive1b: add support for openocd programmer
    - remove support for wsn430-1_3b and wsn430-1_4
    
    CPU
    ---
    * cortexm:
        + Make no_thread_idle compatible with cortex-m0
        + Add thread info to hard fault handler
        + advertise puf_sram feature
        * Skip context save/restore on scheduling the previous thread
        * use mpu stack guard if DEVELHELP is enabled
        * fix check for bitbanding
        * Flush pipeline after triggering PendSV
    + cc2538: add Watchdog implementation
    * cc26xx_cc13xx:
        * add & link CCFG configuration
        * enable periph clocks on sleep
    * fe310:
        + Add custom PLIC driver as peripheral
        * Merge and optimize trap_entry with irq_arch
        * Unify linker scripts
    * msp430: Update to inline-able IRQ API Area
    * nrf5x_common: UART: add support for 1 MBaud
    * stm32:
        + generate vectors C files and IRQ defines from CMSIS headers
        + stm32cmsis: retrieve STM32 CMSIS header from a package
        + g0: add basic support
        + implement periph_timer_periodic
        * Add support for arbitrary SPI clock rate
        * f0/f1/f3/l0/l1/l4/wb: rework clock initialization and configuration
        - disable MPU for cortex-m0+
    * sam0:
        + GPIO: use tamper detection to wake from Deep Sleep
        + add support to run PWM off TC timers
        + ADC: add support for samd5x/same5x
        + Add support for Single-cycle I/O Port for GPIO
        * UART: implement arithmetic BAUD mode
        * merge RTC & RTT implementation
        * flashpage: clean up implementation
    - saml1x: Remove MPU feature
    
    Device Drivers
    --------------
    + at86rf2xx: spi security module
    + at86rf2xx: support frame retry reporting on AT86RFR2
    + soft_uart: add software based UART implementation
    + scd30 : Add driver for scd30 sensor
    + stm32_eth: add 'NETDEV_EVENT_LINK_UP' event
    + Add support for Adafruit Seesaw Soil moisture sensor
    + radio_hal:
        + introduce Radio HAL for IEEE802.15.4 compatible radios
        + cc2538_rf: implement Radio HAL
        + nrf52840: implement Radio HAL
    + mtd: add page addressed operation
    * stmpe811: fix interrupt polarity & interrupt generation
    * sps30: Update units of measurement
    * sps30: Add sleep mode
    - sdcard_spi: remove auto-init
    
    Build System / Tooling
    ----------------------
    + Add libstdcpp feature
    + gnrc_border_router: Add USB Ethernet support
    + buspirate: add Bus Pirate as Debug Adapter
    * README: Add more badges
    * Convert remaining Python2 users to Python3
    * openocd-adapters: select transport based on adapter
    * Makefile.{base,include}: Fix linking for C++ code in external modules
    * link object files instead of archives
    * tapsetup:
        - Add support for listing bridges
        - Add support to configure addresses for bridge
        - Add support for configuring routes and forwarding capabilities for bridge
        - Add TUN support
    
    Testing
    -------
    + vagrant: add Vagrantfile to test native in FreeBSD
    + compile_and_test_for_board.py: add optional JUnit XML support
    * bench_*: Add ticks per iteration results
    
    Kconfig
    -------
    + Finished modelling provided features
    + Modules with support added:
        + credman
        + cord
        + nrf-based
        + ek-lm4f120xl
        + lpc1768-based
        + lpc2387-based
        + native
        + mips32r2-based
        + sam3-based
        + sam0_common
        + same54-xpro
        + saml1x-based
        + saml21-based
        + stm32
        + l2filter
        + dhcpv6
        + hifive1(b) clock area
        + stm32gx clock configuration
        + periph/timer
        + netif
        + skald
        + sock_dtls
        + lora
    + add genconfig script
    * enable incremental compilation on config changes
    * include KCONFIG_OUT_CONFIG unconditionally
    
    API Changes
    ===========
    - gcoap: remove gcoap_finish
    * gpio: IRQs triggered after gpio_irq_disable() are discarded
    * sched: Refactor to return the next scheduled thread
    * sock: Application should pull in the pseudomodules
    * driver-guide.md: Drivers are expected to return negative errno values
    * nrf52xxxdk: configure LEDs as PWM
    
    Known issues
    ============
    
    Networking related issues (42)
    ------------------------------
            packet buffer
            address
           assertion or completely without error
           chars
           address
    
    Timer related issues (15)
    -------------------------
           time.
           _xtimer_now()  and irq_disable()
    
    Drivers related issues (14)
    ---------------------------
            timeout
            clock cycles
           supported
    
    Native related issues (3)
    -------------------------
    
    Other platforms related issues (19)
    -----------------------------------
            __WFI()
            (not previous)
           CS
    
    Build system related issues (14)
    --------------------------------
            evaluation
           image
           value
    
    Other issues (41)
    -----------------
            LLVM
            depending on code layout in flash
            esp32-wroom-32
            shell after flashing with J-Link
            10
           static_asserts in the same scope
           everywhere
    
    There are 148 known issues in this release
    
    Fixed Issues since the last release (2020.07)
    =============================================
    
            ASSERTION.
            after debug break
            sometimes
           boards
    
    42 fixed issues since last release (2020.07)
    
    Acknowledgements
    ================
    We would like to thank all companies that provided us with hardware for porting
    and testing RIOT-OS. Further thanks go to companies and institutions that
    directly sponsored development time. And finally, big thanks to all of you
    contributing in so many different ways to make RIOT worthwhile!
    
    More information
    ================
    http://www.riot-os.org
    
    Mailing lists
    -------------
    * RIOT OS kernel developers list
      devel@riot-os.org (http://lists.riot-os.org/mailman/listinfo/devel)
    * RIOT OS users list
      users@riot-os.org (http://lists.riot-os.org/mailman/listinfo/users)
    * RIOT commits
      commits@riot-os.org (http://lists.riot-os.org/mailman/listinfo/commits)
    * Github notifications
      notifications@riot-os.org (http://lists.riot-os.org/mailman/listinfo/notifications)
    
    IRC & Matrix
    ------------
    * Join the RIOT IRC channel at: irc.freenode.net, #riot-os
    * Join the RIOT Matrix room at: #riot-os:matrix.org
    
    License
    =======
    * The code developed by the RIOT community is licensed under the GNU Lesser
      General Public License (LGPL) version 2.1 as published by the Free Software
      Foundation.
    * Some external sources and packages are published under a separate license.
    
    All code files contain licensing information.
    
    
  • 2020.10-RC4
  • 2020.10-RC3
  • 2020.10-RC2
  • 2021.01-devel
    Development branch towards 2021.01 release
  • 2020.10-RC1
  • 2020.07.1
    RELEASE 2020.07.1
    
    RIOT-2020.07.1 - Release Notes
    ==============================
    This is a bug fixing release for the RIOT 2020.07 release.
    The following bugs were fixed:
    
        - pkg/lwip: Compatibility with IS_USED()
        - pkg/lwip: Use IS_ACTIVE() & NETCONNTYPE_ISIPV6()
    
  • 2020.07
    RELEASE 2020.07
    
    RIOT-2020.07 - Release Notes
    ============================
    RIOT is a multi-threading operating system which enables soft real-time
    capabilities and comes with support for a range of devices that are typically
    found in the Internet of Things: 8-bit and 16-bit microcontrollers as well as
    light-weight 32-bit processors.
    
    RIOT is based on the following design principles: energy-efficiency, soft
    real-time capabilities, small memory footprint, modularity, and uniform API
    access, independent of the underlying hardware (with partial POSIX compliance).
    
    RIOT is developed by an international open-source community which is
    independent of specific vendors (e.g. similarly to the Linux community) and is
    licensed with a non-viral copyleft license (LGPLv2.1), which allows indirect
    business models around the free open-source software platform provided by RIOT.
    
    About this release:
    ===================
    
    The 2020.07 release puts a focus on the improvement of automated testing. In
    that vein, various new CI integrations such as CircleCI for documentation
    building and online presentation, and Github Actions to check the tooling of
    RIOT when merged. The `riotctrl_shell` python module allows to abstract shell
    commands as python methods for testing using the newly created `riotctrl`
    python package [1]. Kconfig migration reached phase 2 with various board
    features being exposed to Kconfig. New network protocols were ported for RIOT
    such as MQTT (in form of the `paho-mqtt` package) and the lookup client
    component for CoRE RD `cord_lc`. The OpenWSN network stack with 6TiSCH support
    was reintegrated into RIOT. Support for several new boards and new sensors was
    added. Additionally, this release contains a number of bug fixes and test
    improvements.
    
    546 pull requests, composed of 10452 commits, have been merged since the
    last release, and 84 issues have been solved. 64 people contributed with
    code in 106 days. 2371 files have been touched with 822149 (+) insertions and
    700313 deletions (-).
    
    [1]: https://pypi.org/project/riotctrl/
    
    Notations used below:
    =====================
    
        + means new feature/item
        * means modified feature/item
        - means removed feature/item
    
    New features and changes
    ========================
    
    Core
    ----
    * core: make idle thread optional
    + macros/units: add unit conversion helper macros
    + msg: add message bus
    * panic: launch USB bootloader on crash for easy recovery
    
    System libraries
    ----------------
    * auto_init: automatically determine auto_init_*.c
    * base64: Clean up / improve implementation
    + hashes: add sha224 and reuse sha256 code
    + luid: provide luid_get_lb()
    + phydat: added phydat to JSON converter
    + posix: initial import of select() function (only support sockets for now)
    * ps: show free stack space in addition to used and total
    * shell:
      + add optional hooks for shell commands
      * native: stop RIOT when the shell reads EOF
      * refactor readline function
      * refactor tokenizer code
    + shell_commands:
      * alias ping=ping6
      + provide command to reboot to bootloader
    + stdio_semihosting: Initial include of Semihosting-based STDIO
    + touch_dev: add generic API for touch device
    + trace: add trace module
    + pm: Add pm_get_blocker()
    * random:
      + add option to use HWRNG as source of randomness
      * optimize sha1prng
    * usb:
      * allow for boards to define default custom VID/PID
      * warn on test-ID usage in a unified location
    + xtimer: xtimer_rmutex_lock_timeout
    * ztimer:
      + add power management for ztimer clocks
      * expose ZTIMER_MSEC/USEC_BASE
    
    Networking
    ----------
    + cord: add CoRE RD lookup client implementation
    + gcoap: add CoAP ping request
    * gnrc:
      + gnrc_ipv6_ext_opt: initial import of hop-by-hop and destination option
        handling
      * gnrc_netif:
        + add IPv6 event bus
        + add option for non-std 6lo MTU
        + add support for internal event loop
        * use gnrc_netif-submodules to pull in upper-layer struct members
      * gnrc_nettype: indirect NETTYPE definition via pseudo-modules
      * gnrc_pktdump: fix dependencies
      * gnrc_tcp:
        + add retransmission timer
        * rewrite API internal messaging
        * rewrite recv buffer allocation/returning
      * use exponent to configure message queue sizes
    * nanocoap: allow coap_opt_add_string() for non-zero-terminated strings
    + netif: add functions to get and get by identifier
    + sock_dtls: provide getter function for UDP sock
    * sock_util: add interface descriptor parsing to str2ep
    
    Packages
    --------
    * pkg: rework checkout process
      * avoid copying Makefiles in package source when possible
      * store packages sources in a global package directory
    * pkg: cleanup build system integration for
      - cryptoauthlib, openthread, semtech-loramac, tinydtls, wakaama, u8g2,
        ucglib, wolfssl
    * pkg: tools: ensure cmake based packages/tools are built out-of-source
    + cryptoauthlib: wake pulse implementation for CPUs supporting
      `periph_i2c_reconfigure`
    + emlearn: add support to RIOT
    * gecko_sdk: update to v2.7.6
    * lwip:
      * add IPv4 support for `netdev_tap`
      * add support for nrf802154
      * enable IPv4/IPv6 dual stack mode
      + lwip_sock: provide implementation for `sock_*_recv_buf()`
    - lua: remove unnecessary patch
    + paho-mqtt: add package and example
    * nimble:
      + add static connection manager `statconn`
      * netif:
        * set host thread prio to 1
        * simplify mbuf pool initialization
      * update NimBLE ver (cd7d7aa286) + timing param cleanup
    + openwsn: re-integrate the network stack as a package
    * tinydtls:
      + add `sock_async` support for `sock_dtls`
      + use latest development version (eda63f000c)
    * ucglib: refactoring and fixes
    
    Boards
    ------
    + cc1352p-launchpad: add support
    * common/blxxxpill:
      + provide periph_rtt
      * improve adc
    + dwm1001: add support to Decawave DWM1001 dev board
    + mcb2388: misc enhancements
    + nrf52840-dongle: add support
    + nrf52840dk: Add MTD configuration
    + nucleo-g474re: add support
    * pic32-clicker: rename to 6lowpan-clicker
    + samr30-xpro: add SPI dev for ext pin header
    + samr3x-xpro: add riotboot feature
    + serpente: add support
    + sltb001a: enable CCS811 sensor
    + sodaq-sff: add support for SODAQ SFF
    + stm32f429i-disco: add support
    + weact-f411ce: add support
    + wemos-zero: add support
    
    CPU
    ---
    * arm7_common: Update to inlineable IRQ API
    * atmega_common: Update to inlineable IRQ API
    * cortexm:
      + allow to define reserved fields in CortexM vector table
      * "free" SVC
    * cc26x2_cc13x2:
      * add oscillator switching functions
      * add periph_i2c implementation
      * trim device registers on `cpu_init`
    * esp32:
      * support of multiple heaps for newlib malloc
      * replace RTC implementation by RTT implementation
    * fe310: migrate to inlined IRQ API
    + kinetis: implement power modes for pm_layered
    * lpc2387:
      * pm: enable SLEEP & POWERDOWN mode
      * timer: use lpc2387_pclk_scale()
    + mips_pic32_common: Implement GPIO IRQ
    + native:
      + add periph_eeprom driver implementation
      * rename trace -> backtrace
    + nrf52:
      + add black magic probe config
      + add missing vendor files
      + implement EasyDMA-based SPI peripheral implementation
    + nrf52811: initial support
    * nrf5x_common:
      * add configurable RTT_FREQUENCY
      * enable bias correction in hwrng
    * sam0_common:
      + add DMA peripheral driver
      + add PWM support for saml21, samd5x
      + implement periph/dac
      * make SPI peripheral DMA compatible
      * move PWM to common code
      * spi: move clk pin muxing into spi_acquire / spi_release
      + UART: implement inverted RX & TX
    * samd21: PWM don't hard-code number of channels to 3
    * samd5x: allow to use XOSC as clock source
    * saml1x: pm: set deep flag
    + stm32:
      + add QDEC support for CPU_FAM_STM32F1
      + add non-blocking UART
      * decrease latency in SPI DMA path
      + implement reset to bootloader
      * filter availability of RNG by CPU not by board
      * stm32_common: make RTT_FREQUENCY configurable
      + stm32f4: Add DMA config for SPI
      + stm32g4: add support
    
    Device Drivers
    --------------
    + atwinc15x0: add WiFi netdev driver
    + at: Add at_urc_isr module to process URCs upon arrival
    + at24cxxx: MTD wrapper for at24cxxx
    + at86rf215:
      + implement MR-O-QPSK
      + implement MR-OFDM
    + at86rf2xx: add support for high data rates
    + dfplayer: New driver for the DFPlayer Mini MP3 player
    * ethos: use luid_get_eui48()
    + edbg_eui: add driver to get MAC address from Atmel EDBG
    + mhz19: initial support
    + mrf24j40: add Turbo Mode
    + mtd_spi_eeprom: add MTD wrapper for AT25XXX EEPROMs
    + pca9633: add new driver
    + periph/timer: add timer_set_periodic()
    + periph/i2c: add periph_i2c_reconfigure feature & implementation for sam0
    + periph/rtt: introduce RTT_MIN_OFFSET
    + periph/spi: add periph_spi_reconfigure feature & implementation for sam0
    * pulse_counter: Use C11 atomics & bugfix
    + sdp3x : Add driver for sdp3x sensor
    
    Build System / Tooling
    ----------------------
    + make:
      + add code generator targets
      + add JLink support for stm32
      * docker.inc.mk: add and use generic docker_run_make
      + allow multiple external board dirs
      + info-global.inc.mk: add info-boards-features-blacklisted
      * resolve dependencies before Makefile.include
    + riotctrl_shell:
      + initial import of shell interaction spawn
      + provide ipv6_nib interactions and parsers
      + provide netif interactions and parsers
    + tools:
      + add script to run radvd on a tun interface
      + provide tool to parse `pktbuf` output
      * kconfiglib:
        * add riot_kconfig to override default behaviours
        * kconfiglib: bump to v14.1.0
    
    Testing
    -------
    + fuzzing framework:
      + add AFL-based fuzzing setup for network modules
      + add fuzzing application for gcoap
    + ci: setup github actions
    + sys/test_utils/dummy_thread: initial commit
    + tests/irq_disable_restore: Add test for irq_disable() / irq_restore()
    + tests/periph_spi: add benchmark for acquire / release
    + tests/periph_spi_dma: Add test for SPI with DMA
    + uncrustify: add auto uncrustify with blacklist
    
    Kconfig migration
    -----------------
    + armv7_m/cortexm: declare CPU_ARCH and CPU_CORE
    + boards: Model features in Kconfig
      + arduino-leonardo, arduino-mega2560, atmega128x-based, atmega256rfr2-based,
        atmega328p-based, cc2538-based, cc26xx_cc13xx-based, efm32-based, esp-based,
        fe310-based, kinetis-based, msp430-based, samr21-xpro, slwstk6220a
    * kconfig: Declare common feature symbols
    + drivers: Expose Configurations to Kconfig
      + ads101x, at, at86rf215, bmx055, cc110x, dose.h, fxos8700, hdc1000, isl29020,
        l3g4200d, lpsxxx, mag3110, mma8x5x, motor_driver, mtd_sdcard, opt3001,
        pn532, rn2xx3, slipdev, sps30, tcs37727, tmp00x
    + networking: Expose configurations to Kconfig
      + asymcute, coap, csma
      + gnrc:
        + gomach, lwmac, mac, pktdump, pktbuf, rpl, tcp
    + usbus/cdc/ecm: Expose configurations to Kconfig
    
    API Changes
    ===========
    - cpu/sam0_common: drop prescaler from timer config
    - cpu/sam0_common: PWM config now requires GCLK source
    - drivers/mtd: Change API to return 0 on success
    - drivers/mtd_mapper: count offset in sectors
    - net/sock_dtls: provide getter function for UDP sock
    - net/sock_dtls: add timeout to sock_dtls_send and add sock_dtls_session_init
    
        diff --git a/sys/include/net/sock/dtls.h b/sys/include/net/sock/dtls.h
        index 96569723fc..6e66048bd4 100644
        --- a/sys/include/net/sock/dtls.h
        +++ b/sys/include/net/sock/dtls.h
        @@ -476,6 +485,13 @@
         extern "C" {
         #endif
    
        +#ifndef DTLS_HANDSHAKE_BUFSIZE
        +#define DTLS_HANDSHAKE_BUFSIZE  (256)   /**< Size buffer used in handshake to
        +                                             hold credentials */
        +#endif
        +
        +#define SOCK_DTLS_HANDSHAKE     (EXDEV) /**< Return value for a successful
        +                                             handshake */
        +
         /**
          * @brief DTLS version number
        @@ -546,26 +564,26 @@ void sock_dtls_init(void);
         int sock_dtls_create(sock_dtls_t *sock, sock_udp_t *udp_sock,
                              credman_tag_t tag, unsigned version, unsigned role);
    
        +
         /**
        - * @brief Creates a new DTLS session
        + * @brief Initialize session handshake.
          *
        - * Initializes handshake process with a DTLS server  at @p ep.
        - *
        - * @param[in]  sock     DLTS sock to use
        - * @param[in]  ep       Remote endpoint of the session
        - * @param[out] remote   The created session, cannot be NULL
        + * Sends a ClientHello message to initialize the handshake. Call
        + * @ref sock_dtls_recv() to finish the handshake.
          *
        - * @return  0 on success
        - * @return  -EAGAIN, if DTLS_HANDSHAKE_TIMEOUT is `0` and no data is available.
        - * @return  -EADDRNOTAVAIL, if the local endpoint of @p sock is not set.
        - * @return  -EINVAL, if @p remote is invalid or @p sock is not properly
        - *          initialized (or closed while sock_udp_recv() blocks).
        - * @return  -ENOBUFS, if buffer space is not large enough to store received
        - *          credentials.
        - * @return  -ETIMEDOUT, if timed out when trying to create session.
        + * @param[in] sock      DTLS sock to use
        + * @param[in] ep        Remote endpoint to start a handshake with
        + * @param[out] remote   Resulting session
        + *
        + * @return 1, if new handshake is started
        + * @return 0, if there is an existing session
        + * @return -ENOMEM, not enough memory to allocate for new peer
        + * @return -EADDRNOTAVAIL, if the local endpoint of @p sock is not set.
        + * @return -EINVAL, if @p remote is invalid or @p sock is not properly
        + *         initialized (or closed while sock_udp_recv() blocks).
          */
        -int sock_dtls_session_create(sock_dtls_t *sock, const sock_udp_ep_t *ep,
        -                             sock_dtls_session_t *remote);
        +int sock_dtls_session_init(sock_dtls_t *sock, const sock_udp_ep_t *ep,
        +                           sock_dtls_session_t *remote);
    
         /**
          * @brief Destroys an existing DTLS session
        @@ -578,7 +596,7 @@ int sock_dtls_session_create(sock_dtls_t *sock, const sock_udp_ep_t *ep,
         void sock_dtls_session_destroy(sock_dtls_t *sock, sock_dtls_session_t *remote);
    
         /**
        - * @brief Decrypts and reads a message from a remote peer.
        + * @brief Receive handshake messages and application data from remote peer.
          *
          * @param[in] sock      DTLS sock to use.
          * @param[out] remote   Remote DTLS session of the received data.
        @@ -593,7 +611,8 @@ void sock_dtls_session_destroy(sock_dtls_t *sock, sock_dtls_session_t *remote);
          *
          * @note Function may block if data is not available and @p timeout != 0
          *
        - * @return The number of bytes received on success
        + * @return  The number of bytes received on success
        + * @return  -SOCK_DTLS_HANDSHAKE when new handshake is completed
          * @return  -EADDRNOTAVAIL, if the local endpoint of @p sock is not set.
          * @return  -EAGAIN, if @p timeout is `0` and no data is available.
          * @return  -EINVAL, if @p remote is invalid or @p sock is not properly
        @@ -657,28 +676,32 @@ ssize_t sock_dtls_recv_buf(sock_dtls_t *sock, sock_dtls_session_t *remote,
          *                      if no session exist between client and server.
          * @param[in] data      Pointer where the data to be send are stored
          * @param[in] len       Length of @p data to be send
        + * @param[in] timeout   Handshake timeout in microseconds.
        + *                      If `timeout > 0`, will start a new handshake if no
        + *                      session exists yet. The function will block until
        + *                      handshake completed or timed out.
        + *                      May be SOCK_NO_TIMEOUT to block indefinitely until
        + *                      handshake complete.
          *
        - * @note Function may block until a session is created if there is no
        - *       existing session with @p remote.
        - *
        - * @note Initiating a session through this function will require
        - * @ref sock_dtls_recv() called from another thread to receive the handshake
        - * messages.
        + * @note    When blocking, we will need an extra thread to call
        + *          @ref sock_dtls_recv() function to handle the incoming handshake
        + *          messages.
          *
          * @return The number of bytes sent on success
        + * @return  -ENOTCONN, if `timeout == 0` and no existing session exists with
        + *          @p remote
          * @return  -EADDRINUSE, if sock_dtls_t::udp_sock has no local end-point.
          * @return  -EAFNOSUPPORT, if `remote->ep != NULL` and
          *          sock_dtls_session_t::ep::family of @p remote is != AF_UNSPEC and
          *          not supported.
        - * @return  -EHOSTUNREACH, if sock_dtls_session_t::ep of @p remote is not
        - *          reachable.
          * @return  -EINVAL, if sock_udp_ep_t::addr of @p remote->ep is an
          *          invalid address.
          * @return  -EINVAL, if sock_udp_ep_t::port of @p remote->ep is 0.
          * @return  -ENOMEM, if no memory was available to send @p data.
        + * @return  -ETIMEDOUT, `0 < timeout < SOCK_NO_TIMEOUT` and timed out.
          */
         ssize_t sock_dtls_send(sock_dtls_t *sock, sock_dtls_session_t *remote,
        -                       const void *data, size_t len);
        +                       const void *data, size_t len, uint32_t timeout);
    
         /**
          * @brief Closes a DTLS sock
        @@ -694,6 +717,47 @@ ssize_t sock_dtls_send(sock_dtls_t *sock, sock_dtls_session_t *remote,
          */
         void sock_dtls_close(sock_dtls_t *sock);
    
        +/**
        + * @brief Creates a new DTLS session
        + *
        + *  Initiates a handshake with a DTLS server at @p ep and wait until it
        + * completes or timed out.
        + *
        + * @deprecated Will not be available after the 2020.10 release.
        + *             Please use @ref sock_dtls_session_init() and
        + *             @ref sock_dtls_recv() instead.
        + *
        + * @param[in]  sock     DLTS sock to use
        + * @param[in]  ep       Remote endpoint of the session
        + * @param[out] remote   The created session, cannot be NULL
        + * @param[in]  timeout  Timeout to wait for handshake to finish.
        + *                      Returns immediately if 0.
        + *                      May be SOCK_NO_TIMEOUT to wait indefinitely until
        + *                      handshake complete.
        + *
        + * @return  0 on success
        + * @return  -ENOMEM, if no memory to allocate for new peer
        + * @return  -EADDRNOTAVAIL, if the local endpoint of @p sock is not set.
        + * @return  -EINVAL, if @p remote is invalid or @p sock is not properly
        + *          initialized (or closed while sock_udp_recv() blocks).
        + */
        +static inline int sock_dtls_session_create(sock_dtls_t *sock, const sock_udp_ep_t *ep,
        +                                    sock_dtls_session_t *remote, unsigned timeout)
        +{
        +    int res;
        +    uint8_t buf[DTLS_HANDSHAKE_BUFSIZE];
        +
        +    assert(sock);
        +    assert(remote);
        +
        +    res = sock_dtls_session_init(sock, ep, remote);
        +    if (res <= 0) {
        +        return res;
        +    }
        +
        +    return sock_dtls_recv(sock, remote, buf, sizeof(buf), timeout);
        +}
        +
         #include "sock_dtls_types.h"
    
         #ifdef __cplusplus
    
    Deprecations
    ============
    
    Warnings
    --------
    - GNRC_MAC_ENABLE_DUTYCYCLE_RECORD: Will be removed after 2021.01 release. Use
      inverse CONFIG_GNRC_MAC_DISABLE_DUTYCYCLE_RECORD instead.
    - saul_reg_rm(): will be removed at a future date
    - sock_dtls_session_create(): will be removed after 2020.10 release. Please
      use sock_dtls_session_init() and sock_dtls_recv() instead
    - pkg/nordic_softdevice_ble: will be removed after the 2020.10 release
    
    Removals
    --------
    - netdev: remove NETOPT_IPV6_IID support for network devices
    
    Known issues
    ============
    
    Networking related issues (44)
    ------------------------------
            after debug break
            sometimes
            packet buffer
            address
           assertion or completely without error
           chars
           address
    
    Timer related issues (17)
    -------------------------
           time.
           _xtimer_now()  and irq_disable()
    
    Drivers related issues (13)
    ---------------------------
            timeout
            clock cycles
           supported
    
    Native related issues (3)
    -------------------------
    
    Other platforms related issues (19)
    -----------------------------------
            __WFI()
            (not previous)
           boards
           CS
    
    Build system related issues (13)
    --------------------------------
            evaluation
           image
           value
    
    Other issues (41)
    -----------------
            esp32-wroom-32
            shell after flashing with J-Link
            10
           static_asserts in the same scope
           everywhere
    
    There are 150 known issues in this release
    
    Fixed Issues since the last release (2020.04)
    =============================================
    
            current page
            RIOT/examples/emcute_mqttsn/.
            on Nucleo-f401re
           configured prefix
           LTO
    
    42 fixed issues since last release (2020.04)
    
    Acknowledgements
    ================
    We would like to thank all companies that provided us with hardware for porting
    and testing RIOT-OS. Further thanks go to companies and institutions that
    directly sponsored development time. And finally, big thanks to all of you
    contributing in so many different ways to make RIOT worthwhile!
    
    More information
    ================
    http://www.riot-os.org
    
    Mailing lists
    -------------
    * RIOT OS kernel developers list
      devel@riot-os.org (http://lists.riot-os.org/mailman/listinfo/devel)
    * RIOT OS users list
      users@riot-os.org (http://lists.riot-os.org/mailman/listinfo/users)
    * RIOT commits
      commits@riot-os.org (http://lists.riot-os.org/mailman/listinfo/commits)
    * Github notifications
      notifications@riot-os.org (http://lists.riot-os.org/mailman/listinfo/notifications)
    
    IRC
    ---
    * Join the RIOT IRC channel at: irc.freenode.net, #riot-os
    
    License
    =======
    * The code developed by the RIOT community is licensed under the GNU Lesser
      General Public License (LGPL) version 2.1 as published by the Free Software
      Foundation.
    * Some external sources and packages are published under a separate license.
    
    All code files contain licensing information.
    
    
  • 2020.07-RC3
  • 2020.07-RC2
  • 2020.10-devel
    Development branch towards 2020.10 release
  • 2020.07-RC1
  • 2020.04
    2020.04         RELEASE 2020.04
    
    RIOT-2020.04 - Release Notes
    ============================
    RIOT is a multi-threading operating system which enables soft real-time
    capabilities and comes with support for a range of devices that are typically
    found in the Internet of Things: 8-bit and 16-bit microcontrollers as well as
    light-weight 32-bit processors.
    
    RIOT is based on the following design principles: energy-efficiency, soft
    real-time capabilities, small memory footprint, modularity, and uniform API
    access, independent of the underlying hardware (with partial POSIX compliance).
    
    RIOT is developed by an international open-source community which is
    independent of specific vendors (e.g. similarly to the Linux community) and is
    licensed with a non-viral copyleft license (LGPLv2.1), which allows indirect
    business models around the free open-source software platform provided by RIOT.
    
    About this release:
    ===================
    
    The 2020.04 release includes:
    
    - Add support for 6LoWPAN IPv6 extension header next header compression
    - Add support for DHCPv6 prefix delegation client
    - Add support for kw41zrf and at86rf215 IEEE 802.15.4 radios
    - Improvements on power management for ESP32
    - Improvements and extensions in support of fe310 and lpc2387
    - lwIP: provide support for asynchronous sock
    - Improvements on xtimer module and testing
    - Initial addition of the new timer subsystem: ztimer
    - Migration to Kconfig - phase I: add multiple GNRC and system modules
    - +10 new boards, +11 new drivers, +7 new packages
    
    555 pull requests, composed of 1514 commits, have been merged since the
    last release, and 22 issues have been solved. 60 people contributed with
    code in 102 days. 3346 files have been touched with 358398 (+) insertions and
    184720 deletions (-).
    
    Notations used below:
    =====================
    
        + means new feature/item
        * means modified feature/item
        - means removed feature/item
    
    New features and changes
    ========================
    
    System libraries
    ----------------
    * core:
        + add optional support for executable space protections
        * sched: sched.h: remove not needed bitarithm include to avoid conflict
        + turn kernel_init.c and panic.c into submodules of core
    + sys/auto_init: allow delayed initialization of SAUL & gnrc_netif
    * sys/base64: implement Base 64 Encoding with URL and Filename Safe Alphabet
    * sys/crypto: define cipher using a module instead of CFLAGS
    * sys/crypto/modes/ccm: handle input_len = 0
    * sys/ecc: fix assertion in golay2412
    * sys/event:
        + add event_wait_timeout64()
        + add shared event threads
    * sys/newlib:
        + enable multiple heaps in _sbrk_r()
        * syscalls_default: update heap_stats for multiple heaps
    * sys/puf_sram: counter based seed after soft reset
    * sys/phydat: improvement of phydat_dump including test application
    * sys/shell:
        + add rtt command
        * correctly detect and handle long lines
    + sys/shell_commands: + provide command to print version
    * sys/spp: randomize canary value on each build
    * sys/suit:
        * cleanup of TinyCBOR to NanoCBOR refactor
        * coap: make use of exposed tree handler function
        * update to draft-ietf-v3
    + sys/uri_parser: initial import of a minimal and non-destructive URI parsing
    * sys/usb: use default VID/PID for RIOT-included peripherals
    * sys/xtimer:
        * set now pointer correctly in _update_short_timers() loop
        + add xtimer_set_timeout_flag64()
        * xtimer_mutex_lock_timeout fix with short timeout
    + sys/ztimer: initial import
    
    Networking
    ----------
    * net/coap:
        * deprecate gcoap_add_qstring() and update uses
        + Packet API function to add Uri-Query option
    + net/dhcpv6: initial implementation of a client (with IA_PD support)
    * net/dns: fix DNS resolution in ping6
    * net/gcoap:
        + add canonical uri query function names
        + allow proxied client requests
        * use sock_async and events
    + net/gnrc_dhcpv6_client_6lbr: initial import of a 6LBR DHCPv6 client
    + net/gnrc_ipv6_ext_frag: initial import of statistics module
    * net/gnrc_ipv6_nib:
        * do not ignore prefix list for route resolution
        * fix border router with DNS & Context Compression
        * only route to prefix list entry if on-link
    * net/gnrc_lorawan:
        * fix the handling of downlink frames without payload
        * remove netdev layer from MAC
    * net/gnrc_netif:
        + add gnrc_netif_send and gnrc_netif_highlander functions
        * implementation of dynamic GNRC_NETIF_NUMOF approach
    * net/gnrc_nettype: deprecate IOVEC type
    * net/gnrc_pktbuf: deprecate gnrc_pktbuf_replace_snip()
    + net/gnrc_sixlowpan_iphc: add support for IPv6 extension header compression
    + net/gnrc_sock: provide implementation for `sock_*_recv_buf()`
    * net/gnrc_sock_udp: choose random ephemeral port
    - net/gnrc_tftp: remove module
    * net/gnrc_uhcpc:
        * ensure compression context is managed by the ABR
        * only configure 6Lo-ND features if wireless-interface is 6LN
        * update compression context with new prefix
    * net/nanocoap:
        + add coap_opt_add_uquery2() with parameter key value length
        + add convenience function for adding path elements
        * add uquery improvements
        * make separate tree handling function
        - remove obsolete functions for addition of Uri-Query option
    + net/netdev: add netdev_trigger_event_isr() function
    - net/nhdp: remove module
    + net/sock:
        * async: add optional callback argument
        + amend with zero-copy receive functions
        + amend API to iterate over stack-internal buffer chunks
    
    Packages
    --------
    + pkg/cmsis-nn: add support
    + pkg/cryptoauthlib: add support
    + pkg/libbase58: add support
    - pkg/libcose: remove monocypher crypto mode
    + pkg/littlefs2: add support for LittleFS v2.x.y
    + pkg/lvgl: add initial support for LittlevGL
    * pkg/lwip:
        + add auto-init support for transceiver ENC28J60
        + provide sock_async support
    * pkg/micropython: bump version for FreeBSD fix
    * pkg/monocypher: bump to version 3.0.0
    * pkg/nanopb: bump version to 0.4.1
    * pkg/nimble/autoconn: various improvements
    - pkg/oonf_api: remove support
    + pkg/qcbor: add support
    * pkg/tinydtls: remove receive buffer indirection via mbox
    * pkg/wolfssl: bump version to 4.3.0
    + pkg/yxml: add support Yxml XML parser library package
    
    Boards
    ------
    * boards: include common dfu logic where applicable
    + boards/adafruit-clue: add initial support
    * boards/arduino-mkr: feather-m0: sodaq-*: provide stdio over USB and
      setup automatic flash with bossa
    + board/arduino-nano-33-ble: add initial support
    + boards/cc1312-launchpad: add support and documentation
    * boards/feather-nrf52840:
        * use CDC ACM as default STDIO
        * fix LED macros
    + boards/esp32-heltec-lora32-v2: add support
    + boards/im880b: add support
    + boards/kw41z-mini: add support
    * boards/mega-xplained: fix ADC line definitions
    * boards/nrf51: fix UART hardware flow-control configuration
    * boards/nucleo-l152re: fix uart1 pinout config
    + boards/nucleo-l412kb: add initial support
    * boards/sam[r/d]21-xpro: prefer XOSC32K for RTC/RTT (GCLK2)
    * boards/same54-xpro:
        * configure remaining EXT connectors
        * don't source peripheral clocks from main clock
    * boards/samr30: add helper for antenna switch
    * boards/stm32l4: add common clock configuration
    + boards/olimexino-stm32: add support
    + boards/openlabs-kw41z-mini-256kib: add support
    * boards/openmote-b: add SAUL configuration and note about flashing
    + boards/p-nucleo-wb55: add initial support
    + boards/pic32*: add GPIO SAUL configuration
    * boards/pinetime:
        * add defines for controlling the backlight pin
        * update mtd_spi_nor config
        * fix battery ADC line define
    * doc/doxygen:
        + add 'Creating boards' section
        * improvements on various board's documentation
    
    CPU
    ---
    * cpu:
        * add CPU feature for stack smash protections
        + add UART RX implementation on PIC32 devices
        * make default idle/main stacksizes configurable on all archs
        * move cpu level dependencies in dedicated Makefile.dep files
        * unify UART hardware flow control use to a generic module
    * cpu/atmega_common: fix reboot issues
    * cpu/cc13x2: rename cpu to cc26x2_cc13x2
    * cpu/cc2538:
        * fix spi_transfer_bytes()
        + implement periph/pm
        * timer: handle power mode
    * cpu/cc26xx_cc13xx: add power common code
    * cpu/cortexm:
        + add support for Cortex-M interrupt sub-priorities
        * cleanup dependencies
        * move CPU_ARCH/FAM to Makefile.features
        * only enable MPU during low low level init
    * cpu/efm32:
        * cleanup of makefiles
        * fix incorrect ADC status register
    * cpu/esp_common:
        * allow WiFi modem sleep mode
        + esp-wifi: allow connecting to open networks
        * fixes in common CPU configurations
        * move dependency resolutions to Makefile.dep
    * cpu/esp32:
        * activate automatic XTAL detection
        + add support for light/deep sleep and pm_layered
        * allow external 32 kHz crystal for the RTC hardware time
        + esp_wifi: add WPA2 enterprise mode with IEEE 802.1x/EAP authentication
        * fix wake-up sources for sleep mode
    + cpu/esp8266: add RTT implementation
    * cpu/fe310:
        * fix power management configuration
        + implement driver for watchdog
    * cpu/lpc2387:
        * fix RTC leap year calculation
        + implement periph/adc
        + implement periph/i2c
        * make SPI configurable
    * cpu/native: fix c11_atomic sizes on FreeBSD
    * cpu/native/can/candev_linux: add check for real can
    + cpu/nrf52/nRF802154: implement CCA
    + cpu/nrf5x: add and enable configuration for the built-in DC/DC converter
    * cpu/sam0:
        + add gpio_disable_mux() function
        + add samd21j17d support
        * enhance power saving by switching EIC clock source during STANDBY mode
        * fix handling of PM_NUM_MODES
        + provide interface to query GCLK frequency
        * use generic exti_config
    * cpu/samd21: pwm: allow to use channels > 3
    * cpu/samd5x: disable RTC on init to prevent undefined RTC state
    * cpu/[saml21/1x]: enable buck voltage regulator when possible
    * cpu/stm32_common:
        + add USB OTG FS/HS usbdev peripheral driver
        * enable EXTI interrupt for rtt
        * eth: fix address and multicast filtering
    * cpu/stm32f1: make RTC Y2038 safe
    + cpu/stm32wb: add initial support
    
    Device Drivers
    --------------
    * doc: various fixes in driver documentation
    + drivers/apds99xx: add support for APDS99XX ambient light and proximity sensors
    + drivers/at24cxxx: add support for AT24Cxxx family of EEPROMs
    + drivers/at24mac: add support for unique ID chip
    + drivers/at25xx: add support for AT25xxx family of EEPROMs
    + drivers/at86rf215: add basic support for AT86RF215 dual-band radio
    * drivers/at86rf2xx:
        * fix receive before send detection
        + implement basic mode
    + drivers/bh1900nux: add support
    + drivers/bme680: add support
    + drivers/can: add CAN support for nucleo-l476rg
    + drivers/cc110x: add support for promiscuous mode
    + drivers/disp_dev: add generic interface for display drivers
    * drivers/ds18: fix temperature conversion
    + drivers/hmc5883l: add support for Honeywell HMC5883L magnetometer
    + drivers/kw41zrf: add support for radio
    + drivers/lis2dh12: add interrupt functionality
    * drivers/mtd_spi_nor: erase timings in struct
    + drivers/periph_common/rtc: add rtc_mktime() & rtc_localtime() helper functions
    + drivers/rtt_rtc: add RTT-based RTC implementation, enable it for cpu/cc2538,
      nrf5x_common
    * drivers/slipdev: provide stdio multiplexing over SLIP
    + drivers/sps30: add support for particulate matter sensor
    * drivers/srf08: cleanup driver configuration scheme
    + drivers/stmpe811: add support for touchscreen controller
    * drivers/ws281x:
        + add support for esp32
        + add VT100 backend for native
    
    Build System / Tooling
    ----------------------
    * build system: Restructure dependency resolution
    * dist:
        * cc2538-bsl: use upstream version
        + dhcpv6-pd_ia: initial import of a DHCPv6 server bootstrapper
        * edbg: update to latest upstream version
        * factor out static tests from build_and_test
        * packer: update vagrant image to Ubuntu 18.04 + refactoring
        + sliptty: introduce a new SLIP to TUN tool
        * sliptty/start_network.sh: configure global address for SLIP interface
        * testbed-support:
            * fix compatibility with cli-tools v3
            * use BINFILE for flashing on iotlab
    + doc: add section on configuration to 'Getting started'
    * make:
        * disable implicit rules
        * remove support for make <4
        * native: turn on creation of debug symbols (CFLAGS += -g)
    * Makefile:
        * arch: mips: Allow CFLAGS_DBG and CFLAGS_OPT to be overridden
        * boards: move remaining uses of USEMODULE from Makefile.include to
          Makefile.dep
        * disable stdio_% modules before they are included
        * fix duplicate modules from USEMODULE
        * fix sock_udp deps for stnp
        * include package deps earlier
        * info-global.inc.mk: reset BOARDSDIR
        * Makefile.dep: remove usage of DEFAULT_MODULE += stdio%
        * mips: cleanup include makefile
        * move cpu level dependencies in dedicated Makefile.dep files
        * periph_init based on USEMODULE
        * pkg/local.mk: add FORCE target to .PHONY
        + provide CPU as a feature
        * use simple expansion for widely used variables
    
    Testing
    -------
    * tests:
        + add check_unittests helper function
        + add interactive_sync adapted to shell
        * fix compilation problems with NDEBUG
        * fix for `GNRC_NETIF_SINGLE`
        * fixes for evtimer_msg and bench_runtime_coreapis
    + tests/bench_xtimer_load: initial commit
    * tests/buttons: fix build failure if BTN0_PIN is not declared
    + tests/candev: add initial version with native support
    + tests/driver_netdev_common: add compile-test for network drivers
    + tests/emcute: provide tests
    + tests/gnrc_ipv6_nib_dns: add test of RDNSS option handling
    * tests/gnrc_rpl_srh: use AsyncSniffer for sniffing
    * tests/periph_rtc: fix system locks in ISR
    + tests/xtimer_overhead: initial commit
    
    Kconfig migration
    -----------------
    Migration to Kconfig as configuration tool is currently on phase 1. Which means
    that we are moving configuration options from modules to Kconfig files, and
    leaving its use optional.
    
    + doc: add Kconfig section
    * Kconfig:
        * add CPU and Board common symbols
        * add Drivers menu
        * include application-specific symbols first
        * net/gnrc/ipv6: group IPv6 related Kconfig options
    + Expose configurations to Kconfig of:
        + drivers/periph/wdt
        + drivers/mrf24j40
        + net/gcoap
        + net/gnrc/ipv6/ext/frag
        + net/gnrc/ipv6/nib
        + net/gnrc/sixlowpan
        + net/ieee802154
        + net/nanocoap
        + pkg/tinydtls
        + pkg/wakaama
        + sys/usbus
        + usbus/cdc/acm
    
    API Changes
    ===========
    - SUIT: update to draft-ietf-v3
    - Makefile.include: remove support for make <4
    - net/gnrc_netif: implementation of dynamic GNRC_NETIF_NUMOF approach
    
    - net/sock: amend with zero-copy receive functions:
    
    + /**
    +  * @brief   Releases the stack-internal buffer space provided by the
    +  *          `sock_*_recv_buf()` functions.
    +  * @param[in] buf_ctx   Stack-internal buffer context to release.
    +  */
    + void sock_recv_buf_free(void *buf_ctx);
    
    + /**
    +  * @brief Decrypts and provides stack-internal buffer space containing a
    +  *        message from a remote peer.
    +  *
    +  */
    + ssize_t sock_dtls_recv_buf(sock_dtls_t *sock, sock_dtls_session_t *remote,
    +                            void **data, void **buf_ctx, uint32_t timeout);
    
    + /**
    + * @brief   Provides stack-internal buffer space containing an IPv4/IPv6
    + *          message from remote end point
    + */
    + ssize_t sock_ip_recv_buf(sock_ip_t *sock, void **data, void **buf_ctx,
    +                         uint32_t timeout, sock_ip_ep_t *remote);
    
    + /**
    +  * @brief   Provides stack-internal buffer space containing a UDP message from
    +  *          a remote end point
    +  */
    + ssize_t sock_udp_recv_buf(sock_udp_t *sock, void **data, void **buf_ctx,
    +                           uint32_t timeout, sock_udp_ep_t *remote);
    
    - net/sock/async: add optional callback argument:
    
    + * @param[in] arg   Argument provided when setting the callback using
    + *                  @ref sock_dtls_set_cb(). May be NULL.
      */
    - typedef void (*sock_dtls_cb_t)(sock_dtls_t *sock, sock_async_flags_t flags);
    + typedef void (*sock_dtls_cb_t)(sock_dtls_t *sock, sock_async_flags_t flags,
    +                                void *arg);
    
    + * @param[in] arg   Argument provided when setting the callback using
    + *                  @ref sock_ip_set_cb(). May be NULL.
      */
    - typedef void (*sock_ip_cb_t)(sock_ip_t *sock, sock_async_flags_t flags);
    + typedef void (*sock_ip_cb_t)(sock_ip_t *sock, sock_async_flags_t flags,
    +                              void *arg);
    
    + * @param[in] arg   Argument provided when setting the callback using
    + *                  @ref sock_tcp_set_cb(). May be NULL.
      */
    - typedef void (*sock_tcp_cb_t)(sock_tcp_t *sock, sock_async_flags_t flags);
    + typedef void (*sock_tcp_cb_t)(sock_tcp_t *sock, sock_async_flags_t flags,
    +                               void *arg);
    
    + * @param[in] arg   Argument provided when setting the callback using
    + *                  @ref sock_tcp_queue_set_cb(). May be NULL.
      */
      typedef void (*sock_tcp_queue_cb_t)(sock_tcp_queue_t *queue,
    -                                     sock_async_flags_t flags);
    +                                     sock_async_flags_t flags,
    +                                     void *arg);
    
    + * @param[in] arg   Argument provided when setting the callback using
    + *                  @ref sock_udp_set_cb(). May be NULL.
      */
    - typedef void (*sock_udp_cb_t)(sock_udp_t *sock, sock_async_flags_t type);
    + typedef void (*sock_udp_cb_t)(sock_udp_t *sock, sock_async_flags_t type,
    +                               void *arg);
    
    - net/sock/dns: make sock_dns_query() return the length of the address:
    
    /**
     * @brief Get IP address for DNS name
     *
    - * @return      0 on success
    - * @return      !=0 otherwise
    + * @return      the size of the resolved address on success
    + * @return      < 0 otherwise
     */
    int sock_dns_query(const char *domain_name, void *addr_out, int family);
    
    - mtd_spi_nor: move const params to separate struct:
    
    + /**
    +  * @brief Compile-time parameters for a serial flash device
    +  */
    + typedef struct {
    +     const mtd_spi_nor_opcode_t *opcode; /**< Opcode table for the device */
    +     spi_clk_t clk;           /**< SPI clock */
    +     uint16_t flag;           /**< Config flags */
    +     spi_t spi;               /**< SPI bus the device is connected to */
    +     spi_mode_t mode;         /**< SPI mode */
    +     gpio_t cs;               /**< CS pin GPIO handle */
    +     uint8_t addr_width;      /**< Number of bytes in addresses, usually 3 for small devices */
    + } mtd_spi_nor_params_t;
    +
    
     typedef struct {
         mtd_dev_t base;          /**< inherit from mtd_dev_t object */
    -    const mtd_spi_nor_opcode_t *opcode; /**< Opcode table for the device */
    -    spi_t spi;               /**< SPI bus the device is connected to */
    -    gpio_t cs;               /**< CS pin GPIO handle */
    -    spi_mode_t mode;         /**< SPI mode */
    -    spi_clk_t clk;           /**< SPI clock */
    -    uint16_t flag;           /**< Config flags */
    +    const mtd_spi_nor_params_t *params; /**< SPI NOR params */
         mtd_jedec_id_t jedec_id; /**< JEDEC ID of the chip */
         uint32_t page_addr_mask;
         uint32_t sec_addr_mask;
    -    uint8_t addr_width;      /**< Number of bytes in addresses, usually 3 for small devices */
         uint8_t page_addr_shift;
         uint8_t sec_addr_shift;
     } mtd_spi_nor_t;
    
    Deprecations
    ============
    
    Warnings
    --------
    - `make all-debug` target will be removed for `native` after the 2020.10 release
    - net/gcoap: `gcoap_add_qstring()` will be removed after the 2020.10 release
    - net/gnrc/nettype: `GNRC_NETTYPE_IOVEC` type will be removed after 2020.10
        release
    - net/gnrc_pktbuf: `gnrc_pktbuf_replace_snip()` will be removed after 2020.10
        release
    - net/gnrc/sixlowpan: Configuration macro
        `GNRC_SIXLOWPAN_FRAG_RBUF_AGGRESSIVE_OVERRIDE` will be removed after 2020.10
        release.
    
    Removals
    --------
    - Makefile.include: remove support for GNU make <4
    - pkg/oonf_api: remove package
    - pkg/tinydtls: remove TINYDTLS_LOG configuration macro
    - sys/net/gnrc_tftp: remove module
    - sys/net/nhdp: remove module
    
    Known issues (136)
    ==================
    
    Networking related issues (48)
    ------------------------------
    13834: DHCPv6 client ends up in busy loop after a while
    13745: ethos: Unable to choose global source address.
    13496: cpu/stm32/eth, board/nucleo-f767z1: ethernet buffering issue (ping >1s)
           after debug break
    13490: cpu/stm32/eth, board/nucleo-f767z1: ethernet initialisation fails
           sometimes
    13209: examples/gnrc_border_router is crashing after some time
    13088: Riot-os freezes with lwip + enc28j60 + stm32L4
    12943: driver/mrf24j40: blocks shell input with auto_init_gnrc_netif
    12884: examples/cord_ep: Dead lock when (re-)registering in callback function
    12858: KW2XRF: Broken network communication without netstats-l2
    12857: examples/gnrc_networking_mac broken on ATmega
    12565: gnrc_icmpv6_echo: flood-pinging another node leads to leaks in own
           packet buffer
    12264: ethos: Unable to handle fragmented IPv6 packets from Linux kernel
    12210: stale border router does not get replaced
    11988: ethos: fails to respond to first message.
    11860: send data with UDP at 10HZ, the program die
    11859: examples: dtls-echo fails silently when DTLS_ECC flag enabled
    11852: scan-build errors found during 2019.07 testing
    11795: gnrc_tftp: string functions on non-null terminated input
    11405: nrfmin: communication not possible after multicast ping with no interval
    11212: POSIX sockets + lwIP: bad file descriptor
    11033: 6lo: RIOT does not receive packets from Linux when short_addr is set
    10969: net: netdev_driver_t::send() doc unclear
    10861: cpu/esp8266: Tracking open problems of esp_wifi netdev driver
    10809: openthread: does not build on current Arch
    10410: Missing drop implementations in netdev_driver_t::recv
    10389: gnrc_sock_udp: Possible Race condition on copy in application buffer
    10380: netdev_ieee802154: Mismatch between radio ll address and in memory
           address
    10370: gomach: Resetting netif with cli doesn't return
    10338: xbee: setting PAN ID sometimes fails
    9709: examples: failed assertion in dtls-echo example
    9656: gnrc/netif: various problems after resetting interface a second time
    8779: CC2538 RF overlapping PIN usage
    8752: mrf24j40: does not link for examples/default
    8271: app/netdev: application stops working after receiving frames with
          assertion or completely without error
    8242: at86rf2xx: Dead lock when sending while receiving
    8199: gcoap example request on tap I/F fails with NIB issue
    8172: gnrc_netif, gnrc_uhcpc: Replacing prefix on border router results in no
          configured prefix
    8086: gnrc_rpl_p2p: port to nib and fix compile errors
    7737: pkg: libcoap is partially broken and outdated
    7474: 6lo gnrc fragmentation expects driver to block on TX
    7304: General 802.15.4/CC2538 RF driver dislikes fast ACKs
    6018: nRF52: gnrc_6lowpan_ble: memory leak with nordic_softdevice_ble
    5863: OSX +  SAMR21-xpro: shell cannot handle command inputs larger than 64
           chars
    5748: gnrc: nodes crashing with too small packet buffer
    5486: at86rf2xx: lost interrupts
    5230: gnrc ipv6: multicast packets are not dispatched to the upper layers
    5051: Forwarding a packet back to its link layer source should not be allowed
    4527: gnrc_ipv6: Multicast is not forwarded if routing node listens to the
           address
    
    Timer related issues (17)
    -------------------------
    13072: periph/timer: `timer_set()` underflow safety check (tracking issue)
    12909: Bug: Unexpected behavior with xtimer_periodic_wakeup() for large periods
           on Nucleo-f401re
    11523: xtimer_periodic_wakeup crashing at high frequencies on frdm-kw41z
    11149: xtimer: hang on xtimer_spin_until (corner case)
    10545: periph_timer: systematic proportional error in timer_set
    10523: saml21 system time vs rtc
    10510: xtimer_set_msg: crash when using same message for 2 timers
    10073: xtimer_usleep wrong delay time
    9187: sys/newlib: gettimeofday() returns time since boot, not current wall
          time.
    9052: misc issues with tests/trickle
    9049: xtimer mis-scaling with long sleep times
    8746: stm32_common/periph/rtc: current implementation broken/poor accuracy
    8251: MSP430: periph_timer clock config wrong
    7347: xtimer_usleep stuck for small values
    7114: xtimer: add's items to the wrong list if the timer overflows between
          _xtimer_now()  and irq_disable()
    6442: cpu/native: timer interrupt issue
    6052: tests: xtimer_drift gets stuck on native
    
    Drivers related issues (9)
    --------------------------
    13444: Potential security and safety race conditions on attached devices
    12445: driver/hts221: Temperature and Humidity readings incorrect
    12371: fail to send data to can bus
    12045: floats and doubles being used all over the place.
    11388: SD card initialization: timeouts effectively blocking
    11104: STM32: SPI clock not returning to idle state and generating additional
           clock cycles
    9419: cpu/msp430: GPIO driver doesn't work properly
    8045: stm32/periph/uart: extra byte transmitted on first transmission
    4876: at86rf2xx: Simultaneous use of different transceiver types is not
          supported
    
    Native related issues (3)
    -------------------------
    11472: Warnings from objcopy and size (binutils 2.32)
    5796: native: tlsf: early malloc will lead to a crash
    495: native not float safe
    
    Other platforms related issues (18)
    -----------------------------------
    13606: gcoap/esp8266: Stack overflow with gcoap example
    13408: Bug: PWM test crashes on Arduino Mega 2560
    13390: Cannot use LLVM with Cortex-M boards
    13267: Failing tests on MSP430 (z1)
    13104: boards/hifive1: flashing issue
    13086:  Failing tests on FE310 (Hifive1b)
    12763: [TRACKING] Fixes for automatic tests of ESP32 boards.
    12651: Failing tests on AVR (tested with atmega256rfr2-xpro)
    12168: pkg/libb2: blake2s doesn't work on AVR
    12057: ESP32 + DHT + SAUL reading two endpoints causes freeze.
    10258: Incorrect default $PORT building for esp32-wroom-32 on macOS
    10122: Indeterministic hard fault in _mutex_lock(), with nRF52 SoftDevice
    10076: cpu/cortexm_common: irq_enable returns the current state of interrupts
           (not previous)
    8408: pkg/fatfs: linker error when build tests/pkg_fatfs_vfs for msb430 based
          boards
    7753: pic32-wifire: race-condition when linking in concurrent build
    6567: periph/spi: Switching between CPOL=0,1 problems on Kinetis with software
          CS
    5774: cpu: cortexm_common: context switching code breaks when compiling with
          LTO
    4954: chronos: compiling with -O0 breaks
    
    Build system related issues (11)
    --------------------------------
    13492: make -j flash broken on esp* (will always flash the previous binary)
    13419: Can't use nimble as prefix for modules
    12771: dist/tools/cppcheck/cppchck.sh: errors when running with Cppcheck 1.89
    10850: Tracking: remove harmful use of `export` in make and immediate
           evaluation
    9913: Build dependencies - processing order issues
    9742: `buildtest` uses wrong build directory
    9645: Different build behavior between `murdock` and `riot/riotbuild:latest`
          image
    8913: make: use of immediate value of variables before they have their final
          value
    8122: doxygen: riot.css modified by 'make doc'
    6120: Windows AVR Mega development makefile Error
    4053: macros: RIOT_FILE_RELATIVE printing wrong file name for headers
    
    Other issues (30)
    -----------------
    13918: cpu/stm32f1: CPU hangs after wake-up from STOP power mode
    13527: examples/dtls-wolfssl not working on pba-d-01-kw2x
    13345: sys/xtimer: segmentation fault: in function xtimer_msg_received_timeout
    13277: Y2038 tracking issue / strategy
    13133: tests/pkg_tensorflow-lite: tests randomly failing on nrf52dk and
           esp32-wroom-32
    13120: tests: broken with stdio_rtt if auto_init is disabled
    13044: _NVIC_SystemReset stuck in infinite loop when calling pm_reboot through
           shell after flashing with J-Link
    12732: tests: some tests don't work with `newlib` lock functions.
    12205: core: atomic: Unable to compile starting with gcc 9.1.0
    12108: `make term` output is inconsistent between boards, `ethos` and `native`
    12105: [TRACKING] sys/shell refactoring.
    11885: arm7: printf() with float/double not working
    11243: sys/riotboot: documentation issues
    10751: Possible memset optimized out in crypto code
    10731: nanocoap: incomplete response to /.well-known/core request
    10639: sys/stdio_uart: dropped data when received at once
    10121: RIOT cannot compile with the latest version of macOS (10.14) and Xcode
           10
    9882: sys/tsrb is not thread safe on AVR
    9518: periph/i2c: tracking bugs and untested acks
    9371: assert: c99 static_assert macro doesn't function for multiple
          static_asserts in the same scope
    8589: Why using -F in avrdude?
    8436: Kinetis PhyNode: failed to flash binary > 256K
    7220: sys/fmt: Missing tests for fmt_float, fmt_lpad
    6533: tests/lwip target board for python test is hardcoded to native
    5769: Possible problem in scheduler
    5009: RIOT is saw-toothing in energy consumption (even when idling)
    4866: periph: GPIO drivers are not thread safe
    4488: Making the newlib thread-safe
    3256: make: Setting constants on compile time doesn't really set them
          everywhere
    2346: Tracker: Reduce scope on unintended COMMON variables
    
    There are 137 known issues in this release
    
    Fixed Issues since the last release (2020.01)
    =============================================
    
    13920: stm32: ztimer RTT backend overflow
    13680: suit-tool runs on every build - ModuleNotFoundError: No module named
           'cbor' when building anything
    13587: drivers/cc110x: Lost IRQs can lead to driver deadlock
    13471: 6ctx: incorrectly removes 6ctx context when the non-zero part of the
           address matches
    13460: Makefile.dep: DEFAULT_MODULE += stdio_rtt will always load dependencies
           - even if other stdio is selected
    13459: cpu/cortex-m23: gcc 9 bug when compiling c11 atomics
    13447: gnrc_sock_dns is not working
    13442: gnrc_networking not sending packets when hardware has multiple
           interfaces
    13369: native:in file gnrc_rpl_p2p.c function trickle_start() has extra and
           some undeclared variables.
    13358: iotlab-m3: long HW address is in reversed order
    13353: tests/unittests/tests-ecc: segfault with golay, when enabling asserts
    13309: cpu/native/can: Segmentation fault when manipulating vcan's through
           socketcan
    13287: Driver for DS18B20 returns invalid values
    13265: tests: compilation of some test applications fail with NDEBUG
    13015: Quickest start does not build with vagrant
    12854: `pm_reboot()` not working on AVR when compiled with `LTO=1`
    12370: Undocumented uint8_t assumptions in nrf52840 peripherals
    12037: cpu/sam0_common: i2c baudrate calculation fails if CLOCK_CORECLOCK > 51
           MHz
    11026: Recent changes effectively killed modular board designs
    8213: at86rf2xx: Basic mode and NETOPT_AUTOACK
    8130: gcoap: can't build with network stacks other than GNRC
    7020: isr_rfcoreerrors while pinging between CC2538DKs
    
    22 fixed issues since last release (2020.01)
    
    Acknowledgements
    ================
    We would like to thank all companies that provided us with hardware for porting
    and testing RIOT-OS. Further thanks go to companies and institutions that
    directly sponsored development time. And finally, big thanks to all of you
    contributing in so many different ways to make RIOT worthwhile!
    
    More information
    ================
    http://www.riot-os.org
    
    Mailing lists
    -------------
    * RIOT OS kernel developers list
      devel@riot-os.org (http://lists.riot-os.org/mailman/listinfo/devel)
    * RIOT OS users list
      users@riot-os.org (http://lists.riot-os.org/mailman/listinfo/users)
    * RIOT commits
      commits@riot-os.org (http://lists.riot-os.org/mailman/listinfo/commits)
    * Github notifications
      notifications@riot-os.org (http://lists.riot-os.org/mailman/listinfo/notifications)
    
    IRC
    ---
    * Join the RIOT IRC channel at: irc.freenode.net, #riot-os
    
    License
    =======
    * The code developed by the RIOT community is licensed under the GNU Lesser
      General Public License (LGPL) version 2.1 as published by the Free Software
      Foundation.
    * Some external sources and packages are published under a separate license.
    
    All code files contain licensing information.
    
    
  • 2020.04-RC3
  • 2020.04-RC2
  • 2020.07-devel
    Development branch towards 2020.07 release
  • 2020.04-RC1
  • 2020.01
    RELEASE 2020.01
    
    RIOT-2020.01 - Release Notes
    ============================
    RIOT is a multi-threading operating system which enables soft real-time
    capabilities and comes with support for a range of devices that are typically
    found in the Internet of Things: 8-bit and 16-bit microcontrollers as well as
    light-weight 32-bit processors.
    
    RIOT is based on the following design principles: energy-efficiency, soft
    real-time capabilities, small memory footprint, modularity, and uniform API
    access, independent of the underlying hardware (with partial POSIX compliance).
    
    RIOT is developed by an international open-source community which is
    independent of specific vendors (e.g. similarly to the Linux community) and is
    licensed with a non-viral copyleft license (LGPLv2.1), which allows indirect
    business models around the free open-source software platform provided by RIOT.
    
    About this release:
    ===================
    
    The 2020.01 release includes:
    
     - Initial support for MicroPython
     - Initial support for GNRC based LoRaWAN stack
     - Initial (experimental) asynchronous sock support
     - Extend support for lpc2387 and fe310 cpus
     - Xtimer concurrency/robustness improvement, fixing #8388, #5338 & #5103
     - Complete re-implementation of esp8266 based on ESP8266 RTOS SDK
     - Improvements in automatic tests
     - Introduce and start using Kconfig as a configuration tool
     - +12 new boards, +7 new drivers, +4 new packages
    
    About 527 pull requests, composed of 1367 commits, have been merged since the
    last release, and about 29 issues have been solved. 61 people contributed with
    code in 111 days. Approximately 3053 files have been touched with 134416 (+)
    insertions and 31870 deletions (-).
    
    Notations used below:
    =====================
        + means new feature/item
        * means modified feature/item
        - means removed feature/item
    
    New features and changes
    ========================
    
    System libraries
    ----------------
        + core/kernel_defines: Introduce 'IS_ACTIVE' macro
        * core/assert: allow multiple static_asserts within a function
        * core/ringbuffer: compensate 'ringbuffer_remove' underflow error
        + core/thread: add zombie thread state
        + sys: basic C++ compatibility with C11 atomics
        + sys/arduino:
            + added Wire (I2C) interface
            + added SPI interface
            * allow use of arduino libraries without need for arduino sketch
            * add implementation for analogWrite
            * fixed frequency selection in SPI
        * sys/bitfield: unify byte order and bit order to both be most significant
            bX first
        * sys/checksum: move crc8 implementation from sht3x to common code
        * sys/color: add color_rgb_set_brightness() and color_rgb_shift()
        * sys/crypto/modes/ccm: support length of AAD > 24
        * sys/crypto/modes/ccm: support plain text length < 2^32
        + sys/frac: add frac library for integer scaling by semi-constant fractions
        + sys/luid: add luid_get_eui48() / luid_get_eui64()
        + sys/progress_bar: add module for managing a progress bar in stdout
        * sys/posix/pthread/pthread.c: fix pthread reaper
        * sys/shell: make shell_run run shell forever
        * sys/shell_commands: make 6Lo compression contexts configurable on non-6LBR
        + sys/stdio_null: add null driver
        * sys/suit: use c25519 instead of hacl
        - sys/suit: remove dependency on tinycbor
        * sys/usbus:
            * add descriptor prefix support
            * unify terminology to use 'descriptor' everywhere
            * cdc_acm: add interface association descriptor, enable Windows
                enumeration and usage of RIOT CDC ACM
            * cdc_acm: fix to avoid lost characters on USBUS CDC ACM STDIO
        * sys/xtimer:
            * concurrency/robustness improvements
            * fix xtimer_mutex_lock_timeout by having _mutex_timeout() check waiting
                list
            - remove dependency to core_msg
    
    Networking
    ----------
        + sys/gnrc_lorawan: add initial support for GNRC based LoRaWAN stack
        * sys/gnrc_netif: make 6LoENC dynamically configurable
        + sys/gnrc_sock: provide asynchronous event implementation
        * sys/gnrc_ipv6: fix source check for loopback address
        * sys/gnrc_ipv6_ext_frag: remove fragment header when n-th fragment is first
        * sys/gnrc_ipv6_nib: allow for configuration of static link-local addresses
        * sys/gnrc_netif: highest source address scope wins selection
        * sys/gnrc_netif: only use prefix matching as tie-breaker in source
            selection
        * sys/gnrc_sixlowpan_frag_rb: split out classic frag specific code
        * sys/gnrc_sixlowpan_frag_rb: fix memory-leak in _rm_by_datagram() and in
            interval marker inherited from base
        * sys/gnrc_sixlowpan_frag: various optimizations on sending
        * sys/gnrc_sixlowpan_iphc: add fragment forwarding stubs
        * sys/gnrc_sixlowpan_iphc_nhc: determine UDP hdr length from reassembly
            buffer, fix fragmented data size allocation
        * sys/gnrc_tcp: return immediately on gnrc_tcp_recv if connection is closing
        + sys/net/gcoap: add macro to delay initialization of gcoap
        * sys/net/gcoap: do not allocate RX buf on stack
        * sys/pthread: check malloc() return value, prevent NULL pointer deference
        * sys/shell/gnrc_netif: use netif API for ifconfig
        * sys/shell/sc_nimble`_netif: allow connecting by name
        + sys/sock: initial definitions for asynchronous event handling
        + sys/sock_async: initial import of event-based implementation
    
    Packages
    --------
        * pkg: cleanup management of dependencies
        * pkg/pkg.mk: use intermediate state files
        * pkg/ccn-lite: bump version
        + pkg/flatbuffers: add support for FlatBuffers serialization library
        * pkg/gecko_sdk: update to version 2.7
        * pkg/libfixmath: several improvements and fixes to support 8bit
        * pkg/littlefs: bump littlefs version to 1.7.2
        * pkg/lora-serialization: bump to latest version and update test for AVR
        * pkg/lwip:
            * add support for esp32 Ethernet device
            * add IPv4 support for LWIP-stm32
            * start DHCP for a netif with lwip_dhcp
            * add stm32 ethernet support
            * enable lwIP for ESP8266
        + pkg/nanopb: add Nanopb protocol buffers library package
        * pkg/nimble:
            * bump version
            + add simple BLE connection manager: autoconn
            + add user event callback to autconn
            + nimble_netif: catch L2CAP connection failures
            + nimble_netif: add additional events
        * pkg/tinydtls: add DTLS sock API implementation
        * pkg/tinydtls: bump version
        + pkg/tensorflow-lite: add support to RIOT
        + pkg/utensor: add support to RIOT
        * pkg/u8g2: refactor the U8g2 package
        * pkg/wakaama: add basic LWM2M client implementation
    
    Boards
    ------
        - boards: remove RTT_NUMOF/RTC_NUMOF
        - boards: unexport PROGRAMMER
        + boards/adafruit-nrf52840: initial support
        * boards/arduino-zero: configure ADC channels
        + boards/atmega328p: initial support for standalone version
        * boards/atmega328p: support variable xtimer frequencies
        + boards/atmega1284P: initial support for standalone version
        + boards/atmega256rfr2: initial support
        + boards/avr-rss2: initial support
        + boards/cc1252: initial support
        * boards/common: clean up msba2 common files
        + boards/derfmega*: initial support
        + boards/esp32-ttgo-t-beam: initial support
        - boards/frdm: remove support for OpenOCD < v0.10.0
        + boards/mcb2288: initial support
        + boards/microduino-corerf: initial support
        * boards/nucleo-f207zg: add ethernet configuration
        * boards/native: allow for native to be reset via SIGUSR1
        * boards/particle-*: configure PCB antenna for 2.4GHz radio
        * boards/pic32-clicker: cleanup uart configuration and initialization
        * boards/pic32-clicker: use pic32prog as default programmer
        + boards/pinetime: initial support for the PINE64 PineTime smartwatch
        + boards/sodaq-*: add arduino support
        * boards/sodaq-*: refactor common code
        + boards/stm32f030f4-demo: initial support
        * boards/stm32-common:
            * allow SPI signals routed on multiple alternate functions
            * add 54MHz and 108MHz SPI divtable entries
            * common programmer/debugger/serial config
        * boards/thingy: add dependency for on-board hts221/lps22hb sensors
    
    CPU
    ---
        + cpu/arm7_common: hook up puf_sram
        + cpu/atmega128rfa1: add initial support
        + cpu/atmega256rfr2: symbol counter based RTT support
        + cpu/atmega_common:
            * clean ups and fix code run at end of ISR to behave like
                `thread_yield_higher`
            * fixed atmega_exit_isr
            * uart: use TX_ISR to check uart transmission end
            + cpuid: provide for every device
            + rtt: initial peripheral driver support
            + wdt: initial peripheral driver support
        * cpu/cortexm: fix -mfpu flag value for CortexM7
        * cpu/fe310:
            * several cleanup in implementation and clock setup
            * change default optimization to "-Os"
            * uart: rework driver and fixes
            + i2c: initial peripheral driver support
            + spi: initial peripheral driver support
            + cpp: add feature
        * cpu/esp*: esp_wifi used as default netdev for lwip
        * cpu/esp32:
            * improvements and cleanup of log_module
            * fix lwip + esp_wfi, esp_wifi send buffer should not be on stack
            * use esptool.py from riot tools
            * rtc: fixes, improvements and cleanups
            * spi: fix CS handling in spi_transfer_bytes
            * uart: workaround uart sporadically set to wrong value when the CPU
                clock is changed
            * spi: enable use of SPI flash drive with pkg_littlefs
        * cpu/esp8266:
            * complete re-implementation based on ESP8266 RTOS SDK
            * fix of esp_wifi_send function
            * fix bootloaders and log outputs in vendor code
        * cpu/efm32: fix uart handling of RX when no RX callback is configured
        * cpu/efm32: normalize time in rtc_series1
        * cpu/lpc2387:
            * allow for more flexible clock selection
            + add support for backup RAM
            * uart: update the UART driver
            + pm: initial support
            + dac: initial support
            * rtc: enable RTC on rtc_init(), align with other RTC implementations
            * lpc2387.ld: cleanups and align with cortexm_base.ld
            * lpc2387.ld: provide thread_isr_stack_*() - MicroPython
        + cpu/kinetis: add flashpage for W & K series
        * cpu/msp430_common: add flashpage_raw
        * cpu/native:
            + initial import of stdio_native
            * allow Access to Hardware SPI Bus on Linux
            * fix all-asan Makefile target
        * cpu/stm32:
            * i2c_2: fix read bytes flag
            - i2c_2: do not support repeated start reading
            * stmclk: fix M-factor shift for SAI PLL
            * stcmlk: add functions for low power mode clock config
            + stm32f0: add support for stm32f030cc CPU
            + stm32f1: add rtt peripheral driver
            + stm32l0: add stm32l010c6 support
        * cpu/sam0_common:
            * uart: implement non-blocking uart write
            + uart: add hardware flow control support
            * rtt: enable COUNTSYNC in CTRLA, fixes `rtt_get_counter()` return value
            * spi: power off spi on release, avoid bus errors affecting application
                code
            * adc: fix API to return `-1` on unsupported resolution
        * cpu/samd21: use dedicated 1kHz GCLK4 for RTC and WDT
    
    Device Drivers
    --------------
        + doc/doxygen: add device driver guide
        + drivers: add Differentially Operated Serial Ethernet (DOSE) driver
        * drivers/at86rf2xx: add support for ATmegaRF MCUs
        * drivers/at86rf2xx: enable Smart Reduced Power Consumption for AT86RFR2
        * drivers/bmx280: added SPI models
        + drivers/dcf77: add driver for DCF77
        * drivers/hd44780: move params header to the right place
        + drivers/ili9341: initial import of ili9341 LCD driver
        * drivers/ina220: re-worked and added SAUL adaptation
        + drivers/ina3221: add driver for INA3221 current, power & voltage monitor
        + drivers/itg320x: add driver for InvenSense ITG-320X 3-axis gyroscope
        * driver/mpu9x50: make mpu9150 more generic
        * drivers/mrf24j40: allow for basic self-test on init
        * drivers/mrf24j40: fix start up code
        + drivers/qmc588rl: add support for QMC5883L
        + drivers/shtc1: add driver for SHTC1 temperature and humidity sensor
        + drivers/ws281x: add driver for WS281x RGB LED driver for ATmega platform
        * drivers/xbee: fix reference to device from netif in send function
        * periph/adc: change return type of `adc_sample()` to `int32_t`
    
    Build System / Tooling
    ----------------------
        + dist/tools:
            + add Kconfiglib
            + add helper script for Black Magic Probe
            + add support for miniterm.py
            * fix 'make reset' with bootloader in avrdude
        + dist/testbed-support: add nrf52{840,832}mdk in IOTLAB_NODE targets
        + doc/advanced-build-system-tricks: handle multiple boards
        + doc/doxygen: add build system doc page for BOARD, CPU, FEATURE
        + doc/doxygen: add build-system-basics.md with general build system tips
        + Kconfig:
            + add build system integration and test application
            + makefiles: include configuration symbols to build system
            + makefiles: add symbols for used packages
            + expose gnrc/ipv6/whitelist configurations
            + expose gnrc/lorawan configurations
            + expose usb configurations
            + expose net/sock/util configurations
            + expose gnrc/netif configurations
            + expose gnrc/ipv6 configurations
        + make:
            + introduce 'BOARDSDIR' to support external boards using common code in
                'RIOTBOARD'
            * fail by default when errors are expected
            + add architectures features
            + add features blacklisting
            + add blob utility header
            * enable SECONDEXPANSION for module/application builds
            + add CXXEXT and CXXEXCLUDE variable for customizing C++ builds
        - makefiles:
            - remove use of export with LINKFLAGS variable
            + add possibility to provide board specific application dependencies in
                a separate Makefile
            * generate proper dependency files when using ccache
            * fix LOG_LEVEL handling
            - disable `-Watomic-alignment` on LLVM
            + introduce 'PROG_DEV' to specify programmer device
            * assert CPU is defined by BOARD/Makefile.features
            + add TERMFLASHDEPS to TERMDEPS so it also applies to `test`
            * tools: allow make reset via avrdude
            * tools: set DEBUG_ADAPTER_ID as JLINK_SERIAL
    
    Testing
    -------
        - dist/tests/philip: Removed old code and tests
        * dist/tools/testrunner:
            * make interactive test sync retries/delay configurable
            * reset before opening terminal
            - reset after opening terminal only if interactive test sync is not used
            * add variable for customizing a delay before reset
            * make interactive test sync retries/delay configurable
        * dist/tools/compile_and_test_for_board.py: allow use of wildcards for
            applications selection
        + murdock: enable esp32-wroom-32 for CI testing
        * tests:
            + use test_interactive_test_util
            + add automated tests guidelines in README
            - remove APPLICATION definition in tests/*
        + tests/gnrc_sock_neterr: proof of concept test for gnrc_sock + gnrc_neterr
        + tests/bench_xtimer: initial import
        * tests/lwip: enable IPv4
        * tests/malloc: improve application and add an automatic test script
        * tests/memarray: add python script for automatic testing
        * tests/nordic_softdevice: cleanup test script and fix test
        + tests/periph_timer_short_relative_set: initial import
        * tests/periph_cpuid: add automatic test script
        * tests/sys_arduino: fix test synchronization issues
        * tests/unittests: fix `tests-pkt` for non-32bit platforms
    
    API Changes
    ===========
    
    - drivers/ina220:  changes to comply with RIOT's design goals & SAUL adaption
    - usbus: unified terminology within USBUS to match the terminology from the
        specs. `hdr`, `hdrs`, `headers`, etc is replaced everywhere with `descr`
        `descriptors` and `descriptors`.
    - Makefile.include: fail by default when errors are expected
    
    ```diff
    /* change return type of `adc_sample()` to `int32_t` to allow support for ADCs
       with resolution of more than 16 bits on 8 bit and 16 bit platforms*/
    - int adc_sample(adc_t line, adc_res_t res)
    = int32_t adc_sample(adc_t line, adc_res_t res)
    
    /* pass memo to resp_handler directly */
    - typedef void (*gcoap_resp_handler_t)(unsigned req_state, coap_pkt_t* pdu,
    -                                      sock_udp_ep_t *remote);
    + typedef void (*gcoap_resp_handler_t)(const gcoap_request_memo_t *memo,
    +                                      coap_pkt_t* pdu,
    +                                      const sock_udp_ep_t *remote);
    
    /* allow to pass user context to requests */
      size_t gcoap_req_send(const uint8_t *buf, size_t len,
                            const sock_udp_ep_t *remote,
    -                       gcoap_resp_handler_t resp_handler);
    +                       gcoap_resp_handler_t resp_handler, void *context);
    
    /* assume `netif->ops->init()` to be set to at least a default */
    -     _init_from_device(netif);
    - #ifdef DEVELHELP
    -     _test_options(netif);
    +     netif->ops->init(netif);
    + #if DEVELHELP
    +     assert(options_tested);
    -     netif->cur_hl = GNRC_NETIF_DEFAULT_HL;
    - #ifdef MODULE_GNRC_IPV6_NIB
    -     gnrc_ipv6_nib_init_iface(netif);
    - #endif
    -     if (netif->ops->init) {
    -         netif->ops->init(netif);
    -     }
    
    /* split the semantic of gnrc_netif_is_6ln() into two check functions */
    /* is the interface performing 6Lo-ND as specified in RFC 6775. */
    - bool gnrc_netif_is_6ln(const gnrc_netif_t *netif);
    + bool gnrc_netif_is_6lo(const gnrc_netif_t *netif);
    + static inline bool gnrc_netif_is_6ln(const gnrc_netif_t *netif
    
    /* add function to start a shell and exit once EOF is reached. */
    + void shell_run_once(const shell_command_t *commands, char *line_buf, int len);
    
    /* return reassembly buffer entry created or updated */
    - void gnrc_sixlowpan_frag_rb_add(gnrc_netif_hdr_t *netif_hdr,
    -                                 gnrc_pktsnip_t *frag, size_t offset,
    -                                 unsigned page);
    + gnrc_sixlowpan_frag_rb_t *gnrc_sixlowpan_frag_rb_add(gnrc_netif_hdr_t *netif_hdr,
    +                                                      gnrc_pktsnip_t *frag,
    +                                                      size_t offset, unsigned page);
    
    /* move gnrc_sixlowpan_frag_rb_dispatch_when_complete() out of
       gnrc_sixlowpan_frag_rb_add(). The caller of the latter function is now
       responsible to call it. */
    + int gnrc_sixlowpan_frag_rb_dispatch_when_complete(gnrc_sixlowpan_frag_rb_t *rbuf,
    +                                                   gnrc_netif_hdr_t *netif);
    
    /* don't assume interface specifier is an int for splitting, add functions to
       split int and string */
    -  * @return          interface number or -1 if none specified
    +  * @return          string containing the interface specifier.
    +  * @return          NULL if no interface was specified.
    +  */
    - static inline int ipv6_addr_split_iface(char *addr_str)
    + static inline char *ipv6_addr_split_iface(char *addr_str)
    
    - int ipv6_addr_split(char *addr_str, char seperator, int _default);
    + int ipv6_addr_split_int(char *addr_str, char seperator, int _default);
    + char *ipv6_addr_split_str(char *addr_str, char separator);
    
    /* change address getter and setter functions to avoid byte order confusion */
    - uint16_t at86rf2xx_get_addr_short(const at86rf2xx_t *dev);
    + void at86rf2xx_get_addr_short(const at86rf2xx_t *dev, network_uint16_t *addr);
    
    - void at86rf2xx_set_addr_short(at86rf2xx_t *dev, uint16_t addr);
    + void at86rf2xx_set_addr_short(at86rf2xx_t *dev, const network_uint16_t *addr);
    
    - uint64_t at86rf2xx_get_addr_long(const at86rf2xx_t *dev);
    + void at86rf2xx_get_addr_long(const at86rf2xx_t *dev, eui64_t *addr);
    
    - void at86rf2xx_set_addr_long(at86rf2xx_t *dev, uint64_t addr);
    + void at86rf2xx_set_addr_long(at86rf2xx_t *dev, const eui64_t *addr);
    ```
    
    Deprecations
    ============
    
    Warnings
    --------
    
    - GNU make <4 will be removed after release 2020.01
    - net/gcoap: gcoap_finish() will be removed after release 2020.04
    - makefiles/vars.inc.mk: PORT_BSL & AVRDUDE_PORT will be removed after release
        2020.04
    - gnrc_nettest: will be removed after release 2020.07
    
    Removals
    --------
    
    - sys/ubjson: remove module
    - dist/tests/philip: removed unneeded and unused tests and code
    - net/gcoap: remove gcoap_req_send2()
    - cpu/efm32: remove EFM32_UART_MODES
    - boards: remove RTT_NUMOF/RTC_NUMOF
    
    Known issues (130)
    ==================
    
    Networking related issues (45)
    ------------------------------
            packet buffer
            address
           assertion or completely without error
           configured prefix
           chars
           address
    
    Timer related issues (17)
    -------------------------
            on Nucleo-f401re
           time.
           _xtimer_now() and irq_disable()
    
    Drivers related issues (12)
    ---------------------------
            MHz
            clock cycles
           supported
    
    Native related issues (3)
    -------------------------
    
    Other platforms related issues (16)
    -----------------------------------
            (not previous)
           boards
           CS
           LTO
    
    Build system related issues (9)
    -------------------------------
            evaluation
           image
           value
    
    Other issues (28)
    -----------------
            esp32-wroom-32
            shell after flashing with J-Link
            10
           static_asserts in the same scope
           everywhere
    
    Fixed Issues since the last release (2019.10) (29)
    =================================================
    
            wrote in tests/pkg_fatfs.
            support
            on host
            flashfile
    
    Acknowledgements
    ================
    We would like to thank all companies that provided us with hardware for porting
    and testing RIOT-OS. Further thanks go to companies and institutions that
    directly sponsored development time. And finally, big thanks to all of you
    contributing in so many different ways to make RIOT worthwhile!
    
    More information
    ================
    http://www.riot-os.org
    
    Mailing lists
    -------------
    * RIOT OS kernel developers list
      devel@riot-os.org (http://lists.riot-os.org/mailman/listinfo/devel)
    * RIOT OS users list
      users@riot-os.org (http://lists.riot-os.org/mailman/listinfo/users)
    * RIOT commits
      commits@riot-os.org (http://lists.riot-os.org/mailman/listinfo/commits)
    * Github notifications
      notifications@riot-os.org (http://lists.riot-os.org/mailman/listinfo/notifications)
    
    IRC
    ---
    * Join the RIOT IRC channel at: irc.freenode.net, #riot-os
    
    License
    =======
    * The code developed by the RIOT community is licensed under the GNU Lesser
      General Public License (LGPL) version 2.1 as published by the Free Software
      Foundation.
    * Some external sources and packages are published under a separate license.
    
    All code files contain licensing information.
    
    
  • 2020.01-RC3
  • 2020.01-RC2