TinyDTLS: integration into RIOT (without sockets)

Support for TinyDTLS (0.8.6) is added together an example at 'examples/dtls-echo'.

examples/dtls-echo/Makefile

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+# name of your application
+APPLICATION = dtls_echo
+
+# If no BOARD is found in the environment, use this default:
+BOARD ?= native
+
+# This has to be the absolute path to the RIOT base directory:
+RIOTBASE ?= $(CURDIR)/../..
+
+BOARD_BLACKLIST := z1 wsn430-v1_4 wsn430-v1_3b waspmote-pro arduino-mega2560  \
+                   msb-430h msb-430 chronos telosb msbiot cc2538dk \
+                   saml21-xpro samr21-xpro arduino-duemilanove arduino-uno
+
+BOARD_INSUFFICIENT_MEMORY := airfy-beacon chronos msb-430 msb-430h nrf51dongle \
+                          nrf6310 nucleo-f103 nucleo-f334 pca10000 pca10005 spark-core \
+                          stm32f0discovery telosb weio wsn430-v1_3b wsn430-v1_4 \
+                          yunjia-nrf51822 z1 nucleo-f072 cc2650stk nucleo-f030\
+                          nucleo-f070
+
+# Include packages that pull up and auto-init the link layer.
+# NOTE: 6LoWPAN will be included if IEEE802.15.4 devices are present
+USEMODULE += gnrc_netdev_default
+USEMODULE += auto_init_gnrc_netif
+# Specify the mandatory networking modules for IPv6 and sUDP
+USEMODULE += gnrc_ipv6_router_default
+USEMODULE += gnrc_udp
+# Add a routing protocol
+USEMODULE += gnrc_rpl
+# This application dumps received packets to STDIO using the pktdump module
+USEMODULE += gnrc_pktdump
+# Additional networking modules that can be dropped if not needed
+USEMODULE += gnrc_icmpv6_echo
+# Add also the shell, some shell commands
+USEMODULE += shell
+USEMODULE += shell_commands
+USEMODULE += ps
+
+#TinyDTLs (crypto.c) made use of pthread
+ ifneq ($(BOARD),native)
+ USEMODULE += pthread
+ endif
+
+# Comment this out to disable code in RIOT that does safety checking
+# which is not needed in a production environment but helps in the
+# development process:
+CFLAGS += -DDEVELHELP
+
+# NOTE: Add the package for TinyDTLS
+USEPKG += tinydtls
+
+# NOTE: Those are taken from TinyDTLS. As the original Makefiles are
+#      overwitten is a good idea to preserve them here.
+CFLAGS += -DDTLSv12 -DWITH_SHA256
+
+# NOTE: This adds support for TLS_PSK_WITH_AES_128_CCM_8
+CFLAGS += -DDTLS_PSK
+
+# NOTE: This adds support for TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8
+CFLAGS += -DDTLS_ECC
+
+# NOTE: If enabled TinyDTLS' log are disabled (if memory is a issue).
+# WARNING: Sometimes the log leads to Stack pointer corrupted.
+#          The reason is not identified yet.
+#          If said issue appears, enable this line.
+#CFLAGS += -DNDEBUG
+
+# NOTE: The configuration for socket or non-socket  communication in TinyDTLS.
+CFLAGS += -DWITH_RIOT_GNRC
+
+# Change this to 0 show compiler invocation lines by default:
+QUIET ?= 1
+
+include $(RIOTBASE)/Makefile.include

examples/dtls-echo/README.md

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+# dtls_echo
+
+This example  shows you how to use TinyDTLS with the non-socket approach.
+
+This code  is based on  ../gnrc_networking and ../gnrc_tftp.
+Is a good idea to read their README.md's for any doubt of how making the
+testings.
+
+## SOCKET vs. Non-socket (GNRC)
+
+This example is configured to use the GNRC instead of  sockets (over GNRC).
+At the moment, the configuration must be done manually in the Makefile of
+this project.
+
+## Fast configuration (Between RIOT instances):
+
+Preparing the logical interfaces:
+
+    ./../../dist/tools/tapsetup/tapsetup --create 2
+
+For the server instance:
+
+    make all; PORT=tap1 make term
+    dtlss start
+    ifconfig
+
+Do not forget to copy the IPv6 addresses!
+
+For the client:
+
+    PORT=tap0 make term
+    dtlsc <IPv6's server address> "DATA TO DATA TO DATA!"
+
+# Testings
+## Boards
+
+Those boards that do not support  the `../gnrc_networking` example are included
+in the `BOARD_INSUFFICIENT_MEMORY`, plus the  board `cc2650stk`.
+
+There are certain boards that are having issues with `crypto.c` and
+`dtls_time.h` Which for now are in the the `BOARD_BLACKLIST`.
+
+The boards that requires `periph_conf.h` are not tested.
+
+Boards with problem type 1 (`crypto.c`):
+    z1
+    wsn430-v1_4
+    wsn430-v1_3b
+    waspmote-pro
+    msb-430h
+    msb-430
+    chronos
+    arduino-mega2560
+
+Boards with problem type 2 (`dtls_time.h`):
+    cc2538dk
+    msbiot
+    telosb
+
+Boards with problem type 3 (Redifinition):
+    saml21-xpro
+    samr21-xpro
+    arduino-uno
+    arduino-duemilanove
+
+NOTE: Those on type 1 can be benefit of the following PR:
+https://github.com/RIOT-OS/RIOT/issues/2360
+However, there are still issues to fix.
+
+NOTE: Those on type 2 can be fixed with the patch at
+https://github.com/RIOT-OS/RIOT/pull/5974
+
+## FIT-LAB
+
+The code has been tested in the FIT-LAB with M3 motes.
+However, erros can occurrs. Enabling the line `CFLAGS += -DNDEBUG` in
+the `Makefile` reduces the risk.