[posix-app] platform UDP (#3070)

This commit defines a set of platform APIs to integrate UDP layer of
OpenThread with that of the platform.

With this commit, services and applications developed upon OpenThread can
also be accessed through platform's own network interface, e.g. socket() on
POSIX.
diff --git a/.travis/before_install.sh b/.travis/before_install.sh
index 480a36e..82fb9ea 100755
--- a/.travis/before_install.sh
+++ b/.travis/before_install.sh
@@ -63,7 +63,29 @@
     }
 
     [ $BUILD_TARGET != posix-app-pty ] || {
-        sudo apt-get install socat expect || die
+        sudo apt-get install socat expect libdbus-1-dev autoconf-archive || die
+        JOBS=$(getconf _NPROCESSORS_ONLN)
+        (
+        WPANTUND_TMPDIR=/tmp/wpantund
+        git clone --depth 1 https://github.com/openthread/wpantund.git $WPANTUND_TMPDIR
+        cd $WPANTUND_TMPDIR
+        ./bootstrap.sh
+        ./configure --prefix= --exec-prefix=/usr --disable-ncp-dummy --enable-static-link-ncp-plugin=spinel
+        make -j $JOBS
+        sudo make install
+        ) || die
+        (
+        LIBCOAP_TMPDIR=/tmp/libcoap
+        mkdir $LIBCOAP_TMPDIR
+        cd $LIBCOAP_TMPDIR
+        wget https://github.com/obgm/libcoap/archive/bsd-licensed.tar.gz
+        tar xvf bsd-licensed.tar.gz
+        cd libcoap-bsd-licensed
+        ./autogen.sh
+        ./configure --prefix= --exec-prefix=/usr --with-boost=internal --disable-tests --disable-documentation
+        make -j $JOBS
+        sudo make install
+        ) || die
     }
 
     [ $BUILD_TARGET != scan-build ] || {
diff --git a/.travis/check-posix-app-pty b/.travis/check-posix-app-pty
new file mode 100755
index 0000000..38d0d5a
--- /dev/null
+++ b/.travis/check-posix-app-pty
@@ -0,0 +1,115 @@
+#!/bin/bash
+#
+#  Copyright (c) 2018, The OpenThread Authors.
+#  All rights reserved.
+#
+#  Redistribution and use in source and binary forms, with or without
+#  modification, are permitted provided that the following conditions are met:
+#  1. Redistributions of source code must retain the above copyright
+#     notice, this list of conditions and the following disclaimer.
+#  2. Redistributions in binary form must reproduce the above copyright
+#     notice, this list of conditions and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#  3. Neither the name of the copyright holder nor the
+#     names of its contributors may be used to endorse or promote products
+#     derived from this software without specific prior written permission.
+#
+#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+#  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+#  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+#  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+#  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+#  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+#  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+#  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+#  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+#  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+#  POSSIBILITY OF SUCH DAMAGE.
+#
+
+set -e
+set -x
+
+die() {
+	echo " *** ERROR: " $*
+	exit 1
+}
+
+at_exit() {
+    EXIT_CODE=$?
+    sudo killall wpantund || true
+    killall socat || true
+    exit $EXIT_CODE
+}
+
+build() {
+    ./bootstrap
+    COVERAGE=1 make -f examples/Makefile-posix
+    COVERAGE=1 make -f src/posix/Makefile-posix PLATFORM_UDP=1
+}
+
+check() {
+    trap at_exit INT TERM EXIT
+
+    SOCAT_OUTPUT=/tmp/ot-socat
+    socat -d -d pty,raw,b115200,echo=0 pty,raw,b115200,echo=0 > /dev/null 2> $SOCAT_OUTPUT &
+    while true; do
+        if test $(head -n2 $SOCAT_OUTPUT | wc -l) = 2; then
+            RADIO_PTY=$(head -n1 $SOCAT_OUTPUT | grep -o '/dev/.\+')
+            CORE_PTY=$(head -n2 $SOCAT_OUTPUT | tail -n1 | grep -o '/dev/.\+')
+            break
+        fi
+        echo 'Waiting for socat ready...'
+        sleep 1
+    done
+    echo 'RADIO_PTY' $DEVICE_PTY
+    echo 'CORE_PTY' $CORE_PTY
+
+    RADIO_NCP_PATH="$(pwd)/$(ls output/*linux*/bin/ot-ncp-radio)"
+    $RADIO_NCP_PATH 1 > $RADIO_PTY < $RADIO_PTY &
+    OT_NCP_PATH="$(pwd)/$(ls output/posix/*linux*/bin/ot-ncp)"
+    PLATFORM_NETIF=wpan0 sudo -E wpantund -I wpan0 -o Thread:Config:FilterRLOCAddresses 0 -s "system:${OT_NCP_PATH} ${CORE_PTY}" &
+
+    while true; do
+        sleep 5
+        if sudo wpanctl status; then
+            break
+        else
+            echo 'Still waiting for wpantund'
+        fi
+    done
+
+    sudo wpanctl leave || true
+    sudo wpanctl form -c 18 OpenThreadTest
+
+    mleid=$(sudo wpanctl status | grep MeshLocalAddress | cut -d'"' -f4)
+    echo "ML-EID is: ${mleid}"
+
+    netstat -an | grep -q 61631 || die 'TMF port is not available!'
+    xaddress=$(sudo wpanctl get 'NCP:ExtendedAddress' | cut -d= -f2 | tr -d ' []')
+    echo "Extended address is: ${xaddress}"
+
+    # Retrievie extended address through network diagnostic get
+    coap_response=$(echo -n '120100' | xxd -r -p | coap-client -m POST coap://[${mleid}]:61631/d/dg -f- | xxd -p -u | grep 0008)
+    echo "CoAP response is: ${coap_response}"
+
+    # Verify CoAP response contains the extended address
+    [[ "${coap_response}" = *${xaddress}* ]] || die 'failed to get extended address'
+
+    # Leave so that code coverage will be flushed
+    sudo wpanctl leave || true
+}
+
+main() {
+    case $1 in
+        check)
+            check
+            ;;
+        *)
+            build
+            check
+            ;;
+    esac
+}
+
+main "$@"
diff --git a/.travis/script.sh b/.travis/script.sh
index 743cfc0..67d6a28 100755
--- a/.travis/script.sh
+++ b/.travis/script.sh
@@ -490,49 +490,7 @@
 }
 
 [ $BUILD_TARGET != posix-app-pty ] || {
-    ./bootstrap
-    COVERAGE=1 make -f examples/Makefile-posix
-    COVERAGE=1 make -f src/posix/Makefile-posix
-
-    SOCAT_OUTPUT=/tmp/ot-socat
-    socat -d -d pty,raw,echo=0 pty,raw,echo=0 > /dev/null 2> $SOCAT_OUTPUT &
-    while true; do
-        if test $(head -n2 $SOCAT_OUTPUT | wc -l) = 2; then
-            RADIO_PTY=$(head -n1 $SOCAT_OUTPUT | grep -o '/dev/.\+')
-            CORE_PTY=$(head -n2 $SOCAT_OUTPUT | tail -n1 | grep -o '/dev/.\+')
-            break
-        fi
-        echo 'Waiting for socat ready...'
-        sleep 1
-    done
-    echo 'RADIO_PTY' $DEVICE_PTY
-    echo 'CORE_PTY' $CORE_PTY
-
-    RADIO_NCP_PATH="$(pwd)/$(ls output/*linux*/bin/ot-ncp-radio)"
-    $RADIO_NCP_PATH 1 > $RADIO_PTY < $RADIO_PTY &
-    OT_CLI_PATH="$(pwd)/$(ls output/posix/*linux*/bin/ot-cli)"
-
-    expect <<EOF || die
-spawn $OT_CLI_PATH $CORE_PTY
-set timeout 2
-send "panid 0xface\r\n"
-expect "Done"
-send "ifconfig up\r\n"
-expect "Done"
-send "thread start\r\n"
-expect "Done"
-sleep 5
-send "state\r\n"
-expect {
-    "leader" {
-        send "exit\r\n"
-        expect eof
-    }
-    timeout abort
-}
-send_user "Success"
-EOF
-    killall socat
+    .travis/check-posix-app-pty || die
 }
 
 [ $BUILD_TARGET != posix-mtd ] || {
diff --git a/configure.ac b/configure.ac
index 3c679bb..aaee8a0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -796,6 +796,35 @@
 AC_DEFINE_UNQUOTED([OPENTHREAD_ENABLE_APPLICATION_COAP_SECURE],[${OPENTHREAD_ENABLE_APPLICATION_COAP_SECURE}],[Define to 1 if you want to enable CoAP Secure to an application.])
 
 #
+# Platform UDP
+#
+
+AC_ARG_ENABLE(platform_udp,
+    [AS_HELP_STRING([--enable-platform-udp],[Enable platform UDP support @<:@default=no@:>@.])],
+    [
+        case "${enableval}" in
+        no|yes)
+            enable_platform_udp=${enableval}
+            ;;
+        *)
+            AC_MSG_ERROR([Invalid value ${enable_platform_udp} for --enable-platform-udp])
+            ;;
+        esac
+    ],
+    [enable_platform_udp=no])
+
+if test "$enable_platform_udp" = "yes"; then
+    OPENTHREAD_ENABLE_PLATFORM_UDP=1
+else
+    OPENTHREAD_ENABLE_PLATFORM_UDP=0
+fi
+
+AC_MSG_RESULT(${enable_platform_udp})
+AC_SUBST(OPENTHREAD_ENABLE_PLATFORM_UDP)
+AM_CONDITIONAL([OPENTHREAD_ENABLE_PLATFORM_UDP], [test "${enable_platform_udp}" = "yes"])
+AC_DEFINE_UNQUOTED([OPENTHREAD_ENABLE_PLATFORM_UDP], [${OPENTHREAD_ENABLE_PLATFORM_UDP}], [Define to 1 to enable platform UDP.])
+
+#
 # Thread Commissioner
 #
 
diff --git a/include/openthread/platform/Makefile.am b/include/openthread/platform/Makefile.am
index 179ad3b..e0cc783 100644
--- a/include/openthread/platform/Makefile.am
+++ b/include/openthread/platform/Makefile.am
@@ -40,6 +40,7 @@
     random.h                              \
     time.h                                \
     uart.h                                \
+    udp.h                                 \
     spi-slave.h                           \
     settings.h                            \
     messagepool.h                         \
diff --git a/include/openthread/platform/udp.h b/include/openthread/platform/udp.h
new file mode 100644
index 0000000..e8d0e7a
--- /dev/null
+++ b/include/openthread/platform/udp.h
@@ -0,0 +1,103 @@
+/*
+ *  Copyright (c) 2018, The OpenThread Authors.
+ *  All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions are met:
+ *  1. Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *  3. Neither the name of the copyright holder nor the
+ *     names of its contributors may be used to endorse or promote products
+ *     derived from this software without specific prior written permission.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *  POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * @file
+ * @brief
+ *   This file includes the abstraction for the platform UDP service.
+ */
+
+#ifndef OPENTHREAD_PLATFORM_UDP_H_
+#define OPENTHREAD_PLATFORM_UDP_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * This function initializes the UDP socket by platform.
+ *
+ * @param[in]   aUdpSocket  A pointer to the UDP socket.
+ *
+ * @retval  OT_ERROR_NONE   Successfully initialized UDP socket by platform.
+ * @retval  OT_ERROR_FAILED Failed to initialize UDP Socket.
+ *
+ */
+otError otPlatUdpSocket(otUdpSocket *aUdpSocket);
+
+/**
+ * This function closes the UDP socket by platform.
+ *
+ * @param[in]   aUdpSocket  A pointer to the UDP socket.
+ *
+ * @retval  OT_ERROR_NONE   Successfully closed UDP socket by platform.
+ * @retval  OT_ERROR_FAILED Failed to close UDP Socket.
+ *
+ */
+otError otPlatUdpClose(otUdpSocket *aUdpSocket);
+
+/**
+ * This function binds the UDP socket by platform.
+ *
+ * @param[in]   aUdpSocket  A pointer to the UDP socket.
+ *
+ * @retval  OT_ERROR_NONE   Successfully binded UDP socket by platform.
+ * @retval  OT_ERROR_FAILED Failed to bind UDP socket.
+ *
+ */
+otError otPlatUdpBind(otUdpSocket *aUdpSocket);
+
+/**
+ * This function connects UDP socket by platform.
+ *
+ * @param[in]   aUdpSocket  A pointer to the UDP socket.
+ *
+ * @retval  OT_ERROR_NONE   Successfully connected by platform.
+ * @retval  OT_ERROR_FAILED Failed to connect UDP socket.
+ *
+ */
+otError otPlatUdpConnect(otUdpSocket *aUdpSocket);
+
+/**
+ * This function sends UDP payload by platform.
+ *
+ * @param[in]   aUdpSocket      A pointer to the UDP socket.
+ * @param[in]   aMessage        A pointer to the message to send.
+ * @param[in]   aMessageInfo    A pointer to the message info associated with @p aMessage.
+ *
+ * @retval  OT_ERROR_NONE   Successfully sent by platform, and @p aMessage is freed.
+ * @retval  OT_ERROR_FAILED Failed to binded UDP socket.
+ *
+ */
+otError otPlatUdpSend(otUdpSocket *aUdpSocket, otMessage *aMessage, const otMessageInfo *aMessageInfo);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif // OPENTHREAD_PLATFORM_UDP_H_
diff --git a/include/openthread/udp.h b/include/openthread/udp.h
index 3c42384..ae336dd 100644
--- a/include/openthread/udp.h
+++ b/include/openthread/udp.h
@@ -89,6 +89,7 @@
     otSockAddr          mPeerName; ///< The peer IPv6 socket address.
     otUdpReceive        mHandler;  ///< A function pointer to the application callback.
     void *              mContext;  ///< A pointer to application-specific context.
+    void *              mHandle;   ///< A handle to platform's UDP
     struct otUdpSocket *mNext;     ///< A pointer to the next UDP socket (internal use only).
 } otUdpSocket;
 
@@ -254,6 +255,16 @@
                        uint16_t            aSockPort);
 
 /**
+ * This function gets the existing UDP Sockets.
+ *
+ * @param[in]  aInstance            A pointer to an OpenThread instance.
+ *
+ * @returns A pointer to the first UDP Socket.
+ *
+ */
+otUdpSocket *otUdpGetSockets(otInstance *aInstance);
+
+/**
  * @}
  *
  */
diff --git a/src/core/api/udp_api.cpp b/src/core/api/udp_api.cpp
index 672c980..710ba0b 100644
--- a/src/core/api/udp_api.cpp
+++ b/src/core/api/udp_api.cpp
@@ -124,3 +124,12 @@
     static_cast<ot::Message *>(aMessage)->Free();
 }
 #endif // OPENTHREAD_ENABLE_UDP_PROXY
+
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+otUdpSocket *otUdpGetSockets(otInstance *aInstance)
+{
+    Instance &instance = *static_cast<Instance *>(aInstance);
+
+    return instance.Get<Ip6::Ip6>().GetUdp().GetUdpSockets();
+}
+#endif
diff --git a/src/core/net/ip6.cpp b/src/core/net/ip6.cpp
index 55b663d..ee465e4 100644
--- a/src/core/net/ip6.cpp
+++ b/src/core/net/ip6.cpp
@@ -644,6 +644,7 @@
 
                 break;
 
+#if OPENTHREAD_ENABLE_PLATFORM_UDP == 0
             case kCoapUdpPort:
 
                 // do not pass TMF messages
@@ -653,8 +654,15 @@
                 }
 
                 break;
+#endif // OPENTHREAD_ENABLE_PLATFORM_UDP
 
             default:
+#if OPENTHREAD_FTD
+                if (udp.GetDestinationPort() == GetInstance().Get<MeshCoP::JoinerRouter>().GetJoinerUdpPort())
+                {
+                    ExitNow(error = OT_ERROR_NO_ROUTE);
+                }
+#endif
                 break;
             }
 
diff --git a/src/core/net/udp6.cpp b/src/core/net/udp6.cpp
index c6aec4a..5bc8757 100644
--- a/src/core/net/udp6.cpp
+++ b/src/core/net/udp6.cpp
@@ -35,6 +35,8 @@
 
 #include <stdio.h>
 
+#include <openthread/platform/udp.h>
+
 #include "common/code_utils.hpp"
 #include "common/encoding.hpp"
 #include "common/instance.hpp"
@@ -45,9 +47,21 @@
 namespace ot {
 namespace Ip6 {
 
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+static bool IsMle(Instance &aInstance, uint16_t aPort)
+{
+#if OPENTHREAD_FTD
+    return aPort == ot::Mle::kUdpPort || aPort == aInstance.Get<MeshCoP::JoinerRouter>().GetJoinerUdpPort();
+#else
+    return aPort == ot::Mle::kUdpPort;
+#endif
+}
+#endif
+
 UdpSocket::UdpSocket(Udp &aUdp)
     : InstanceLocator(aUdp.GetInstance())
 {
+    mHandle = NULL;
 }
 
 Udp &UdpSocket::GetUdp(void)
@@ -62,36 +76,70 @@
 
 otError UdpSocket::Open(otUdpReceive aHandler, void *aContext)
 {
+    otError error;
+
     memset(&mSockName, 0, sizeof(mSockName));
     memset(&mPeerName, 0, sizeof(mPeerName));
     mHandler = aHandler;
     mContext = aContext;
 
-    return GetUdp().AddSocket(*this);
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+    SuccessOrExit(error = otPlatUdpSocket(this));
+#endif
+    SuccessOrExit(error = GetUdp().AddSocket(*this));
+
+exit:
+    return error;
 }
 
 otError UdpSocket::Bind(const SockAddr &aSockAddr)
 {
+    otError error = OT_ERROR_NONE;
+
     mSockName = aSockAddr;
 
-    if (GetSockName().mPort == 0)
+    if (mSockName.mPort == 0)
     {
-        mSockName.mPort = GetUdp().GetEphemeralPort();
+        do
+        {
+            mSockName.mPort = GetUdp().GetEphemeralPort();
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+            error = otPlatUdpBind(this);
+#endif
+        } while (error != OT_ERROR_NONE);
     }
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+    else if (!IsMle(GetInstance(), mSockName.mPort))
+    {
+        error = otPlatUdpBind(this);
+    }
+#endif
 
-    return OT_ERROR_NONE;
+    return error;
 }
 
 otError UdpSocket::Connect(const SockAddr &aSockAddr)
 {
+    otError error = OT_ERROR_NONE;
+
     mPeerName = aSockAddr;
-    return OT_ERROR_NONE;
+
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+    if (!IsMle(GetInstance(), mSockName.mPort))
+    {
+        error = otPlatUdpConnect(this);
+    }
+#endif
+    return error;
 }
 
 otError UdpSocket::Close(void)
 {
     otError error = OT_ERROR_NONE;
 
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+    SuccessOrExit(error = otPlatUdpClose(this));
+#endif
     SuccessOrExit(error = GetUdp().RemoveSocket(*this));
     memset(&mSockName, 0, sizeof(mSockName));
     memset(&mPeerName, 0, sizeof(mPeerName));
@@ -127,11 +175,21 @@
 
     if (GetSockName().mPort == 0)
     {
-        GetSockName().mPort = GetUdp().GetEphemeralPort();
+        SuccessOrExit(error = Bind(GetSockName()));
     }
     messageInfoLocal.SetSockPort(GetSockName().mPort);
 
-    SuccessOrExit(error = GetUdp().SendDatagram(aMessage, messageInfoLocal, kProtoUdp));
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+    if (!IsMle(GetInstance(), mSockName.mPort) &&
+        !(mSockName.mPort == ot::kCoapUdpPort && aMessage.GetSubType() == Message::kSubTypeJoinerEntrust))
+    {
+        SuccessOrExit(error = otPlatUdpSend(this, &aMessage, &messageInfoLocal));
+    }
+    else
+#endif
+    {
+        SuccessOrExit(error = GetUdp().SendDatagram(aMessage, messageInfoLocal, kProtoUdp));
+    }
 
 exit:
     return error;
@@ -305,6 +363,10 @@
     aMessageInfo.mPeerPort = udpHeader.GetSourcePort();
     aMessageInfo.mSockPort = udpHeader.GetDestinationPort();
 
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+    VerifyOrExit(IsMle(GetInstance(), aMessageInfo.mSockPort));
+#endif
+
     for (UdpReceiver *receiver = mReceivers; receiver; receiver = receiver->GetNext())
     {
         VerifyOrExit(!receiver->HandleMessage(aMessage, aMessageInfo));
diff --git a/src/core/net/udp6.hpp b/src/core/net/udp6.hpp
index 2539d8b..33487f3 100644
--- a/src/core/net/udp6.hpp
+++ b/src/core/net/udp6.hpp
@@ -324,6 +324,10 @@
      */
     otError UpdateChecksum(Message &aMessage, uint16_t aPseudoHeaderChecksum);
 
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+    otUdpSocket *GetUdpSockets(void) { return mSockets; }
+#endif
+
 #if OPENTHREAD_ENABLE_UDP_PROXY
     /**
      * This method sets the proxy sender.
diff --git a/src/posix/Makefile-posix b/src/posix/Makefile-posix
index 113b0a2..241995b 100644
--- a/src/posix/Makefile-posix
+++ b/src/posix/Makefile-posix
@@ -90,6 +90,12 @@
 COMMONCFLAGS                   += -DOPENTHREAD_POSIX_VIRTUAL_TIME=1
 endif
 
+ifeq ($(PLATFORM_UDP),1)
+configure_OPTIONS              += \
+    --enable-platform-udp         \
+    $(NULL)
+endif
+
 CPPFLAGS                       += \
     $(COMMONCFLAGS)               \
     $(NULL)
diff --git a/src/posix/platform/Makefile.am b/src/posix/platform/Makefile.am
index 5f0c4b9..c57314f 100644
--- a/src/posix/platform/Makefile.am
+++ b/src/posix/platform/Makefile.am
@@ -65,6 +65,12 @@
 inc_%: ../../ncp/%
 	echo '#include "$<"' > $@
 
+if OPENTHREAD_ENABLE_PLATFORM_UDP
+libopenthread_posix_a_SOURCES            += \
+    udp.cpp                                 \
+    $(NULL)
+endif
+
 noinst_HEADERS                            = \
     frame_queue.hpp                         \
     openthread-system.h                     \
diff --git a/src/posix/platform/platform-posix.h b/src/posix/platform/platform-posix.h
index 35e312e..23f2438 100644
--- a/src/posix/platform/platform-posix.h
+++ b/src/posix/platform/platform-posix.h
@@ -315,6 +315,30 @@
 #define otSysGetTime(aTime) gettimeofday(aTime, NULL)
 #endif
 
+/**
+ * This function initializes platform UDP driver.
+ *
+ */
+void platformUdpInit(void);
+
+/**
+ * This function performs platform UDP driver processing.
+ *
+ * @param[in]   aInstance   The OpenThread instance structure.
+ * @param[in]   aReadFdSet  A pointer to the read file descriptors.
+ *
+ */
+void platformUdpProcess(otInstance *aInstance, const fd_set *aReadSet);
+
+/**
+ * This function updates the file descriptor sets with file descriptors used by the platform UDP driver.
+ *
+ * @param[in]     aInstance    The OpenThread instance structure.
+ * @param[inout]  aReadFdSet   A pointer to the read file descriptors.
+ * @param[inout]  aMaxFd       A pointer to the max file descriptor.
+ */
+void platformUdpUpdateFdSet(otInstance *aInstance, fd_set *aReadFdSet, int *aMaxFd);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/posix/platform/system.c b/src/posix/platform/system.c
index b37a983..7af1e32 100644
--- a/src/posix/platform/system.c
+++ b/src/posix/platform/system.c
@@ -107,6 +107,9 @@
     platformAlarmInit(speedUpFactor);
     platformRadioInit(radioFile, radioConfig);
     platformRandomInit();
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+    platformUdpInit();
+#endif
 }
 
 bool otSysPseudoResetWasRequested(void)
@@ -170,6 +173,9 @@
 
     platformAlarmUpdateTimeout(&timeout);
     platformUartUpdateFdSet(&readFdSet, &writeFdSet, &errorFdSet, &maxFd);
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+    platformUdpUpdateFdSet(aInstance, &readFdSet, &maxFd);
+#endif
 #if OPENTHREAD_POSIX_VIRTUAL_TIME
     otSimUpdateFdSet(&readFdSet, &writeFdSet, &errorFdSet, &maxFd, &timeout);
 #else
@@ -230,4 +236,7 @@
 #endif
     platformUartProcess(&readFdSet, &writeFdSet, &errorFdSet);
     platformAlarmProcess(aInstance);
+#if OPENTHREAD_ENABLE_PLATFORM_UDP
+    platformUdpProcess(aInstance, &readFdSet);
+#endif
 }
diff --git a/src/posix/platform/udp.cpp b/src/posix/platform/udp.cpp
new file mode 100644
index 0000000..701fddb
--- /dev/null
+++ b/src/posix/platform/udp.cpp
@@ -0,0 +1,399 @@
+/*
+ *  Copyright (c) 2018, The OpenThread Authors.
+ *  All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions are met:
+ *  1. Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *  3. Neither the name of the copyright holder nor the
+ *     names of its contributors may be used to endorse or promote products
+ *     derived from this software without specific prior written permission.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *  POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * @file
+ * @brief
+ *   This file includes the platform UDP driver.
+ */
+
+#include "platform-posix.h"
+
+#include <arpa/inet.h>
+#include <net/if.h>
+#include <stdlib.h>
+#include <sys/select.h>
+
+#include <openthread/udp.h>
+#include <openthread/platform/udp.h>
+
+#include "common/code_utils.hpp"
+
+static int sPlatNetifIndex = 0;
+
+static const size_t kMaxUdpSize = 1280;
+
+static void *FdToHandle(int aFd)
+{
+    return reinterpret_cast<void *>(aFd);
+}
+
+static int FdFromHandle(void *aHandle)
+{
+    return reinterpret_cast<long>(aHandle);
+}
+
+static bool IsLinkLocal(const struct in6_addr &aAddress)
+{
+    return aAddress.s6_addr[0] == 0xfe && aAddress.s6_addr[1] == 0x80;
+}
+
+static bool IsMulticast(const struct in6_addr &aAddress)
+{
+    return aAddress.s6_addr[0] == 0xff;
+}
+
+static otError transmitPacket(int aFd, uint8_t *aPayload, uint16_t aLength, const otMessageInfo &aMessageInfo)
+{
+    struct sockaddr_in6 peerAddr;
+    uint8_t             control[CMSG_SPACE(sizeof(struct in6_pktinfo)) + CMSG_SPACE(sizeof(int))];
+    ssize_t             controlLength = 0;
+    struct iovec        iov;
+    struct msghdr       msg;
+    struct cmsghdr *    cmsg;
+    ssize_t             rval;
+
+    memset(&peerAddr, 0, sizeof(peerAddr));
+    peerAddr.sin6_port   = htons(aMessageInfo.mPeerPort);
+    peerAddr.sin6_family = AF_INET6;
+    memcpy(&peerAddr.sin6_addr, &aMessageInfo.mPeerAddr, sizeof(peerAddr.sin6_addr));
+
+    if (IsLinkLocal(peerAddr.sin6_addr) && aMessageInfo.mInterfaceId == OT_NETIF_INTERFACE_ID_THREAD)
+    {
+        // sin6_scope_id only works for link local destinations
+        peerAddr.sin6_scope_id = sPlatNetifIndex;
+    }
+
+    memset(control, 0, sizeof(control));
+
+    iov.iov_base = aPayload;
+    iov.iov_len  = aLength;
+
+    msg.msg_name       = &peerAddr;
+    msg.msg_namelen    = sizeof(peerAddr);
+    msg.msg_control    = control;
+    msg.msg_controllen = sizeof(control);
+    msg.msg_iov        = &iov;
+    msg.msg_iovlen     = 1;
+    msg.msg_flags      = 0;
+
+    cmsg = CMSG_FIRSTHDR(&msg);
+
+    {
+        cmsg->cmsg_level = IPPROTO_IPV6;
+        cmsg->cmsg_type  = IPV6_HOPLIMIT;
+        cmsg->cmsg_len   = CMSG_LEN(sizeof(int));
+
+        *reinterpret_cast<int *>(CMSG_DATA(cmsg)) = (aMessageInfo.mHopLimit ? aMessageInfo.mHopLimit : -1);
+
+        cmsg = CMSG_NXTHDR(&msg, cmsg);
+        controlLength += CMSG_SPACE(sizeof(int));
+    }
+
+    {
+        struct in6_pktinfo *pktinfo = NULL;
+
+        cmsg->cmsg_level = IPPROTO_IPV6;
+        cmsg->cmsg_type  = IPV6_PKTINFO;
+        cmsg->cmsg_len   = CMSG_LEN(sizeof(*pktinfo));
+
+        pktinfo               = reinterpret_cast<struct in6_pktinfo *>(CMSG_DATA(cmsg));
+        pktinfo->ipi6_ifindex = (aMessageInfo.mInterfaceId == OT_NETIF_INTERFACE_ID_THREAD ? sPlatNetifIndex : 0);
+
+        if (!IsMulticast(reinterpret_cast<const struct in6_addr &>(aMessageInfo.mSockAddr)) &&
+            memcmp(&aMessageInfo.mSockAddr, &in6addr_any, sizeof(aMessageInfo.mSockAddr)))
+        {
+            memcpy(&pktinfo->ipi6_addr, &aMessageInfo.mSockAddr, sizeof(pktinfo->ipi6_addr));
+        }
+
+        if (pktinfo->ipi6_ifindex || memcmp(&pktinfo->ipi6_addr, &in6addr_any, sizeof(pktinfo->ipi6_addr)))
+        {
+            controlLength += CMSG_SPACE(sizeof(*pktinfo));
+            cmsg = CMSG_NXTHDR(&msg, cmsg);
+        }
+    }
+
+    msg.msg_controllen = controlLength;
+
+    rval = sendmsg(aFd, &msg, 0);
+    VerifyOrExit(rval > 0, perror("sendmsg"));
+
+exit:
+    return rval > 0 ? OT_ERROR_NONE : OT_ERROR_FAILED;
+}
+
+static otError receivePacket(int aFd, uint8_t *aPayload, uint16_t &aLength, otMessageInfo &aMessageInfo)
+{
+    struct sockaddr_in6 peerAddr;
+    uint8_t             control[kMaxUdpSize];
+    struct iovec        iov;
+    struct msghdr       msg;
+    ssize_t             rval;
+
+    iov.iov_base = aPayload;
+    iov.iov_len  = aLength;
+
+    msg.msg_name       = &peerAddr;
+    msg.msg_namelen    = sizeof(peerAddr);
+    msg.msg_control    = control;
+    msg.msg_controllen = sizeof(control);
+    msg.msg_iov        = &iov;
+    msg.msg_iovlen     = 1;
+    msg.msg_flags      = 0;
+
+    rval = recvmsg(aFd, &msg, 0);
+    VerifyOrExit(rval > 0, perror("recvmsg"));
+    aLength = static_cast<uint16_t>(rval);
+
+    for (struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL; cmsg = CMSG_NXTHDR(&msg, cmsg))
+    {
+        if (cmsg->cmsg_level == IPPROTO_IPV6)
+        {
+            if (cmsg->cmsg_type == IPV6_HOPLIMIT)
+            {
+                int hoplimit           = *reinterpret_cast<int *>(CMSG_DATA(cmsg));
+                aMessageInfo.mHopLimit = hoplimit;
+            }
+            else if (cmsg->cmsg_type == IPV6_PKTINFO)
+            {
+                struct in6_pktinfo *pktinfo;
+
+                pktinfo = reinterpret_cast<in6_pktinfo *>(CMSG_DATA(cmsg));
+                memcpy(&aMessageInfo.mSockAddr, &pktinfo->ipi6_addr, sizeof(aMessageInfo.mSockAddr));
+            }
+        }
+    }
+
+    aMessageInfo.mPeerPort = ntohs(peerAddr.sin6_port);
+    memcpy(&aMessageInfo.mPeerAddr, &peerAddr.sin6_addr, sizeof(aMessageInfo.mPeerAddr));
+
+exit:
+    return rval > 0 ? OT_ERROR_NONE : OT_ERROR_FAILED;
+}
+
+otError otPlatUdpSocket(otUdpSocket *aUdpSocket)
+{
+    otError error = OT_ERROR_NONE;
+    int     fd;
+
+    assert(aUdpSocket->mHandle == NULL);
+
+    fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+    VerifyOrExit(fd > 0, error = OT_ERROR_FAILED);
+
+    aUdpSocket->mHandle = FdToHandle(fd);
+
+exit:
+    return error;
+}
+
+otError otPlatUdpClose(otUdpSocket *aUdpSocket)
+{
+    otError error = OT_ERROR_NONE;
+    int     fd;
+
+    VerifyOrExit(aUdpSocket->mHandle != NULL, error = OT_ERROR_INVALID_ARGS);
+    fd = FdFromHandle(aUdpSocket->mHandle);
+    VerifyOrExit(0 == close(fd), error = OT_ERROR_FAILED);
+
+    aUdpSocket->mHandle = NULL;
+
+exit:
+    return error;
+}
+
+otError otPlatUdpBind(otUdpSocket *aUdpSocket)
+{
+    otError error = OT_ERROR_NONE;
+    int     fd;
+
+    assert(sPlatNetifIndex != 0);
+    assert(aUdpSocket->mHandle != NULL);
+    VerifyOrExit(sPlatNetifIndex != 0, error = OT_ERROR_INVALID_STATE);
+    VerifyOrExit(aUdpSocket->mHandle != NULL, error = OT_ERROR_INVALID_ARGS);
+    VerifyOrExit(aUdpSocket->mSockName.mPort != 0, error = OT_ERROR_INVALID_ARGS);
+    fd = FdFromHandle(aUdpSocket->mHandle);
+
+    {
+        struct sockaddr_in6 sin6;
+
+        memset(&sin6, 0, sizeof(struct sockaddr_in6));
+        sin6.sin6_port   = htons(aUdpSocket->mSockName.mPort);
+        sin6.sin6_family = AF_INET6;
+        memcpy(&sin6.sin6_addr, &aUdpSocket->mSockName.mAddress, sizeof(sin6.sin6_addr));
+        VerifyOrExit(0 == bind(fd, reinterpret_cast<struct sockaddr *>(&sin6), sizeof(sin6)), error = OT_ERROR_FAILED);
+    }
+
+    {
+        int on = 1;
+        VerifyOrExit(0 == setsockopt(fd, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &on, sizeof(on)), error = OT_ERROR_FAILED);
+        VerifyOrExit(0 == setsockopt(fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &on, sizeof(on)), error = OT_ERROR_FAILED);
+    }
+
+    VerifyOrExit(0 == setsockopt(fd, IPPROTO_IPV6, IPV6_MULTICAST_IF, &sPlatNetifIndex, sizeof(sPlatNetifIndex)),
+                 error = OT_ERROR_FAILED);
+
+exit:
+    if (error == OT_ERROR_FAILED)
+    {
+        perror("otPlatUdpBind");
+    }
+
+    return error;
+}
+
+otError otPlatUdpConnect(otUdpSocket *aUdpSocket)
+{
+    otError             error = OT_ERROR_NONE;
+    struct sockaddr_in6 sin6;
+    int                 fd;
+
+    VerifyOrExit(aUdpSocket->mHandle != NULL, error = OT_ERROR_INVALID_ARGS);
+
+    fd = FdFromHandle(aUdpSocket->mHandle);
+
+    memset(&sin6, 0, sizeof(struct sockaddr_in6));
+    sin6.sin6_port   = htons(aUdpSocket->mPeerName.mPort);
+    sin6.sin6_family = AF_INET6;
+    memcpy(&sin6.sin6_addr, &aUdpSocket->mPeerName.mAddress, sizeof(sin6.sin6_addr));
+
+    VerifyOrExit(0 == connect(fd, reinterpret_cast<struct sockaddr *>(&sin6), sizeof(sin6)), error = OT_ERROR_FAILED);
+
+exit:
+    return error;
+}
+
+otError otPlatUdpSend(otUdpSocket *aUdpSocket, otMessage *aMessage, const otMessageInfo *aMessageInfo)
+{
+    otError error = OT_ERROR_NONE;
+    int     fd;
+
+    VerifyOrExit(aUdpSocket->mHandle != NULL, error = OT_ERROR_INVALID_ARGS);
+    fd = FdFromHandle(aUdpSocket->mHandle);
+
+    {
+        uint8_t  payload[kMaxUdpSize];
+        uint16_t len = otMessageGetLength(aMessage);
+
+        VerifyOrExit(len == otMessageRead(aMessage, 0, payload, len), error = OT_ERROR_INVALID_ARGS);
+        SuccessOrExit(error = transmitPacket(fd, payload, len, *aMessageInfo));
+    }
+
+exit:
+    if (error == OT_ERROR_NONE)
+    {
+        otMessageFree(aMessage);
+    }
+
+    return error;
+}
+
+void platformUdpUpdateFdSet(otInstance *aInstance, fd_set *aReadFdSet, int *aMaxFd)
+{
+    VerifyOrExit(sPlatNetifIndex != 0);
+
+    for (otUdpSocket *socket = otUdpGetSockets(aInstance); socket != NULL; socket = socket->mNext)
+    {
+        int fd;
+
+        if (socket->mHandle == NULL)
+        {
+            continue;
+        }
+
+        fd = FdFromHandle(socket->mHandle);
+        FD_SET(fd, aReadFdSet);
+
+        if (aMaxFd != NULL && *aMaxFd < fd)
+        {
+            *aMaxFd = fd;
+        }
+    }
+
+exit:
+    return;
+}
+
+void platformUdpInit(void)
+{
+    const char *platformNetif = getenv("PLATFORM_NETIF");
+    sPlatNetifIndex           = if_nametoindex(platformNetif);
+
+    if (sPlatNetifIndex == 0)
+    {
+        perror("if_nametoindex");
+    }
+}
+
+void platformUdpProcess(otInstance *aInstance, const fd_set *aReadFdSet)
+{
+    VerifyOrExit(sPlatNetifIndex != 0);
+
+    for (otUdpSocket *socket = otUdpGetSockets(aInstance); socket != NULL; socket = socket->mNext)
+    {
+        int fd = FdFromHandle(socket->mHandle);
+
+        if (fd > 0 && FD_ISSET(fd, aReadFdSet))
+        {
+            otMessageInfo messageInfo;
+            otMessage *   message = NULL;
+            uint8_t       payload[kMaxUdpSize];
+            uint16_t      length = sizeof(payload);
+
+            memset(&messageInfo, 0, sizeof(messageInfo));
+            messageInfo.mSockPort    = socket->mSockName.mPort;
+            messageInfo.mInterfaceId = OT_NETIF_INTERFACE_ID_THREAD;
+
+            if (OT_ERROR_NONE != receivePacket(fd, payload, length, messageInfo))
+            {
+                continue;
+            }
+
+            message = otUdpNewMessage(aInstance, false);
+
+            if (message == NULL)
+            {
+                continue;
+            }
+
+            if (otMessageAppend(message, payload, length) != OT_ERROR_NONE)
+            {
+                otMessageFree(message);
+                continue;
+            }
+
+            socket->mHandler(socket->mContext, message, &messageInfo);
+            otMessageFree(message);
+            // only process one socket a time
+            break;
+        }
+    }
+
+exit:
+    return;
+}