udp example:Optimization udp example with recv_msg

examples/protocols/sockets/udp_server/README.md

@@ -12,6 +12,7 @@ In order to create UDP client that communicates with UDP server example, choose
 There are many host-side tools which can be used to interact with the UDP/TCP server/client. 
 One command line tool is [netcat](http://netcat.sourceforge.net) which can send and receive many kinds of packets. 
 Note: please replace `192.168.0.167 3333` with desired IPV4/IPV6 address (displayed in monitor console) and port number in the following commands.
+If want to use this RECVINFO function, please enable LWIP_NETBUF_RECVINFO in menuconfig,this function can only resolve the destination address of IPV4.
 
 In addition to those tools, simple Python scripts can be found under sockets/scripts directory. Every script is designed to interact with one of the examples.
 

examples/protocols/sockets/udp_server/main/udp_server.c

@@ -57,6 +57,11 @@ static void udp_server_task(void *pvParameters)
         }
         ESP_LOGI(TAG, "Socket created");
 
+#if defined(CONFIG_LWIP_NETBUF_RECVINFO) && !defined(CONFIG_EXAMPLE_IPV6)
+        int enable = 1;
+        lwip_setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &enable, sizeof(enable));
+#endif
+
 #if defined(CONFIG_EXAMPLE_IPV4) && defined(CONFIG_EXAMPLE_IPV6)
         if (addr_family == AF_INET6) {
             // Note that by default IPV6 binds to both protocols, it is must be disabled
@@ -73,13 +78,33 @@ static void udp_server_task(void *pvParameters)
         }
         ESP_LOGI(TAG, "Socket bound, port %d", PORT);
 
-        while (1) {
+        struct sockaddr_storage source_addr; // Large enough for both IPv4 or IPv6
+        socklen_t socklen = sizeof(source_addr);
+
+#if defined(CONFIG_LWIP_NETBUF_RECVINFO) && !defined(CONFIG_EXAMPLE_IPV6)
+        struct iovec iov;
+        struct msghdr msg;
+        struct cmsghdr *cmsgtmp;
+        u8_t cmsg_buf[CMSG_SPACE(sizeof(struct in_pktinfo))];
+
+        iov.iov_base = rx_buffer;
+        iov.iov_len = sizeof(rx_buffer);
+        msg.msg_control = cmsg_buf;
+        msg.msg_controllen = sizeof(cmsg_buf);
+        msg.msg_flags = 0;
+        msg.msg_iov = &iov;
+        msg.msg_iovlen = 1;
+        msg.msg_name = (struct sockaddr *)&source_addr;
+        msg.msg_namelen = socklen;
+#endif
 
+        while (1) {
             ESP_LOGI(TAG, "Waiting for data");
-            struct sockaddr_storage source_addr; // Large enough for both IPv4 or IPv6
-            socklen_t socklen = sizeof(source_addr);
+#if defined(CONFIG_LWIP_NETBUF_RECVINFO) && !defined(CONFIG_EXAMPLE_IPV6)
+            int len = recvmsg(sock, &msg, 0);
+#else
             int len = recvfrom(sock, rx_buffer, sizeof(rx_buffer) - 1, 0, (struct sockaddr *)&source_addr, &socklen);
-
+#endif
             // Error occurred during receiving
             if (len < 0) {
                 ESP_LOGE(TAG, "recvfrom failed: errno %d", errno);
@@ -90,6 +115,15 @@ static void udp_server_task(void *pvParameters)
                 // Get the sender's ip address as string
                 if (source_addr.ss_family == PF_INET) {
                     inet_ntoa_r(((struct sockaddr_in *)&source_addr)->sin_addr, addr_str, sizeof(addr_str) - 1);
+#if defined(CONFIG_LWIP_NETBUF_RECVINFO) && !defined(CONFIG_EXAMPLE_IPV6)
+                    for ( cmsgtmp = CMSG_FIRSTHDR(&msg); cmsgtmp != NULL; cmsgtmp = CMSG_NXTHDR(&msg, cmsgtmp) ) {
+                        if ( cmsgtmp->cmsg_level == IPPROTO_IP && cmsgtmp->cmsg_type == IP_PKTINFO ) {
+                            struct in_pktinfo *pktinfo;
+                            pktinfo = (struct in_pktinfo*)CMSG_DATA(cmsgtmp);
+                            ESP_LOGI(TAG, "dest ip: %s\n", inet_ntoa(pktinfo->ipi_addr));
+                        }
+                    }
+#endif
                 } else if (source_addr.ss_family == PF_INET6) {
                     inet6_ntoa_r(((struct sockaddr_in6 *)&source_addr)->sin6_addr, addr_str, sizeof(addr_str) - 1);
                 }