IPv4 mapping to IPv6 implementation. Just for UDP. From Macs Neklyudov

net/socket/recvfrom.c

@@ -937,6 +937,7 @@ static inline void recvfrom_udpsender(struct net_driver_s *dev, struct recvfrom_
     {
       FAR struct sockaddr_in6 *infrom =
         (FAR struct sockaddr_in6 *)pstate->rf_from;
+      FAR socklen_t *fromlen = pstate->rf_fromlen;
 
       if (infrom)
         {
@@ -945,6 +946,7 @@ static inline void recvfrom_udpsender(struct net_driver_s *dev, struct recvfrom_
 
           infrom->sin6_family = AF_INET6;
           infrom->sin6_port   = udp->srcport;
+          *fromlen = sizeof(struct sockaddr_in6);
 
           net_ipv6addr_copy(infrom->sin6_addr.s6_addr, ipv6->srcipaddr);
         }
@@ -958,17 +960,39 @@ static inline void recvfrom_udpsender(struct net_driver_s *dev, struct recvfrom_
     {
       FAR struct sockaddr_in *infrom  =
         (FAR struct sockaddr_in *)pstate->rf_from;
+      FAR socklen_t *fromlen = pstate->rf_fromlen;
 
       if (infrom)
         {
           FAR struct udp_hdr_s *udp   = UDPIPv4BUF;
           FAR struct ipv4_hdr_s *ipv4 = IPv4BUF;
 
-          infrom->sin_family = AF_INET;
+#ifdef CONFIG_NET_IPv6
-          infrom->sin_port   = udp->srcport;
+          FAR struct udp_conn_s *conn = (FAR struct udp_conn_s*)pstate->rf_sock->s_conn;
+          FAR struct sockaddr_in6 *infrom6 = (FAR struct sockaddr_in6 *)infrom;
 
-          net_ipv4addr_copy(infrom->sin_addr.s_addr,
+          if (conn->domain == PF_INET6)
-                            net_ip4addr_conv32(ipv4->srcipaddr));
+            {
+              infrom6->sin6_family = AF_INET6;
+              infrom6->sin6_port = udp->srcport;
+              *fromlen = sizeof(struct sockaddr_in6);
+
+              memset(infrom6->sin6_addr.s6_addr, 0, sizeof(infrom6->sin6_addr.s6_addr) - sizeof(in_addr_t));
+
+              infrom6->sin6_addr.s6_addr[10] = 0xFF;
+              infrom6->sin6_addr.s6_addr[11] = 0xFF;
+
+              memcpy(&infrom6->sin6_addr.s6_addr[12], ipv4->srcipaddr, sizeof(in_addr_t));
+            }
+          else
+#endif
+            {
+              infrom->sin_family = AF_INET;
+              infrom->sin_port   = udp->srcport;
+
+              net_ipv4addr_copy(infrom->sin_addr.s_addr,
+                                net_ip4addr_conv32(ipv4->srcipaddr));
+            }
         }
     }
 #endif /* CONFIG_NET_IPv4 */

net/udp/udp_callback.c

@@ -132,14 +132,34 @@ static uint16_t udp_datahandler(FAR struct net_driver_s *dev, FAR struct udp_con
       FAR struct udp_hdr_s *udp   = UDPIPv4BUF;
       FAR struct ipv4_hdr_s *ipv4 = IPv4BUF;
 
-      src_addr4.sin_family = AF_INET;
+#ifdef CONFIG_NET_IPv6
-      src_addr4.sin_port   = udp->srcport;
+      if (conn->domain == PF_INET6)
+        {
+          src_addr6.sin6_family = AF_INET6;
+          src_addr6.sin6_port = udp->srcport;
 
-      net_ipv4addr_copy(src_addr4.sin_addr.s_addr,
+          memset(src_addr6.sin6_addr.s6_addr, 0, sizeof(src_addr6.sin6_addr.s6_addr) - sizeof(in_addr_t));
+
+          src_addr6.sin6_addr.s6_addr[10] = 0xFF;
+          src_addr6.sin6_addr.s6_addr[11] = 0xFF;
+
+          memcpy(&src_addr6.sin6_addr.s6_addr[12], ipv4->srcipaddr, sizeof(in_addr_t));
+
+          src_addr_size = sizeof(src_addr6);
+          src_addr = &src_addr6;
+        }
+      else
+#endif
+        {
+          src_addr4.sin_family = AF_INET;
+          src_addr4.sin_port   = udp->srcport;
+
+          net_ipv4addr_copy(src_addr4.sin_addr.s_addr,
                             net_ip4addr_conv32(ipv4->srcipaddr));
 
-      src_addr_size = sizeof(src_addr4);
+          src_addr_size = sizeof(src_addr4);
-      src_addr = &src_addr4;
+          src_addr = &src_addr4;
+        }
     }
 #endif /* CONFIG_NET_IPv4 */
 

net/udp/udp_send.c

@@ -69,6 +69,13 @@
 #define UDPIPv4BUF ((struct udp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv4_HDRLEN])
 #define UDPIPv6BUF ((struct udp_hdr_s *)&dev->d_buf[NET_LL_HDRLEN(dev) + IPv6_HDRLEN])
 
+#define IN6_IS_ADDR_IPV4(a)  ((a)->s6_addr32[0] == 0 && (a)->s6_addr32[1] == 0 && \
+                              (a)->s6_addr16[4] == 0 && (a)->s6_addr16[5] == 0xFFFF)
+
+#define IN6_GET_ADDR_IPV4(a) (((in_addr_t)(a)->s6_addr[12])       | ((in_addr_t)(a)->s6_addr[13] << 8) | \
+                              ((in_addr_t)(a)->s6_addr[14] << 16) | ((in_addr_t)(a)->s6_addr[15] << 24))
+
+
 /****************************************************************************
  * Public Variables
  ****************************************************************************/
@@ -115,7 +122,8 @@ void udp_send(FAR struct net_driver_s *dev, FAR struct udp_conn_s *conn)
 
 #ifdef CONFIG_NET_IPv4
 #ifdef CONFIG_NET_IPv6
-      if (conn->domain == PF_INET)
+      if (conn->domain == PF_INET ||
+         (conn->domain == PF_INET6 && IN6_IS_ADDR_IPV4((FAR struct in6_addr*)conn->u.ipv6.raddr)))
 #endif
         {
           /* Get pointers to the IPv4 header and the offset TCP header */
@@ -138,7 +146,18 @@ void udp_send(FAR struct net_driver_s *dev, FAR struct udp_conn_s *conn)
           ipv4->proto       = IP_PROTO_UDP;
 
           net_ipv4addr_hdrcopy(ipv4->srcipaddr, &dev->d_ipaddr);
-          net_ipv4addr_hdrcopy(ipv4->destipaddr, &conn->u.ipv4.raddr);
+
+#ifdef CONFIG_NET_IPv6
+          if (conn->domain == PF_INET6 && IN6_IS_ADDR_IPV4((FAR struct in6_addr*)conn->u.ipv6.raddr))
+            {
+              in_addr_t raddr = IN6_GET_ADDR_IPV4((FAR struct in6_addr*)conn->u.ipv6.raddr);
+              net_ipv4addr_hdrcopy(ipv4->destipaddr, &raddr);
+            }
+          else
+#endif
+            {
+              net_ipv4addr_hdrcopy(ipv4->destipaddr, &conn->u.ipv4.raddr);
+            }
 
           /* The total length to send is the size of the application data
            * plus the IPv4 and UDP headers (and, eventually, the link layer
@@ -221,7 +240,8 @@ void udp_send(FAR struct net_driver_s *dev, FAR struct udp_conn_s *conn)
 
 #ifdef CONFIG_NET_IPv4
 #ifdef CONFIG_NET_IPv6
-      if (conn->domain == PF_INET)
+      if (conn->domain == PF_INET ||
+          (conn->domain == PF_INET6 && IN6_IS_ADDR_IPV4((FAR struct in6_addr*)conn->u.ipv6.raddr)))
 #endif
         {
           udp->udpchksum = ~udp_ipv4_chksum(dev);