ipv6: Support IPv4/IPv6 mapped PCBs

This change also drops UDP IPv4 packet received on IPv6-only socket.

Ref IDF-4845

src/api/api_msg.c

@@ -248,6 +248,16 @@ recv_udp(void *arg, struct udp_pcb *pcb, struct pbuf *p,
     return;
   }
 
+#if ESP_LWIP && LWIP_IPV6
+  /* This should be eventually moved to a flag on the UDP PCB, and this drop can happen
+     more correctly in udp_input(). This will also allow icmp_dest_unreach() to be called. */
+  if (conn->flags & NETCONN_FLAG_IPV6_V6ONLY && !ip_current_is_v6()) {
+    LWIP_DEBUGF(API_MSG_DEBUG, ("recv_udp: Dropping IPv4 UDP packet (IPv6-only socket)"));
+    pbuf_free(p);
+    return;
+  }
+#endif /* ESP_LWIP && LWIP_IPV6 */
+
   buf = (struct netbuf *)memp_malloc(MEMP_NETBUF);
   if (buf == NULL) {
     pbuf_free(p);
@@ -668,6 +678,15 @@ pcb_new(struct api_msg *msg)
   if (msg->conn->pcb.ip == NULL) {
     msg->err = ERR_MEM;
   }
+#if ESP_LWIP && LWIP_IPV4 && LWIP_IPV6
+  else {
+    if (NETCONNTYPE_ISIPV6(msg->conn->type)) {
+      /* Convert IPv4 PCB manually to an IPv6 PCB */
+      IP_SET_TYPE_VAL(msg->conn->pcb.ip->local_ip,  IPADDR_TYPE_V6);
+      IP_SET_TYPE_VAL(msg->conn->pcb.ip->remote_ip, IPADDR_TYPE_V6);
+    }
+  }
+#endif /* ESP_LWIP && LWIP_IPV4 && LWIP_IPV6 */
 }
 
 /**
@@ -1233,6 +1252,20 @@ lwip_netconn_do_bind(void *m)
   err_t err;
 
   if (msg->conn->pcb.tcp != NULL) {
+#if ESP_LWIP && LWIP_IPV4 && LWIP_IPV6
+      /* "Socket API like" dual-stack support: If IP to bind to is IP6_ADDR_ANY,
+       * and NETCONN_FLAG_IPV6_V6ONLY is NOT set, use IP_ANY_TYPE to bind
+       */
+      if (ip_addr_cmp(API_EXPR_REF(msg->msg.bc.ipaddr), IP6_ADDR_ANY) &&
+          (netconn_get_ipv6only(msg->conn) == 0)) {
+        /* change PCB type to IPADDR_TYPE_ANY */
+        IP_SET_TYPE_VAL(msg->conn->pcb.ip->local_ip,  IPADDR_TYPE_ANY);
+        IP_SET_TYPE_VAL(msg->conn->pcb.ip->remote_ip, IPADDR_TYPE_ANY);
+
+        /* bind to IPADDR_TYPE_ANY */
+        API_EXPR_REF(msg->msg.bc.ipaddr) = IP_ANY_TYPE;
+      }
+#endif /* ESP_LWIP && LWIP_IPV4 && LWIP_IPV6 */
     switch (NETCONNTYPE_GROUP(msg->conn->type)) {
 #if LWIP_RAW
       case NETCONN_RAW:
@@ -1548,6 +1581,14 @@ lwip_netconn_do_send(void *m)
   struct api_msg *msg = (struct api_msg *)m;
 
   err_t err = netconn_err(msg->conn);
+
+#if ESP_LWIP && LWIP_IPV4 && LWIP_IPV6
+  if ((msg->conn->flags & NETCONN_FLAG_IPV6_V6ONLY) &&IP_IS_V4MAPPEDV6(&msg->msg.b->addr)) {
+    LWIP_DEBUGF(API_MSG_DEBUG, ("lwip_netconn_do_send: Dropping IPv4 packet on IPv6-only socket"));
+    msg->err = ERR_VAL;
+   }  
+#endif /* ESP_LWIP && LWIP_IPV4 && LWIP_IPV6 */
+
   if (err == ERR_OK) {
     if (msg->conn->pcb.tcp != NULL) {
       switch (NETCONNTYPE_GROUP(msg->conn->type)) {

src/api/netdb.c

@@ -335,6 +335,11 @@ lwip_getaddrinfo(const char *nodename, const char *servname,
         type = NETCONN_DNS_IPV4;
       } else if (ai_family == AF_INET6) {
         type = NETCONN_DNS_IPV6;
+#if ESP_LWIP
+        if (hints->ai_flags & AI_V4MAPPED) {
+          type = NETCONN_DNS_IPV6_IPV4;
+        }
+#endif /* ESP_LWIP */
       }
 #endif /* LWIP_IPV4 && LWIP_IPV6 */
       err = netconn_gethostbyname_addrtype(nodename, &addr, type);
@@ -351,6 +356,14 @@ lwip_getaddrinfo(const char *nodename, const char *servname,
     }
   }
 
+#if ESP_LWIP && LWIP_IPV4 && LWIP_IPV6
+  if (ai_family == AF_INET6 && (hints->ai_flags & AI_V4MAPPED)
+      && IP_GET_TYPE(&addr) == IPADDR_TYPE_V4) {
+    /* Convert native V4 address to a V4-mapped IPV6 address */
+    ip4_2_ipv4_mapped_ipv6(ip_2_ip6(&addr), ip_2_ip4(&addr));
+  }
+#endif /* ESP_LWIP && LWIP_IPV4 && LWIP_IPV6 */
+
   total_size = sizeof(struct addrinfo) + sizeof(struct sockaddr_storage);
   if (nodename != NULL) {
     namelen = strlen(nodename);

src/core/udp.c

@@ -540,9 +540,20 @@ udp_sendto_chksum(struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *dst_ip,
   if (!IP_ADDR_PCB_VERSION_MATCH(pcb, dst_ip)) {
     return ERR_VAL;
   }
+#if ESP_LWIP && LWIP_IPV4 && LWIP_IPV6
+  /* Unwrap IPV4-mapped IPV6 addresses and convert to native IPV4 here */
+  if (IP_IS_V4MAPPEDV6(dst_ip)) {
+    ip_addr_t dest_ipv4;
+    unmap_ipv4_mapped_ipv6(ip_2_ip4(&dest_ipv4), ip_2_ip6(dst_ip));
+#if LWIP_CHECKSUM_ON_COPY
+    return udp_sendto_chksum(pcb, p, &dest_ipv4, dst_port, have_chksum, chksum);
+#else
+    return udp_sendto(pcb, p, &dest_ipv4, dst_port);
+#endif /* LWIP_CHECKSUM_ON_COPY  */
+  }
+#endif /* ESP_LWIP && LWIP_IPV4 && LWIP_IPV6 */
 
   LWIP_DEBUGF(UDP_DEBUG | LWIP_DBG_TRACE, ("udp_send\n"));
-
   if (pcb->netif_idx != NETIF_NO_INDEX) {
     netif = netif_get_by_index(pcb->netif_idx);
   } else {

src/include/lwip/ip_addr.h

@@ -133,6 +133,11 @@ extern const ip_addr_t ip_addr_any_type;
                                    ip_2_ip6(ipaddr)->addr[3] = 0; \
                                    ip6_addr_clear_zone(ip_2_ip6(ipaddr)); }while(0)
 
+#if ESP_LWIP && LWIP_IPV6
+#define IP_V6_EQ_PART(ipaddr, WORD, VAL) (ip_2_ip6(ipaddr)->addr[WORD] == htonl(VAL))
+#define IP_IS_V4MAPPEDV6(ipaddr) (IP_IS_V6(ipaddr) && IP_V6_EQ_PART(ipaddr, 0, 0) && IP_V6_EQ_PART(ipaddr, 1, 0) && IP_V6_EQ_PART(ipaddr, 2, 0x0000FFFF))
+#endif /* ESP_LWIP && LWIP_IPV6 */
+
 /** @ingroup ipaddr */
 #define ip_addr_copy(dest, src)      do{ IP_SET_TYPE_VAL(dest, IP_GET_TYPE(&src)); if(IP_IS_V6_VAL(src)){ \
   ip6_addr_copy(*ip_2_ip6(&(dest)), *ip_2_ip6(&(src))); }else{ \