sys/net/gnrc: Implement sock_aux_local

Provide address the IP packet / UDP datagram was received on in the auxiliary
data, if module sock_aux_local is used.

sys/net/gnrc/sock/gnrc_sock.c

@@ -89,8 +89,11 @@ void gnrc_sock_create(gnrc_sock_reg_t *reg, gnrc_nettype_t type, uint32_t demux_
 }
 
 ssize_t gnrc_sock_recv(gnrc_sock_reg_t *reg, gnrc_pktsnip_t **pkt_out,
-                       uint32_t timeout, sock_ip_ep_t *remote)
+                       uint32_t timeout, sock_ip_ep_t *remote,
+                       gnrc_sock_recv_aux_t aux)
 {
+    /* only used when some sock_aux_% module is used */
+    (void)aux;
     gnrc_pktsnip_t *pkt, *netif;
     msg_t msg;
 
@@ -150,6 +153,12 @@ ssize_t gnrc_sock_recv(gnrc_sock_reg_t *reg, gnrc_pktsnip_t **pkt_out,
     assert(ipv6_hdr != NULL);
     memcpy(&remote->addr, &ipv6_hdr->src, sizeof(ipv6_addr_t));
     remote->family = AF_INET6;
+#if IS_USED(MODULE_SOCK_AUX_LOCAL)
+    if (aux.local != NULL) {
+        memcpy(&aux.local->addr, &ipv6_hdr->dst, sizeof(ipv6_addr_t));
+        aux.local->family = AF_INET6;
+    }
+#endif /* MODULE_SOCK_AUX_LOCAL */
     netif = gnrc_pktsnip_search_type(pkt, GNRC_NETTYPE_NETIF);
     if (netif == NULL) {
         remote->netif = SOCK_ADDR_ANY_NETIF;

sys/net/gnrc/sock/include/gnrc_sock_internal.h

@@ -55,6 +55,33 @@ extern "C" {
  */
 #define GNRC_SOCK_DYN_PORTRANGE_ERR (0)
 
+/**
+ * @brief   Structure to retrieve auxiliary data from @ref gnrc_sock_recv
+ *
+ * @details The members of this function depend on the modules used
+ * @internal
+ */
+typedef struct {
+#if IS_USED(MODULE_SOCK_AUX_LOCAL) || DOXYGEN
+    /**
+     * @brief   local IP address PDU was received on
+     *
+     * This member is only present if module `sock_aux_local` is used.
+     */
+    sock_ip_ep_t *local;
+#endif
+#if !IS_USED(MODULE_SOCK_AUX_LOCAL) || DOXYGEN
+    /**
+     * @brief   Workaround in case no `sock_aux_%` module is used
+     *
+     * Empty structures are only allowed with a GNU extension. For portability,
+     * this member is present if and only if this structure would be otherwise
+     * empty.
+     */
+    uint8_t this_struct_is_not_empty;
+#endif
+} gnrc_sock_recv_aux_t;
+
 /**
  * @brief   Internal helper functions for GNRC
  * @internal
@@ -116,7 +143,7 @@ void gnrc_sock_create(gnrc_sock_reg_t *reg, gnrc_nettype_t type, uint32_t demux_
  * @internal
  */
 ssize_t gnrc_sock_recv(gnrc_sock_reg_t *reg, gnrc_pktsnip_t **pkt, uint32_t timeout,
-                       sock_ip_ep_t *remote);
+                       sock_ip_ep_t *remote, gnrc_sock_recv_aux_t aux);
 
 /**
  * @brief   Send a packet internally

sys/net/gnrc/sock/ip/gnrc_sock_ip.c

@@ -117,6 +117,7 @@ ssize_t sock_ip_recv_buf_aux(sock_ip_t *sock, void **data, void **buf_ctx,
     gnrc_pktsnip_t *pkt;
     sock_ip_ep_t tmp;
     int res;
+    gnrc_sock_recv_aux_t _aux = { 0 };
 
     assert((sock != NULL) && (data != NULL) && (buf_ctx != NULL));
     if (*buf_ctx != NULL) {
@@ -129,7 +130,12 @@ ssize_t sock_ip_recv_buf_aux(sock_ip_t *sock, void **data, void **buf_ctx,
         return -EADDRNOTAVAIL;
     }
     tmp.family = sock->local.family;
-    res = gnrc_sock_recv((gnrc_sock_reg_t *)sock, &pkt, timeout, &tmp);
+#if IS_USED(MODULE_SOCK_AUX_LOCAL)
+    if ((aux != NULL) && (aux->flags & SOCK_AUX_GET_LOCAL)) {
+        _aux.local = &aux->local;
+    }
+#endif
+    res = gnrc_sock_recv((gnrc_sock_reg_t *)sock, &pkt, timeout, &tmp, _aux);
     if (res < 0) {
         return res;
     }
@@ -146,6 +152,11 @@ ssize_t sock_ip_recv_buf_aux(sock_ip_t *sock, void **data, void **buf_ctx,
         gnrc_pktbuf_release(pkt);
         return -EPROTO;
     }
+#if IS_USED(MODULE_SOCK_AUX_LOCAL)
+    if ((aux != NULL) && (aux->flags & SOCK_AUX_GET_LOCAL)) {
+        aux->flags &= ~(SOCK_AUX_GET_LOCAL);
+    }
+#endif
     *data = pkt->data;
     *buf_ctx = pkt;
     res = (int)pkt->size;

sys/net/gnrc/sock/udp/gnrc_sock_udp.c

@@ -206,6 +206,7 @@ ssize_t sock_udp_recv_buf_aux(sock_udp_t *sock, void **data, void **buf_ctx,
     udp_hdr_t *hdr;
     sock_ip_ep_t tmp;
     int res;
+    gnrc_sock_recv_aux_t _aux = { 0 };
 
     assert((sock != NULL) && (data != NULL) && (buf_ctx != NULL));
     if (*buf_ctx != NULL) {
@@ -218,7 +219,12 @@ ssize_t sock_udp_recv_buf_aux(sock_udp_t *sock, void **data, void **buf_ctx,
         return -EADDRNOTAVAIL;
     }
     tmp.family = sock->local.family;
-    res = gnrc_sock_recv((gnrc_sock_reg_t *)sock, &pkt, timeout, &tmp);
+#if IS_USED(MODULE_SOCK_AUX_LOCAL)
+    if ((aux != NULL) && (aux->flags & SOCK_AUX_GET_LOCAL)) {
+        _aux.local = (sock_ip_ep_t *)&aux->local;
+    }
+#endif
+    res = gnrc_sock_recv((gnrc_sock_reg_t *)sock, &pkt, timeout, &tmp, _aux);
     if (res < 0) {
         return res;
     }
@@ -240,6 +246,12 @@ ssize_t sock_udp_recv_buf_aux(sock_udp_t *sock, void **data, void **buf_ctx,
         gnrc_pktbuf_release(pkt);
         return -EPROTO;
     }
+#if IS_USED(MODULE_SOCK_AUX_LOCAL)
+    if ((aux != NULL) && (aux->flags & SOCK_AUX_GET_LOCAL)) {
+        aux->flags &= ~SOCK_AUX_GET_LOCAL;
+        aux->local.port = sock->local.port;
+    }
+#endif
     *data = pkt->data;
     *buf_ctx = pkt;
     res = (int)pkt->size;