sys/net/sock: add sock_aux_ttl

makefiles/pseudomodules.inc.mk

@@ -513,6 +513,7 @@ PSEUDOMODULES += sock_async
 PSEUDOMODULES += sock_aux_local
 PSEUDOMODULES += sock_aux_rssi
 PSEUDOMODULES += sock_aux_timestamp
+PSEUDOMODULES += sock_aux_ttl
 PSEUDOMODULES += sock_dtls
 PSEUDOMODULES += sock_ip
 PSEUDOMODULES += sock_tcp

sys/include/net/sock.h

@@ -319,6 +319,21 @@ enum {
      * @ref sock_dtls_aux_tx_t::local.
      */
     SOCK_AUX_SET_LOCAL = (1LU << 3),
+    /**
+     * @brief   Flag to request the TTL value of received frame
+     *
+     * @note    Select module `sock_aux_ttl` and a compatible network stack to
+     *          use this
+     *
+     * Set this flag in the auxiliary data structure prior to the call of
+     * @ref sock_udp_recv_aux / @ref sock_ip_recv_aux / etc. to request the
+     * TTL value of a received frame. This flag will be cleared if the
+     * time to live was stored, otherwise it remains set.
+     *
+     * Depending on the family of the socket, the TTL value will be stored in
+     * @ref sock_udp_aux_rx_t::ttl or @ref sock_dtls_aux_rx_t::ttl.
+     */
+    SOCK_AUX_GET_TTL = (1LU << 4),
 };
 
 /**

sys/include/net/sock/udp.h

@@ -332,6 +332,14 @@ typedef struct {
      */
     int16_t rssi;
 #endif /* MODULE_SOCK_AUX_RSSI */
+#if defined(MODULE_SOCK_AUX_TTL) || defined(DOXYGEN)
+    /**
+     * @brief   TTL value of the received frame
+     *
+     * @see SOCK_AUX_GET_TTL
+     */
+    uint8_t ttl;
+#endif /* MODULE_SOCK_AUX_TTL */
     sock_aux_flags_t flags; /**< Flags used request information */
 } sock_udp_aux_rx_t;
 

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

@@ -305,6 +305,16 @@ ssize_t sock_udp_recv_buf_aux(sock_udp_t *sock, void **data, void **buf_ctx,
     if ((aux != NULL) && (_aux.flags & GNRC_SOCK_RECV_AUX_FLAG_RSSI)) {
         aux->flags &= ~SOCK_AUX_GET_RSSI;
     }
+#endif
+#if IS_USED(MODULE_SOCK_AUX_TTL)
+    if ((aux != NULL) && (aux->flags & SOCK_AUX_GET_TTL)) {
+        gnrc_pktsnip_t *ip = gnrc_pktsnip_search_type(pkt, GNRC_NETTYPE_IPV6);
+        if (ip) {
+            ipv6_hdr_t *ip_hdr = ip->data;
+            aux->ttl = ip_hdr->hl;
+            aux->flags &= ~SOCK_AUX_GET_TTL;
+        }
+    }
 #endif
     *data = pkt->data;
     *buf_ctx = pkt;

tests/net/gnrc_sock_udp/Makefile

@@ -3,6 +3,7 @@ include ../Makefile.net_common
 AUX_LOCAL ?= 1
 AUX_TIMESTAMP ?= 1
 AUX_RSSI ?= 1
+AUX_TTL ?= 1
 
 ifeq (1, $(AUX_LOCAL))
   USEMODULE += sock_aux_local
@@ -16,6 +17,10 @@ ifeq (1, $(AUX_RSSI))
   USEMODULE += sock_aux_rssi
 endif
 
+ifeq (1, $(AUX_TTL))
+  USEMODULE += sock_aux_ttl
+endif
+
 USEMODULE += gnrc_sock_check_reuse
 USEMODULE += sock_udp
 USEMODULE += gnrc_ipv6

tests/net/gnrc_sock_udp/main.c

@@ -451,7 +451,7 @@ static void test_sock_udp_recv__aux(void)
     static const inject_aux_t inject_aux = { .timestamp = 1337, .rssi = -11 };
     sock_udp_ep_t result;
     sock_udp_aux_rx_t aux = {
-        .flags = SOCK_AUX_GET_LOCAL | SOCK_AUX_GET_TIMESTAMP | SOCK_AUX_GET_RSSI
+        .flags = SOCK_AUX_GET_LOCAL | SOCK_AUX_GET_TIMESTAMP | SOCK_AUX_GET_RSSI | SOCK_AUX_GET_TTL
     };
 
     expect(0 == sock_udp_create(&_sock, &local, NULL, SOCK_FLAGS_REUSE_EP));
@@ -483,6 +483,12 @@ static void test_sock_udp_recv__aux(void)
     expect(inject_aux.rssi == aux.rssi);
 #else
     expect(aux.flags & SOCK_AUX_GET_RSSI);
+#endif
+#if IS_USED(MODULE_SOCK_AUX_TTL)
+    expect(!(aux.flags & SOCK_AUX_GET_TTL));
+    expect(64 == aux.ttl);
+#else
+    expect(aux.flags & SOCK_AUX_GET_TTL);
 #endif
     expect(_check_net());
 }