enabled gratuitous arp packets (#474)

Co-authored-by: Logan007 <you@example.com>

src/edge.c

@@ -664,59 +664,6 @@ static int loadFromFile(const char *path, n2n_edge_conf_t *conf, n2n_tuntap_priv
 
 /* ************************************** */
 
-#if defined(DUMMY_ID_00001) /* Disabled waiting for config option to enable it */
-
-static char gratuitous_arp[] = {
-				0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* Dest mac */
-				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* Src mac */
-				0x08, 0x06, /* ARP */
-				0x00, 0x01, /* Ethernet */
-				0x08, 0x00, /* IP */
-				0x06, /* Hw Size */
-				0x04, /* Protocol Size */
-				0x00, 0x01, /* ARP Request */
-				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* Src mac */
-				0x00, 0x00, 0x00, 0x00, /* Src IP */
-				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* Target mac */
-				0x00, 0x00, 0x00, 0x00 /* Target IP */
-};
-
-/* ************************************** */
-
-/** Build a gratuitous ARP packet for a /24 layer 3 (IP) network. */
-static int build_gratuitous_arp(char *buffer, uint16_t buffer_len) {
-  if(buffer_len < sizeof(gratuitous_arp)) return(-1);
-
-  memcpy(buffer, gratuitous_arp, sizeof(gratuitous_arp));
-  memcpy(&buffer[6], device.mac_addr, 6);
-  memcpy(&buffer[22], device.mac_addr, 6);
-  memcpy(&buffer[28], &device.ip_addr, 4);
-
-  /* REVISIT: BbMaj7 - use a real netmask here. This is valid only by accident
-   * for /24 IPv4 networks. */
-  buffer[31] = 0xFF; /* Use a faked broadcast address */
-  memcpy(&buffer[38], &device.ip_addr, 4);
-  return(sizeof(gratuitous_arp));
-}
-
-/* ************************************** */
-
-/** Called from update_supernode_reg to periodically send gratuitous ARP
- *  broadcasts. */
-static void send_grat_arps(n2n_edge_t * eee,) {
-  char buffer[48];
-  size_t len;
-
-  traceEvent(TRACE_NORMAL, "Sending gratuitous ARP...");
-  len = build_gratuitous_arp(buffer, sizeof(buffer));
-  send_packet2net(eee, buffer, len);
-  send_packet2net(eee, buffer, len); /* Two is better than one :-) */
-}
-
-#endif /* #if defined(DUMMY_ID_00001) */
-
-/* ************************************** */
-
 static void daemonize() {
 #ifndef WIN32
   int childpid;

src/edge_utils.c

@@ -929,6 +929,49 @@ static void send_register_ack(n2n_edge_t * eee,
 
 /* ************************************** */
 
+static char gratuitous_arp[] = {
+  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* dest MAC */
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* src MAC */
+  0x08, 0x06, /* ARP */
+  0x00, 0x01, /* ethernet */
+  0x08, 0x00, /* IP */
+  0x06, /* hw Size */
+  0x04, /* protocol Size */
+  0x00, 0x02, /* ARP reply */
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* src MAC */
+  0x00, 0x00, 0x00, 0x00, /* src IP */
+  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, /* target MAC */
+  0x00, 0x00, 0x00, 0x00 /* target IP */
+};
+
+// build a gratuitous ARP packet */
+static int build_gratuitous_arp(n2n_edge_t * eee, char *buffer, uint16_t buffer_len) {
+  if(buffer_len < sizeof(gratuitous_arp)) return(-1);
+
+  memcpy(buffer, gratuitous_arp, sizeof(gratuitous_arp));
+  memcpy(&buffer[6], eee->device.mac_addr, 6);
+  memcpy(&buffer[22], eee->device.mac_addr, 6);
+  memcpy(&buffer[28], &(eee->device.ip_addr), 4);
+
+  memcpy(&buffer[38], &(eee->device.ip_addr), 4);
+  return(sizeof(gratuitous_arp));
+}
+
+/** Called from update_supernode_reg to periodically send gratuitous ARP
+ *  broadcasts. */
+static void send_grat_arps(n2n_edge_t * eee) {
+  char buffer[48];
+  size_t len;
+
+  traceEvent(TRACE_DEBUG, "Sending gratuitous ARP...");
+  len = build_gratuitous_arp(eee, buffer, sizeof(buffer));
+
+  edge_send_packet2net(eee, buffer, len);
+  edge_send_packet2net(eee, buffer, len); /* Two is better than one :-) */
+}
+
+/* ************************************** */
+
 /** @brief Check to see if we should re-register with the supernode.
  *
  *  This is frequently called by the main loop.
@@ -982,8 +1025,7 @@ void update_supernode_reg(n2n_edge_t * eee, time_t nowTime) {
 
   eee->sn_wait=1;
 
-  /* REVISIT: turn-on gratuitous ARP with config option. */
-  /* send_grat_arps(sock_fd, is_udp_sock); */
+  send_grat_arps(eee);
 
   eee->last_register_req = nowTime;
 }

src/sn_utils.c

@@ -323,7 +323,7 @@ static int update_edge(n2n_sn_t *sss,
                        time_t now) {
   macstr_t mac_buf;
   n2n_sock_str_t sockbuf;
-  struct peer_info *scan;
+  struct peer_info *scan, *iter, *tmp;
 
   traceEvent(TRACE_DEBUG, "update_edge for %s [%s]",
 	     macaddr_str(mac_buf, reg->edgeMac),
@@ -331,6 +331,19 @@ static int update_edge(n2n_sn_t *sss,
 
   HASH_FIND_PEER(comm->edges, reg->edgeMac, scan);
 
+ // if unknown, make sure it is also not known by IP address
+  if (NULL == scan) {
+    HASH_ITER(hh,comm->edges,iter,tmp) {
+      if(iter->dev_addr.net_addr == reg->dev_addr.net_addr) {
+        scan = iter;
+        HASH_DEL(comm->edges, scan);
+        memcpy(&(scan->mac_addr), reg->edgeMac, sizeof(n2n_mac_t));
+        HASH_ADD_PEER(comm->edges, scan);
+        break;
+      }
+    }
+  }
+
   if (NULL == scan) {
     /* Not known */