Add multicast join for mdns

sepfy · Jul 28, 2024 · d320271 · d320271
1 parent 0e40619
commit d320271
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Showing 3 changed files with 35 additions and 4 deletions.
diff --git a/src/mdns.c b/src/mdns.c
@@ -123,14 +123,18 @@ int mdns_resolve_addr(const char *hostname, Address *addr) {
   fd_set rfds;
   int maxfd, send_retry, recv_retry, size, ret;
 
-  addr_from_string(MDNS_GROUP, &mcast_addr);
-  addr_set_port(&mcast_addr, MDNS_PORT);
-
   if (udp_socket_open(&udp_socket, AF_INET, MDNS_PORT) < 0) {
     LOGE("Failed to create socket");
     return -1;
   }
 
+  addr_from_string(MDNS_GROUP, &mcast_addr);
+  addr_set_port(&mcast_addr, MDNS_PORT);
+  if (udp_socket_add_multicast_group(&udp_socket, &mcast_addr) < 0) {
+    LOGE("Failed to add multicast group");
+    return -1;
+  }
+
   maxfd = udp_socket.fd;
   FD_ZERO(&rfds);
 
@@ -145,13 +149,15 @@ int mdns_resolve_addr(const char *hostname, Address *addr) {
         LOGE("select error");
         break;
       } else if (ret > 0 && FD_ISSET(udp_socket.fd, &rfds)) {
-        ret = udp_socket_recvfrom(&udp_socket, &mcast_addr, buf, sizeof(buf));
+        ret = udp_socket_recvfrom(&udp_socket, NULL, buf, sizeof(buf));
         if (!mdns_parse_answer(buf, ret, addr)) {
           addr_to_string(addr, addr_string, sizeof(addr_string));
           addr_set_family(addr, AF_INET);
           LOGI("Resolved %s -> %s", hostname, addr_string);
           udp_socket_close(&udp_socket);
           return 1;
+        } else {
+          LOGD("timeout");
         }
       }
     }

diff --git a/src/socket.c b/src/socket.c
@@ -13,6 +13,29 @@
 #include "utils.h"
 #include "socket.h"
 
+int udp_socket_add_multicast_group(UdpSocket *udp_socket, Address *mcast_addr) {
+
+  int ret = 0;
+  struct ip_mreq imreq = {0};
+  struct in_addr iaddr = {0};
+
+  imreq.imr_interface.s_addr = INADDR_ANY;
+  // IPV4 only
+  imreq.imr_multiaddr.s_addr = mcast_addr->sin.sin_addr.s_addr;
+
+  if ((ret = setsockopt(udp_socket->fd, IPPROTO_IP, IP_MULTICAST_IF, &iaddr, sizeof(struct in_addr))) < 0) {
+    LOGE("Failed to set IP_MULTICAST_IF: %d", ret);
+    return ret;
+  }
+
+  if ((ret = setsockopt(udp_socket->fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &imreq, sizeof(struct ip_mreq))) < 0) {
+    LOGE("Failed to set IP_ADD_MEMBERSHIP: %d", ret);
+    return ret;
+  }
+
+  return 0;
+}
+
 int udp_socket_open(UdpSocket *udp_socket, int family, int port) {
 
   int ret;

diff --git a/src/socket.h b/src/socket.h
@@ -23,6 +23,8 @@ int udp_socket_sendto(UdpSocket *udp_socket, Address *bind_addr, const uint8_t *
 
 int udp_socket_recvfrom(UdpSocket *udp_sock, Address *bind_addr, uint8_t *buf, int len);
 
+int udp_socket_add_multicast_group(UdpSocket *udp_socket, Address *mcast_addr);
+
 int tcp_socket_open(TcpSocket *tcp_socket, int family);
 
 int tcp_socket_connect(TcpSocket *tcp_socket, Address *addr);