socket-dynamic: when sending from port zero, allocate a free port dynamically

src/libcharon/plugins/socket_dynamic/socket_dynamic_socket.c

@@ -325,14 +325,61 @@ METHOD(socket_t, receiver, status_t,
 	return FAILED;
 }
 
+/**
+ * Get the port allocated dynamically using bind()
+ */
+static bool get_dynamic_port(int fd, int family, u_int16_t *port)
+{
+	union {
+		struct sockaddr_storage ss;
+		struct sockaddr s;
+		struct sockaddr_in sin;
+		struct sockaddr_in6 sin6;
+	} addr;
+	socklen_t addrlen;
+
+	addrlen = sizeof(addr);
+	if (getsockname(fd, &addr.s, &addrlen) != 0)
+	{
+		DBG1(DBG_NET, "unable to getsockname: %s", strerror(errno));
+		return FALSE;
+	}
+	switch (family)
+	{
+		case AF_INET:
+			if (addrlen != sizeof(addr.sin) || addr.sin.sin_family != family)
+			{
+				break;
+			}
+			*port = ntohs(addr.sin.sin_port);
+			return TRUE;
+		case AF_INET6:
+			if (addrlen != sizeof(addr.sin6) || addr.sin6.sin6_family != family)
+			{
+				break;
+			}
+			*port = ntohs(addr.sin6.sin6_port);
+			return TRUE;
+		default:
+			return FALSE;
+	}
+	DBG1(DBG_NET, "received invalid getsockname() result");
+	return FALSE;
+}
+
 /**
  * open a socket to send and receive packets
  */
 static int open_socket(private_socket_dynamic_socket_t *this,
-					   int family, u_int16_t port)
+					   int family, u_int16_t *port)
 {
+	union {
+		struct sockaddr_storage ss;
+		struct sockaddr s;
+		struct sockaddr_in sin;
+		struct sockaddr_in6 sin6;
+	} addr;
 	int on = TRUE;
-	struct sockaddr_storage addr;
 	socklen_t addrlen;
 	u_int sol, pktinfo = 0;
 	int fd;
@@ -342,27 +389,21 @@ static int open_socket(private_socket_dynamic_socket_t *this,
 	switch (family)
 	{
 		case AF_INET:
-		{
+			addr.sin.sin_family = AF_INET;
-			struct sockaddr_in *sin = (struct sockaddr_in *)&addr;
+			addr.sin.sin_addr.s_addr = INADDR_ANY;
-			sin->sin_family = AF_INET;
+			addr.sin.sin_port = htons(*port);
-			sin->sin_addr.s_addr = INADDR_ANY;
+			addrlen = sizeof(addr.sin);
-			sin->sin_port = htons(port);
-			addrlen = sizeof(struct sockaddr_in);
 			sol = SOL_IP;
 			pktinfo = IP_PKTINFO;
 			break;
-		}
 		case AF_INET6:
-		{
+			addr.sin6.sin6_family = AF_INET6;
-			struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&addr;
+			memset(&addr.sin6.sin6_addr, 0, sizeof(addr.sin6));
-			sin6->sin6_family = AF_INET6;
+			addr.sin6.sin6_port = htons(*port);
-			memset(&sin6->sin6_addr, 0, sizeof(sin6->sin6_addr));
+			addrlen = sizeof(addr.sin6);
-			sin6->sin6_port = htons(port);
-			addrlen = sizeof(struct sockaddr_in6);
 			sol = SOL_IPV6;
 			pktinfo = IPV6_RECVPKTINFO;
 			break;
-		}
 		default:
 			return 0;
 	}
@@ -380,13 +421,17 @@ static int open_socket(private_socket_dynamic_socket_t *this,
 		return 0;
 	}
 
-	/* bind the socket */
+	if (bind(fd, &addr.s, addrlen) < 0)
-	if (bind(fd, (struct sockaddr *)&addr, addrlen) < 0)
 	{
 		DBG1(DBG_NET, "unable to bind socket: %s", strerror(errno));
 		close(fd);
 		return 0;
 	}
+	if (*port == 0 && !get_dynamic_port(fd, family, port))
+	{
+		close(fd);
+		return 0;
+	}
 
 	/* get additional packet info on receive */
 	if (setsockopt(fd, sol, pktinfo, &on, sizeof(on)) < 0)
@@ -404,15 +449,40 @@ static int open_socket(private_socket_dynamic_socket_t *this,
 
 	/* enable UDP decapsulation on each socket */
 	if (!hydra->kernel_interface->enable_udp_decap(hydra->kernel_interface,
-												   fd, family, port))
+												   fd, family, *port))
 	{
 		DBG1(DBG_NET, "enabling UDP decapsulation for %s on port %d failed",
-			 family == AF_INET ? "IPv4" : "IPv6", port);
+			 family == AF_INET ? "IPv4" : "IPv6", *port);
 	}
 
 	return fd;
 }
 
+/**
+ * Get the first usable socket for an address family
+ */
+static dynsock_t *get_any_socket(private_socket_dynamic_socket_t *this,
+								 int family)
+{
+	dynsock_t *key, *value, *found = NULL;
+	enumerator_t *enumerator;
+
+	this->lock->read_lock(this->lock);
+	enumerator = this->sockets->create_enumerator(this->sockets);
+	while (enumerator->enumerate(enumerator, &key, &value))
+	{
+		if (value->family == family)
+		{
+			found = value;
+			break;
+		}
+	}
+	enumerator->destroy(enumerator);
+	this->lock->unlock(this->lock);
+
+	return found;
+}
+
 /**
  * Find/Create a socket to send from host
  */
@@ -433,7 +503,15 @@ static dynsock_t *find_socket(private_socket_dynamic_socket_t *this,
 	{
 		return skt;
 	}
-	fd = open_socket(this, family, port);
+	if (!port)
+	{
+		skt = get_any_socket(this, family);
+		if (skt)
+		{
+			return skt;
+		}
+	}
+	fd = open_socket(this, family, &port);
 	if (!fd)
 	{
 		return NULL;
@@ -457,7 +535,7 @@ METHOD(socket_t, sender, status_t,
 {
 	dynsock_t *skt;
 	host_t *src, *dst;
-	int port, family;
+	int family;
 	ssize_t len;
 	chunk_t data;
 	struct msghdr msg;
@@ -467,9 +545,7 @@ METHOD(socket_t, sender, status_t,
 	src = packet->get_source(packet);
 	dst = packet->get_destination(packet);
 	family = src->get_family(src);
-	port = src->get_port(src);
+	skt = find_socket(this, family, src->get_port(src));
-	port = port ?: CHARON_UDP_PORT;
-	skt = find_socket(this, family, port);
 	if (!skt)
 	{
 		return FAILED;
@@ -597,4 +673,3 @@ socket_dynamic_socket_t *socket_dynamic_socket_create()
 
 	return &this->public;
 }
-