Dynamically create and destroy sockets without fixed binds

src/config.c

@@ -434,7 +434,6 @@ bool fastd_read_config(fastd_context *ctx, fastd_config *conf, const char *filen
 }
 
 static void count_peers(fastd_context *ctx, fastd_config *conf) {
-	conf->n_peers = 0;
 	conf->n_floating = 0;
 	conf->n_v4 = 0;
 	conf->n_v6 = 0;
@@ -444,8 +443,6 @@ static void count_peers(fastd_context *ctx, fastd_config *conf) {
 
 	fastd_peer_config *peer;
 	for (peer = conf->peers; peer; peer = peer->next) {
-		conf->n_peers++;
-
 		switch (peer->address.sa.sa_family) {
 		case AF_UNSPEC:
 			if (peer->hostname)

src/fastd.c

@@ -256,6 +256,21 @@ static void bind_sockets(fastd_context *ctx) {
 	}
 }
 
+fastd_socket* fastd_socket_open(fastd_context *ctx, int af) {
+	const fastd_bind_address any_address = { .addr.sa.sa_family = af };
+
+	int fd = bind_socket(ctx, &any_address, true);
+	if (fd < 0)
+		return NULL;
+
+	fastd_socket *sock = malloc(sizeof(fastd_socket));
+
+	sock->fd = fd;
+	sock->addr = NULL;
+
+	return sock;
+}
+
 static void init_tuntap(fastd_context *ctx) {
 	struct ifreq ifr;
 
@@ -309,19 +324,10 @@ static void close_tuntap(fastd_context *ctx) {
 	free(ctx->ifname);
 }
 
-static void close_socket(fastd_context *ctx, fastd_socket *sock) {
-	if (sock->fd >= 0) {
-		if(close(sock->fd))
-			pr_error_errno(ctx, "closing socket: close");
-
-		sock->fd = -2;
-	}
-}
-
 static void close_sockets(fastd_context *ctx) {
 	unsigned i;
 	for (i = 0; i < ctx->n_socks; i++)
-		close_socket(ctx, &ctx->socks[i]);
+		fastd_socket_close(ctx, &ctx->socks[i]);
 
 	free(ctx->socks);
 }
@@ -555,8 +561,10 @@ static void init_peers(fastd_context *ctx) {
 	for (peer_conf = ctx->conf->peers; peer_conf; peer_conf = peer_conf->next) {
 		ctx->conf->protocol->peer_configure(ctx, peer_conf);
 
-		if (peer_conf->enabled)
+		if (peer_conf->enabled) {
 			fastd_peer_add(ctx, peer_conf);
+			ctx->n_peers++;
+		}
 	}
 }
 
@@ -574,7 +582,10 @@ static inline void update_time(fastd_context *ctx) {
 }
 
 static inline void send_handshake(fastd_context *ctx, fastd_peer *peer) {
-	if (peer->address.sa.sa_family && peer->sock) {
+	if (!fastd_peer_is_established(peer))
+		fastd_peer_reset_socket(ctx, peer);
+
+	if (peer->sock) {
 		if (timespec_diff(&ctx->now, &peer->last_handshake) < ctx->conf->min_handshake_interval*1000
 		    && fastd_peer_address_equal(&peer->address, &peer->last_handshake_address)) {
 			pr_debug(ctx, "not sending a handshake to %P as we sent one a short time ago", peer);
@@ -663,7 +674,7 @@ static void handle_tun(fastd_context *ctx) {
 	}
 }
 
-static void handle_socket(fastd_context *ctx, const fastd_socket *sock) {
+static void handle_socket(fastd_context *ctx, fastd_socket *sock) {
 	size_t max_len = PACKET_TYPE_LEN + methods_max_packet_size(ctx);
 	fastd_buffer buffer = fastd_buffer_alloc(max_len, methods_min_decrypt_head_space(ctx), methods_min_decrypt_tail_space(ctx));
 	uint8_t *packet_type;
@@ -752,17 +763,6 @@ static void handle_resolv_returns(fastd_context *ctx) {
 		peer->last_resolve_return = ctx->now;
 
 		if (fastd_peer_claim_address(ctx, peer, NULL, &resolve_return.addr)) {
-			if (!peer->sock) {
-				switch(resolve_return.addr.sa.sa_family) {
-				case AF_INET:
-					peer->sock = ctx->sock_default_v4;
-					break;
-
-				case AF_INET6:
-					peer->sock = ctx->sock_default_v6;
-				}
-			}
-
 			send_handshake(ctx, peer);
 		}
 		else {
@@ -781,28 +781,44 @@ static inline void handle_socket_error(fastd_context *ctx, fastd_socket *sock) {
 	else
 		pr_warn(ctx, "socket bind %I lost", &sock->addr->addr);
 
-	close_socket(ctx, sock);
+	fastd_socket_close(ctx, sock);
 }
 
 static void handle_input(fastd_context *ctx) {
-	struct pollfd fds[ctx->n_socks + 2];
+	const size_t n_fds = 2 + ctx->n_socks + ctx->n_peers;
+	struct pollfd fds[n_fds];
 	fds[0].fd = ctx->tunfd;
 	fds[0].events = POLLIN;
 	fds[1].fd = ctx->resolverfd;
 	fds[1].events = POLLIN;
 
 	unsigned i;
-	for (i = 0; i < ctx->n_socks; i++) {
+	for (i = 2; i < ctx->n_socks+2; i++) {
-		fds[i+2].fd = ctx->socks[i].fd;
+		fds[i].fd = ctx->socks[i-2].fd;
-		fds[i+2].events = POLLIN;
+		fds[i].events = POLLIN;
 	}
 
+	fastd_peer *peer;
+	for (peer = ctx->peers; peer; peer = peer->next) {
+		if (peer->sock && fastd_peer_is_socket_dynamic(peer))
+			fds[i].fd = peer->sock->fd;
+		else
+			fds[i].fd = -1;
+
+		fds[i].events = POLLIN;
+
+		i++;
+	}
+
+	if (i != n_fds)
+		exit_bug(ctx, "fd count mismatch");
+
 	int timeout = fastd_task_timeout(ctx);
 
 	if (timeout < 0 || timeout > 60000)
 		timeout = 60000; /* call maintenance at least once a minute */
 
-	int ret = poll(fds, ctx->n_socks + 2, timeout);
+	int ret = poll(fds, n_fds, timeout);
 	if (ret < 0) {
 		if (errno == EINTR)
 			return;
@@ -817,15 +833,24 @@ static void handle_input(fastd_context *ctx) {
 	if (fds[1].revents & POLLIN)
 		handle_resolv_returns(ctx);
 
-	for (i = 0; i < ctx->n_socks; i++) {
+	for (i = 2; i < ctx->n_socks+2; i++) {
-		if (fds[i+2].revents & (POLLERR|POLLHUP|POLLNVAL)) {
+		if (fds[i].revents & (POLLERR|POLLHUP|POLLNVAL))
-			handle_socket_error(ctx, &ctx->socks[i]);
+			handle_socket_error(ctx, &ctx->socks[i-2]);
-			continue;
+		else if (fds[i].revents & POLLIN)
-		}
+			handle_socket(ctx, &ctx->socks[i-2]);
-
-		if (fds[i+2].revents & POLLIN)
-			handle_socket(ctx, &ctx->socks[i]);
 	}
+
+	for (peer = ctx->peers; peer; peer = peer->next) {
+		if (fds[i].revents & (POLLERR|POLLHUP|POLLNVAL))
+			fastd_peer_reset_socket(ctx, peer);
+		else if (fds[i].revents & POLLIN)
+			handle_socket(ctx, peer->sock);
+
+		i++;
+	}
+
+	if (i != n_fds)
+		exit_bug(ctx, "fd count mismatch");
 }
 
 static void cleanup_peers(fastd_context *ctx) {

src/fastd.h

@@ -73,7 +73,7 @@ struct _fastd_protocol {
 	void (*peer_configure)(fastd_context *ctx, fastd_peer_config *peer_conf);
 
 	void (*handshake_init)(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, const fastd_peer_config *peer_conf);
-	void (*handshake_handle)(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, const fastd_peer_config *peer_conf, const fastd_handshake *handshake, const fastd_method *method);
+	void (*handshake_handle)(fastd_context *ctx, fastd_socket *sock, const fastd_peer_address *address, const fastd_peer_config *peer_conf, const fastd_handshake *handshake, const fastd_method *method);
 
 	void (*handle_recv)(fastd_context *ctx, fastd_peer *peer, fastd_buffer buffer);
 	void (*send)(fastd_context *ctx, fastd_peer *peer, fastd_buffer buffer);
@@ -189,7 +189,6 @@ struct _fastd_config {
 	fastd_string_stack *peer_dirs;
 	fastd_peer_config *peers;
 
-	unsigned n_peers;
 	unsigned n_floating;
 	unsigned n_v4;
 	unsigned n_v6;
@@ -228,6 +227,7 @@ struct _fastd_context {
 
 	struct timespec now;
 
+	unsigned n_peers;
 	fastd_peer *peers;
 	fastd_queue task_queue;
 
@@ -268,6 +268,8 @@ void fastd_send(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_a
 void fastd_send_handshake(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, fastd_buffer buffer);
 void fastd_handle_receive(fastd_context *ctx, fastd_peer *peer, fastd_buffer buffer);
 
+fastd_socket* fastd_socket_open(fastd_context *ctx, int af);
+
 void fastd_resolve_peer(fastd_context *ctx, fastd_peer *peer);
 
 int fastd_vsnprintf(const fastd_context *ctx, char *buffer, size_t size, const char *format, va_list ap);
@@ -394,6 +396,15 @@ static inline void fastd_string_stack_free(fastd_string_stack *str) {
 	}
 }
 
+static inline void fastd_socket_close(fastd_context *ctx, fastd_socket *sock) {
+	if (sock->fd >= 0) {
+		if(close(sock->fd))
+			pr_error_errno(ctx, "closing socket: close");
+
+		sock->fd = -2;
+	}
+}
+
 static inline bool timespec_after(const struct timespec *tp1, const struct timespec *tp2) {
 	return (tp1->tv_sec > tp2->tv_sec ||
 		(tp1->tv_sec == tp2->tv_sec && tp1->tv_nsec > tp2->tv_nsec));

src/handshake.c

@@ -180,7 +180,7 @@ static fastd_string_stack* parse_string_list(uint8_t *data, size_t len) {
 	return ret;
 }
 
-void fastd_handshake_handle(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, const fastd_peer_config *peer_conf, fastd_buffer buffer) {
+void fastd_handshake_handle(fastd_context *ctx, fastd_socket *sock, const fastd_peer_address *address, const fastd_peer_config *peer_conf, fastd_buffer buffer) {
 	if (buffer.len < sizeof(fastd_packet)) {
 		pr_warn(ctx, "received a short handshake from %I", address);
 		goto end_free;

src/handshake.h

@@ -71,7 +71,7 @@ struct _fastd_handshake {
 fastd_buffer fastd_handshake_new_init(fastd_context *ctx, size_t tail_space);
 fastd_buffer fastd_handshake_new_reply(fastd_context *ctx, const fastd_handshake *handshake, const fastd_method *method, size_t tail_space);
 
-void fastd_handshake_handle(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, const fastd_peer_config *peer_conf, fastd_buffer buffer);
+void fastd_handshake_handle(fastd_context *ctx, fastd_socket *sock, const fastd_peer_address *address, const fastd_peer_config *peer_conf, fastd_buffer buffer);
 
 
 static inline void fastd_handshake_add(fastd_context *ctx, fastd_buffer *buffer, fastd_handshake_record_type type, size_t len, const void *data) {

src/peer.c

@@ -146,10 +146,46 @@ static void on_disestablish(fastd_context *ctx, fastd_peer *peer) {
 	free(cwd);
 }
 
-static inline void reset_peer(fastd_context *ctx, fastd_peer *peer) {
+static inline void free_socket(fastd_context *ctx, fastd_peer *peer) {
+	if (peer->sock) {
+		if (fastd_peer_is_socket_dynamic(peer)) {
+			fastd_socket_close(ctx, peer->sock);
+			free(peer->sock);
+		}
+		peer->sock = NULL;
+	}
+}
+
+void fastd_peer_reset_socket(fastd_context *ctx, fastd_peer *peer) {
+	if (!fastd_peer_is_socket_dynamic(peer))
+		return;
+
+	pr_debug(ctx, "resetting socket for peer %P", peer);
+
+	free_socket(ctx, peer);
+
+	switch (peer->address.sa.sa_family) {
+	case AF_INET:
+		if (ctx->sock_default_v4)
+			peer->sock = ctx->sock_default_v4;
+		else
+			peer->sock = fastd_socket_open(ctx, AF_INET);
+		break;
+
+	case AF_INET6:
+		if (ctx->sock_default_v6)
+			peer->sock = ctx->sock_default_v6;
+		else
+			peer->sock = fastd_socket_open(ctx, AF_INET6);
+	}
+}
+
+static void reset_peer(fastd_context *ctx, fastd_peer *peer) {
 	if (peer->established)
 		on_disestablish(ctx, peer);
 
+	free_socket(ctx, peer);
+
 	ctx->conf->protocol->reset_peer_state(ctx, peer);
 
 	int i, deleted = 0;
@@ -167,7 +203,7 @@ static inline void reset_peer(fastd_context *ctx, fastd_peer *peer) {
 	fastd_task_delete_peer(ctx, peer);
 }
 
-static inline void setup_peer(fastd_context *ctx, fastd_peer *peer) {
+static void setup_peer(fastd_context *ctx, fastd_peer *peer) {
 	if (peer->config->hostname)
 		peer->address.sa.sa_family = AF_UNSPEC;
 	else
@@ -175,19 +211,6 @@ static inline void setup_peer(fastd_context *ctx, fastd_peer *peer) {
 
 	peer->established = false;
 
-	switch (peer->address.sa.sa_family) {
-	case AF_INET:
-		peer->sock = ctx->sock_default_v4;
-		break;
-
-	case AF_INET6:
-		peer->sock = ctx->sock_default_v6;
-		break;
-
-	default:
-		peer->sock = NULL;
-	}
-
 	peer->last_resolve = (struct timespec){0, 0};
 	peer->last_resolve_return = (struct timespec){0, 0};
 	peer->seen = (struct timespec){0, 0};
@@ -292,7 +315,7 @@ bool fastd_peer_address_equal(const fastd_peer_address *addr1, const fastd_peer_
 	return true;
 }
 
-bool fastd_peer_claim_address(fastd_context *ctx, fastd_peer *new_peer, const fastd_socket *sock, const fastd_peer_address *addr) {
+bool fastd_peer_claim_address(fastd_context *ctx, fastd_peer *new_peer, fastd_socket *sock, const fastd_peer_address *addr) {
 	if (addr->sa.sa_family != AF_UNSPEC) {
 		fastd_peer *peer;
 		for (peer = ctx->peers; peer; peer = peer->next) {
@@ -316,8 +339,10 @@ bool fastd_peer_claim_address(fastd_context *ctx, fastd_peer *new_peer, const fa
 	}
 
 	new_peer->address = *addr;
-	if (sock)
+	if (sock && sock->addr && sock != new_peer->sock) {
+		free_socket(ctx, new_peer);
 		new_peer->sock = sock;
+	}
 
 	return true;
 }
@@ -358,6 +383,7 @@ fastd_peer* fastd_peer_add(fastd_context *ctx, fastd_peer_config *peer_conf) {
 
 	peer->config = peer_conf;
 	peer->protocol_state = NULL;
+	peer->sock = NULL;
 	setup_peer(ctx, peer);
 
 	pr_verbose(ctx, "adding peer %P", peer);

src/peer.h

@@ -35,7 +35,7 @@ struct _fastd_peer {
 
 	const fastd_peer_config *config;
 
-	const fastd_socket *sock;
+	fastd_socket *sock;
 	fastd_peer_address address;
 
 	bool established;
@@ -88,7 +88,8 @@ void fastd_peer_reset(fastd_context *ctx, fastd_peer *peer);
 void fastd_peer_delete(fastd_context *ctx, fastd_peer *peer);
 fastd_peer* fastd_peer_add(fastd_context *ctx, fastd_peer_config *conf);
 void fastd_peer_set_established(fastd_context *ctx, fastd_peer *peer);
-bool fastd_peer_claim_address(fastd_context *ctx, fastd_peer *peer, const fastd_socket *sock, const fastd_peer_address *addr);
+bool fastd_peer_claim_address(fastd_context *ctx, fastd_peer *peer, fastd_socket *sock, const fastd_peer_address *addr);
+void fastd_peer_reset_socket(fastd_context *ctx, fastd_peer *peer);
 
 const fastd_eth_addr* fastd_get_source_address(const fastd_context *ctx, fastd_buffer buffer);
 const fastd_eth_addr* fastd_get_dest_address(const fastd_context *ctx, fastd_buffer buffer);
@@ -119,6 +120,10 @@ static inline void fastd_peer_seen(fastd_context *ctx, fastd_peer *peer) {
 	peer->seen = ctx->now;
 }
 
+static inline bool fastd_peer_is_socket_dynamic(const fastd_peer *peer) {
+	return (!peer->sock || !peer->sock->addr);
+}
+
 static inline bool fastd_eth_addr_is_unicast(const fastd_eth_addr *addr) {
 	return ((addr->data[0] & 1) == 0);
 }

src/protocol_ec25519_fhmqvc.c

@@ -305,7 +305,7 @@ static void respond_handshake(fastd_context *ctx, const fastd_socket *sock, cons
 	fastd_send_handshake(ctx, sock, address, buffer);
 }
 
-static bool establish(fastd_context *ctx, fastd_peer *peer, const fastd_method *method, const fastd_socket *sock, const fastd_peer_address *address, bool initiator,
+static bool establish(fastd_context *ctx, fastd_peer *peer, const fastd_method *method, fastd_socket *sock, const fastd_peer_address *address, bool initiator,
 		      const ecc_public_key_256 *A, const ecc_public_key_256 *B, const ecc_public_key_256 *X,
 		      const ecc_public_key_256 *Y, const ecc_public_key_256 *sigma, uint64_t serial) {
 	uint8_t hashinput[5*PUBLICKEYBYTES];
@@ -362,7 +362,7 @@ static bool establish(fastd_context *ctx, fastd_peer *peer, const fastd_method *
 	return true;
 }
 
-static void finish_handshake(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, fastd_peer *peer, const handshake_key *handshake_key, const ecc_public_key_256 *peer_handshake_key,
+static void finish_handshake(fastd_context *ctx, fastd_socket *sock, const fastd_peer_address *address, fastd_peer *peer, const handshake_key *handshake_key, const ecc_public_key_256 *peer_handshake_key,
 			     const fastd_handshake *handshake, const fastd_method *method) {
 	pr_debug(ctx, "finishing handshake with %P[%I]...", peer, address);
 
@@ -433,7 +433,7 @@ static void finish_handshake(fastd_context *ctx, const fastd_socket *sock, const
 	fastd_send_handshake(ctx, sock, address, buffer);
 }
 
-static void handle_finish_handshake(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, fastd_peer *peer, const handshake_key *handshake_key, const ecc_public_key_256 *peer_handshake_key,
+static void handle_finish_handshake(fastd_context *ctx, fastd_socket *sock, const fastd_peer_address *address, fastd_peer *peer, const handshake_key *handshake_key, const ecc_public_key_256 *peer_handshake_key,
 				    const fastd_handshake *handshake, const fastd_method *method) {
 	pr_debug(ctx, "handling handshake finish with %P[%I]...", peer, address);
 
@@ -522,7 +522,7 @@ static inline bool has_field(const fastd_handshake *handshake, uint8_t type, siz
 	return (handshake->records[type].length == length);
 }
 
-static void protocol_handshake_handle(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, const fastd_peer_config *peer_conf, const fastd_handshake *handshake, const fastd_method *method) {
+static void protocol_handshake_handle(fastd_context *ctx, fastd_socket *sock, const fastd_peer_address *address, const fastd_peer_config *peer_conf, const fastd_handshake *handshake, const fastd_method *method) {
 	handshake_key *handshake_key;
 	char *peer_version_name = NULL;