Add support for multiple binds

10 files changed, 284 insertions, 135 deletions

diff --git a/src/config.c b/src/config.c
index 4eee712..be67e2b 100644
--- a/src/config.c
+++ b/src/config.c
@@ -629,26 +629,34 @@ static void option_bind(fastd_context *ctx, fastd_config *conf, const char *arg)
 		l = 0;
 	}
 
-	if (strcmp(addrstr, "any") == 0) {
-		conf->bind_addr_in.sin_addr.s_addr = htonl(INADDR_ANY);
-		conf->bind_addr_in.sin_port = htons(l);
+	fastd_bind_address *addr = calloc(1, sizeof(fastd_bind_address));
+	addr->next = conf->bind_addrs;
+	conf->bind_addrs = addr;
 
-		conf->bind_addr_in6.sin6_addr = in6addr_any;
-		conf->bind_addr_in6.sin6_port = htons(l);
+	if (strcmp(addrstr, "any") == 0) {
+		/* nothing to do */
 	}
 	else if (arg[0] == '[') {
-		conf->bind_addr_in6.sin6_family = AF_INET6;
-		if (inet_pton(AF_INET6, addrstr, &conf->bind_addr_in6.sin6_addr) != 1)
+		addr->addr.in6.sin6_family = AF_INET6;
+		addr->addr.in6.sin6_port = htons(l);
+
+		if (inet_pton(AF_INET6, addrstr, &addr->addr.in6.sin6_addr) != 1)
 			exit_error(ctx, "invalid bind address `%s'", addrstr);
-		conf->bind_addr_in6.sin6_port = htons(l);
 	}
 	else {
-		conf->bind_addr_in.sin_family = AF_INET;
-		if (inet_pton(AF_INET, addrstr, &conf->bind_addr_in.sin_addr) != 1)
+		addr->addr.in.sin_family = AF_INET;
+		addr->addr.in.sin_port = htons(l);
+
+		if (inet_pton(AF_INET, addrstr, &addr->addr.in.sin_addr) != 1)
 			exit_error(ctx, "invalid bind address `%s'", addrstr);
-		conf->bind_addr_in.sin_port = htons(l);
 	}
 
+	if (!conf->bind_addr_default_v4 && addr->addr.sa.sa_family != AF_INET6)
+		conf->bind_addr_default_v4 = addr;
+
+	if (!conf->bind_addr_default_v6 && addr->addr.sa.sa_family != AF_INET)
+		conf->bind_addr_default_v6 = addr;
+
 	free(addrstr);
 }
 
@@ -886,6 +894,13 @@ void fastd_config_release(fastd_context *ctx, fastd_config *conf) {
 		conf->log_files = next;
 	}
 
+	while (conf->bind_addrs) {
+		fastd_bind_address *next = conf->bind_addrs->next;
+		free(conf->bind_addrs->bindtodev);
+		free(conf->bind_addrs);
+		conf->bind_addrs = next;
+	}
+
 	free(conf->ifname);
 	free(conf->secret);
 	free(conf->on_up);
diff --git a/src/config.y b/src/config.y
index 2b1af0f..d87c151 100644
--- a/src/config.y
+++ b/src/config.y
@@ -187,21 +187,32 @@ log_level:	TOK_FATAL	{ $$ = LOG_CRIT; }
 interface:	TOK_STRING	{ free(conf->ifname); conf->ifname = strdup($1->str); }
 	;
 
-bind:		TOK_ADDR maybe_port {
-			conf->bind_addr_in.sin_family = AF_INET;
-			conf->bind_addr_in.sin_addr = $1;
-			conf->bind_addr_in.sin_port = htons($2);
+bind_new:	{
+			fastd_bind_address *addr = calloc(1, sizeof(fastd_bind_address));
+			addr->next = conf->bind_addrs;
+			conf->bind_addrs = addr;
 		}
-	|	TOK_ADDR6 maybe_port {
-			conf->bind_addr_in6.sin6_family = AF_INET6;
-			conf->bind_addr_in6.sin6_addr = $1;
-			conf->bind_addr_in6.sin6_port = htons($2);
+
+bind:		bind_new TOK_ADDR maybe_port {
+			conf->bind_addrs->addr.in.sin_family = AF_INET;
+			conf->bind_addrs->addr.in.sin_addr = $2;
+			conf->bind_addrs->addr.in.sin_port = htons($3);
+			if (!conf->bind_addr_default_v4)
+				conf->bind_addr_default_v4 = conf->bind_addrs;
+		}
+	|	bind_new TOK_ADDR6 maybe_port {
+			conf->bind_addrs->addr.in6.sin6_family = AF_INET6;
+			conf->bind_addrs->addr.in6.sin6_addr = $2;
+			conf->bind_addrs->addr.in6.sin6_port = htons($3);
+			if (!conf->bind_addr_default_v6)
+				conf->bind_addr_default_v6 = conf->bind_addrs;
 		}
-	|	TOK_ANY maybe_port {
-			conf->bind_addr_in.sin_addr.s_addr = htonl(INADDR_ANY);
-			conf->bind_addr_in.sin_port = htons($2);
-			conf->bind_addr_in6.sin6_addr = in6addr_any;
-			conf->bind_addr_in6.sin6_port = htons($2);
+	|	bind_new TOK_ANY maybe_port {
+			conf->bind_addrs->addr.in.sin_port = htons($3);
+			if (!conf->bind_addr_default_v4)
+				conf->bind_addr_default_v4 = conf->bind_addrs;
+			if (!conf->bind_addr_default_v6)
+				conf->bind_addr_default_v6 = conf->bind_addrs;
 		}
 	;
 
diff --git a/src/fastd.c b/src/fastd.c
index 5388384..fc6f016 100644
--- a/src/fastd.c
+++ b/src/fastd.c
@@ -146,62 +146,141 @@ static void crypto_free(fastd_context *ctx) {
 #endif
 }
 
+
+static unsigned max_sockets(const fastd_config *conf) {
+	unsigned n = 0;
+	fastd_bind_address *addr;
+
+	for (addr = conf->bind_addrs; addr; addr = addr->next)
+		n++;
+
+	return n;
+}
+
 static void init_sockets(fastd_context *ctx) {
-	struct sockaddr_in addr_in = ctx->conf->bind_addr_in;
-	struct sockaddr_in6 addr_in6 = ctx->conf->bind_addr_in6;
+	static const fastd_bind_address bind_any = {};
 
-	if (addr_in.sin_family == AF_UNSPEC && addr_in6.sin6_family == AF_UNSPEC) {
-		if (ctx->conf->peer_dirs || ctx->conf->n_floating || ctx->conf->n_v4 || ctx->conf->n_dynamic || ctx->conf->n_dynamic_v4)
-			addr_in.sin_family = AF_INET;
+	const fastd_bind_address *addr = ctx->conf->bind_addrs;
+	const fastd_bind_address *default_v4 = ctx->conf->bind_addr_default_v4;
+	const fastd_bind_address *default_v6 = ctx->conf->bind_addr_default_v6;
 
-		if (ctx->conf->peer_dirs || ctx->conf->n_floating || ctx->conf->n_v6 || ctx->conf->n_dynamic || ctx->conf->n_dynamic_v6)
-			addr_in6.sin6_family = AF_INET6;
-	}
+	if (!addr)
+		addr = default_v4 = default_v6 = &bind_any;
 
-	if (addr_in.sin_family == AF_UNSPEC && ctx->conf->n_v4)
-		pr_warn(ctx, "there are IPv4 peers defined, but bind is explicitly set to IPv6");
+	unsigned n_v4 = 0, n_v6 = 0;
+	bool info_ipv6 = true;
 
-	if (addr_in6.sin6_family == AF_UNSPEC && ctx->conf->n_v6)
-		pr_warn(ctx, "there are IPv6 peers defined, but bind is explicitly set to IPv4");
+	ctx->socks = calloc(max_sockets(ctx->conf), sizeof(fastd_socket));
 
-	if (addr_in.sin_family == AF_INET) {
-		pr_debug(ctx, "initializing IPv4 socket...");
+	while (addr) {
+		int fd = -1;
+		int af = AF_UNSPEC;
 
-		if ((ctx->sockfd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
-			exit_errno(ctx, "socket");
+		if (addr->addr.sa.sa_family != AF_INET) {
+			fd = socket(PF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+			if (fd < 0) {
+				if (info_ipv6) {
+					pr_warn(ctx, "there seems to be no IPv6 support; explicitely bind to an IPv4 address (or 0.0.0.0) to disable this warning");
+					info_ipv6 = false;
+				}
+			}
+			else {
+				af = AF_INET6;
 
-		if (bind(ctx->sockfd, (struct sockaddr*)&addr_in, sizeof(struct sockaddr_in)))
-			exit_errno(ctx, "bind");
+				int val = (addr->addr.sa.sa_family == AF_INET6);
+				if (setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val))) {
+					pr_warn_errno(ctx, "setsockopt");
+					goto error;
+				}
+			}
+		}
+		if (fd < 0 && addr->addr.sa.sa_family != AF_INET6) {
+			fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
+			if (fd < 0)
+				exit_errno(ctx, "unable to create socket");
+			else
+				af = AF_INET;
+		}
 
-		pr_debug(ctx, "IPv4 socket initialized.");
-	}
-	else {
-		ctx->sockfd = -1;
-	}
+		if (fd < 0)
+			goto error;
+
+		if (addr->bindtodev) {
+			if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, addr->bindtodev, strlen(addr->bindtodev))) {
+				pr_warn_errno(ctx, "setsockopt: unable to bind to device");
+				goto error;
+			}
+		}
+
+		fastd_peer_address bind_address = addr->addr;
 
-	if (addr_in6.sin6_family == AF_INET6) {
-		pr_debug(ctx, "initializing IPv6 socket...");
+		if (bind_address.sa.sa_family == AF_UNSPEC) {
+			memset(&bind_address, 0, sizeof(bind_address));
+			bind_address.sa.sa_family = af;
 
-		if ((ctx->sock6fd = socket(PF_INET6, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
-			if (ctx->sockfd >= 0)
-				pr_warn_errno(ctx, "socket");
+			if (af == AF_INET6)
+				bind_address.in6.sin6_port = addr->addr.in.sin_port;
 			else
-				exit_errno(ctx, "socket");
+				bind_address.in.sin_port = addr->addr.in.sin_port;
+		}
+
+		if (bind(fd, (struct sockaddr*)&bind_address, af == AF_INET6 ? sizeof(struct sockaddr_in6) : sizeof(struct sockaddr_in))) {
+			pr_warn(ctx, "bind");
+			goto error;
+		}
+
+		ctx->socks[ctx->n_socks] = (fastd_socket){fd, addr};
+
+		if (af == AF_INET6) {
+			if (addr == default_v6)
+				ctx->sock_default_v6 = &ctx->socks[ctx->n_socks];
+
+			n_v6++;
+
+			if (addr->addr.sa.sa_family == AF_UNSPEC) {
+				if (addr == default_v4)
+					ctx->sock_default_v4 = &ctx->socks[ctx->n_socks];
+
+				n_v4++;
+			}
 		}
 		else {
-			int val = 1;
-			if (setsockopt(ctx->sock6fd, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val)))
-				exit_errno(ctx, "setsockopt");
+			if (addr == default_v4)
+				ctx->sock_default_v4 = &ctx->socks[ctx->n_socks];
 
-			if (bind(ctx->sock6fd, (struct sockaddr*)&addr_in6, sizeof(struct sockaddr_in6)))
-				exit_errno(ctx, "bind");
+			n_v4++;
+		}
 
-			pr_debug(ctx, "IPv6 socket initialized.");
+		ctx->n_socks++;
+
+		addr = addr->next;
+		continue;
+
+	error:
+		if (fd >= 0) {
+			if (close(fd))
+				pr_error_errno(ctx, "close");
 		}
+
+		if (addr->bindtodev)
+			pr_warn(ctx, "unable to bind to %I on `%s'", addr->addr, addr->bindtodev);
+		else
+			pr_warn(ctx, "unable to bind to %I", addr->addr);
+
+		if (addr == default_v4 || addr == default_v6)
+			exit_error(ctx, "unable to bind to default address");
+
+		addr = addr->next;
 	}
-	else {
-		ctx->sock6fd = -1;
-	}
+
+	if (!ctx->n_socks)
+		exit_error(ctx, "all bind attempts failed");
+
+	if (!n_v4 && ctx->conf->n_v4)
+		pr_warn(ctx, "there are IPv4 peers defined, but there was no successful IPv4 bind");
+
+	if (!n_v6 && ctx->conf->n_v6)
+		pr_warn(ctx, "there are IPv6 peers defined, but there was no successful IPv4 bind");
 }
 
 static void init_tuntap(fastd_context *ctx) {
@@ -236,9 +315,7 @@ static void init_tuntap(fastd_context *ctx) {
 
 	ctx->ifname = strndup(ifr.ifr_name, IFNAMSIZ);
 
-	int ctl_sock = ctx->sockfd;
-	if (ctl_sock < 0)
-		ctl_sock = ctx->sock6fd;
+	int ctl_sock = ctx->socks[0].fd;
 
 	ifr.ifr_mtu = ctx->conf->mtu;
 	if (ioctl(ctl_sock, SIOCSIFMTU, &ifr) < 0)
@@ -255,15 +332,13 @@ static void close_tuntap(fastd_context *ctx) {
 }
 
 static void close_sockets(fastd_context *ctx) {
-	if (ctx->sockfd >= 0) {
-		if(close(ctx->sockfd))
+	unsigned i;
+	for (i = 0; i < ctx->n_socks; i++) {
+		if(close(ctx->socks[i].fd))
 			pr_warn_errno(ctx, "closing IPv4 socket: close");
 	}
 
-	if (ctx->sock6fd >= 0) {
-		if(close(ctx->sock6fd))
-			pr_warn_errno(ctx, "closing IPv6 socket: close");
-	}
+	free(ctx->socks);
 }
 
 static size_t methods_max_packet_size(fastd_context *ctx) {
@@ -347,8 +422,10 @@ static size_t methods_min_decrypt_tail_space(fastd_context *ctx) {
 	return ret;
 }
 
-static void fastd_send_type(fastd_context *ctx, const fastd_peer_address *address, uint8_t packet_type, fastd_buffer buffer) {
-	int sockfd;
+static void fastd_send_type(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, uint8_t packet_type, fastd_buffer buffer) {
+	if (!sock)
+		exit_bug(ctx, "send: sock == NULL");
+
 	struct msghdr msg;
 	memset(&msg, 0, sizeof(msg));
 
@@ -356,13 +433,11 @@ static void fastd_send_type(fastd_context *ctx, const fastd_peer_address *addres
 	case AF_INET:
 		msg.msg_name = (void*)&address->in;
 		msg.msg_namelen = sizeof(struct sockaddr_in);
-		sockfd = ctx->sockfd;
 		break;
 
 	case AF_INET6:
 		msg.msg_name = (void*)&address->in6;
 		msg.msg_namelen = sizeof(struct sockaddr_in6);
-		sockfd = ctx->sock6fd;
 		break;
 
 	default:
@@ -379,7 +454,7 @@ static void fastd_send_type(fastd_context *ctx, const fastd_peer_address *addres
 
 	int ret;
 	do {
-		ret = sendmsg(sockfd, &msg, 0);
+		ret = sendmsg(sock->fd, &msg, 0);
 	} while (ret < 0 && errno == EINTR);
 
 	if (ret < 0)
@@ -388,12 +463,12 @@ static void fastd_send_type(fastd_context *ctx, const fastd_peer_address *addres
 	fastd_buffer_free(buffer);
 }
 
-void fastd_send(fastd_context *ctx, const fastd_peer_address *address, fastd_buffer buffer) {
-	fastd_send_type(ctx, address, PACKET_DATA, buffer);
+void fastd_send(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, fastd_buffer buffer) {
+	fastd_send_type(ctx, sock, address, PACKET_DATA, buffer);
 }
 
-void fastd_send_handshake(fastd_context *ctx, const fastd_peer_address *address, fastd_buffer buffer) {
-	fastd_send_type(ctx, address, PACKET_HANDSHAKE, buffer);
+void fastd_send_handshake(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, fastd_buffer buffer) {
+	fastd_send_type(ctx, sock, address, PACKET_HANDSHAKE, buffer);
 }
 
 void fastd_handle_receive(fastd_context *ctx, fastd_peer *peer, fastd_buffer buffer) {
@@ -514,7 +589,7 @@ 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 != AF_UNSPEC) {
+	if (peer->address.sa.sa_family && 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);
@@ -523,7 +598,7 @@ static inline void send_handshake(fastd_context *ctx, fastd_peer *peer) {
 			pr_debug(ctx, "sending handshake to %P...", peer);
 			peer->last_handshake = ctx->now;
 			peer->last_handshake_address = peer->address;
-			ctx->conf->protocol->handshake_init(ctx, &peer->address, peer->config);
+			ctx->conf->protocol->handshake_init(ctx, peer->sock, &peer->address, peer->config);
 		}
 	}
 
@@ -603,7 +678,7 @@ static void handle_tun(fastd_context *ctx) {
 	}
 }
 
-static void handle_socket(fastd_context *ctx, int sockfd) {
+static void handle_socket(fastd_context *ctx, const 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;
@@ -611,7 +686,7 @@ static void handle_socket(fastd_context *ctx, int sockfd) {
 	fastd_peer_address recvaddr;
 	socklen_t recvaddrlen = sizeof(recvaddr);
 			
-	ssize_t len = recvfrom(sockfd, buffer.data, buffer.len, 0, (struct sockaddr*)&recvaddr, &recvaddrlen);
+	ssize_t len = recvfrom(sock->fd, buffer.data, buffer.len, 0, (struct sockaddr*)&recvaddr, &recvaddrlen);
 	if (len < 0) {
 		if (errno != EINTR)
 			pr_warn(ctx, "recvfrom: %s", strerror(errno));
@@ -638,7 +713,7 @@ static void handle_socket(fastd_context *ctx, int sockfd) {
 			break;
 
 		case PACKET_HANDSHAKE:
-			fastd_handshake_handle(ctx, &recvaddr, peer->config, buffer);
+			fastd_handshake_handle(ctx, sock, &recvaddr, peer->config, buffer);
 			break;
 
 		default:
@@ -651,11 +726,11 @@ static void handle_socket(fastd_context *ctx, int sockfd) {
 		switch (*packet_type) {
 		case PACKET_DATA:
 			fastd_buffer_free(buffer);
-			ctx->conf->protocol->handshake_init(ctx, &recvaddr, NULL);
+			ctx->conf->protocol->handshake_init(ctx, sock, &recvaddr, NULL);
 			break;
 
 		case PACKET_HANDSHAKE:
-			fastd_handshake_handle(ctx, &recvaddr, NULL, buffer);
+			fastd_handshake_handle(ctx, sock, &recvaddr, NULL, buffer);
 			break;
 
 		default:
@@ -691,7 +766,18 @@ static void handle_resolv_returns(fastd_context *ctx) {
 
 		peer->last_resolve_return = ctx->now;
 
-		if (fastd_peer_claim_address(ctx, peer, &resolve_return.addr)) {
+		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 {
@@ -705,22 +791,24 @@ static void handle_resolv_returns(fastd_context *ctx) {
 }
 
 static void handle_input(fastd_context *ctx) {
-	struct pollfd fds[4];
+	struct pollfd fds[ctx->n_socks + 2];
 	fds[0].fd = ctx->tunfd;
 	fds[0].events = POLLIN;
-	fds[1].fd = ctx->sockfd;
+	fds[1].fd = ctx->resolverfd;
 	fds[1].events = POLLIN;
-	fds[2].fd = ctx->sock6fd;
-	fds[2].events = POLLIN;
-	fds[3].fd = ctx->resolverfd;
-	fds[3].events = POLLIN;
+
+	unsigned i;
+	for (i = 0; i < ctx->n_socks; i++) {
+		fds[i+2].fd = ctx->socks[i].fd;
+		fds[i+2].events = POLLIN;
+	}
 
 	int timeout = fastd_task_timeout(ctx);
 
 	if (timeout < 0 || timeout > 60000)
 		timeout = 60000; /* call maintenance at least once a minute */
 
-	int ret = poll(fds, 4, timeout);
+	int ret = poll(fds, ctx->n_socks + 2, timeout);
 	if (ret < 0) {
 		if (errno == EINTR)
 			return;
@@ -731,13 +819,14 @@ static void handle_input(fastd_context *ctx) {
 	update_time(ctx);
 
 	if (fds[0].revents & POLLIN)
-	  handle_tun(ctx);
+		handle_tun(ctx);
 	if (fds[1].revents & POLLIN)
-		handle_socket(ctx, ctx->sockfd);
-	if (fds[2].revents & POLLIN)
-		handle_socket(ctx, ctx->sock6fd);
-	if (fds[3].revents & POLLIN)
 		handle_resolv_returns(ctx);
+
+	for (i = 0; i < ctx->n_socks; i++) {
+		if (fds[i+2].revents & POLLIN)
+			handle_socket(ctx, &ctx->socks[i]);
+	}
 }
 
 static void cleanup_peers(fastd_context *ctx) {
@@ -875,7 +964,6 @@ int main(int argc, char *argv[]) {
 			init_log(&ctx);
 
 			fastd_reconfigure(&ctx, &conf);
-
 		}
 
 		pthread_sigmask(SIG_SETMASK, &oldset, NULL);
diff --git a/src/fastd.h b/src/fastd.h
index 1694105..cf5aaf1 100644
--- a/src/fastd.h
+++ b/src/fastd.h
@@ -71,8 +71,8 @@ struct _fastd_protocol {
 	fastd_protocol_config* (*init)(fastd_context *ctx);
 	void (*peer_configure)(fastd_context *ctx, fastd_peer_config *peer_conf);
 
-	void (*handshake_init)(fastd_context *ctx, const fastd_peer_address *address, const fastd_peer_config *peer_conf);
-	void (*handshake_handle)(fastd_context *ctx, const fastd_peer_address *address, const fastd_peer_config *peer_conf, const fastd_handshake *handshake, const fastd_method *method);
+	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 (*handle_recv)(fastd_context *ctx, fastd_peer *peer, fastd_buffer buffer);
 	void (*send)(fastd_context *ctx, fastd_peer *peer, fastd_buffer buffer);
@@ -131,6 +131,17 @@ struct _fastd_log_fd {
 	int fd;
 };
 
+struct _fastd_bind_address {
+	fastd_bind_address *next;
+	fastd_peer_address addr;
+	char *bindtodev;
+};
+
+struct _fastd_socket {
+	int fd;
+	const fastd_bind_address *addr;
+};
+
 struct _fastd_config {
 	int log_stderr_level;
 	int log_syslog_level;
@@ -149,8 +160,10 @@ struct _fastd_config {
 
 	char *ifname;
 
-	struct sockaddr_in bind_addr_in;
-	struct sockaddr_in6 bind_addr_in6;
+	fastd_bind_address *bind_addrs;
+
+	fastd_bind_address *bind_addr_default_v4;
+	fastd_bind_address *bind_addr_default_v6;
 
 	uint16_t mtu;
 	fastd_mode mode;
@@ -219,8 +232,12 @@ struct _fastd_context {
 	int resolvewfd;
 
 	int tunfd;
-	int sockfd;
-	int sock6fd;
+
+	unsigned n_socks;
+	fastd_socket *socks;
+
+	fastd_socket *sock_default_v4;
+	fastd_socket *sock_default_v6;
 
 #ifdef USE_CRYPTO_AES128CTR
 	fastd_crypto_aes128ctr_context *crypto_aes128ctr;
@@ -244,8 +261,8 @@ struct _fastd_string_stack {
 };
 
 
-void fastd_send(fastd_context *ctx, const fastd_peer_address *address, fastd_buffer buffer);
-void fastd_send_handshake(fastd_context *ctx, const fastd_peer_address *address, fastd_buffer buffer);
+void fastd_send(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, fastd_buffer buffer);
+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);
 
 void fastd_resolve_peer(fastd_context *ctx, fastd_peer *peer);
diff --git a/src/handshake.c b/src/handshake.c
index f2bdb4c..e823a0e 100644
--- a/src/handshake.c
+++ b/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_peer_address *address, const fastd_peer_config *peer_conf, fastd_buffer buffer) {
+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) {
 	if (buffer.len < sizeof(fastd_packet)) {
 		pr_warn(ctx, "received a short handshake from %I", address);
 		goto end_free;
@@ -304,10 +304,10 @@ void fastd_handshake_handle(fastd_context *ctx, const fastd_peer_address *addres
 			fastd_handshake_add_uint8(ctx, &reply_buffer, RECORD_REPLY_CODE, reply_code);
 			fastd_handshake_add_uint8(ctx, &reply_buffer, RECORD_ERROR_DETAIL, error_detail);
 
-			fastd_send_handshake(ctx, address, reply_buffer);
+			fastd_send_handshake(ctx, sock, address, reply_buffer);
 		}
 		else {
-			ctx->conf->protocol->handshake_handle(ctx, address, peer_conf, &handshake, method);
+			ctx->conf->protocol->handshake_handle(ctx, sock, address, peer_conf, &handshake, method);
 		}
 	}
 	else {
@@ -334,7 +334,7 @@ void fastd_handshake_handle(fastd_context *ctx, const fastd_peer_address *addres
 				goto end_free;
 			}
 
-			ctx->conf->protocol->handshake_handle(ctx, address, peer_conf, &handshake, method);
+			ctx->conf->protocol->handshake_handle(ctx, sock, address, peer_conf, &handshake, method);
 		}
 		else {
 			const char *error_field_str;
diff --git a/src/handshake.h b/src/handshake.h
index 0db4e2f..7744665 100644
--- a/src/handshake.h
+++ b/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_peer_address *address, const fastd_peer_config *peer_conf, fastd_buffer buffer);
+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);
 
 
 static inline void fastd_handshake_add(fastd_context *ctx, fastd_buffer *buffer, fastd_handshake_record_type type, size_t len, const void *data) {
diff --git a/src/peer.c b/src/peer.c
index 54db531..e29e350 100644
--- a/src/peer.c
+++ b/src/peer.c
@@ -176,6 +176,19 @@ 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};
@@ -280,7 +293,7 @@ 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_peer_address *addr) {
+bool fastd_peer_claim_address(fastd_context *ctx, fastd_peer *new_peer, const 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) {
@@ -304,6 +317,9 @@ bool fastd_peer_claim_address(fastd_context *ctx, fastd_peer *new_peer, const fa
 	}
 
 	new_peer->address = *addr;
+	if (sock)
+		new_peer->sock = sock;
+
 	return true;
 }
 
diff --git a/src/peer.h b/src/peer.h
index b326ad1..37b5ba2 100644
--- a/src/peer.h
+++ b/src/peer.h
@@ -35,6 +35,7 @@ struct _fastd_peer {
 
 	const fastd_peer_config *config;
 
+	const fastd_socket *sock;
 	fastd_peer_address address;
 
 	bool established;
@@ -87,7 +88,7 @@ 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_peer_address *addr);
+bool fastd_peer_claim_address(fastd_context *ctx, fastd_peer *peer, const fastd_socket *sock, const fastd_peer_address *addr);
 
 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);
diff --git a/src/protocol_ec25519_fhmqvc.c b/src/protocol_ec25519_fhmqvc.c
index 02920f4..8c96c01 100644
--- a/src/protocol_ec25519_fhmqvc.c
+++ b/src/protocol_ec25519_fhmqvc.c
@@ -228,7 +228,7 @@ static void maintenance(fastd_context *ctx) {
 	}
 }
 
-static void protocol_handshake_init(fastd_context *ctx, const fastd_peer_address *address, const fastd_peer_config *peer_conf) {
+static void protocol_handshake_init(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, const fastd_peer_config *peer_conf) {
 	maintenance(ctx);
 
 	fastd_buffer buffer = fastd_handshake_new_init(ctx, 3*(4+PUBLICKEYBYTES) /* sender key, receipient key, handshake key */);
@@ -242,10 +242,10 @@ static void protocol_handshake_init(fastd_context *ctx, const fastd_peer_address
 
 	fastd_handshake_add(ctx, &buffer, RECORD_SENDER_HANDSHAKE_KEY, PUBLICKEYBYTES, ctx->protocol_state->handshake_key.public_key.p);
 
-	fastd_send_handshake(ctx, address, buffer);
+	fastd_send_handshake(ctx, sock, address, buffer);
 }
 
-static void respond_handshake(fastd_context *ctx, const fastd_peer_address *address, const fastd_peer *peer, const handshake_key *handshake_key, const ecc_public_key_256 *peer_handshake_key,
+static void respond_handshake(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, const 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, "responding handshake with %P[%I]...", peer, address);
 
@@ -302,10 +302,10 @@ static void respond_handshake(fastd_context *ctx, const fastd_peer_address *addr
 	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES, peer_handshake_key->p);
 	fastd_handshake_add(ctx, &buffer, RECORD_T, HMACBYTES, hmacbuf);
 
-	fastd_send_handshake(ctx, address, buffer);
+	fastd_send_handshake(ctx, sock, address, buffer);
 }
 
-static bool establish(fastd_context *ctx, fastd_peer *peer, const fastd_method *method, const fastd_peer_address *address, bool initiator,
+static bool establish(fastd_context *ctx, fastd_peer *peer, const fastd_method *method, const 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];
@@ -344,7 +344,7 @@ static bool establish(fastd_context *ctx, fastd_peer *peer, const fastd_method *
 
 	fastd_peer_seen(ctx, peer);
 
-	if (!fastd_peer_claim_address(ctx, peer, address)) {
+	if (!fastd_peer_claim_address(ctx, peer, sock, address)) {
 		pr_warn(ctx, "can't set address %I which is used by a fixed peer", address);
 		fastd_peer_reset(ctx, peer);
 		return false;
@@ -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_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, 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,
 			     const fastd_handshake *handshake, const fastd_method *method) {
 	pr_debug(ctx, "finishing handshake with %P[%I]...", peer, address);
 
@@ -418,7 +418,7 @@ static void finish_handshake(fastd_context *ctx, const fastd_peer_address *addre
 	memcpy(hashinput+PUBLICKEYBYTES, handshake_key->public_key.p, PUBLICKEYBYTES);
 	crypto_auth_hmacsha256(hmacbuf, hashinput, 2*PUBLICKEYBYTES, shared_handshake_key);
 
-	if (!establish(ctx, peer, method, address, true, &handshake_key->public_key, peer_handshake_key, &ctx->conf->protocol_config->public_key,
+	if (!establish(ctx, peer, method, sock, address, true, &handshake_key->public_key, peer_handshake_key, &ctx->conf->protocol_config->public_key,
 		       &peer->config->protocol_config->public_key, &sigma, handshake_key->serial))
 		return;
 
@@ -430,11 +430,10 @@ static void finish_handshake(fastd_context *ctx, const fastd_peer_address *addre
 	fastd_handshake_add(ctx, &buffer, RECORD_RECEIPIENT_HANDSHAKE_KEY, PUBLICKEYBYTES, peer_handshake_key->p);
 	fastd_handshake_add(ctx, &buffer, RECORD_T, HMACBYTES, hmacbuf);
 
-	fastd_send_handshake(ctx, address, buffer);
-
+	fastd_send_handshake(ctx, sock, address, buffer);
 }
 
-static void handle_finish_handshake(fastd_context *ctx, 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, 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,
 				    const fastd_handshake *handshake, const fastd_method *method) {
 	pr_debug(ctx, "handling handshake finish with %P[%I]...", peer, address);
 
@@ -485,11 +484,11 @@ static void handle_finish_handshake(fastd_context *ctx, const fastd_peer_address
 		return;
 	}
 
-	establish(ctx, peer, method, address, false, peer_handshake_key, &handshake_key->public_key, &peer->config->protocol_config->public_key,
+	establish(ctx, peer, method, sock, address, false, peer_handshake_key, &handshake_key->public_key, &peer->config->protocol_config->public_key,
 		  &ctx->conf->protocol_config->public_key, &sigma, handshake_key->serial);
 }
 
-static const fastd_peer_config* match_sender_key(fastd_context *ctx, const fastd_peer_address *address, const fastd_peer_config *peer_conf, const unsigned char key[32]) {
+static const fastd_peer_config* match_sender_key(fastd_context *ctx, const fastd_socket *sock, const fastd_peer_address *address, const fastd_peer_config *peer_conf, const unsigned char key[32]) {
 	if (peer_conf) {
 		if (memcmp(peer_conf->protocol_config->public_key.p, key, PUBLICKEYBYTES) == 0)
 			return peer_conf;
@@ -523,7 +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_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, const 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;
 
@@ -534,7 +533,7 @@ static void protocol_handshake_handle(fastd_context *ctx, const fastd_peer_addre
 		return;
 	}
 
-	peer_conf = match_sender_key(ctx, address, peer_conf, handshake->records[RECORD_SENDER_KEY].data);
+	peer_conf = match_sender_key(ctx, sock, address, peer_conf, handshake->records[RECORD_SENDER_KEY].data);
 	if (!peer_conf) {
 		pr_debug(ctx, "ignoring handshake from %I (unknown key or unresolved host)", address);
 		return;
@@ -589,7 +588,7 @@ static void protocol_handshake_handle(fastd_context *ctx, const fastd_peer_addre
 
 		peer->last_handshake_response = ctx->now;
 		peer->last_handshake_response_address = *address;
-		respond_handshake(ctx, address, peer, &ctx->protocol_state->handshake_key, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, handshake, method);
+		respond_handshake(ctx, sock, address, peer, &ctx->protocol_state->handshake_key, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, handshake, method);
 		break;
 
 	case 2:
@@ -610,7 +609,7 @@ static void protocol_handshake_handle(fastd_context *ctx, const fastd_peer_addre
 		pr_verbose(ctx, "received handshake response from %P[%I] using fastd %s", peer, address, peer_version_name);
 		free(peer_version_name);
 
-		finish_handshake(ctx, address, peer, handshake_key, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, handshake, method);
+		finish_handshake(ctx, sock, address, peer, handshake_key, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, handshake, method);
 		break;
 
 	case 3:
@@ -627,7 +626,7 @@ static void protocol_handshake_handle(fastd_context *ctx, const fastd_peer_addre
 
 		pr_debug(ctx, "received handshake finish from %P[%I]", peer, address);
 
-		handle_finish_handshake(ctx, address, peer, handshake_key, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, handshake, method);
+		handle_finish_handshake(ctx, sock, address, peer, handshake_key, handshake->records[RECORD_SENDER_HANDSHAKE_KEY].data, handshake, method);
 		break;
 
 	default:
@@ -702,7 +701,7 @@ static void session_send(fastd_context *ctx, fastd_peer *peer, fastd_buffer buff
 		return;
 	}
 
-	fastd_send(ctx, &peer->address, send_buffer);
+	fastd_send(ctx, peer->sock, &peer->address, send_buffer);
 
 	fastd_task_delete_peer_keepalives(ctx, peer);
 	fastd_task_schedule_keepalive(ctx, peer, ctx->conf->keepalive_interval*1000);
diff --git a/src/types.h b/src/types.h
index f079d3c..13236b6 100644
--- a/src/types.h
+++ b/src/types.h
@@ -44,6 +44,8 @@ typedef enum _fastd_mode {
 typedef struct _fastd_buffer fastd_buffer;
 
 typedef union _fastd_peer_address fastd_peer_address;
+typedef struct _fastd_bind_address fastd_bind_address;
+typedef struct _fastd_socket fastd_socket;
 typedef struct _fastd_peer_config fastd_peer_config;
 typedef struct _fastd_eth_addr fastd_eth_addr;
 typedef struct _fastd_peer fastd_peer;