conf, tcp, udp: Allow address specification for forwarded ports

This feature is available in slirp4netns but was missing in passt and
pasta.

Given that we don't do dynamic memory allocation, we need to bind
sockets while parsing port configuration. This means we need to
process all other options first, as they might affect addressing and
IP version support. It also implies a minor rework of how TCP and UDP
implementations bind sockets.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 99 insertions, 63 deletions

diff --git a/udp.c b/udp.c
index 86d806a..f425d14 100644
--- a/udp.c
+++ b/udp.c
@@ -1000,7 +1000,8 @@ int udp_tap_handler(struct ctx *c, int af, const void *addr,
 			union udp_epoll_ref uref = { .udp.bound = 1,
 						     .udp.port = src };
 
-			s = sock_l4(c, AF_INET, IPPROTO_UDP, src, 0, uref.u32);
+			s = sock_l4(c, AF_INET, IPPROTO_UDP, NULL, src,
+				    uref.u32);
 			if (s < 0)
 				return p->count;
 
@@ -1026,7 +1027,7 @@ int udp_tap_handler(struct ctx *c, int af, const void *addr,
 			.sin6_port = uh->dest,
 			.sin6_addr = *(struct in6_addr *)addr,
 		};
-		enum bind_type bind_to = BIND_ANY;
+		const void *bind_addr = &in6addr_any;
 
 		sa = (struct sockaddr *)&s_in6;
 		sl = sizeof(s_in6);
@@ -1043,7 +1044,7 @@ int udp_tap_handler(struct ctx *c, int af, const void *addr,
 			   ntohs(s_in6.sin6_port) == 53) {
 			s_in6.sin6_addr = c->dns6[0];
 		} else if (IN6_IS_ADDR_LINKLOCAL(&s_in6.sin6_addr)) {
-			bind_to = BIND_LL;
+			bind_addr = &c->addr6_ll;
 		}
 
 		if (!(s = udp_tap_map[V6][src].sock)) {
@@ -1051,7 +1052,7 @@ int udp_tap_handler(struct ctx *c, int af, const void *addr,
 						     .udp.v6 = 1,
 						     .udp.port = src };
 
-			s = sock_l4(c, AF_INET6, IPPROTO_UDP, src, bind_to,
+			s = sock_l4(c, AF_INET6, IPPROTO_UDP, bind_addr, src,
 				    uref.u32);
 			if (s < 0)
 				return p->count;
@@ -1093,6 +1094,96 @@ int udp_tap_handler(struct ctx *c, int af, const void *addr,
 }
 
 /**
+ * udp_sock_init() - Initialise listening sockets for a given port
+ * @c:		Execution context
+ * @ns:		In pasta mode, if set, bind with loopback address in namespace
+ * @af:		Address family to select a specific IP version, or AF_UNSPEC
+ * @addr:	Pointer to address for binding, NULL if not configured
+ * @port:	Port, host order
+ */
+void udp_sock_init(const struct ctx *c, int ns, sa_family_t af,
+		   const void *addr, in_port_t port)
+{
+	union udp_epoll_ref uref = { .udp.bound = 1 };
+	const void *bind_addr;
+	int s;
+
+	if (ns) {
+		uref.udp.port = (in_port_t)(port +
+					    udp_port_delta_to_init[port]);
+	} else {
+		uref.udp.port = (in_port_t)(port +
+					    udp_port_delta_to_tap[port]);
+	}
+
+	if (af == AF_INET || af == AF_UNSPEC) {
+		if (!addr && c->mode == MODE_PASTA)
+			bind_addr = &c->addr4;
+		else
+			bind_addr = addr;
+
+		uref.udp.v6 = 0;
+
+		if (!ns) {
+			uref.udp.splice = 0;
+			s = sock_l4(c, AF_INET, IPPROTO_UDP, bind_addr, port,
+				    uref.u32);
+
+			udp_tap_map[V4][uref.udp.port].sock = s;
+		}
+
+		if (c->mode == MODE_PASTA) {
+			bind_addr = &(uint32_t){ htonl(INADDR_LOOPBACK) };
+			uref.udp.splice = UDP_TO_NS;
+
+			sock_l4(c, AF_INET, IPPROTO_UDP, bind_addr, port,
+				uref.u32);
+		}
+
+		if (ns) {
+			bind_addr = &(uint32_t){ htonl(INADDR_LOOPBACK) };
+			uref.udp.splice = UDP_TO_INIT;
+
+			sock_l4(c, AF_INET, IPPROTO_UDP, bind_addr, port,
+				uref.u32);
+		}
+	}
+
+	if (af == AF_INET6 || af == AF_UNSPEC) {
+		if (!addr && c->mode == MODE_PASTA)
+			bind_addr = &c->addr6;
+		else
+			bind_addr = addr;
+
+		uref.udp.v6 = 1;
+
+		if (!ns) {
+			uref.udp.splice = 0;
+			s = sock_l4(c, AF_INET6, IPPROTO_UDP, bind_addr, port,
+				    uref.u32);
+
+			udp_tap_map[V6][uref.udp.port].sock = s;
+		}
+
+		if (c->mode == MODE_PASTA) {
+			bind_addr = &in6addr_loopback;
+			uref.udp.splice = UDP_TO_NS;
+
+			sock_l4(c, AF_INET6, IPPROTO_UDP, bind_addr, port,
+				uref.u32);
+		}
+
+		if (ns) {
+			bind_addr = &in6addr_loopback;
+			uref.udp.splice = UDP_TO_INIT;
+
+			sock_l4(c, AF_INET6, IPPROTO_UDP, bind_addr, port,
+				uref.u32);
+		}
+	}
+}
+
+/**
  * udp_sock_init_ns() - Bind sockets in namespace for inbound connections
  * @arg:	Execution context
  *
@@ -1100,8 +1191,6 @@ int udp_tap_handler(struct ctx *c, int af, const void *addr,
  */
 int udp_sock_init_ns(void *arg)
 {
-	union udp_epoll_ref uref = { .udp.bound = 1,
-				     .udp.splice = UDP_TO_INIT };
 	struct ctx *c = (struct ctx *)arg;
 	int dst;
 
@@ -1112,19 +1201,7 @@ int udp_sock_init_ns(void *arg)
 		if (!bitmap_isset(c->udp.port_to_init, dst))
 			continue;
 
-		uref.udp.port = dst + udp_port_delta_to_init[dst];
-
-		if (c->v4) {
-			uref.udp.v6 = 0;
-			sock_l4(c, AF_INET, IPPROTO_UDP, dst, BIND_LOOPBACK,
-				uref.u32);
-		}
-
-		if (c->v6) {
-			uref.udp.v6 = 1;
-			sock_l4(c, AF_INET6, IPPROTO_UDP, dst, BIND_LOOPBACK,
-				uref.u32);
-		}
+		udp_sock_init(c, 1, AF_UNSPEC, NULL, dst);
 	}
 
 	return 0;
@@ -1178,54 +1255,13 @@ static void udp_splice_iov_init(void)
 }
 
 /**
- * udp_sock_init() - Create and bind listening sockets for inbound packets
+ * udp_init() - Initialise per-socket data, and sockets in namespace
  * @c:		Execution context
  *
- * Return: 0 on success, -1 on failure
+ * Return: 0
  */
-int udp_sock_init(const struct ctx *c)
+int udp_init(const struct ctx *c)
 {
-	union udp_epoll_ref uref = { .udp.bound = 1 };
-	int dst, s;
-
-	for (dst = 0; dst < USHRT_MAX; dst++) {
-		if (!bitmap_isset(c->udp.port_to_tap, dst))
-			continue;
-
-		uref.udp.port = dst + udp_port_delta_to_tap[dst];
-
-		if (c->v4) {
-			uref.udp.splice = 0;
-			uref.udp.v6 = 0;
-			s = sock_l4(c, AF_INET, IPPROTO_UDP, dst,
-				    c->mode == MODE_PASTA ? BIND_EXT : BIND_ANY,
-				    uref.u32);
-			if (s > 0)
-				udp_tap_map[V4][uref.udp.port].sock = s;
-
-			if (c->mode == MODE_PASTA) {
-				uref.udp.splice = UDP_TO_NS;
-				sock_l4(c, AF_INET, IPPROTO_UDP, dst,
-					BIND_LOOPBACK, uref.u32);
-			}
-		}
-		if (c->v6) {
-			uref.udp.splice = 0;
-			uref.udp.v6 = 1;
-			s = sock_l4(c, AF_INET6, IPPROTO_UDP, dst,
-				    c->mode == MODE_PASTA ? BIND_EXT : BIND_ANY,
-				    uref.u32);
-			if (s > 0)
-				udp_tap_map[V6][uref.udp.port].sock = s;
-
-			if (c->mode == MODE_PASTA) {
-				uref.udp.splice = UDP_TO_NS;
-				sock_l4(c, AF_INET6, IPPROTO_UDP, dst,
-					BIND_LOOPBACK, uref.u32);
-			}
-		}
-	}
-
 	if (c->v4)
 		udp_sock4_iov_init();