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, 12 insertions, 15 deletions

diff --git a/util.c b/util.c
index c3475d6..9afd2a5 100644
--- a/util.c
+++ b/util.c
@@ -218,14 +218,14 @@ found:
  * @c:		Execution context
  * @af:		Address family, AF_INET or AF_INET6
  * @proto:	Protocol number
+ * @bind_addr:	Address for binding, NULL for any
  * @port:	Port, host order
- * @bind_type:	Type of address for binding
  * @data:	epoll reference portion for protocol handlers
  *
  * Return: newly created socket, -1 on error
  */
-int sock_l4(const struct ctx *c, int af, uint8_t proto, uint16_t port,
-	    enum bind_type bind_addr, uint32_t data)
+int sock_l4(const struct ctx *c, int af, uint8_t proto,
+	    const void *bind_addr, uint16_t port, uint32_t data)
 {
 	union epoll_ref ref = { .r.proto = proto, .r.p.data = data };
 	struct sockaddr_in addr4 = {
@@ -264,23 +264,20 @@ int sock_l4(const struct ctx *c, int af, uint8_t proto, uint16_t port,
 	ref.r.s = fd;
 
 	if (af == AF_INET) {
-		if (bind_addr == BIND_LOOPBACK)
-			addr4.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
-		else if (bind_addr == BIND_EXT)
-			addr4.sin_addr.s_addr = c->addr4;
+		if (bind_addr)
+			addr4.sin_addr.s_addr = *(in_addr_t *)bind_addr;
 		else
 			addr4.sin_addr.s_addr = htonl(INADDR_ANY);
 
 		sa = (const struct sockaddr *)&addr4;
 		sl = sizeof(addr4);
 	} else {
-		if (bind_addr == BIND_LOOPBACK) {
-			addr6.sin6_addr = in6addr_loopback;
-		} else if (bind_addr == BIND_EXT) {
-			addr6.sin6_addr = c->addr6;
-		} else if (bind_addr == BIND_LL) {
-			addr6.sin6_addr = c->addr6_ll;
-			addr6.sin6_scope_id = c->ifi;
+		if (bind_addr) {
+			addr6.sin6_addr = *(struct in6_addr *)bind_addr;
+
+			if (!memcmp(bind_addr, &c->addr6_ll,
+			    sizeof(c->addr6_ll)))
+				addr6.sin6_scope_id = c->ifi;
 		} else {
 			addr6.sin6_addr = in6addr_any;
 		}
@@ -303,7 +300,7 @@ int sock_l4(const struct ctx *c, int af, uint8_t proto, uint16_t port,
 		 */
 		if (proto != IPPROTO_ICMP && proto != IPPROTO_ICMPV6) {
 			close(fd);
-			return 0;
+			return -1;
 		}
 	}