udp: Don't use separate sockets to listen for spliced packets

Currently, when ports are forwarded inbound in pasta mode, we open two
sockets for incoming traffic: one listens on the public IP address and will
forward packets to the tuntap interface.  The other listens on localhost
and forwards via "splicing" (resending directly via sockets in the ns).

Now that we've improved the logic about whether we "splice" any individual
packet, we don't need this.  Instead we can have a single socket bound to
0.0.0.0 or ::, marked as able to splice and udp_sock_handler() will deal
with each packet as appropriate.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 13 insertions, 40 deletions

diff --git a/udp.c b/udp.c
index 3f216ed..dbfdb61 100644
--- a/udp.c
+++ b/udp.c
@@ -1124,7 +1124,6 @@ void udp_sock_init(const struct ctx *c, int ns, sa_family_t af,
 		   const void *addr, const char *ifname, in_port_t port)
 {
 	union udp_epoll_ref uref = { .u32 = 0 };
-	const void *bind_addr;
 	int s;
 
 	if (ns) {
@@ -1136,67 +1135,41 @@ void udp_sock_init(const struct ctx *c, int ns, sa_family_t af,
 	}
 
 	if ((af == AF_INET || af == AF_UNSPEC) && c->ifi4) {
-		if (!addr && c->mode == MODE_PASTA)
-			bind_addr = &c->ip4.addr;
-		else
-			bind_addr = addr;
-
 		uref.udp.v6 = 0;
+		uref.udp.splice = (c->mode == MODE_PASTA);
+		uref.udp.orig = true;
 
 		if (!ns) {
-			uref.udp.splice = 0;
-			s = sock_l4(c, AF_INET, IPPROTO_UDP, bind_addr, ifname,
+			s = sock_l4(c, AF_INET, IPPROTO_UDP, addr, ifname,
 				    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 = uref.udp.orig = true;
-
-				s = sock_l4(c, AF_INET, IPPROTO_UDP, bind_addr,
-					    ifname, port, uref.u32);
-				udp_splice_init[V4][port].sock = s;
-			}
+			udp_splice_init[V4][port].sock = s;
 		} else {
-			uref.udp.splice = uref.udp.orig = uref.udp.ns = true;
-
-			bind_addr = &(uint32_t){ htonl(INADDR_LOOPBACK) };
+			struct in_addr loopback = { htonl(INADDR_LOOPBACK) };
+			uref.udp.ns = true;
 
-			s = sock_l4(c, AF_INET, IPPROTO_UDP, bind_addr,
+			s = sock_l4(c, AF_INET, IPPROTO_UDP, &loopback,
 				    ifname, port, uref.u32);
 			udp_splice_ns[V4][port].sock = s;
 		}
 	}
 
 	if ((af == AF_INET6 || af == AF_UNSPEC) && c->ifi6) {
-		if (!addr && c->mode == MODE_PASTA)
-			bind_addr = &c->ip6.addr;
-		else
-			bind_addr = addr;
-
 		uref.udp.v6 = 1;
+		uref.udp.splice = (c->mode == MODE_PASTA);
+		uref.udp.orig = true;
 
 		if (!ns) {
-			uref.udp.splice = 0;
-			s = sock_l4(c, AF_INET6, IPPROTO_UDP, bind_addr, ifname,
+			s = sock_l4(c, AF_INET6, IPPROTO_UDP, addr, ifname,
 				    port, uref.u32);
 
 			udp_tap_map[V6][uref.udp.port].sock = s;
-
-			if (c->mode == MODE_PASTA) {
-				bind_addr = &in6addr_loopback;
-				uref.udp.splice = uref.udp.orig = true;
-
-				s = sock_l4(c, AF_INET6, IPPROTO_UDP, bind_addr,
-					    ifname, port, uref.u32);
-				udp_splice_init[V6][port].sock = s;
-			}
+			udp_splice_init[V6][port].sock = s;
 		} else {
-			bind_addr = &in6addr_loopback;
-			uref.udp.splice = uref.udp.orig = uref.udp.ns = true;
+			uref.udp.ns = true;
 
-			s = sock_l4(c, AF_INET6, IPPROTO_UDP, bind_addr,
+			s = sock_l4(c, AF_INET6, IPPROTO_UDP, &in6addr_loopback,
 				    ifname, port, uref.u32);
 			udp_splice_ns[V6][port].sock = s;
 		}