tcp: Remove v6 flag from tcp_epoll_ref

This bit in the TCP specific epoll reference indicates whether the
connection is IPv6 or IPv4.  However the sites which refer to it are
already calling accept() which (optionally) returns an address for the
remote end of the connection.  We can use the sa_family field in that
address to determine the connection type independent of the epoll
reference.

This does have a cost: for the spliced case, it means we now need to get
that address from accept() which introduces an extran copy_to_user().
However, in future we want to allow handling IPv4 connectons through IPv6
sockets, which means we won't be able to determine the IP version at the
time we create the listening socket and epoll reference.  So, at some point
we'll have to pay this cost anyway.

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

3 files changed, 7 insertions, 13 deletions

diff --git a/tcp.c b/tcp.c
index 559e271..7d5ac6c 100644
--- a/tcp.c
+++ b/tcp.c
@@ -662,8 +662,7 @@ static int tcp_epoll_ctl(const struct ctx *c, struct tcp_tap_conn *conn)
 {
 	int m = conn->c.in_epoll ? EPOLL_CTL_MOD : EPOLL_CTL_ADD;
 	union epoll_ref ref = { .r.proto = IPPROTO_TCP, .r.s = conn->sock,
-				.r.p.tcp.tcp.index = CONN_IDX(conn),
-				.r.p.tcp.tcp.v6 = CONN_V6(conn) };
+				.r.p.tcp.tcp.index = CONN_IDX(conn) };
 	struct epoll_event ev = { .data.u64 = ref.u64 };
 
 	if (conn->events == CLOSED) {
@@ -2745,7 +2744,7 @@ static void tcp_tap_conn_from_sock(struct ctx *c, union epoll_ref ref,
 	conn->ws_to_tap = conn->ws_from_tap = 0;
 	conn_event(c, conn, SOCK_ACCEPTED);
 
-	if (ref.r.p.tcp.tcp.v6) {
+	if (sa->sa_family == AF_INET6) {
 		struct sockaddr_in6 sa6;
 
 		memcpy(&sa6, sa, sizeof(sa6));
@@ -3019,8 +3018,7 @@ static void tcp_sock_init6(const struct ctx *c,
 			   in_port_t port)
 {
 	in_port_t idx = port + c->tcp.fwd_in.delta[port];
-	union tcp_epoll_ref tref = { .tcp.listen = 1, .tcp.v6 = 1,
-				     .tcp.index = idx };
+	union tcp_epoll_ref tref = { .tcp.listen = 1, .tcp.index = idx };
 	int s;
 
 	s = sock_l4(c, AF_INET6, IPPROTO_TCP, addr, ifname, port, tref.u32);
@@ -3084,7 +3082,7 @@ static void tcp_ns_sock_init6(const struct ctx *c, in_port_t port)
 {
 	in_port_t idx = port + c->tcp.fwd_out.delta[port];
 	union tcp_epoll_ref tref = { .tcp.listen = 1, .tcp.outbound = 1,
-				     .tcp.v6 = 1, .tcp.index = idx };
+				     .tcp.index = idx };
 	int s;
 
 	assert(c->mode == MODE_PASTA);
diff --git a/tcp.h b/tcp.h
index a940682..739b451 100644
--- a/tcp.h
+++ b/tcp.h
@@ -33,7 +33,6 @@ void tcp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s,
  * union tcp_epoll_ref - epoll reference portion for TCP connections
  * @listen:		Set if this file descriptor is a listening socket
  * @outbound:		Listening socket maps to outbound, spliced connection
- * @v6:			Set for IPv6 sockets or connections
  * @timer:		Reference is a timerfd descriptor for connection
  * @index:		Index of connection in table, or port for bound sockets
  * @u32:		Opaque u32 value of reference
@@ -42,7 +41,6 @@ union tcp_epoll_ref {
 	struct {
 		uint32_t	listen:1,
 				outbound:1,
-				v6:1,
 				timer:1,
 				index:20;
 	} tcp;
diff --git a/tcp_splice.c b/tcp_splice.c
index 2be9b77..1bbd085 100644
--- a/tcp_splice.c
+++ b/tcp_splice.c
@@ -167,11 +167,9 @@ static int tcp_splice_epoll_ctl(const struct ctx *c,
 {
 	int m = conn->c.in_epoll ? EPOLL_CTL_MOD : EPOLL_CTL_ADD;
 	union epoll_ref ref_a = { .r.proto = IPPROTO_TCP, .r.s = conn->a,
-				  .r.p.tcp.tcp.index = CONN_IDX(conn),
-				  .r.p.tcp.tcp.v6 = CONN_V6(conn) };
+				  .r.p.tcp.tcp.index = CONN_IDX(conn) };
 	union epoll_ref ref_b = { .r.proto = IPPROTO_TCP, .r.s = conn->b,
-				  .r.p.tcp.tcp.index = CONN_IDX(conn),
-				  .r.p.tcp.tcp.v6 = CONN_V6(conn) };
+				  .r.p.tcp.tcp.index = CONN_IDX(conn) };
 	struct epoll_event ev_a = { .data.u64 = ref_a.u64 };
 	struct epoll_event ev_b = { .data.u64 = ref_b.u64 };
 	uint32_t events_a, events_b;
@@ -517,7 +515,7 @@ bool tcp_splice_conn_from_sock(struct ctx *c, union epoll_ref ref,
 {
 	assert(c->mode == MODE_PASTA);
 
-	if (ref.r.p.tcp.tcp.v6) {
+	if (sa->sa_family == AF_INET6) {
 		const struct sockaddr_in6 *sa6;
 
 		sa6 = (const struct sockaddr_in6 *)sa;