[PATCH 4/8] tcp: Never hash match closed connections

[David Gibson <david@gibson.dropbear.id.au>]

From a practical point of view, when a TCP connection ends, whether by
FIN or by RST, we set the CLOSED event, then some time later we remove the
connection from the hash table and clean it up.  However, from a protocol
point of view, once it's closed, it's gone, and any new packets with
matching addresses and ports are either forming a new connection, or are
invalid packets to discard.

Enforce these semantics in the TCP hash logic by never hash matching closed
connections.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 tcp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tcp.c b/tcp.c
index 6a34f82..5592998 100644
--- a/tcp.c
+++ b/tcp.c
@@ -1146,7 +1146,7 @@ static int tcp_hash_match(const struct tcp_tap_conn *conn,
 			  const union inany_addr *faddr,
 			  in_port_t eport, in_port_t fport)
 {
-	if (inany_equals(&conn->faddr, faddr) &&
+	if (conn->events != CLOSED && inany_equals(&conn->faddr, faddr) &&
 	    conn->eport == eport && conn->fport == fport)
 		return 1;
 
-- 
@@ -1146,7 +1146,7 @@ static int tcp_hash_match(const struct tcp_tap_conn *conn,
 			  const union inany_addr *faddr,
 			  in_port_t eport, in_port_t fport)
 {
-	if (inany_equals(&conn->faddr, faddr) &&
+	if (conn->events != CLOSED && inany_equals(&conn->faddr, faddr) &&
 	    conn->eport == eport && conn->fport == fport)
 		return 1;
 
-- 
2.41.0