[PATCH 5/8] tcp_splice: Simplify shutdown(2) handling

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

At the end of tcp_splice_forward(), we check for half-closed connections
in either direction and propagate the FIN to the other side with a
shutdown(2).

However, it's unnecessary to check both directions: a FIN from side X will
cause an EPOLLRDUP on side X's socket, which will trigger
tcp_splice_forward() from side X to side !X.  Likewise for the other side.
So we only need to check for "forward" FIN propagation.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 tcp_splice.c | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/tcp_splice.c b/tcp_splice.c
index 8c8e3bbb..42902684 100644
--- a/tcp_splice.c
+++ b/tcp_splice.c
@@ -544,22 +544,15 @@ static int tcp_splice_forward(struct ctx *c,
 			break;
 	}
 
-	if (!conn->pending[fromsidei] &&
-	    conn->events & FIN_RCVD(fromsidei)) {
-		unsigned sidei;
-
-		flow_foreach_sidei(sidei) {
-			if ((conn->events & FIN_RCVD(sidei)) &&
-			    !(conn->events & FIN_SENT(!sidei))) {
-				if (shutdown(conn->s[!sidei], SHUT_WR) < 0) {
-					flow_perror_ratelimit(
-						conn, now, "shutdown() on %s",
-						pif_name(conn->f.pif[!sidei]));
-					return -1;
-				}
-				conn_event(conn, FIN_SENT(!sidei));
-			}
+	if ((conn->events & FIN_RCVD(fromsidei)) &&
+	    !(conn->events & FIN_SENT(!fromsidei)) &&
+	    !conn->pending[fromsidei]) {
+		if (shutdown(conn->s[!fromsidei], SHUT_WR) < 0) {
+			flow_perror_ratelimit(conn, now, "shutdown() on %s",
+					      pif_name(conn->f.pif[!fromsidei]));
+			return -1;
 		}
+		conn_event(conn, FIN_SENT(!fromsidei));
 	}
 
 	return 0;
-- 
2.54.0