tcp: Skip redundant ACK on partial sendmsg() failure

...we'll send a duplicate ACK right away in this case, and this
redundant, earlier check is not just useless, but it might actually
be harmful as we'll now send a triple ACK which might cause two
retransmissions.

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

1 files changed, 3 insertions, 6 deletions

diff --git a/tcp.c b/tcp.c
index 2ad9764..17fda5d 100644
--- a/tcp.c
+++ b/tcp.c
@@ -2027,13 +2027,10 @@ eintr:
 		return -1;
 	}
 
-	if (n < (int)(seq_from_tap - conn->seq_from_tap)) {
+	if (n < (int)(seq_from_tap - conn->seq_from_tap))
 		partial_send = 1;
-		conn->seq_from_tap += n;
-		tcp_send_flag(c, conn, ACK_IF_NEEDED);
-	} else {
-		conn->seq_from_tap += n;
-	}
+
+	conn->seq_from_tap += n;
 
 out:
 	if (keep != -1 || partial_send) {