tcp: Send a duplicate ACK also on complete sendmsg() failure

...in order to trigger a fast retransmit as soon as possible. There's
no benefit in forcing the sender to wait for a longer time than that.

We already do this on partial failures (short socket writes), but for
historical reason not on complete failures. Make these two cases
consistent between each other.

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

1 files changed, 1 insertions, 1 deletions

diff --git a/tcp.c b/tcp.c
index 1f57fda..2ad9764 100644
--- a/tcp.c
+++ b/tcp.c
@@ -2020,7 +2020,7 @@ eintr:
 			goto eintr;
 
 		if (errno == EAGAIN || errno == EWOULDBLOCK) {
-			tcp_send_flag(c, conn, ACK_IF_NEEDED);
+			tcp_send_flag(c, conn, ACK | DUP_ACK);
 			return p->count - idx;
 
 		}