netdev - [PATCH net] tcp: Fix TLP implementation in case receive window limits send

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Message-ID: <6cbd68ba1ef44c5ca4b21bd3f65846af@AM3PR06MB388.eurprd06.prod.outlook.com>
Date:	Tue, 23 Sep 2014 16:28:56 +0000
From:	Itzcak Pechtalt <itzcak@...shnetworks.com>
To:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: [PATCH net] tcp: Fix TLP implementation in case receive window limits
 send

From: Itzcak Pechtalt <itzcak@...shnetworks.com>

TCP Tail loss probe (TLP) algorithm implementation has some problem.
According to paper (draft-dukkipati-tcpm-tcp-loss-probe-0 ):
In case recive window of receiver limits send of new packet in probe time than
a retransmit of last packet send should be done.

Actually, return code from tcp_write_xmit is not checked and only RTO is
scheduled,
So, it will take more time for reovery in this case than without TLP.

Signed-off-by: Itzcak Pechtalt <itzcak@...shnetworks.com>
---
net/ipv4/tcp_output.c  |    2 +-
1 file changed, 1 insertions(+),  1 deletions(-)

diff -up a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
--- a/net/ipv4/tcp_output.c     2014-09-23 18:35:37.113771694 +0300
+++ b/net/ipv4/tcp_output.c     2014-09-23 18:39:58.207726420 +0300
@@ -2100,7 +2100,8 @@ void tcp_send_loss_probe(struct sock *sk

        if (tcp_send_head(sk) != NULL) {
                err = tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
-              goto rearm_timer;
+             if (!err)
+                       goto rearm_timer;
        }

        /* At most one outstanding TLP retransmission. */

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