[PATCH 4.4 37/73] tcp: refresh skb timestamp at retransmit time

Greg Kroah-Hartman
2016-05-17T01:51:46Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 10a81980fc47e64ffac26a073139813d3f697b64 ]

In the very unlikely case __tcp_retransmit_skb() can not use the cloning
done in tcp_transmit_skb(), we need to refresh skb_mstamp before doing
the copy and transmit, otherwise TCP TS val will be an exact copy of
original transmit.

Fixes: 7faee5c0d514 ("tcp: remove TCP_SKB_CB(skb)->when")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/tcp_output.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2625,8 +2625,10 @@ int __tcp_retransmit_skb(struct sock *sk
*/
if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) ||
skb_headroom(skb) >= 0xFFFF)) {
- struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER,
- GFP_ATOMIC);
+ struct sk_buff *nskb;
+
+ skb_mstamp_get(&skb->skb_mstamp);
+ nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
-ENOBUFS;
} else {