[PATCH net] tcp: refresh skb timestamp at retransmit time

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

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 <eduma...@google.com>
Cc: Yuchung Cheng <ych...@google.com>
---
 net/ipv4/tcp_output.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 441ae9da3a23..79a03b87a771 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2640,8 +2640,10 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff 
*skb)
         */
        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 {