4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@xxxxxxxxx>
[ Upstream commit 8c72c65b426b47b3c166a8fef0d8927fe5e8a28d ]
liujian reported a problem in TCP_USER_TIMEOUT processing with a patch
in tcp_probe_timer() :
https://www.spinics.net/lists/netdev/msg454496.html
After investigations, the root cause of the problem is that we update
skb->skb_mstamp of skbs in write queue, even if the attempt to send a
clone or copy of it failed. One reason being a routing problem.
This patch prevents this, solving liujian issue.
It also removes a potential RTT miscalculation, since
__tcp_retransmit_skb() is not OR-ing TCP_SKB_CB(skb)->sacked with
TCPCB_EVER_RETRANS if a failure happens, but skb->skb_mstamp has
been changed.
A future ACK would then lead to a very small RTT sample and min_rtt
would then be lowered to this too small value.
Tested:
# cat user_timeout.pkt
--local_ip=192.168.102.64
0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+0 bind(3, ..., ...) = 0
+0 listen(3, 1) = 0
+0 `ifconfig tun0 192.168.102.64/16; ip ro add 192.0.2.1 dev tun0`
+0 < S 0:0(0) win 0 <mss 1460>
+0 > S. 0:0(0) ack 1 <mss 1460>
+.1 < . 1:1(0) ack 1 win 65530
+0 accept(3, ..., ...) = 4
+0 setsockopt(4, SOL_TCP, TCP_USER_TIMEOUT, [3000], 4) = 0
+0 write(4, ..., 24) = 24
+0 > P. 1:25(24) ack 1 win 29200
+.1 < . 1:1(0) ack 25 win 65530
//change the ipaddress
+1 `ifconfig tun0 192.168.0.10/16`
+1 write(4, ..., 24) = 24
+1 write(4, ..., 24) = 24
+1 write(4, ..., 24) = 24
+1 write(4, ..., 24) = 24
+0 `ifconfig tun0 192.168.102.64/16`
+0 < . 1:2(1) ack 25 win 65530
+0 `ifconfig tun0 192.168.0.10/16`
+3 write(4, ..., 24) = -1
# ./packetdrill user_timeout.pkt
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxx>
Reported-by: liujian <liujian56@xxxxxxxxxx>
Acked-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Acked-by: Yuchung Cheng <ycheng@xxxxxxxxxx>
Acked-by: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/tcp_output.c | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -914,6 +914,7 @@ static int tcp_transmit_skb(struct sock
struct tcp_skb_cb *tcb;
struct tcp_out_options opts;
unsigned int tcp_options_size, tcp_header_size;
+ struct sk_buff *oskb = NULL;
struct tcp_md5sig_key *md5;
struct tcphdr *th;
int err;
@@ -922,11 +923,11 @@ static int tcp_transmit_skb(struct sock
tp = tcp_sk(sk);
if (clone_it) {
- skb_mstamp_get(&skb->skb_mstamp);
TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
- tp->snd_una;
tcp_rate_skb_sent(sk, skb);
+ oskb = skb;
if (unlikely(skb_cloned(skb)))
skb = pskb_copy(skb, gfp_mask);
else
@@ -934,6 +935,7 @@ static int tcp_transmit_skb(struct sock
if (unlikely(!skb))
return -ENOBUFS;
}
+ skb_mstamp_get(&skb->skb_mstamp);
inet = inet_sk(sk);
tcb = TCP_SKB_CB(skb);
@@ -1035,12 +1037,14 @@ static int tcp_transmit_skb(struct sock
err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
- if (likely(err <= 0))
- return err;
-
- tcp_enter_cwr(sk);
+ if (unlikely(err > 0)) {
+ tcp_enter_cwr(sk);
+ err = net_xmit_eval(err);
+ }
+ if (!err && oskb)
+ skb_mstamp_get(&oskb->skb_mstamp);
- return net_xmit_eval(err);
+ return err;
}
/* This routine just queues the buffer for sending.
@@ -2709,10 +2713,11 @@ int __tcp_retransmit_skb(struct sock *sk
skb_headroom(skb) >= 0xFFFF)) {
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;
+ if (!err)
+ skb_mstamp_get(&skb->skb_mstamp);
} else {
err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
}