tcp: xps: fix reordering issues

[ Upstream commit 547669d483e5783d722772af1483fa474da7caf9 ]

commit 3853b5841c01a ("xps: Improvements in TX queue selection")
introduced ooo_okay flag, but the condition to set it is slightly wrong.

In our traces, we have seen ACK packets being received out of order,
and RST packets sent in response.

We should test if we have any packets still in host queue.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 9db21e3..12999a3 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -835,11 +835,13 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
                                                           &md5);
        tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
 
-       if (tcp_packets_in_flight(tp) == 0) {
+       if (tcp_packets_in_flight(tp) == 0)
                tcp_ca_event(sk, CA_EVENT_TX_START);
-               skb->ooo_okay = 1;
-       } else
-               skb->ooo_okay = 0;
+
+       /* if no packet is in qdisc/device queue, then allow XPS to select
+        * another queue.
+        */
+       skb->ooo_okay = sk_wmem_alloc_get(sk) == 0;
 
        skb_push(skb, tcp_header_size);
        skb_reset_transport_header(skb);