| From foo@baz Tue Nov 21 15:37:44 CET 2017 |
| From: Eric Dumazet <edumazet@google.com> |
| Date: Thu, 2 Nov 2017 12:30:25 -0700 |
| Subject: tcp: do not mangle skb->cb[] in tcp_make_synack() |
| |
| From: Eric Dumazet <edumazet@google.com> |
| |
| |
| [ Upstream commit 3b11775033dc87c3d161996c54507b15ba26414a ] |
| |
| Christoph Paasch sent a patch to address the following issue : |
| |
| tcp_make_synack() is leaving some TCP private info in skb->cb[], |
| then send the packet by other means than tcp_transmit_skb() |
| |
| tcp_transmit_skb() makes sure to clear skb->cb[] to not confuse |
| IPv4/IPV6 stacks, but we have no such cleanup for SYNACK. |
| |
| tcp_make_synack() should not use tcp_init_nondata_skb() : |
| |
| tcp_init_nondata_skb() really should be limited to skbs put in write/rtx |
| queues (the ones that are only sent via tcp_transmit_skb()) |
| |
| This patch fixes the issue and should even save few cpu cycles ;) |
| |
| Fixes: 971f10eca186 ("tcp: better TCP_SKB_CB layout to reduce cache line misses") |
| Signed-off-by: Eric Dumazet <edumazet@google.com> |
| Reported-by: Christoph Paasch <cpaasch@apple.com> |
| Reviewed-by: Christoph Paasch <cpaasch@apple.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| net/ipv4/tcp_output.c | 9 ++------- |
| 1 file changed, 2 insertions(+), 7 deletions(-) |
| |
| --- a/net/ipv4/tcp_output.c |
| +++ b/net/ipv4/tcp_output.c |
| @@ -2911,13 +2911,8 @@ struct sk_buff *tcp_make_synack(struct s |
| tcp_ecn_make_synack(req, th, sk); |
| th->source = htons(ireq->ir_num); |
| th->dest = ireq->ir_rmt_port; |
| - /* Setting of flags are superfluous here for callers (and ECE is |
| - * not even correctly set) |
| - */ |
| - tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn, |
| - TCPHDR_SYN | TCPHDR_ACK); |
| - |
| - th->seq = htonl(TCP_SKB_CB(skb)->seq); |
| + skb->ip_summed = CHECKSUM_PARTIAL; |
| + th->seq = htonl(tcp_rsk(req)->snt_isn); |
| /* XXX data is queued and acked as is. No buffer/window check */ |
| th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt); |
| |