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| author | Eric Dumazet <edumazet@google.com> | 2016-06-27 17:38:50 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-06-29 05:25:11 -0400 |
| commit | a3d2e9f8eb1487f4191ff08ce2d3d63702c65a90 (patch) | |
| tree | 6bd92ff1c7e9c968a795b73804f7cc2869f68659 /net/ipv4 | |
| parent | 96183182ad05d1ce31b9048921c12bf4ad621eaf (diff) | |
| download | blackbird-op-linux-a3d2e9f8eb1487f4191ff08ce2d3d63702c65a90.tar.gz blackbird-op-linux-a3d2e9f8eb1487f4191ff08ce2d3d63702c65a90.zip | |
tcp: do not send too big packets at retransmit time
Arjun reported a bug in TCP stack and bisected it to a recent commit.
In case where we process SACK, we can coalesce multiple skbs
into fat ones (tcp_shift_skb_data()), to lower write queue
overhead, because we do not expect to retransmit these packets.
However, SACK reneging can happen, forcing the sender to retransmit
all these packets. If skb->len is above 64KB, we then send buggy
IP packets that could hang TSO engine on cxgb4.
Neal suggested to use tcp_tso_autosize() instead of tp->gso_segs
so that we cook packets of optimal size vs TCP/pacing.
Thanks to Arjun for reporting the bug and running the tests !
Fixes: 10d3be569243 ("tcp-tso: do not split TSO packets at retransmit time")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Arjun V <arjun@chelsio.com>
Tested-by: Arjun V <arjun@chelsio.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/tcp_output.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 8bd9911fdd16..e00e972c4e6a 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2751,7 +2751,7 @@ void tcp_xmit_retransmit_queue(struct sock *sk) struct tcp_sock *tp = tcp_sk(sk); struct sk_buff *skb; struct sk_buff *hole = NULL; - u32 last_lost; + u32 max_segs, last_lost; int mib_idx; int fwd_rexmitting = 0; @@ -2771,6 +2771,7 @@ void tcp_xmit_retransmit_queue(struct sock *sk) last_lost = tp->snd_una; } + max_segs = tcp_tso_autosize(sk, tcp_current_mss(sk)); tcp_for_write_queue_from(skb, sk) { __u8 sacked = TCP_SKB_CB(skb)->sacked; int segs; @@ -2784,6 +2785,10 @@ void tcp_xmit_retransmit_queue(struct sock *sk) segs = tp->snd_cwnd - tcp_packets_in_flight(tp); if (segs <= 0) return; + /* In case tcp_shift_skb_data() have aggregated large skbs, + * we need to make sure not sending too bigs TSO packets + */ + segs = min_t(int, segs, max_segs); if (fwd_rexmitting) { begin_fwd: |
