netdev - Re: [PATCH 1/1] tcp: Honor the eor bit in tcp_mtu

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Date:   Mon, 05 Feb 2018 09:10:19 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Ilya Lesokhin <ilyal@...lanox.com>, netdev@...r.kernel.org,
        kafai@...com
Cc:     borisp@...lanox.com
Subject: Re: [PATCH 1/1] tcp: Honor the eor bit in tcp_mtu_probe

On Mon, 2018-02-05 at 07:52 -0800, Eric Dumazet wrote:
> On Mon, 2018-02-05 at 17:11 +0200, Ilya Lesokhin wrote:
> > Avoid SKB coalescing if eor bit is set in one of the relevant
> > SKBs.
> > 
> > Fixes: c134ecb87817 ("tcp: Make use of MSG_EOR in tcp_sendmsg")
> > Signed-off-by: Ilya Lesokhin <ilyal@...lanox.com>
> > ---
> 
> Reviewed-by: Eric Dumazet <edumazet@...gle.com>
> 
> Thanks.


I am taking this approval back.

You missed an eor propagation if it is in the last skb that is copied
to the new skb.

Something like this added to your patch :

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e9f985e42405a38fc95980da5debb7ac8b51fbb5..87c2ff458f7528ee3cd3e5e1154375a906c1bc67 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2134,6 +2134,7 @@ static int tcp_mtu_probe(struct sock *sk)
 			/* We've eaten all the data from this skb.
 			 * Throw it away. */
 			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
+			TCP_SKB_CB(nskb)->eor = TCP_SKB_CB(skb)->eor;
 			tcp_unlink_write_queue(skb, sk);
 			sk_wmem_free_skb(sk, skb);
 		} else {