netdev - Re: [PATCH] tcp: fix TCP_MAXSEG for established IPv6 passive sockets

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Date:	Sun, 22 Apr 2012 22:14:54 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Neal Cardwell <ncardwell@...gle.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Eric Dumazet <edumazet@...gle.com>,
	Nandita Dukkipati <nanditad@...gle.com>,
	Yuchung Cheng <ycheng@...gle.com>, ilpo.jarvinen@...sinki.fi,
	maze@...gle.com, Tom Herbert <therbert@...gle.com>
Subject: Re: [PATCH] tcp: fix TCP_MAXSEG for established IPv6 passive
 sockets

On Sun, 2012-04-22 at 15:45 -0400, Neal Cardwell wrote:
> Commit f5fff5d forgot to fix TCP_MAXSEG behavior IPv6 sockets, so IPv6
> TCP server sockets that used TCP_MAXSEG would find that the advmss of
> child sockets would be incorrect. This commit mirrors the advmss logic
> from tcp_v4_syn_recv_sock in tcp_v6_syn_recv_sock. Eventually this
> logic should probably be shared between IPv4 and IPv6, but this at
> least fixes this issue.
> 
> Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
> ---
>  net/ipv6/tcp_ipv6.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index 86cfe60..98256cf 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -1383,6 +1383,10 @@ static struct sock * tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
>  	tcp_mtup_init(newsk);
>  	tcp_sync_mss(newsk, dst_mtu(dst));
>  	newtp->advmss = dst_metric_advmss(dst);
> +	if (tcp_sk(sk)->rx_opt.user_mss &&
> +	    tcp_sk(sk)->rx_opt.user_mss < newtp->advmss)
> +		newtp->advmss = tcp_sk(sk)->rx_opt.user_mss;
> +
>  	tcp_initialize_rcv_mss(newsk);
>  	if (tcp_rsk(req)->snt_synack)
>  		tcp_valid_rtt_meas(newsk,

Acked-by: Eric Dumazet <edumazet@...gle.com>


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