linux-kernel - Re: [PATCH nf v2] netfilter: conntrack: connection timeout after re-register

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Date:   Tue, 20 Oct 2020 17:21:35 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Francesco Ruggeri <fruggeri@...sta.com>
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        coreteam@...filter.org, netfilter-devel@...r.kernel.org,
        kuba@...nel.org, davem@...emloft.net, fw@...len.org,
        kadlec@...filter.org
Subject: Re: [PATCH nf v2] netfilter: conntrack: connection timeout after
 re-register

On Wed, Oct 07, 2020 at 12:32:52PM -0700, Francesco Ruggeri wrote:
> If the first packet conntrack sees after a re-register is an outgoing
> keepalive packet with no data (SEG.SEQ = SND.NXT-1), td_end is set to
> SND.NXT-1.
> When the peer correctly acknowledges SND.NXT, tcp_in_window fails
> check III (Upper bound for valid (s)ack: sack <= receiver.td_end) and
> returns false, which cascades into nf_conntrack_in setting
> skb->_nfct = 0 and in later conntrack iptables rules not matching.
> In cases where iptables are dropping packets that do not match
> conntrack rules this can result in idle tcp connections to time out.

Applied, thanks.