netdev - Re: [FYI] xfrm: Don't lookup sk_policy for timewait sockets

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Date:	Thu, 09 Apr 2015 14:37:27 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	sebastian.poehn@...il.com, netdev@...r.kernel.org
Subject: Re: [FYI] xfrm: Don't lookup sk_policy for timewait sockets

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 09 Apr 2015 02:07:41 -0700

> TCP stack never sends packets attached to a socket in timewait state.

TPROXY assigns timewait sockets to skb->sk, that's the bug.

In net/netfilter/xt_TPROXY.c:

	tproxy_tg4()
 ...
		sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,
				   iph->saddr, iph->daddr,
				   hp->source, hp->dest,
				   skb->dev, NFT_LOOKUP_ESTABLISHED);
	/* NOTE: assign_sock consumes our sk reference */
	if (sk && tproxy_sk_is_transparent(sk)) {
		/* This should be in a separate target, but we don't do multiple
		   targets on the same rule yet */
		skb->mark = (skb->mark & ~mark_mask) ^ mark_value;

		pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n",
			 iph->protocol, &iph->daddr, ntohs(hp->dest),
			 &laddr, ntohs(lport), skb->mark);

		nf_tproxy_assign_sock(skb, sk);
 ...
 /* assign a socket to the skb -- consumes sk */
static void
nf_tproxy_assign_sock(struct sk_buff *skb, struct sock *sk)
{
	skb_orphan(skb);
	skb->sk = sk;
	skb->destructor = sock_edemux;
}
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