netdev - Re: [patch net-next 2/3] netfilter: ip6_tables: use reasm skb for matching

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Date:	Tue, 05 Nov 2013 09:50:28 -0200
From:	Marcelo Ricardo Leitner <mleitner@...hat.com>
To:	Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org
CC:	davem@...emloft.net, pablo@...filter.org,
	netfilter-devel@...r.kernel.org, yoshfuji@...ux-ipv6.org,
	kadlec@...ckhole.kfki.hu, kaber@...sh.net, kuznet@....inr.ac.ru,
	jmorris@...ei.org, wensong@...ux-vs.org, horms@...ge.net.au,
	ja@....bg, edumazet@...gle.com, pshelar@...ira.com,
	jasowang@...hat.com, alexander.h.duyck@...el.com,
	coreteam@...filter.org, fw@...len.de
Subject: Re: [patch net-next 2/3] netfilter: ip6_tables: use reasm skb for
 matching

Em 05-11-2013 09:02, Jiri Pirko escreveu:
> Currently, when ipv6 fragment goes through the netfilter, match
> functions are called on them directly. This might cause match function
> to fail. So benefit from the fact that nf_defrag_ipv6 constructs
> reassembled skb for us and use this reassembled skb for matching.
>
> This patch fixes for example following situation:
> On HOSTA do:
> ip6tables -I INPUT -p icmpv6 -j DROP
> ip6tables -I INPUT -p icmpv6 -m icmp6 --icmpv6-type 128 -j ACCEPT
>
> and on HOSTB you do:
> ping6 HOSTA -s2000    (MTU is 1500)
>
> Incoming echo requests will be filtered out on HOSTA. This issue does
> not occur with smaller packets than MTU (where fragmentation does not happen).
>
> Signed-off-by: Jiri Pirko <jiri@...nulli.us>

Signed-off-by: Marcelo Ricardo Leitner <mleitner@...hat.com>

> ---
>   net/ipv6/netfilter/ip6_tables.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
> index 710238f..ec9cb1a 100644
> --- a/net/ipv6/netfilter/ip6_tables.c
> +++ b/net/ipv6/netfilter/ip6_tables.c
> @@ -328,6 +328,10 @@ ip6t_do_table(struct sk_buff *skb,
>   	const struct xt_table_info *private;
>   	struct xt_action_param acpar;
>   	unsigned int addend;
> +	struct sk_buff *reasm = skb_nfct_reasm(skb);
> +
> +	if (!reasm)
> +		reasm = skb;
>
>   	/* Initialization */
>   	indev = in ? in->name : nulldevname;
> @@ -368,7 +372,7 @@ ip6t_do_table(struct sk_buff *skb,
>
>   		IP_NF_ASSERT(e);
>   		acpar.thoff = 0;
> -		if (!ip6_packet_match(skb, indev, outdev, &e->ipv6,
> +		if (!ip6_packet_match(reasm, indev, outdev, &e->ipv6,
>   		    &acpar.thoff, &acpar.fragoff, &acpar.hotdrop)) {
>    no_match:
>   			e = ip6t_next_entry(e);
> @@ -378,7 +382,7 @@ ip6t_do_table(struct sk_buff *skb,
>   		xt_ematch_foreach(ematch, e) {
>   			acpar.match     = ematch->u.kernel.match;
>   			acpar.matchinfo = ematch->data;
> -			if (!acpar.match->match(skb, &acpar))
> +			if (!acpar.match->match(reasm, &acpar))
>   				goto no_match;
>   		}
>
>

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