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Commit f83a7ea2 authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
Browse files

netfilter: xt_rpfilter: skip locally generated broadcast/multicast, too 



Alex Efros reported rpfilter module doesn't match following packets:
IN=br.qemu SRC=192.168.2.1 DST=192.168.2.255 [ .. ]
(netfilter bugzilla #814).

Problem is that network stack arranges for the locally generated broadcasts
to appear on the interface they were sent out, so the IFF_LOOPBACK check
doesn't trigger.

As -m rpfilter is restricted to PREROUTING, we can check for existing
rtable instead, it catches locally-generated broad/multicast case, too.

Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 5add189a

net/ipv4/netfilter/ipt_rpfilter.c

+7 −1
Original line number Diff line number Diff line
@@ -66,6 +66,12 @@ static bool rpfilter_lookup_reverse(struct flowi4 *fl4, 
	return dev_match;

}



static bool rpfilter_is_local(const struct sk_buff *skb)

{

	const struct rtable *rt = skb_rtable(skb);

	return rt && (rt->rt_flags & RTCF_LOCAL);

}



static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)

{

	const struct xt_rpfilter_info *info;
@@ -76,7 +82,7 @@ static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par) 
	info = par->matchinfo;

	invert = info->flags & XT_RPFILTER_INVERT;



	if (par->in->flags & IFF_LOOPBACK)

	if (rpfilter_is_local(skb))

		return true ^ invert;



	iph = ip_hdr(skb);

net/ipv6/netfilter/ip6t_rpfilter.c

+7 −1
Original line number Diff line number Diff line
@@ -71,6 +71,12 @@ static bool rpfilter_lookup_reverse6(const struct sk_buff *skb, 
	return ret;

}



static bool rpfilter_is_local(const struct sk_buff *skb)

{

	const struct rt6_info *rt = (const void *) skb_dst(skb);

	return rt && (rt->rt6i_flags & RTF_LOCAL);

}



static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)

{

	const struct xt_rpfilter_info *info = par->matchinfo;
@@ -78,7 +84,7 @@ static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par) 
	struct ipv6hdr *iph;

	bool invert = info->flags & XT_RPFILTER_INVERT;



	if (par->in->flags & IFF_LOOPBACK)

	if (rpfilter_is_local(skb))

		return true ^ invert;



	iph = ipv6_hdr(skb);