[ 102/136 ] netfilter: xt_rpfilter: skip locally generated broadcast/multicast, too

Steven Rostedt
2013-05-18T03:12:00Z

[-- Attachment #1: 0102-netfilter-xt_rpfilter-skip-locally-generated-broadca.patch --]
[-- Type: text/plain, Size: 2745 bytes --]

3.6.11.4 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Florian Westphal <fw@strlen.de>

[ Upstream commit f83a7ea2075ca896f2dbf07672bac9cf3682ff74 ]

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: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
net/ipv4/netfilter/ipt_rpfilter.c | 8 +++++++-
net/ipv6/netfilter/ip6t_rpfilter.c | 8 +++++++-
2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/netfilter/ipt_rpfilter.c b/net/ipv4/netfilter/ipt_rpfilter.c
index 31371be..5d60ca1 100644
--- a/net/ipv4/netfilter/ipt_rpfilter.c
+++ b/net/ipv4/netfilter/ipt_rpfilter.c
@@ -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);
diff --git a/net/ipv6/netfilter/ip6t_rpfilter.c b/net/ipv6/netfilter/ip6t_rpfilter.c
index 5d1d8b0..a7b522f 100644
--- a/net/ipv6/netfilter/ip6t_rpfilter.c
+++ b/net/ipv6/netfilter/ip6t_rpfilter.c
@@ -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);
--
1.7.10.4