diff options
author | Liping Zhang <zlpnobody@gmail.com> | 2017-01-07 20:49:18 +0800 |
---|---|---|
committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2017-01-16 14:23:01 +0100 |
commit | 6443ebc3fdd6f3c766d9442c18be274b3d736050 (patch) | |
tree | 3074af3b09ed120ad74198e669fad6464127d66e /net/ipv4/netfilter/ipt_rpfilter.c | |
parent | d7f5762c5e532dfe8247ce1bc60d97af27ff8d00 (diff) |
netfilter: rpfilter: fix incorrect loopback packet judgment
Currently, we check the existing rtable in PREROUTING hook, if RTCF_LOCAL
is set, we assume that the packet is loopback.
But this assumption is incorrect, for example, a packet encapsulated
in ipsec transport mode was received and routed to local, after
decapsulation, it would be delivered to local again, and the rtable
was not dropped, so RTCF_LOCAL check would trigger. But actually, the
packet was not loopback.
So for these normal loopback packets, we can check whether the in device
is IFF_LOOPBACK or not. For these locally generated broadcast/multicast,
we can check whether the skb->pkt_type is PACKET_LOOPBACK or not.
Finally, there's a subtle difference between nft fib expr and xtables
rpfilter extension, user can add the following nft rule to do strict
rpfilter check:
# nft add rule x y meta iif eth0 fib saddr . iif oif != eth0 drop
So when the packet is loopback, it's better to store the in device
instead of the LOOPBACK_IFINDEX, otherwise, after adding the above
nft rule, locally generated broad/multicast packets will be dropped
incorrectly.
Fixes: f83a7ea2075c ("netfilter: xt_rpfilter: skip locally generated broadcast/multicast, too")
Fixes: f6d0cbcf09c5 ("netfilter: nf_tables: add fib expression")
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net/ipv4/netfilter/ipt_rpfilter.c')
-rw-r--r-- | net/ipv4/netfilter/ipt_rpfilter.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/net/ipv4/netfilter/ipt_rpfilter.c b/net/ipv4/netfilter/ipt_rpfilter.c index f273098e48fd..37fb9552e858 100644 --- a/net/ipv4/netfilter/ipt_rpfilter.c +++ b/net/ipv4/netfilter/ipt_rpfilter.c @@ -63,10 +63,10 @@ static bool rpfilter_lookup_reverse(struct net *net, struct flowi4 *fl4, return dev_match || flags & XT_RPFILTER_LOOSE; } -static bool rpfilter_is_local(const struct sk_buff *skb) +static bool +rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in) { - const struct rtable *rt = skb_rtable(skb); - return rt && (rt->rt_flags & RTCF_LOCAL); + return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK; } static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par) @@ -79,7 +79,7 @@ static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par) info = par->matchinfo; invert = info->flags & XT_RPFILTER_INVERT; - if (rpfilter_is_local(skb)) + if (rpfilter_is_loopback(skb, xt_in(par))) return true ^ invert; iph = ip_hdr(skb); |