path: root/net/ipv6/netfilter/nft_fib_ipv6.c
diff options
authorLiping Zhang <>2017-01-07 20:49:18 +0800
committerPablo Neira Ayuso <>2017-01-16 14:23:01 +0100
commit6443ebc3fdd6f3c766d9442c18be274b3d736050 (patch)
tree3074af3b09ed120ad74198e669fad6464127d66e /net/ipv6/netfilter/nft_fib_ipv6.c
parentd7f5762c5e532dfe8247ce1bc60d97af27ff8d00 (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 <> Signed-off-by: Pablo Neira Ayuso <>
Diffstat (limited to 'net/ipv6/netfilter/nft_fib_ipv6.c')
1 files changed, 4 insertions, 9 deletions
diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c
index c947aad8bcc6..765facf03d45 100644
--- a/net/ipv6/netfilter/nft_fib_ipv6.c
+++ b/net/ipv6/netfilter/nft_fib_ipv6.c
@@ -18,13 +18,6 @@
#include <net/ip6_fib.h>
#include <net/ip6_route.h>
-static bool fib6_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 int get_ifindex(const struct net_device *dev)
return dev ? dev->ifindex : 0;
@@ -164,8 +157,10 @@ void nft_fib6_eval(const struct nft_expr *expr, struct nft_regs *regs,
lookup_flags = nft_fib6_flowi_init(&fl6, priv, pkt, oif);
- if (nft_hook(pkt) == NF_INET_PRE_ROUTING && fib6_is_local(pkt->skb)) {
- nft_fib_store_result(dest, priv->result, pkt, LOOPBACK_IFINDEX);
+ if (nft_hook(pkt) == NF_INET_PRE_ROUTING &&
+ nft_fib_is_loopback(pkt->skb, nft_in(pkt))) {
+ nft_fib_store_result(dest, priv->result, pkt,
+ nft_in(pkt)->ifindex);