[PATCH 5.12 026/178] netfilter: nft_fib_ipv6: skip ipv6 packets from any to link-local

Greg Kroah-Hartman
2021-06-21T16:40:51Z

From: Florian Westphal <fw@strlen.de>

[ Upstream commit 12f36e9bf678a81d030ca1b693dcda62b55af7c5 ]

The ip6tables rpfilter match has an extra check to skip packets with
"::" source address.

Extend this to ipv6 fib expression. Else ipv6 duplicate address detection
packets will fail rpf route check -- lookup returns -ENETUNREACH.

While at it, extend the prerouting check to also cover the ingress hook.

Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1543
Fixes: f6d0cbcf09c5 ("netfilter: nf_tables: add fib expression")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/netfilter/nft_fib_ipv6.c | 22 ++++++++++++++++++----
1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c
index e204163c7036..92f3235fa287 100644
--- a/net/ipv6/netfilter/nft_fib_ipv6.c
+++ b/net/ipv6/netfilter/nft_fib_ipv6.c
@@ -135,6 +135,17 @@ void nft_fib6_eval_type(const struct nft_expr *expr, struct nft_regs *regs,
}
EXPORT_SYMBOL_GPL(nft_fib6_eval_type);

+static bool nft_fib_v6_skip_icmpv6(const struct sk_buff *skb, u8 next, const struct ipv6hdr *iph)
+{
+ if (likely(next != IPPROTO_ICMPV6))
+ return false;
+
+ if (ipv6_addr_type(&iph->saddr) != IPV6_ADDR_ANY)
+ return false;
+
+ return ipv6_addr_type(&iph->daddr) & IPV6_ADDR_LINKLOCAL;
+}
+
void nft_fib6_eval(const struct nft_expr *expr, struct nft_regs *regs,
const struct nft_pktinfo *pkt)
{
@@ -163,10 +174,13 @@ void nft_fib6_eval(const struct nft_expr *expr, struct nft_regs *regs,

lookup_flags = nft_fib6_flowi_init(&fl6, priv, pkt, oif, iph);

- if (nft_hook(pkt) == NF_INET_PRE_ROUTING &&
- nft_fib_is_loopback(pkt->skb, nft_in(pkt))) {
- nft_fib_store_result(dest, priv, nft_in(pkt));
- return;
+ if (nft_hook(pkt) == NF_INET_PRE_ROUTING ||
+ nft_hook(pkt) == NF_INET_INGRESS) {
+ if (nft_fib_is_loopback(pkt->skb, nft_in(pkt)) ||
+ nft_fib_v6_skip_icmpv6(pkt->skb, pkt->tprot, iph)) {
+ nft_fib_store_result(dest, priv, nft_in(pkt));
+ return;
+ }
}

*dest = 0;
--
2.30.2