[RFCv2 bpf-next 07/12] inet6: Run inet_lookup bpf program on socket lookup

[Jakub Sitnicki <jakub@cloudflare.com>]

Following the ipv4 changes, run a BPF program attached to netns in context
of which we're doing the socket lookup so that it can redirect the skb to a
socket of its choice. The program runs before the listening socket lookup.

Suggested-by: Marek Majkowski <marek@cloudflare.com>
Reviewed-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
---
 include/net/inet6_hashtables.h | 19 +++++++++++++++++++
 net/ipv6/inet6_hashtables.c    |  5 +++++
 2 files changed, 24 insertions(+)

diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h
index fe96bf247aac..c2393d148d8d 100644
--- a/include/net/inet6_hashtables.h
+++ b/include/net/inet6_hashtables.h
@@ -104,6 +104,25 @@ struct sock *inet6_lookup(struct net *net, struct inet_hashinfo *hashinfo,
 			  const int dif);
 
 int inet6_hash(struct sock *sk);
+
+static inline struct sock *inet6_lookup_run_bpf(struct net *net, u8 proto,
+						const struct in6_addr *saddr,
+						__be16 sport,
+						const struct in6_addr *daddr,
+						unsigned short hnum)
+{
+	struct bpf_inet_lookup_kern ctx = {
+		.family		= AF_INET6,
+		.protocol	= proto,
+		.saddr6		= *saddr,
+		.sport		= sport,
+		.daddr6		= *daddr,
+		.hnum		= hnum,
+	};
+
+	return __inet_lookup_run_bpf(net, &ctx);
+}
+
 #endif /* IS_ENABLED(CONFIG_IPV6) */
 
 #define INET6_MATCH(__sk, __net, __saddr, __daddr, __ports, __dif, __sdif) \
diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c
index cf60fae9533b..40dd0a3d80ed 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -157,6 +157,11 @@ struct sock *inet6_lookup_listener(struct net *net,
 	struct sock *result = NULL;
 	unsigned int hash2;
 
+	result = inet6_lookup_run_bpf(net, hashinfo->protocol,
+				      saddr, sport, daddr, hnum);
+	if (result)
+		goto done;
+
 	hash2 = ipv6_portaddr_hash(net, daddr, hnum);
 	ilb2 = inet_lhash2_bucket(hashinfo, hash2);
 
-- 
2.20.1