[PATCH bpf-next 12/17] udp6: Run SK_LOOKUP BPF program on socket lookup

[Jakub Sitnicki]

Same as for udp4, let BPF program override the socket lookup result, by
selecting a receiving socket of its choice or failing the lookup, if no
connected UDP socket matched packet 4-tuple.

Suggested-by: Marek Majkowski <ma...@cloudflare.com>
Reviewed-by: Lorenz Bauer <l...@cloudflare.com>
Signed-off-by: Jakub Sitnicki <ja...@cloudflare.com>
---
 net/ipv6/udp.c | 37 ++++++++++++++++++++++++++++---------
 1 file changed, 28 insertions(+), 9 deletions(-)

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index ee2073329d25..934f41a5e6ca 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -197,28 +197,47 @@ struct sock *__udp6_lib_lookup(struct net *net,
                               int dif, int sdif, struct udp_table *udptable,
                               struct sk_buff *skb)
 {
+       struct sock *result, *sk, *reuse_sk;
        unsigned short hnum = ntohs(dport);
        unsigned int hash2, slot2;
        struct udp_hslot *hslot2;
-       struct sock *result;
 
        hash2 = ipv6_portaddr_hash(net, daddr, hnum);
        slot2 = hash2 & udptable->mask;
        hslot2 = &udptable->hash2[slot2];
 
+       /* Lookup connected or non-wildcard sockets */
        result = udp6_lib_lookup2(net, saddr, sport,
                                  daddr, hnum, dif, sdif,
                                  hslot2, skb);
-       if (!result) {
-               hash2 = ipv6_portaddr_hash(net, &in6addr_any, hnum);
-               slot2 = hash2 & udptable->mask;
+       if (!IS_ERR_OR_NULL(result) && result->sk_state == TCP_ESTABLISHED)
+               goto done;
 
-               hslot2 = &udptable->hash2[slot2];
-
-               result = udp6_lib_lookup2(net, saddr, sport,
-                                         &in6addr_any, hnum, dif, sdif,
-                                         hslot2, skb);
+       /* Lookup redirect from BPF */
+       sk = inet6_lookup_run_bpf(net, udptable->protocol,
+                                 saddr, sport, daddr, hnum);
+       if (IS_ERR(sk))
+               return NULL;
+       if (sk) {
+               reuse_sk = lookup_reuseport(net, sk, skb,
+                                           saddr, sport, daddr, hnum);
+               result = reuse_sk ? : sk;
+               goto done;
        }
+
+       /* Got non-wildcard socket or error on first lookup */
+       if (result)
+               goto done;
+
+       /* Lookup wildcard sockets */
+       hash2 = ipv6_portaddr_hash(net, &in6addr_any, hnum);
+       slot2 = hash2 & udptable->mask;
+       hslot2 = &udptable->hash2[slot2];
+
+       result = udp6_lib_lookup2(net, saddr, sport,
+                                 &in6addr_any, hnum, dif, sdif,
+                                 hslot2, skb);
+done:
        if (IS_ERR(result))
                return NULL;
        return result;
-- 
2.25.3