[PATCH bpf-next 10/17] udp: Run SK_LOOKUP BPF program on socket lookup

[Jakub Sitnicki]

Following INET/TCP socket lookup changes, modify UDP socket lookup to let
BPF program select a receiving socket before searching for a socket by
destination address and port as usual.

Lookup of connected sockets that match packet 4-tuple is unaffected by this
change. BPF program runs, and potentially overrides the lookup result, only
if a 4-tuple match was not found.

Suggested-by: Marek Majkowski <ma...@cloudflare.com>
Reviewed-by: Lorenz Bauer <l...@cloudflare.com>
Signed-off-by: Jakub Sitnicki <ja...@cloudflare.com>
---
 net/ipv4/udp.c | 36 ++++++++++++++++++++++++++++--------
 1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index d4842f29294a..18d8432f6551 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -460,7 +460,7 @@ struct sock *__udp4_lib_lookup(struct net *net, __be32 
saddr,
                __be16 sport, __be32 daddr, __be16 dport, int dif,
                int sdif, struct udp_table *udptable, struct sk_buff *skb)
 {
-       struct sock *result;
+       struct sock *result, *sk, *reuse_sk;
        unsigned short hnum = ntohs(dport);
        unsigned int hash2, slot2;
        struct udp_hslot *hslot2;
@@ -469,18 +469,38 @@ struct sock *__udp4_lib_lookup(struct net *net, __be32 
saddr,
        slot2 = hash2 & udptable->mask;
        hslot2 = &udptable->hash2[slot2];
 
+       /* Lookup connected or non-wildcard socket */
        result = udp4_lib_lookup2(net, saddr, sport,
                                  daddr, hnum, dif, sdif,
                                  hslot2, skb);
-       if (!result) {
-               hash2 = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
-               slot2 = hash2 & udptable->mask;
-               hslot2 = &udptable->hash2[slot2];
+       if (!IS_ERR_OR_NULL(result) && result->sk_state == TCP_ESTABLISHED)
+               goto done;
 
-               result = udp4_lib_lookup2(net, saddr, sport,
-                                         htonl(INADDR_ANY), hnum, dif, sdif,
-                                         hslot2, skb);
+       /* Lookup redirect from BPF */
+       sk = inet_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 = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
+       slot2 = hash2 & udptable->mask;
+       hslot2 = &udptable->hash2[slot2];
+
+       result = udp4_lib_lookup2(net, saddr, sport,
+                                 htonl(INADDR_ANY), hnum, dif, sdif,
+                                 hslot2, skb);
+done:
        if (IS_ERR(result))
                return NULL;
        return result;
-- 
2.25.3