udp: Run SK_LOOKUP BPF program on socket lookup
authorJakub Sitnicki <jakub@cloudflare.com>
Fri, 17 Jul 2020 10:35:29 +0000 (12:35 +0200)
committerAlexei Starovoitov <ast@kernel.org>
Sat, 18 Jul 2020 03:18:17 +0000 (20:18 -0700)
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 <marek@cloudflare.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200717103536.397595-9-jakub@cloudflare.com
net/ipv4/udp.c

index 9296fae..b738c63 100644 (file)
@@ -456,6 +456,29 @@ static struct sock *udp4_lib_lookup2(struct net *net,
        return result;
 }
 
+static inline struct sock *udp4_lookup_run_bpf(struct net *net,
+                                              struct udp_table *udptable,
+                                              struct sk_buff *skb,
+                                              __be32 saddr, __be16 sport,
+                                              __be32 daddr, u16 hnum)
+{
+       struct sock *sk, *reuse_sk;
+       bool no_reuseport;
+
+       if (udptable != &udp_table)
+               return NULL; /* only UDP is supported */
+
+       no_reuseport = bpf_sk_lookup_run_v4(net, IPPROTO_UDP,
+                                           saddr, sport, daddr, hnum, &sk);
+       if (no_reuseport || IS_ERR_OR_NULL(sk))
+               return sk;
+
+       reuse_sk = lookup_reuseport(net, sk, skb, saddr, sport, daddr, hnum);
+       if (reuse_sk)
+               sk = reuse_sk;
+       return sk;
+}
+
 /* UDP is nearly always wildcards out the wazoo, it makes no sense to try
  * harder than this. -DaveM
  */
@@ -463,27 +486,45 @@ 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;
        unsigned short hnum = ntohs(dport);
        unsigned int hash2, slot2;
        struct udp_hslot *hslot2;
+       struct sock *result, *sk;
 
        hash2 = ipv4_portaddr_hash(net, daddr, hnum);
        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];
-
-               result = udp4_lib_lookup2(net, saddr, sport,
-                                         htonl(INADDR_ANY), hnum, dif, sdif,
-                                         hslot2, skb);
+       if (!IS_ERR_OR_NULL(result) && result->sk_state == TCP_ESTABLISHED)
+               goto done;
+
+       /* Lookup redirect from BPF */
+       if (static_branch_unlikely(&bpf_sk_lookup_enabled)) {
+               sk = udp4_lookup_run_bpf(net, udptable, skb,
+                                        saddr, sport, daddr, hnum);
+               if (sk) {
+                       result = 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;