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>
Signed-off-by: Jakub Sitnicki <ja...@cloudflare.com>
---
Notes:
v4:
- Adapt to change in bpf_sk_lookup_run_v4 return value semantics.
v3:
- Use a static_key to minimize the hook overhead when not used. (Alexei)
- Adapt for running an array of attached programs. (Alexei)
- Adapt for optionally skipping reuseport selection. (Martin)
net/ipv4/udp.c | 59 ++++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 50 insertions(+), 9 deletions(-)
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 0d03e0277263..e82db3ab49d3 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -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;
--
2.25.4
