Commit 72f7e944 authored by Jakub Sitnicki's avatar Jakub Sitnicki Committed by Alexei Starovoitov
Browse files

udp: Run SK_LOOKUP BPF program on socket lookup 



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: default avatarMarek Majkowski <marek@cloudflare.com>
Signed-off-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200717103536.397595-9-jakub@cloudflare.com
parent 7629c73a

net/ipv4/udp.c

+50 −9
Original line number Diff line number Diff line
@@ -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

 */
@@ -463,19 +486,37 @@ 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) {

	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];
@@ -483,7 +524,7 @@ struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr, 
	result = udp4_lib_lookup2(net, saddr, sport,

				  htonl(INADDR_ANY), hnum, dif, sdif,

				  hslot2, skb);

	}

done:

	if (IS_ERR(result))

		return NULL;

	return result;