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

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Date:   Wed,  6 May 2020 14:55:08 +0200
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     netdev@...r.kernel.org, bpf@...r.kernel.org
Cc:     dccp@...r.kernel.org, kernel-team@...udflare.com,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Gerrit Renker <gerrit@....abdn.ac.uk>,
        Jakub Kicinski <kuba@...nel.org>,
        Marek Majkowski <marek@...udflare.com>,
        Lorenz Bauer <lmb@...udflare.com>
Subject: [PATCH bpf-next 12/17] udp6: Run SK_LOOKUP BPF program on socket lookup

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 <marek@...udflare.com>
Reviewed-by: Lorenz Bauer <lmb@...udflare.com>
Signed-off-by: Jakub Sitnicki <jakub@...udflare.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