net: udp: prefer listeners bound to an address
A relatively common use case is to have several IPs configured on a host, and have different listeners for each of them. We would like to add a "catch all" listener on addr_any, to match incoming connections not served by any of the listeners bound to a specific address. However, port-only lookups can match addr_any sockets when sockets listening on specific addresses are present if so_reuseport flag is set. This patch eliminates lookups into port-only hashtable, as lookups by (addr,port) tuple are easily available. In addition, compute_score() is tweaked to _not_ match addr_any sockets to specific addresses, as hash collisions could result in the unwanted behavior described above. Tested: the patch compiles; full test in the last patch in this patchset. Existing reuseport_* selftests also pass. Suggested-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Peter Oskolkov <posk@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -380,15 +380,12 @@ static int compute_score(struct sock *sk, struct net *net,
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ipv6_only_sock(sk))
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return -1;
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if (sk->sk_rcv_saddr != daddr)
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return -1;
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score = (sk->sk_family == PF_INET) ? 2 : 1;
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inet = inet_sk(sk);
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if (inet->inet_rcv_saddr) {
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if (inet->inet_rcv_saddr != daddr)
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return -1;
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score += 4;
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}
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if (inet->inet_daddr) {
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if (inet->inet_daddr != saddr)
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return -1;
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@ -464,65 +461,30 @@ struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
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__be16 sport, __be32 daddr, __be16 dport, int dif,
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int sdif, struct udp_table *udptable, struct sk_buff *skb)
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{
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struct sock *sk, *result;
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struct sock *result;
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unsigned short hnum = ntohs(dport);
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unsigned int hash2, slot2, slot = udp_hashfn(net, hnum, udptable->mask);
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struct udp_hslot *hslot2, *hslot = &udptable->hash[slot];
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unsigned int hash2, slot2;
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struct udp_hslot *hslot2;
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bool exact_dif = udp_lib_exact_dif_match(net, skb);
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int score, badness;
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u32 hash = 0;
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if (hslot->count > 10) {
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hash2 = ipv4_portaddr_hash(net, daddr, hnum);
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hash2 = ipv4_portaddr_hash(net, daddr, hnum);
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slot2 = hash2 & udptable->mask;
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hslot2 = &udptable->hash2[slot2];
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result = udp4_lib_lookup2(net, saddr, sport,
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daddr, hnum, dif, sdif,
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exact_dif, hslot2, skb);
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if (!result) {
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hash2 = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
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slot2 = hash2 & udptable->mask;
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hslot2 = &udptable->hash2[slot2];
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if (hslot->count < hslot2->count)
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goto begin;
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result = udp4_lib_lookup2(net, saddr, sport,
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daddr, hnum, dif, sdif,
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htonl(INADDR_ANY), hnum, dif, sdif,
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exact_dif, hslot2, skb);
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if (!result) {
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unsigned int old_slot2 = slot2;
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hash2 = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
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slot2 = hash2 & udptable->mask;
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/* avoid searching the same slot again. */
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if (unlikely(slot2 == old_slot2))
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return result;
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hslot2 = &udptable->hash2[slot2];
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if (hslot->count < hslot2->count)
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goto begin;
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result = udp4_lib_lookup2(net, saddr, sport,
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daddr, hnum, dif, sdif,
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exact_dif, hslot2, skb);
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}
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if (unlikely(IS_ERR(result)))
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return NULL;
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return result;
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}
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begin:
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result = NULL;
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badness = 0;
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sk_for_each_rcu(sk, &hslot->head) {
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score = compute_score(sk, net, saddr, sport,
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daddr, hnum, dif, sdif, exact_dif);
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if (score > badness) {
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if (sk->sk_reuseport) {
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hash = udp_ehashfn(net, daddr, hnum,
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saddr, sport);
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result = reuseport_select_sock(sk, hash, skb,
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sizeof(struct udphdr));
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if (unlikely(IS_ERR(result)))
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return NULL;
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if (result)
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return result;
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}
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result = sk;
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badness = score;
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}
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}
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if (unlikely(IS_ERR(result)))
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return NULL;
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return result;
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}
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EXPORT_SYMBOL_GPL(__udp4_lib_lookup);
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