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Commit d9fbc7f6 authored by Peter Oskolkov's avatar Peter Oskolkov Committed by David S. Miller
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net: tcp: 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: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarPeter Oskolkov <posk@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 23b0269e

net/ipv4/inet_hashtables.c

+8 −52
Original line number Diff line number Diff line
@@ -234,24 +234,16 @@ static inline int compute_score(struct sock *sk, struct net *net, 
				const int dif, const int sdif, bool exact_dif)

{

	int score = -1;

	struct inet_sock *inet = inet_sk(sk);

	bool dev_match;



	if (net_eq(sock_net(sk), net) && inet->inet_num == hnum &&

	if (net_eq(sock_net(sk), net) && sk->sk_num == hnum &&

			!ipv6_only_sock(sk)) {

		__be32 rcv_saddr = inet->inet_rcv_saddr;

		score = sk->sk_family == PF_INET ? 2 : 1;

		if (rcv_saddr) {

			if (rcv_saddr != daddr)

		if (sk->sk_rcv_saddr != daddr)

			return -1;

			score += 4;

		}

		dev_match = inet_sk_bound_dev_eq(net, sk->sk_bound_dev_if,

						 dif, sdif);

		if (!dev_match)



		if (!inet_sk_bound_dev_eq(net, sk->sk_bound_dev_if, dif, sdif))

			return -1;

		score += 4;



		score = sk->sk_family == PF_INET ? 2 : 1;

		if (sk->sk_incoming_cpu == raw_smp_processor_id())

			score++;

	}
@@ -307,26 +299,12 @@ struct sock *__inet_lookup_listener(struct net *net, 
				    const __be32 daddr, const unsigned short hnum,

				    const int dif, const int sdif)

{

	unsigned int hash = inet_lhashfn(net, hnum);

	struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash];

	bool exact_dif = inet_exact_dif_match(net, skb);

	struct inet_listen_hashbucket *ilb2;

	struct sock *sk, *result = NULL;

	int score, hiscore = 0;

	struct sock *result = NULL;

	unsigned int hash2;

	u32 phash = 0;



	if (ilb->count <= 10 || !hashinfo->lhash2)

		goto port_lookup;



	/* Too many sk in the ilb bucket (which is hashed by port alone).

	 * Try lhash2 (which is hashed by port and addr) instead.

	 */



	hash2 = ipv4_portaddr_hash(net, daddr, hnum);

	ilb2 = inet_lhash2_bucket(hashinfo, hash2);

	if (ilb2->count > ilb->count)

		goto port_lookup;



	result = inet_lhash2_lookup(net, ilb2, skb, doff,

				    saddr, sport, daddr, hnum,
@@ -335,34 +313,12 @@ struct sock *__inet_lookup_listener(struct net *net, 
		goto done;



	/* Lookup lhash2 with INADDR_ANY */



	hash2 = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum);

	ilb2 = inet_lhash2_bucket(hashinfo, hash2);

	if (ilb2->count > ilb->count)

		goto port_lookup;



	result = inet_lhash2_lookup(net, ilb2, skb, doff,

				    saddr, sport, daddr, hnum,

				    saddr, sport, htonl(INADDR_ANY), hnum,

				    dif, sdif);

	goto done;



port_lookup:

	sk_for_each_rcu(sk, &ilb->head) {

		score = compute_score(sk, net, hnum, daddr,

				      dif, sdif, exact_dif);

		if (score > hiscore) {

			if (sk->sk_reuseport) {

				phash = inet_ehashfn(net, daddr, hnum,

						     saddr, sport);

				result = reuseport_select_sock(sk, phash,

							       skb, doff);

				if (result)

					goto done;

			}

			result = sk;

			hiscore = score;

		}

	}

done:

	if (unlikely(IS_ERR(result)))

		return NULL;