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Commit 23b0269e authored by Peter Oskolkov's avatar Peter Oskolkov Committed by David S. Miller
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net: udp6: 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 4cdeeee9

net/ipv6/udp.c

+21 −58
Original line number Diff line number Diff line
@@ -125,6 +125,9 @@ static int compute_score(struct sock *sk, struct net *net, 
	    sk->sk_family != PF_INET6)

		return -1;



	if (!ipv6_addr_equal(&sk->sk_v6_rcv_saddr, daddr))

		return -1;



	score = 0;

	inet = inet_sk(sk);
@@ -134,12 +137,6 @@ static int compute_score(struct sock *sk, struct net *net, 
		score++;

	}



	if (!ipv6_addr_any(&sk->sk_v6_rcv_saddr)) {

		if (!ipv6_addr_equal(&sk->sk_v6_rcv_saddr, daddr))

			return -1;

		score++;

	}



	if (!ipv6_addr_any(&sk->sk_v6_daddr)) {

		if (!ipv6_addr_equal(&sk->sk_v6_daddr, saddr))

			return -1;
@@ -197,38 +194,27 @@ struct sock *__udp6_lib_lookup(struct net *net, 
			       int dif, int sdif, struct udp_table *udptable,

			       struct sk_buff *skb)

{

	struct sock *sk, *result;

	unsigned short hnum = ntohs(dport);

	unsigned int hash2, slot2, slot = udp_hashfn(net, hnum, udptable->mask);

	struct udp_hslot *hslot2, *hslot = &udptable->hash[slot];

	unsigned int hash2, slot2;

	struct udp_hslot *hslot2;

	struct sock *result;

	bool exact_dif = udp6_lib_exact_dif_match(net, skb);

	int score, badness;

	u32 hash = 0;



	if (hslot->count > 10) {

	hash2 = ipv6_portaddr_hash(net, daddr, hnum);

	slot2 = hash2 & udptable->mask;

	hslot2 = &udptable->hash2[slot2];

		if (hslot->count < hslot2->count)

			goto begin;



	result = udp6_lib_lookup2(net, saddr, sport,

				  daddr, hnum, dif, sdif, exact_dif,

				  hslot2, skb);

	if (!result) {

			unsigned int old_slot2 = slot2;

		hash2 = ipv6_portaddr_hash(net, &in6addr_any, hnum);

		slot2 = hash2 & udptable->mask;

			/* avoid searching the same slot again. */

			if (unlikely(slot2 == old_slot2))

				return result;



		hslot2 = &udptable->hash2[slot2];

			if (hslot->count < hslot2->count)

				goto begin;



		result = udp6_lib_lookup2(net, saddr, sport,

						  daddr, hnum, dif, sdif,

					  &in6addr_any, hnum, dif, sdif,

					  exact_dif, hslot2,

					  skb);

	}
@@ -236,29 +222,6 @@ struct sock *__udp6_lib_lookup(struct net *net, 
		return NULL;

	return result;

}

begin:

	result = NULL;

	badness = -1;

	sk_for_each_rcu(sk, &hslot->head) {

		score = compute_score(sk, net, saddr, sport, daddr, hnum, dif,

				      sdif, exact_dif);

		if (score > badness) {

			if (sk->sk_reuseport) {

				hash = udp6_ehashfn(net, daddr, hnum,

						    saddr, sport);

				result = reuseport_select_sock(sk, hash, skb,

							sizeof(struct udphdr));

				if (unlikely(IS_ERR(result)))

					return NULL;

				if (result)

					return result;

			}

			result = sk;

			badness = score;

		}

	}

	return result;

}

EXPORT_SYMBOL_GPL(__udp6_lib_lookup);



static struct sock *__udp6_lib_lookup_skb(struct sk_buff *skb,