Merge branch 'net-prefer-listeners-bound-to-an-address'

Peter Oskolkov says:

====================
net: 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 patchset eliminates lookups into port-only hashtable,
as lookups by (addr,port) tuple are easily available.

In a future patchset I plan to explore whether it is possible
to remove port-only hashtables completely: additional refactoring
will be required, as some non-lookup code uses the hashtables.
====================

Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

8 files changed, 325 insertions, 217 deletions

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 13890d5bfc34..cd03ab42705b 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -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)
-				return -1;
-			score += 4;
-		}
-		dev_match = inet_sk_bound_dev_eq(net, sk->sk_bound_dev_if,
-						 dif, sdif);
-		if (!dev_match)
+		if (sk->sk_rcv_saddr != daddr)
+			return -1;
+
+		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;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index aff2a8e99e01..3fb0ed5e4789 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -380,15 +380,12 @@ static int compute_score(struct sock *sk, struct net *net,
 	    ipv6_only_sock(sk))
 		return -1;
 
-	score = (sk->sk_family == PF_INET) ? 2 : 1;
-	inet = inet_sk(sk);
+	if (sk->sk_rcv_saddr != daddr)
+		return -1;
 
-	if (inet->inet_rcv_saddr) {
-		if (inet->inet_rcv_saddr != daddr)
-			return -1;
-		score += 4;
-	}
+	score = (sk->sk_family == PF_INET) ? 2 : 1;
 
+	inet = inet_sk(sk);
 	if (inet->inet_daddr) {
 		if (inet->inet_daddr != saddr)
 			return -1;
@@ -464,65 +461,30 @@ 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 *sk, *result;
+	struct sock *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;
 	bool exact_dif = udp_lib_exact_dif_match(net, skb);
-	int score, badness;
-	u32 hash = 0;
 
-	if (hslot->count > 10) {
-		hash2 = ipv4_portaddr_hash(net, daddr, hnum);
+	hash2 = ipv4_portaddr_hash(net, daddr, hnum);
+	slot2 = hash2 & udptable->mask;
+	hslot2 = &udptable->hash2[slot2];
+
+	result = udp4_lib_lookup2(net, saddr, sport,
+				  daddr, hnum, dif, sdif,
+				  exact_dif, hslot2, skb);
+	if (!result) {
+		hash2 = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
 		slot2 = hash2 & udptable->mask;
 		hslot2 = &udptable->hash2[slot2];
-		if (hslot->count < hslot2->count)
-			goto begin;
 
 		result = udp4_lib_lookup2(net, saddr, sport,
-					  daddr, hnum, dif, sdif,
+					  htonl(INADDR_ANY), hnum, dif, sdif,
 					  exact_dif, hslot2, skb);
-		if (!result) {
-			unsigned int old_slot2 = slot2;
-			hash2 = ipv4_portaddr_hash(net, htonl(INADDR_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 = udp4_lib_lookup2(net, saddr, sport,
-						  daddr, hnum, dif, sdif,
-						  exact_dif, hslot2, skb);
-		}
-		if (unlikely(IS_ERR(result)))
-			return NULL;
-		return result;
-	}
-begin:
-	result = NULL;
-	badness = 0;
-	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 = udp_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;
-		}
 	}
+	if (unlikely(IS_ERR(result)))
+		return NULL;
 	return result;
 }
 EXPORT_SYMBOL_GPL(__udp4_lib_lookup);
diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c
index 5eeeba7181a1..f3515ebe9b3a 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -99,23 +99,16 @@ static inline int compute_score(struct sock *sk, struct net *net,
 				const int dif, const int sdif, bool exact_dif)
 {
 	int score = -1;
-	bool dev_match;
 
 	if (net_eq(sock_net(sk), net) && inet_sk(sk)->inet_num == hnum &&
 	    sk->sk_family == PF_INET6) {
+		if (!ipv6_addr_equal(&sk->sk_v6_rcv_saddr, daddr))
+			return -1;
 
-		score = 1;
-		if (!ipv6_addr_any(&sk->sk_v6_rcv_saddr)) {
-			if (!ipv6_addr_equal(&sk->sk_v6_rcv_saddr, daddr))
-				return -1;
-			score++;
-		}
-		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++;
 
+		score = 1;
 		if (sk->sk_incoming_cpu == raw_smp_processor_id())
 			score++;
 	}
@@ -164,26 +157,12 @@ struct sock *inet6_lookup_listener(struct net *net,
 		const __be16 sport, const struct in6_addr *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 = inet6_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 = ipv6_portaddr_hash(net, daddr, hnum);
 	ilb2 = inet_lhash2_bucket(hashinfo, hash2);
-	if (ilb2->count > ilb->count)
-		goto port_lookup;
 
 	result = inet6_lhash2_lookup(net, ilb2, skb, doff,
 				     saddr, sport, daddr, hnum,
@@ -192,33 +171,12 @@ struct sock *inet6_lookup_listener(struct net *net,
 		goto done;
 
 	/* Lookup lhash2 with in6addr_any */
-
 	hash2 = ipv6_portaddr_hash(net, &in6addr_any, hnum);
 	ilb2 = inet_lhash2_bucket(hashinfo, hash2);
-	if (ilb2->count > ilb->count)
-		goto port_lookup;
 
 	result = inet6_lhash2_lookup(net, ilb2, skb, doff,
-				     saddr, sport, daddr, hnum,
+				     saddr, sport, &in6addr_any, hnum,
 				     dif, sdif);
-	goto done;
-
-port_lookup:
-	sk_for_each(sk, &ilb->head) {
-		score = compute_score(sk, net, hnum, daddr, dif, sdif, exact_dif);
-		if (score > hiscore) {
-			if (sk->sk_reuseport) {
-				phash = inet6_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;
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 09cba4cfe31f..9cbf363172bd 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -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;
@@ -197,66 +194,32 @@ 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);
+	hash2 = ipv6_portaddr_hash(net, daddr, hnum);
+	slot2 = hash2 & udptable->mask;
+	hslot2 = &udptable->hash2[slot2];
+
+	result = udp6_lib_lookup2(net, saddr, sport,
+				  daddr, hnum, dif, sdif, exact_dif,
+				  hslot2, skb);
+	if (!result) {
+		hash2 = ipv6_portaddr_hash(net, &in6addr_any, 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,
-						  exact_dif, hslot2,
-						  skb);
-		}
-		if (unlikely(IS_ERR(result)))
-			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;
-		}
+					  &in6addr_any, hnum, dif, sdif,
+					  exact_dif, hslot2,
+					  skb);
 	}
+	if (unlikely(IS_ERR(result)))
+		return NULL;
 	return result;
 }
 EXPORT_SYMBOL_GPL(__udp6_lib_lookup);
diff --git a/tools/testing/selftests/net/.gitignore b/tools/testing/selftests/net/.gitignore
index 7f57b916e6b2..6f81130605d7 100644
--- a/tools/testing/selftests/net/.gitignore
+++ b/tools/testing/selftests/net/.gitignore
@@ -3,6 +3,7 @@ socket
 psock_fanout
 psock_snd
 psock_tpacket
+reuseport_addr_any
 reuseport_bpf
 reuseport_bpf_cpu
 reuseport_bpf_numa
diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index ee2e27b1cd0d..aeecc3ef53d0 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -7,10 +7,10 @@ CFLAGS += -I../../../../usr/include/
 TEST_PROGS := run_netsocktests run_afpackettests test_bpf.sh netdevice.sh rtnetlink.sh
 TEST_PROGS += fib_tests.sh fib-onlink-tests.sh pmtu.sh udpgso.sh ip_defrag.sh
 TEST_PROGS += udpgso_bench.sh fib_rule_tests.sh msg_zerocopy.sh psock_snd.sh
-TEST_PROGS += udpgro_bench.sh udpgro.sh test_vxlan_under_vrf.sh
+TEST_PROGS += udpgro_bench.sh udpgro.sh test_vxlan_under_vrf.sh reuseport_addr_any.sh
 TEST_PROGS_EXTENDED := in_netns.sh
 TEST_GEN_FILES =  socket
-TEST_GEN_FILES += psock_fanout psock_tpacket msg_zerocopy
+TEST_GEN_FILES += psock_fanout psock_tpacket msg_zerocopy reuseport_addr_any
 TEST_GEN_FILES += tcp_mmap tcp_inq psock_snd txring_overwrite
 TEST_GEN_FILES += udpgso udpgso_bench_tx udpgso_bench_rx ip_defrag
 TEST_GEN_PROGS = reuseport_bpf reuseport_bpf_cpu reuseport_bpf_numa
diff --git a/tools/testing/selftests/net/reuseport_addr_any.c b/tools/testing/selftests/net/reuseport_addr_any.c
new file mode 100644
index 000000000000..f5e01d989519
--- /dev/null
+++ b/tools/testing/selftests/net/reuseport_addr_any.c
@@ -0,0 +1,264 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* Test that sockets listening on a specific address are preferred
+ * over sockets listening on addr_any.
+ */
+
+#define _GNU_SOURCE
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <error.h>
+#include <linux/in.h>
+#include <linux/unistd.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/epoll.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+static const char *IP4_ADDR = "127.0.0.1";
+static const char *IP6_ADDR = "::1";
+static const char *IP4_MAPPED6 = "::ffff:127.0.0.1";
+
+static const int PORT = 8888;
+
+static void build_rcv_fd(int family, int proto, int *rcv_fds, int count,
+			 const char *addr_str)
+{
+	struct sockaddr_in  addr4 = {0};
+	struct sockaddr_in6 addr6 = {0};
+	struct sockaddr *addr;
+	int opt, i, sz;
+
+	memset(&addr, 0, sizeof(addr));
+
+	switch (family) {
+	case AF_INET:
+		addr4.sin_family = family;
+		if (!addr_str)
+			addr4.sin_addr.s_addr = htonl(INADDR_ANY);
+		else if (!inet_pton(family, addr_str, &addr4.sin_addr.s_addr))
+			error(1, errno, "inet_pton failed: %s", addr_str);
+		addr4.sin_port = htons(PORT);
+		sz = sizeof(addr4);
+		addr = (struct sockaddr *)&addr4;
+		break;
+	case AF_INET6:
+		addr6.sin6_family = AF_INET6;
+		if (!addr_str)
+			addr6.sin6_addr = in6addr_any;
+		else if (!inet_pton(family, addr_str, &addr6.sin6_addr))
+			error(1, errno, "inet_pton failed: %s", addr_str);
+		addr6.sin6_port = htons(PORT);
+		sz = sizeof(addr6);
+		addr = (struct sockaddr *)&addr6;
+		break;
+	default:
+		error(1, 0, "Unsupported family %d", family);
+	}
+
+	for (i = 0; i < count; ++i) {
+		rcv_fds[i] = socket(family, proto, 0);
+		if (rcv_fds[i] < 0)
+			error(1, errno, "failed to create receive socket");
+
+		opt = 1;
+		if (setsockopt(rcv_fds[i], SOL_SOCKET, SO_REUSEPORT, &opt,
+			       sizeof(opt)))
+			error(1, errno, "failed to set SO_REUSEPORT");
+
+		if (bind(rcv_fds[i], addr, sz))
+			error(1, errno, "failed to bind receive socket");
+
+		if (proto == SOCK_STREAM && listen(rcv_fds[i], 10))
+			error(1, errno, "failed to listen on receive port");
+	}
+}
+
+static int connect_and_send(int family, int proto)
+{
+	struct sockaddr_in  saddr4 = {0};
+	struct sockaddr_in  daddr4 = {0};
+	struct sockaddr_in6 saddr6 = {0};
+	struct sockaddr_in6 daddr6 = {0};
+	struct sockaddr *saddr, *daddr;
+	int fd, sz;
+
+	switch (family) {
+	case AF_INET:
+		saddr4.sin_family = AF_INET;
+		saddr4.sin_addr.s_addr = htonl(INADDR_ANY);
+		saddr4.sin_port = 0;
+
+		daddr4.sin_family = AF_INET;
+		if (!inet_pton(family, IP4_ADDR, &daddr4.sin_addr.s_addr))
+			error(1, errno, "inet_pton failed: %s", IP4_ADDR);
+		daddr4.sin_port = htons(PORT);
+
+		sz = sizeof(saddr4);
+		saddr = (struct sockaddr *)&saddr4;
+		daddr = (struct sockaddr *)&daddr4;
+	break;
+	case AF_INET6:
+		saddr6.sin6_family = AF_INET6;
+		saddr6.sin6_addr = in6addr_any;
+
+		daddr6.sin6_family = AF_INET6;
+		if (!inet_pton(family, IP6_ADDR, &daddr6.sin6_addr))
+			error(1, errno, "inet_pton failed: %s", IP6_ADDR);
+		daddr6.sin6_port = htons(PORT);
+
+		sz = sizeof(saddr6);
+		saddr = (struct sockaddr *)&saddr6;
+		daddr = (struct sockaddr *)&daddr6;
+	break;
+	default:
+		error(1, 0, "Unsupported family %d", family);
+	}
+
+	fd = socket(family, proto, 0);
+	if (fd < 0)
+		error(1, errno, "failed to create send socket");
+
+	if (bind(fd, saddr, sz))
+		error(1, errno, "failed to bind send socket");
+
+	if (connect(fd, daddr, sz))
+		error(1, errno, "failed to connect send socket");
+
+	if (send(fd, "a", 1, 0) < 0)
+		error(1, errno, "failed to send message");
+
+	return fd;
+}
+
+static int receive_once(int epfd, int proto)
+{
+	struct epoll_event ev;
+	int i, fd;
+	char buf[8];
+
+	i = epoll_wait(epfd, &ev, 1, 3);
+	if (i < 0)
+		error(1, errno, "epoll_wait failed");
+
+	if (proto == SOCK_STREAM) {
+		fd = accept(ev.data.fd, NULL, NULL);
+		if (fd < 0)
+			error(1, errno, "failed to accept");
+		i = recv(fd, buf, sizeof(buf), 0);
+		close(fd);
+	} else {
+		i = recv(ev.data.fd, buf, sizeof(buf), 0);
+	}
+
+	if (i < 0)
+		error(1, errno, "failed to recv");
+
+	return ev.data.fd;
+}
+
+static void test(int *rcv_fds, int count, int family, int proto, int fd)
+{
+	struct epoll_event ev;
+	int epfd, i, send_fd, recv_fd;
+
+	epfd = epoll_create(1);
+	if (epfd < 0)
+		error(1, errno, "failed to create epoll");
+
+	ev.events = EPOLLIN;
+	for (i = 0; i < count; ++i) {
+		ev.data.fd = rcv_fds[i];
+		if (epoll_ctl(epfd, EPOLL_CTL_ADD, rcv_fds[i], &ev))
+			error(1, errno, "failed to register sock epoll");
+	}
+
+	send_fd = connect_and_send(family, proto);
+
+	recv_fd = receive_once(epfd, proto);
+	if (recv_fd != fd)
+		error(1, 0, "received on an unexpected socket");
+
+	close(send_fd);
+	close(epfd);
+}
+
+int main(void)
+{
+	/* Below we test that a socket listening on a specific address
+	 * is always selected in preference over a socket listening
+	 * on addr_any. Bugs where this is not the case often result
+	 * in sockets created first or last to get picked. So below
+	 * we make sure that there are always addr_any sockets created
+	 * before and after a specific socket is created.
+	 */
+	int rcv_fds[10], i;
+
+	fprintf(stderr, "---- UDP IPv4 ----\n");
+	build_rcv_fd(AF_INET, SOCK_DGRAM, rcv_fds, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_DGRAM, rcv_fds + 2, 2, NULL);
+	build_rcv_fd(AF_INET, SOCK_DGRAM, rcv_fds + 4, 1, IP4_ADDR);
+	build_rcv_fd(AF_INET, SOCK_DGRAM, rcv_fds + 5, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_DGRAM, rcv_fds + 7, 2, NULL);
+	test(rcv_fds, 9, AF_INET, SOCK_DGRAM, rcv_fds[4]);
+	for (i = 0; i < 9; ++i)
+		close(rcv_fds[i]);
+
+	fprintf(stderr, "---- UDP IPv6 ----\n");
+	build_rcv_fd(AF_INET, SOCK_DGRAM, rcv_fds, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_DGRAM, rcv_fds + 2, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_DGRAM, rcv_fds + 4, 1, IP6_ADDR);
+	build_rcv_fd(AF_INET, SOCK_DGRAM, rcv_fds + 5, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_DGRAM, rcv_fds + 7, 2, NULL);
+	test(rcv_fds, 9, AF_INET6, SOCK_DGRAM, rcv_fds[4]);
+	for (i = 0; i < 9; ++i)
+		close(rcv_fds[i]);
+
+	fprintf(stderr, "---- UDP IPv4 mapped to IPv6 ----\n");
+	build_rcv_fd(AF_INET, SOCK_DGRAM, rcv_fds, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_DGRAM, rcv_fds + 2, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_DGRAM, rcv_fds + 4, 1, IP4_MAPPED6);
+	build_rcv_fd(AF_INET, SOCK_DGRAM, rcv_fds + 5, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_DGRAM, rcv_fds + 7, 2, NULL);
+	test(rcv_fds, 9, AF_INET, SOCK_DGRAM, rcv_fds[4]);
+	for (i = 0; i < 9; ++i)
+		close(rcv_fds[i]);
+
+	fprintf(stderr, "---- TCP IPv4 ----\n");
+	build_rcv_fd(AF_INET, SOCK_STREAM, rcv_fds, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_STREAM, rcv_fds + 2, 2, NULL);
+	build_rcv_fd(AF_INET, SOCK_STREAM, rcv_fds + 4, 1, IP4_ADDR);
+	build_rcv_fd(AF_INET, SOCK_STREAM, rcv_fds + 5, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_STREAM, rcv_fds + 7, 2, NULL);
+	test(rcv_fds, 9, AF_INET, SOCK_STREAM, rcv_fds[4]);
+	for (i = 0; i < 9; ++i)
+		close(rcv_fds[i]);
+
+	fprintf(stderr, "---- TCP IPv6 ----\n");
+	build_rcv_fd(AF_INET, SOCK_STREAM, rcv_fds, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_STREAM, rcv_fds + 2, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_STREAM, rcv_fds + 4, 1, IP6_ADDR);
+	build_rcv_fd(AF_INET, SOCK_STREAM, rcv_fds + 5, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_STREAM, rcv_fds + 7, 2, NULL);
+	test(rcv_fds, 9, AF_INET6, SOCK_STREAM, rcv_fds[4]);
+	for (i = 0; i < 9; ++i)
+		close(rcv_fds[i]);
+
+	fprintf(stderr, "---- TCP IPv4 mapped to IPv6 ----\n");
+	build_rcv_fd(AF_INET, SOCK_STREAM, rcv_fds, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_STREAM, rcv_fds + 2, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_STREAM, rcv_fds + 4, 1, IP4_MAPPED6);
+	build_rcv_fd(AF_INET, SOCK_STREAM, rcv_fds + 5, 2, NULL);
+	build_rcv_fd(AF_INET6, SOCK_STREAM, rcv_fds + 7, 2, NULL);
+	test(rcv_fds, 9, AF_INET, SOCK_STREAM, rcv_fds[4]);
+	for (i = 0; i < 9; ++i)
+		close(rcv_fds[i]);
+
+	fprintf(stderr, "SUCCESS\n");
+	return 0;
+}
diff --git a/tools/testing/selftests/net/reuseport_addr_any.sh b/tools/testing/selftests/net/reuseport_addr_any.sh
new file mode 100755
index 000000000000..104592f62ad4
--- /dev/null
+++ b/tools/testing/selftests/net/reuseport_addr_any.sh
@@ -0,0 +1,4 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+./in_netns.sh ./reuseport_addr_any