Merge branch 'net-inet-retire-port-only-listening_hash'

Martin KaFai Lau says:

====================
net: inet: Retire port only listening_hash

This series is to retire the port only listening_hash.

The listen sk is currently stored in two hash tables,
listening_hash (hashed by port) and lhash2 (hashed by port and address).

After commit 0ee58dad ("net: tcp6: prefer listeners bound to an address")
and commit d9fbc7f6 ("net: tcp: prefer listeners bound to an address"),
the TCP-SYN lookup fast path does not use listening_hash.

The commit 05c0b357 ("tcp: seq_file: Replace listening_hash with lhash2")
also moved the seq_file (/proc/net/tcp) iteration usage from
listening_hash to lhash2.

There are still a few listening_hash usages left.
One of them is inet_reuseport_add_sock() which uses the listening_hash
to search a listen sk during the listen() system call.  This turns
out to be very slow on use cases that listen on many different
VIPs at a popular port (e.g. 443).  [ On top of the slowness in
adding to the tail in the IPv6 case ]. A latter patch has a
selftest to demonstrate this case.

This series takes this chance to move all remaining listening_hash
usages to lhash2 and then retire listening_hash.
====================

Link: https://lore.kernel.org/r/20220512000546.188616-1-kafai@fb.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/inet_connection_sock.h

@@ -66,7 +66,6 @@ struct inet_connection_sock_af_ops {
  * @icsk_ulp_ops	   Pluggable ULP control hook
  * @icsk_ulp_data	   ULP private data
  * @icsk_clean_acked	   Clean acked data hook
- * @icsk_listen_portaddr_node	hash to the portaddr listener hashtable
  * @icsk_ca_state:	   Congestion control state
  * @icsk_retransmits:	   Number of unrecovered [RTO] timeouts
  * @icsk_pending:	   Scheduled timer event
@@ -96,7 +95,6 @@ struct inet_connection_sock {
 	const struct tcp_ulp_ops  *icsk_ulp_ops;
 	void __rcu		  *icsk_ulp_data;
 	void (*icsk_clean_acked)(struct sock *sk, u32 acked_seq);
-	struct hlist_node         icsk_listen_portaddr_node;
 	unsigned int		  (*icsk_sync_mss)(struct sock *sk, u32 pmtu);
 	__u8			  icsk_ca_state:5,
 				  icsk_ca_initialized:1,

include/net/inet_hashtables.h

@@ -111,11 +111,7 @@ struct inet_bind_hashbucket {
 #define LISTENING_NULLS_BASE (1U << 29)
 struct inet_listen_hashbucket {
 	spinlock_t		lock;
-	unsigned int		count;
-	union {
-		struct hlist_head	head;
-		struct hlist_nulls_head	nulls_head;
-	};
+	struct hlist_nulls_head	nulls_head;
 };
 
 /* This is for listening sockets, thus all sockets which possess wildcards. */
@@ -143,32 +139,8 @@ struct inet_hashinfo {
 	/* The 2nd listener table hashed by local port and address */
 	unsigned int			lhash2_mask;
 	struct inet_listen_hashbucket	*lhash2;
-
-	/* All the above members are written once at bootup and
-	 * never written again _or_ are predominantly read-access.
-	 *
-	 * Now align to a new cache line as all the following members
-	 * might be often dirty.
-	 */
-	/* All sockets in TCP_LISTEN state will be in listening_hash.
-	 * This is the only table where wildcard'd TCP sockets can
-	 * exist.  listening_hash is only hashed by local port number.
-	 * If lhash2 is initialized, the same socket will also be hashed
-	 * to lhash2 by port and address.
-	 */
-	struct inet_listen_hashbucket	listening_hash[INET_LHTABLE_SIZE]
-					____cacheline_aligned_in_smp;
 };
 
-#define inet_lhash2_for_each_icsk_continue(__icsk) \
-	hlist_for_each_entry_continue(__icsk, icsk_listen_portaddr_node)
-
-#define inet_lhash2_for_each_icsk(__icsk, list) \
-	hlist_for_each_entry(__icsk, list, icsk_listen_portaddr_node)
-
-#define inet_lhash2_for_each_icsk_rcu(__icsk, list) \
-	hlist_for_each_entry_rcu(__icsk, list, icsk_listen_portaddr_node)
-
 static inline struct inet_listen_hashbucket *
 inet_lhash2_bucket(struct inet_hashinfo *h, u32 hash)
 {
@@ -230,23 +202,11 @@ static inline u32 inet_bhashfn(const struct net *net, const __u16 lport,
 void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
 		    const unsigned short snum);
 
-/* These can have wildcards, don't try too hard. */
-static inline u32 inet_lhashfn(const struct net *net, const unsigned short num)
-{
-	return (num + net_hash_mix(net)) & (INET_LHTABLE_SIZE - 1);
-}
-
-static inline int inet_sk_listen_hashfn(const struct sock *sk)
-{
-	return inet_lhashfn(sock_net(sk), inet_sk(sk)->inet_num);
-}
-
 /* Caller must disable local BH processing. */
 int __inet_inherit_port(const struct sock *sk, struct sock *child);
 
 void inet_put_port(struct sock *sk);
 
-void inet_hashinfo_init(struct inet_hashinfo *h);
 void inet_hashinfo2_init(struct inet_hashinfo *h, const char *name,
 			 unsigned long numentries, int scale,
 			 unsigned long low_limit,

net/dccp/proto.c

@@ -1110,7 +1110,6 @@ static int __init dccp_init(void)
 
 	BUILD_BUG_ON(sizeof(struct dccp_skb_cb) >
 		     sizeof_field(struct sk_buff, cb));
-	inet_hashinfo_init(&dccp_hashinfo);
 	rc = inet_hashinfo2_init_mod(&dccp_hashinfo);
 	if (rc)
 		goto out_fail;

net/ipv4/inet_diag.c

@@ -1028,12 +1028,13 @@ void inet_diag_dump_icsk(struct inet_hashinfo *hashinfo, struct sk_buff *skb,
 		if (!(idiag_states & TCPF_LISTEN) || r->id.idiag_dport)
 			goto skip_listen_ht;
 
-		for (i = s_i; i < INET_LHTABLE_SIZE; i++) {
+		for (i = s_i; i <= hashinfo->lhash2_mask; i++) {
 			struct inet_listen_hashbucket *ilb;
 			struct hlist_nulls_node *node;
 
 			num = 0;
-			ilb = &hashinfo->listening_hash[i];
+			ilb = &hashinfo->lhash2[i];
+
 			spin_lock(&ilb->lock);
 			sk_nulls_for_each(sk, node, &ilb->nulls_head) {
 				struct inet_sock *inet = inet_sk(sk);

net/ipv4/inet_hashtables.c

@@ -193,42 +193,6 @@ inet_lhash2_bucket_sk(struct inet_hashinfo *h, struct sock *sk)
 	return inet_lhash2_bucket(h, hash);
 }
 
-static void inet_hash2(struct inet_hashinfo *h, struct sock *sk)
-{
-	struct inet_listen_hashbucket *ilb2;
-
-	if (!h->lhash2)
-		return;
-
-	ilb2 = inet_lhash2_bucket_sk(h, sk);
-
-	spin_lock(&ilb2->lock);
-	if (sk->sk_reuseport && sk->sk_family == AF_INET6)
-		hlist_add_tail_rcu(&inet_csk(sk)->icsk_listen_portaddr_node,
-				   &ilb2->head);
-	else
-		hlist_add_head_rcu(&inet_csk(sk)->icsk_listen_portaddr_node,
-				   &ilb2->head);
-	ilb2->count++;
-	spin_unlock(&ilb2->lock);
-}
-
-static void inet_unhash2(struct inet_hashinfo *h, struct sock *sk)
-{
-	struct inet_listen_hashbucket *ilb2;
-
-	if (!h->lhash2 ||
-	    WARN_ON_ONCE(hlist_unhashed(&inet_csk(sk)->icsk_listen_portaddr_node)))
-		return;
-
-	ilb2 = inet_lhash2_bucket_sk(h, sk);
-
-	spin_lock(&ilb2->lock);
-	hlist_del_init_rcu(&inet_csk(sk)->icsk_listen_portaddr_node);
-	ilb2->count--;
-	spin_unlock(&ilb2->lock);
-}
-
 static inline int compute_score(struct sock *sk, struct net *net,
 				const unsigned short hnum, const __be32 daddr,
 				const int dif, const int sdif)
@@ -282,12 +246,11 @@ static struct sock *inet_lhash2_lookup(struct net *net,
 				const __be32 daddr, const unsigned short hnum,
 				const int dif, const int sdif)
 {
-	struct inet_connection_sock *icsk;
 	struct sock *sk, *result = NULL;
+	struct hlist_nulls_node *node;
 	int score, hiscore = 0;
 
-	inet_lhash2_for_each_icsk_rcu(icsk, &ilb2->head) {
-		sk = (struct sock *)icsk;
+	sk_nulls_for_each_rcu(sk, node, &ilb2->nulls_head) {
 		score = compute_score(sk, net, hnum, daddr, dif, sdif);
 		if (score > hiscore) {
 			result = lookup_reuseport(net, sk, skb, doff,
@@ -633,7 +596,7 @@ static int inet_reuseport_add_sock(struct sock *sk,
 int __inet_hash(struct sock *sk, struct sock *osk)
 {
 	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
-	struct inet_listen_hashbucket *ilb;
+	struct inet_listen_hashbucket *ilb2;
 	int err = 0;
 
 	if (sk->sk_state != TCP_LISTEN) {
@@ -643,25 +606,23 @@ int __inet_hash(struct sock *sk, struct sock *osk)
 		return 0;
 	}
 	WARN_ON(!sk_unhashed(sk));
-	ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
+	ilb2 = inet_lhash2_bucket_sk(hashinfo, sk);
 
-	spin_lock(&ilb->lock);
+	spin_lock(&ilb2->lock);
 	if (sk->sk_reuseport) {
-		err = inet_reuseport_add_sock(sk, ilb);
+		err = inet_reuseport_add_sock(sk, ilb2);
 		if (err)
 			goto unlock;
 	}
 	if (IS_ENABLED(CONFIG_IPV6) && sk->sk_reuseport &&
 		sk->sk_family == AF_INET6)
-		__sk_nulls_add_node_tail_rcu(sk, &ilb->nulls_head);
+		__sk_nulls_add_node_tail_rcu(sk, &ilb2->nulls_head);
 	else
-		__sk_nulls_add_node_rcu(sk, &ilb->nulls_head);
-	inet_hash2(hashinfo, sk);
-	ilb->count++;
+		__sk_nulls_add_node_rcu(sk, &ilb2->nulls_head);
 	sock_set_flag(sk, SOCK_RCU_FREE);
 	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
 unlock:
-	spin_unlock(&ilb->lock);
+	spin_unlock(&ilb2->lock);
 
 	return err;
 }
@@ -678,23 +639,6 @@ int inet_hash(struct sock *sk)
 }
 EXPORT_SYMBOL_GPL(inet_hash);
 
-static void __inet_unhash(struct sock *sk, struct inet_listen_hashbucket *ilb)
-{
-	if (sk_unhashed(sk))
-		return;
-
-	if (rcu_access_pointer(sk->sk_reuseport_cb))
-		reuseport_stop_listen_sock(sk);
-	if (ilb) {
-		struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
-
-		inet_unhash2(hashinfo, sk);
-		ilb->count--;
-	}
-	__sk_nulls_del_node_init_rcu(sk);
-	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
-}
-
 void inet_unhash(struct sock *sk)
 {
 	struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
@@ -703,20 +647,34 @@ void inet_unhash(struct sock *sk)
 		return;
 
 	if (sk->sk_state == TCP_LISTEN) {
-		struct inet_listen_hashbucket *ilb;
+		struct inet_listen_hashbucket *ilb2;
 
-		ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
+		ilb2 = inet_lhash2_bucket_sk(hashinfo, sk);
 		/* Don't disable bottom halves while acquiring the lock to
 		 * avoid circular locking dependency on PREEMPT_RT.
 		 */
-		spin_lock(&ilb->lock);
-		__inet_unhash(sk, ilb);
-		spin_unlock(&ilb->lock);
+		spin_lock(&ilb2->lock);
+		if (sk_unhashed(sk)) {
+			spin_unlock(&ilb2->lock);
+			return;
+		}
+
+		if (rcu_access_pointer(sk->sk_reuseport_cb))
+			reuseport_stop_listen_sock(sk);
+
+		__sk_nulls_del_node_init_rcu(sk);
+		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
+		spin_unlock(&ilb2->lock);
 	} else {
 		spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
 
 		spin_lock_bh(lock);
-		__inet_unhash(sk, NULL);
+		if (sk_unhashed(sk)) {
+			spin_unlock_bh(lock);
+			return;
+		}
+		__sk_nulls_del_node_init_rcu(sk);
+		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
 		spin_unlock_bh(lock);
 	}
 }
@@ -874,29 +832,14 @@ int inet_hash_connect(struct inet_timewait_death_row *death_row,
 }
 EXPORT_SYMBOL_GPL(inet_hash_connect);
 
-void inet_hashinfo_init(struct inet_hashinfo *h)
-{
-	int i;
-
-	for (i = 0; i < INET_LHTABLE_SIZE; i++) {
-		spin_lock_init(&h->listening_hash[i].lock);
-		INIT_HLIST_NULLS_HEAD(&h->listening_hash[i].nulls_head,
-				      i + LISTENING_NULLS_BASE);
-		h->listening_hash[i].count = 0;
-	}
-
-	h->lhash2 = NULL;
-}
-EXPORT_SYMBOL_GPL(inet_hashinfo_init);
-
 static void init_hashinfo_lhash2(struct inet_hashinfo *h)
 {
 	int i;
 
 	for (i = 0; i <= h->lhash2_mask; i++) {
 		spin_lock_init(&h->lhash2[i].lock);
-		INIT_HLIST_HEAD(&h->lhash2[i].head);
-		h->lhash2[i].count = 0;
+		INIT_HLIST_NULLS_HEAD(&h->lhash2[i].nulls_head,
+				      i + LISTENING_NULLS_BASE);
 	}
 }
 

net/ipv4/tcp.c

@@ -4595,7 +4595,6 @@ void __init tcp_init(void)
 	timer_setup(&tcp_orphan_timer, tcp_orphan_update, TIMER_DEFERRABLE);
 	mod_timer(&tcp_orphan_timer, jiffies + TCP_ORPHAN_TIMER_PERIOD);
 
-	inet_hashinfo_init(&tcp_hashinfo);
 	inet_hashinfo2_init(&tcp_hashinfo, "tcp_listen_portaddr_hash",
 			    thash_entries, 21,  /* one slot per 2 MB*/
 			    0, 64 * 1024);

net/ipv4/tcp_ipv4.c

@@ -2283,16 +2283,15 @@ static void *listening_get_first(struct seq_file *seq)
 	st->offset = 0;
 	for (; st->bucket <= tcp_hashinfo.lhash2_mask; st->bucket++) {
 		struct inet_listen_hashbucket *ilb2;
-		struct inet_connection_sock *icsk;
+		struct hlist_nulls_node *node;
 		struct sock *sk;
 
 		ilb2 = &tcp_hashinfo.lhash2[st->bucket];
-		if (hlist_empty(&ilb2->head))
+		if (hlist_nulls_empty(&ilb2->nulls_head))
 			continue;
 
 		spin_lock(&ilb2->lock);
-		inet_lhash2_for_each_icsk(icsk, &ilb2->head) {
-			sk = (struct sock *)icsk;
+		sk_nulls_for_each(sk, node, &ilb2->nulls_head) {
 			if (seq_sk_match(seq, sk))
 				return sk;
 		}
@@ -2311,15 +2310,14 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
 {
 	struct tcp_iter_state *st = seq->private;
 	struct inet_listen_hashbucket *ilb2;
-	struct inet_connection_sock *icsk;
+	struct hlist_nulls_node *node;
 	struct sock *sk = cur;
 
 	++st->num;
 	++st->offset;
 
-	icsk = inet_csk(sk);
-	inet_lhash2_for_each_icsk_continue(icsk) {
-		sk = (struct sock *)icsk;
+	sk = sk_nulls_next(sk);
+	sk_nulls_for_each_from(sk, node) {
 		if (seq_sk_match(seq, sk))
 			return sk;
 	}
@@ -2728,16 +2726,15 @@ static unsigned int bpf_iter_tcp_listening_batch(struct seq_file *seq,
 {
 	struct bpf_tcp_iter_state *iter = seq->private;
 	struct tcp_iter_state *st = &iter->state;
-	struct inet_connection_sock *icsk;
+	struct hlist_nulls_node *node;
 	unsigned int expected = 1;
 	struct sock *sk;
 
 	sock_hold(start_sk);
 	iter->batch[iter->end_sk++] = start_sk;
 
-	icsk = inet_csk(start_sk);
-	inet_lhash2_for_each_icsk_continue(icsk) {
-		sk = (struct sock *)icsk;
+	sk = sk_nulls_next(start_sk);
+	sk_nulls_for_each_from(sk, node) {
 		if (seq_sk_match(seq, sk)) {
 			if (iter->end_sk < iter->max_sk) {
 				sock_hold(sk);

net/ipv6/inet6_hashtables.c

@@ -138,12 +138,11 @@ static struct sock *inet6_lhash2_lookup(struct net *net,
 		const __be16 sport, const struct in6_addr *daddr,
 		const unsigned short hnum, const int dif, const int sdif)
 {
-	struct inet_connection_sock *icsk;
 	struct sock *sk, *result = NULL;
+	struct hlist_nulls_node *node;
 	int score, hiscore = 0;
 
-	inet_lhash2_for_each_icsk_rcu(icsk, &ilb2->head) {
-		sk = (struct sock *)icsk;
+	sk_nulls_for_each_rcu(sk, node, &ilb2->nulls_head) {
 		score = compute_score(sk, net, hnum, daddr, dif, sdif);
 		if (score > hiscore) {
 			result = lookup_reuseport(net, sk, skb, doff,

net/mptcp/mptcp_diag.c

@@ -83,13 +83,13 @@ static void mptcp_diag_dump_listeners(struct sk_buff *skb, struct netlink_callba
 	struct net *net = sock_net(skb->sk);
 	int i;
 
-	for (i = diag_ctx->l_slot; i < INET_LHTABLE_SIZE; i++) {
+	for (i = diag_ctx->l_slot; i <= tcp_hashinfo.lhash2_mask; i++) {
 		struct inet_listen_hashbucket *ilb;
 		struct hlist_nulls_node *node;
 		struct sock *sk;
 		int num = 0;
 
-		ilb = &tcp_hashinfo.listening_hash[i];
+		ilb = &tcp_hashinfo.lhash2[i];
 
 		rcu_read_lock();
 		spin_lock(&ilb->lock);

tools/testing/selftests/net/Makefile

@@ -38,6 +38,7 @@ TEST_PROGS += srv6_end_dt6_l3vpn_test.sh
 TEST_PROGS += vrf_strict_mode_test.sh
 TEST_PROGS += arp_ndisc_evict_nocarrier.sh
 TEST_PROGS += ndisc_unsolicited_na_test.sh
+TEST_PROGS += stress_reuseport_listen.sh
 TEST_PROGS_EXTENDED := in_netns.sh setup_loopback.sh setup_veth.sh
 TEST_PROGS_EXTENDED += toeplitz_client.sh toeplitz.sh
 TEST_GEN_FILES =  socket nettest
@@ -56,6 +57,7 @@ TEST_GEN_PROGS = reuseport_bpf reuseport_bpf_cpu reuseport_bpf_numa
 TEST_GEN_PROGS += reuseport_dualstack reuseaddr_conflict tls
 TEST_GEN_FILES += toeplitz
 TEST_GEN_FILES += cmsg_sender
+TEST_GEN_FILES += stress_reuseport_listen
 TEST_PROGS += test_vxlan_vnifiltering.sh
 
 TEST_FILES := settings

tools/testing/selftests/net/stress_reuseport_listen.c

+// SPDX-License-Identifier: GPL-2.0
+
+/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
+
+/* Test listening on the same port 443 with multiple VIPS.
+ * Each VIP:443 will have multiple sk listening on by using
+ * SO_REUSEPORT.
+ */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <error.h>
+#include <errno.h>
+#include <time.h>
+#include <arpa/inet.h>
+
+#define IP6_LADDR_START "2401:dead::1"
+#define IP6_LPORT 443
+#define NSEC_PER_SEC 1000000000L
+#define NSEC_PER_USEC 1000L
+
+static unsigned int nr_socks_per_vip;
+static unsigned int nr_vips;
+
+static int *bind_reuseport_sock6(void)
+{
+	int *lfds, *cur_fd, err, optvalue = 1;
+	struct sockaddr_in6 sa6 = {};
+	unsigned int i, j;
+
+	sa6.sin6_family = AF_INET6;
+	sa6.sin6_port = htons(IP6_LPORT);
+	err = inet_pton(AF_INET6, IP6_LADDR_START, &sa6.sin6_addr);
+	if (err != 1)
+		error(1, err, "inet_pton(%s)", IP6_LADDR_START);
+
+	lfds = malloc(nr_vips * nr_socks_per_vip * sizeof(lfds[0]));
+	if (!lfds)
+		error(1, errno, "cannot alloc array of lfds");
+
+	cur_fd = lfds;
+	for (i = 0; i < nr_vips; i++) {
+		for (j = 0; j < nr_socks_per_vip; j++) {
+			*cur_fd = socket(AF_INET6, SOCK_STREAM, 0);
+			if (*cur_fd == -1)
+				error(1, errno,
+				      "lfds[%u,%u] = socket(AF_INET6)", i, j);
+
+			err = setsockopt(*cur_fd, SOL_SOCKET, SO_REUSEPORT,
+					 &optvalue, sizeof(optvalue));
+			if (err)
+				error(1, errno,
+				      "setsockopt(lfds[%u,%u], SO_REUSEPORT)",
+				      i, j);
+
+			err = bind(*cur_fd, (struct sockaddr *)&sa6,
+				   sizeof(sa6));
+			if (err)
+				error(1, errno, "bind(lfds[%u,%u])", i, j);
+			cur_fd++;
+		}
+		sa6.sin6_addr.s6_addr32[3]++;
+	}
+
+	return lfds;
+}
+
+int main(int argc, const char *argv[])
+{
+	struct timespec start_ts, end_ts;
+	unsigned long start_ns, end_ns;
+	unsigned int nr_lsocks;
+	int *lfds, i, err;
+
+	if (argc != 3 || atoi(argv[1]) <= 0 || atoi(argv[2]) <= 0)
+		error(1, 0, "Usage: %s <nr_vips> <nr_socks_per_vip>\n",
+		      argv[0]);
+
+	nr_vips = atoi(argv[1]);
+	nr_socks_per_vip = atoi(argv[2]);
+	nr_lsocks = nr_vips * nr_socks_per_vip;
+	lfds = bind_reuseport_sock6();
+
+	clock_gettime(CLOCK_MONOTONIC, &start_ts);
+	for (i = 0; i < nr_lsocks; i++) {
+		err = listen(lfds[i], 0);
+		if (err)
+			error(1, errno, "listen(lfds[%d])", i);
+	}
+	clock_gettime(CLOCK_MONOTONIC, &end_ts);
+
+	start_ns = start_ts.tv_sec * NSEC_PER_SEC + start_ts.tv_nsec;
+	end_ns = end_ts.tv_sec * NSEC_PER_SEC + end_ts.tv_nsec;
+
+	printf("listen %d socks took %lu.%lu\n", nr_lsocks,
+	       (end_ns - start_ns) / NSEC_PER_SEC,
+	       (end_ns - start_ns) / NSEC_PER_USEC);
+
+	for (i = 0; i < nr_lsocks; i++)
+		close(lfds[i]);
+
+	free(lfds);
+	return 0;
+}

tools/testing/selftests/net/stress_reuseport_listen.sh

+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
+
+NS='stress_reuseport_listen_ns'
+NR_FILES=24100
+SAVED_NR_FILES=$(ulimit -n)
+
+setup() {
+	ip netns add $NS
+	ip netns exec $NS sysctl -q -w net.ipv6.ip_nonlocal_bind=1
+	ulimit -n $NR_FILES
+}
+
+cleanup() {
+	ip netns del $NS
+	ulimit -n $SAVED_NR_FILES
+}
+
+trap cleanup EXIT
+setup
+# 300 different vips listen on port 443
+# Each vip:443 sockaddr has 80 LISTEN sock by using SO_REUSEPORT
+# Total 24000 listening socks
+ip netns exec $NS ./stress_reuseport_listen 300 80