ipv4: Link IPv4 address to per-netns hash table.

As a prep for per-netns RTNL conversion, we want to namespacify
the IPv4 address hash table and the GC work.

Let's allocate the per-netns IPv4 address hash table to
net->ipv4.inet_addr_lst and link IPv4 addresses into it.

The actual users will be converted later.

Note that the IPv6 address hash table is already namespacified.

Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20241008172906.1326-2-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/inetdevice.h

@@ -142,6 +142,7 @@ static inline void ipv4_devconf_setall(struct in_device *in_dev)
 
 struct in_ifaddr {
 	struct hlist_node	hash;
+	struct hlist_node	addr_lst;
 	struct in_ifaddr	__rcu *ifa_next;
 	struct in_device	*ifa_dev;
 	struct rcu_head		rcu_head;

include/net/netns/ipv4.h

@@ -270,5 +270,6 @@ struct netns_ipv4 {
 
 	atomic_t	rt_genid;
 	siphash_key_t	ip_id_key;
+	struct hlist_head	*inet_addr_lst;
 };
 #endif

net/ipv4/devinet.c

@@ -134,11 +134,13 @@ static void inet_hash_insert(struct net *net, struct in_ifaddr *ifa)
 
 	ASSERT_RTNL();
 	hlist_add_head_rcu(&ifa->hash, &inet_addr_lst[hash]);
+	hlist_add_head_rcu(&ifa->addr_lst, &net->ipv4.inet_addr_lst[hash]);
 }
 
 static void inet_hash_remove(struct in_ifaddr *ifa)
 {
 	ASSERT_RTNL();
+	hlist_del_init_rcu(&ifa->addr_lst);
 	hlist_del_init_rcu(&ifa->hash);
 }
 
@@ -228,6 +230,7 @@ static struct in_ifaddr *inet_alloc_ifa(struct in_device *in_dev)
 	ifa->ifa_dev = in_dev;
 
 	INIT_HLIST_NODE(&ifa->hash);
+	INIT_HLIST_NODE(&ifa->addr_lst);
 
 	return ifa;
 }
@@ -2663,14 +2666,21 @@ static struct ctl_table ctl_forward_entry[] = {
 
 static __net_init int devinet_init_net(struct net *net)
 {
-	int err;
-	struct ipv4_devconf *all, *dflt;
 #ifdef CONFIG_SYSCTL
-	struct ctl_table *tbl;
 	struct ctl_table_header *forw_hdr;
+	struct ctl_table *tbl;
 #endif
+	struct ipv4_devconf *all, *dflt;
+	int err;
+	int i;
 
 	err = -ENOMEM;
+	net->ipv4.inet_addr_lst = kmalloc_array(IN4_ADDR_HSIZE,
+						sizeof(struct hlist_head),
+						GFP_KERNEL);
+	if (!net->ipv4.inet_addr_lst)
+		goto err_alloc_hash;
+
 	all = kmemdup(&ipv4_devconf, sizeof(ipv4_devconf), GFP_KERNEL);
 	if (!all)
 		goto err_alloc_all;
@@ -2731,6 +2741,9 @@ static __net_init int devinet_init_net(struct net *net)
 	net->ipv4.forw_hdr = forw_hdr;
 #endif
 
+	for (i = 0; i < IN4_ADDR_HSIZE; i++)
+		INIT_HLIST_HEAD(&net->ipv4.inet_addr_lst[i]);
+
 	net->ipv4.devconf_all = all;
 	net->ipv4.devconf_dflt = dflt;
 	return 0;
@@ -2748,6 +2761,8 @@ static __net_init int devinet_init_net(struct net *net)
 err_alloc_dflt:
 	kfree(all);
 err_alloc_all:
+	kfree(net->ipv4.inet_addr_lst);
+err_alloc_hash:
 	return err;
 }
 
@@ -2766,6 +2781,7 @@ static __net_exit void devinet_exit_net(struct net *net)
 #endif
 	kfree(net->ipv4.devconf_dflt);
 	kfree(net->ipv4.devconf_all);
+	kfree(net->ipv4.inet_addr_lst);
 }
 
 static __net_initdata struct pernet_operations devinet_ops = {