[NET] sysctl: make sysctl_somaxconn per-namespace

Just move the variable on the struct net and adjust
its usage.

Others sysctls from sys.net.core table are more
difficult to virtualize (i.e. make them per-namespace),
but I'll look at them as well a bit later.
Signed-off-by: Pavel Emelyanov <xemul@oenvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/socket.h

@@ -24,7 +24,6 @@ struct __kernel_sockaddr_storage {
 #include <linux/types.h>		/* pid_t			*/
 #include <linux/compiler.h>		/* __user			*/
 
-extern int sysctl_somaxconn;
 #ifdef CONFIG_PROC_FS
 struct seq_file;
 extern void socket_seq_show(struct seq_file *seq);

include/net/net_namespace.h

@@ -39,6 +39,7 @@ struct net {
 
 	/* core sysctls */
 	struct ctl_table_header	*sysctl_core_hdr;
+	int			sysctl_somaxconn;
 
 	/* List of all packet sockets. */
 	rwlock_t		packet_sklist_lock;

net/core/sysctl_net_core.c

@@ -127,7 +127,7 @@ static struct ctl_table net_core_table[] = {
 	{
 		.ctl_name	= NET_CORE_SOMAXCONN,
 		.procname	= "somaxconn",
-		.data		= &sysctl_somaxconn,
+		.data		= &init_net.sysctl_somaxconn,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec
@@ -161,6 +161,8 @@ static __net_init int sysctl_core_net_init(struct net *net)
 {
 	struct ctl_table *tbl, *tmp;
 
+	net->sysctl_somaxconn = SOMAXCONN;
+
 	tbl = net_core_table;
 	if (net != &init_net) {
 		tbl = kmemdup(tbl, sizeof(net_core_table), GFP_KERNEL);

net/socket.c

@@ -1365,17 +1365,17 @@ asmlinkage long sys_bind(int fd, struct sockaddr __user *umyaddr, int addrlen)
  *	ready for listening.
  */
 
-int sysctl_somaxconn __read_mostly = SOMAXCONN;
-
 asmlinkage long sys_listen(int fd, int backlog)
 {
 	struct socket *sock;
 	int err, fput_needed;
+	int somaxconn;
 
 	sock = sockfd_lookup_light(fd, &err, &fput_needed);
 	if (sock) {
-		if ((unsigned)backlog > sysctl_somaxconn)
-			backlog = sysctl_somaxconn;
+		somaxconn = sock->sk->sk_net->sysctl_somaxconn;
+		if ((unsigned)backlog > somaxconn)
+			backlog = somaxconn;
 
 		err = security_socket_listen(sock, backlog);
 		if (!err)