[NET]: Allow SOMAXCONN to be adjusted via sysctl.

include/linux/sysctl.h

@@ -217,7 +217,8 @@ enum
 	NET_CORE_NO_CONG=14,
 	NET_CORE_LO_CONG=15,
 	NET_CORE_MOD_CONG=16,
-	NET_CORE_DEV_WEIGHT=17
+	NET_CORE_DEV_WEIGHT=17,
+	NET_CORE_SOMAXCONN=18,
 };
 
 /* /proc/sys/net/ethernet */

net/core/sysctl_net_core.c

@@ -29,6 +29,7 @@ extern __u32 sysctl_rmem_default;
 
 extern int sysctl_core_destroy_delay;
 extern int sysctl_optmem_max;
+extern int sysctl_somaxconn;
 
 #ifdef CONFIG_NET_DIVERT
 extern char sysctl_divert_version[];
@@ -174,6 +175,14 @@ ctl_table core_table[] = {
 	},
 #endif /* CONFIG_NET_DIVERT */
 #endif /* CONFIG_NET */
+	{
+		.ctl_name	= NET_CORE_SOMAXCONN,
+		.procname	= "somaxconn",
+		.data		= &sysctl_somaxconn,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec
+	},
 	{ .ctl_name = 0 }
 };
 

net/socket.c

@@ -1206,14 +1206,16 @@ asmlinkage long sys_bind(int fd, struct sockaddr __user *umyaddr, int addrlen)
  *	ready for listening.
  */
 
+int sysctl_somaxconn = SOMAXCONN;
+
 asmlinkage long sys_listen(int fd, int backlog)
 {
 	struct socket *sock;
 	int err;
 	
 	if ((sock = sockfd_lookup(fd, &err)) != NULL) {
-		if ((unsigned) backlog > SOMAXCONN)
-			backlog = SOMAXCONN;
+		if ((unsigned) backlog > sysctl_somaxconn)
+			backlog = sysctl_somaxconn;
 
 		err = security_socket_listen(sock, backlog);
 		if (err) {