From: jolsa@redhat.com <jolsa@redhat.com>
Date: Fri, 17 Jul 2009 18:43:42 +0200
Subject: [net] ipv6: add 'disable' module parameter support
Message-id: 1247849024-9640-2-git-send-email-jolsa@redhat.com
O-Subject: [RHEL5 PATCH 1/3] IPv6: add "disable" module parameter support to ipv6.ko
Bugzilla: 512258
RH-Acked-by: Prarit Bhargava <prarit@redhat.com>
RH-Acked-by: David Miller <davem@redhat.com>

Add "disable" module parameter support to ipv6.ko by specifying
"disable=1" on module load.  We just do the minimum of initializing
inetsw6[] so calls from other modules to inet6_register_protosw()
won't OOPs, then bail out.  No IPv6 addresses or sockets can be
created as a result, and a reboot is required to enable IPv6.

wbr,
jirka

diff --git a/Documentation/networking/ipv6.txt b/Documentation/networking/ipv6.txt
new file mode 100644
index 0000000..268e5c1
--- /dev/null
+++ b/Documentation/networking/ipv6.txt
@@ -0,0 +1,35 @@
+
+Options for the ipv6 module are supplied as parameters at load time.
+
+Module options may be given as command line arguments to the insmod
+or modprobe command, but are usually specified in either the
+/etc/modules.conf or /etc/modprobe.conf configuration file, or in a
+distro-specific configuration file.
+
+The available ipv6 module parameters are listed below.  If a parameter
+is not specified the default value is used.
+
+The parameters are as follows:
+
+disable
+
+	Specifies whether to load the IPv6 module, but disable all
+	its functionality.  This might be used when another module
+	has a dependency on the IPv6 module being loaded, but no
+	IPv6 addresses or operations are desired.
+
+	The possible values and their effects are:
+
+	0
+		IPv6 is enabled.
+
+		This is the default value.
+
+	1
+		IPv6 is disabled.
+
+		No IPv6 addresses will be added to interfaces, and
+		it will not be possible to open an IPv6 socket.
+
+		A reboot is required to enable IPv6.
+
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 939db23..4f4d975 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -75,6 +75,10 @@ int sysctl_ipv6_bindv6only;
 static struct list_head inetsw6[SOCK_MAX];
 static DEFINE_SPINLOCK(inetsw6_lock);
 
+static int disable_ipv6 = 0;
+module_param_named(disable, disable_ipv6, int, 0);
+MODULE_PARM_DESC(disable, "Disable IPv6 such that it is non-functional");
+
 static __inline__ struct ipv6_pinfo *inet6_sk_generic(struct sock *sk)
 {
 	const int offset = sk->sk_prot->obj_size - sizeof(struct ipv6_pinfo);
@@ -761,7 +765,7 @@ static int __init inet6_init(void)
 {
 	struct sk_buff *dummy_skb;
         struct list_head *r;
-	int err;
+	int err = 0;
 
 #ifdef MODULE
 #if 0 /* FIXME --RR */
@@ -777,6 +781,17 @@ static int __init inet6_init(void)
 		return -EINVAL;
 	}
 
+	/* Register the socket-side information for inet6_create.  */
+	for(r = &inetsw6[0]; r < &inetsw6[SOCK_MAX]; ++r)
+		INIT_LIST_HEAD(r);
+
+	if (disable_ipv6) {
+		printk(KERN_INFO
+		       "IPv6: Loaded, but administratively disabled, "
+		       "reboot required to enable\n");
+		goto out;
+	}
+
 	err = proto_register(&tcpv6_prot, 1);
 	if (err)
 		goto out;
@@ -790,10 +805,6 @@ static int __init inet6_init(void)
 		goto out_unregister_udp_proto;
 
 
-	/* Register the socket-side information for inet6_create.  */
-	for(r = &inetsw6[0]; r < &inetsw6[SOCK_MAX]; ++r)
-		INIT_LIST_HEAD(r);
-
 	/* We MUST register RAW sockets before we create the ICMP6,
 	 * IGMP6, or NDISC control sockets.
 	 */