IPv6: add "disable" module parameter support to ipv6.ko

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.

Signed-off-by: Brian Haley <brian.haley@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 51 insertions, 5 deletions

diff --git a/Documentation/networking/ipv6.txt b/Documentation/networking/ipv6.txt
new file mode 100644
index 000000000000..268e5c103dd8
--- /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 c802bc1658a8..da944eca2ca6 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -72,6 +72,10 @@ MODULE_LICENSE("GPL");
 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);
@@ -991,10 +995,21 @@ static int __init inet6_init(void)
 {
         struct sk_buff *dummy_skb;
         struct list_head *r;
-        int err;
+        int err = 0;
 
         BUILD_BUG_ON(sizeof(struct inet6_skb_parm) > sizeof(dummy_skb->cb));
 
+        /* 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;
@@ -1012,10 +1027,6 @@ static int __init inet6_init(void)
                 goto out_unregister_udplite_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.
          */