ipv6: Add disable_ipv6 sysctl to disable IPv6 operaion on specific interface.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

Documentation/networking/ip-sysctl.txt

@@ -1025,6 +1025,10 @@ max_addresses - INTEGER
 	autoconfigured addresses.
 	Default: 16
 
+disable_ipv6 - BOOLEAN
+	Disable IPv6 operation.
+	Default: FALSE (enable IPv6 operation)
+
 icmp/*:
 ratelimit - INTEGER
 	Limit the maximal rates for sending ICMPv6 packets.

include/linux/ipv6.h

@@ -163,6 +163,7 @@ struct ipv6_devconf {
 #ifdef CONFIG_IPV6_MROUTE
 	__s32		mc_forwarding;
 #endif
+	__s32		disable_ipv6;
 	void		*sysctl;
 };
 
@@ -194,6 +195,7 @@ enum {
 	DEVCONF_OPTIMISTIC_DAD,
 	DEVCONF_ACCEPT_SOURCE_ROUTE,
 	DEVCONF_MC_FORWARDING,
+	DEVCONF_DISABLE_IPV6,
 	DEVCONF_MAX
 };
 

net/ipv6/addrconf.c

@@ -183,6 +183,7 @@ struct ipv6_devconf ipv6_devconf __read_mostly = {
 #endif
 	.proxy_ndp		= 0,
 	.accept_source_route	= 0,	/* we do not accept RH0 by default. */
+	.disable_ipv6		= 0,
 };
 
 static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
@@ -215,6 +216,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
 #endif
 	.proxy_ndp		= 0,
 	.accept_source_route	= 0,	/* we do not accept RH0 by default. */
+	.disable_ipv6		= 0,
 };
 
 /* IPv6 Wildcard Address and Loopback Address defined by RFC2553 */
@@ -3657,6 +3659,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
 #ifdef CONFIG_IPV6_MROUTE
 	array[DEVCONF_MC_FORWARDING] = cnf->mc_forwarding;
 #endif
+	array[DEVCONF_DISABLE_IPV6] = cnf->disable_ipv6;
 }
 
 static inline size_t inet6_if_nlmsg_size(void)
@@ -4215,6 +4218,14 @@ static struct addrconf_sysctl_table
 			.proc_handler	=	&proc_dointvec,
 		},
 #endif
+		{
+			.ctl_name	=	CTL_UNNUMBERED,
+			.procname	=	"disable_ipv6",
+			.data		=	&ipv6_devconf.disable_ipv6,
+			.maxlen		=	sizeof(int),
+			.mode		=	0644,
+			.proc_handler	=	&proc_dointvec,
+		},
 		{
 			.ctl_name	=	0,	/* sentinel */
 		}

net/ipv6/ip6_input.c

@@ -71,7 +71,8 @@ int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt
 
 	IP6_INC_STATS_BH(idev, IPSTATS_MIB_INRECEIVES);
 
-	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) {
+	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
+	    !idev || unlikely(idev->cnf.disable_ipv6)) {
 		IP6_INC_STATS_BH(idev, IPSTATS_MIB_INDISCARDS);
 		rcu_read_unlock();
 		goto out;

net/ipv6/ip6_output.c

@@ -173,6 +173,13 @@ static inline int ip6_skb_dst_mtu(struct sk_buff *skb)
 
 int ip6_output(struct sk_buff *skb)
 {
+	struct inet6_dev *idev = ip6_dst_idev(skb->dst);
+	if (unlikely(idev->cnf.disable_ipv6)) {
+		IP6_INC_STATS(idev, IPSTATS_MIB_OUTDISCARDS);
+		kfree_skb(skb);
+		return 0;
+	}
+
 	if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) ||
 				dst_allfrag(skb->dst))
 		return ip6_fragment(skb, ip6_output2);