[IPV6]: ROUTE: Add accept_ra_defrtr sysctl.

This controls whether we accept default router information
in RAs.
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/ip-sysctl.txt

@@ -717,6 +717,12 @@ accept_ra - BOOLEAN
 	Functional default: enabled if local forwarding is disabled.
 			    disabled if local forwarding is enabled.
 
+accept_ra_defrtr - BOOLEAN
+	Learn default router in Router Advertisement.
+
+	Functional default: enabled if accept_ra is enabled.
+			    disabled if accept_ra is disabled.
+
 accept_redirects - BOOLEAN
 	Accept Redirects.
 

include/linux/ipv6.h

@@ -145,6 +145,7 @@ struct ipv6_devconf {
 	__s32		max_desync_factor;
 #endif
 	__s32		max_addresses;
+	__s32		accept_ra_defrtr;
 	void		*sysctl;
 };
 
@@ -167,6 +168,7 @@ enum {
 	DEVCONF_MAX_DESYNC_FACTOR,
 	DEVCONF_MAX_ADDRESSES,
 	DEVCONF_FORCE_MLD_VERSION,
+	DEVCONF_ACCEPT_RA_DEFRTR,
 	DEVCONF_MAX
 };
 

include/linux/sysctl.h

@@ -531,6 +531,7 @@ enum {
 	NET_IPV6_MAX_DESYNC_FACTOR=15,
 	NET_IPV6_MAX_ADDRESSES=16,
 	NET_IPV6_FORCE_MLD_VERSION=17,
+	NET_IPV6_ACCEPT_RA_DEFRTR=18,
 	__NET_IPV6_MAX
 };
 

net/ipv6/addrconf.c

@@ -165,6 +165,7 @@ struct ipv6_devconf ipv6_devconf = {
 	.max_desync_factor	= MAX_DESYNC_FACTOR,
 #endif
 	.max_addresses		= IPV6_MAX_ADDRESSES,
+	.accept_ra_defrtr	= 1,
 };
 
 static struct ipv6_devconf ipv6_devconf_dflt = {
@@ -186,6 +187,7 @@ static struct ipv6_devconf ipv6_devconf_dflt = {
 	.max_desync_factor	= MAX_DESYNC_FACTOR,
 #endif
 	.max_addresses		= IPV6_MAX_ADDRESSES,
+	.accept_ra_defrtr	= 1,
 };
 
 /* IPv6 Wildcard Address and Loopback Address defined by RFC2553 */
@@ -3116,6 +3118,7 @@ static void inline ipv6_store_devconf(struct ipv6_devconf *cnf,
 	array[DEVCONF_MAX_DESYNC_FACTOR] = cnf->max_desync_factor;
 #endif
 	array[DEVCONF_MAX_ADDRESSES] = cnf->max_addresses;
+	array[DEVCONF_ACCEPT_RA_DEFRTR] = cnf->accept_ra_defrtr;
 }
 
 static int inet6_fill_ifinfo(struct sk_buff *skb, struct inet6_dev *idev, 
@@ -3568,6 +3571,14 @@ static struct addrconf_sysctl_table
 			.mode		=	0644,
 			.proc_handler	=	&proc_dointvec,
 		},
+		{
+			.ctl_name	=	NET_IPV6_ACCEPT_RA_DEFRTR,
+			.procname	=	"accept_ra_defrtr",
+         		.data		=	&ipv6_devconf.accept_ra_defrtr,
+			.maxlen		=	sizeof(int),
+			.mode		=	0644,
+         		.proc_handler	=	&proc_dointvec,
+		},
 		{
 			.ctl_name	=	0,	/* sentinel */
 		}

net/ipv6/ndisc.c

@@ -1019,7 +1019,7 @@ static void ndisc_router_discovery(struct sk_buff *skb)
         struct ra_msg *ra_msg = (struct ra_msg *) skb->h.raw;
 	struct neighbour *neigh = NULL;
 	struct inet6_dev *in6_dev;
-	struct rt6_info *rt;
+	struct rt6_info *rt = NULL;
 	int lifetime;
 	struct ndisc_options ndopts;
 	int optlen;
@@ -1081,6 +1081,9 @@ static void ndisc_router_discovery(struct sk_buff *skb)
 				(ra_msg->icmph.icmp6_addrconf_other ?
 					IF_RA_OTHERCONF : 0);
 
+	if (!in6_dev->cnf.accept_ra_defrtr)
+		goto skip_defrtr;
+
 	lifetime = ntohs(ra_msg->icmph.icmp6_rt_lifetime);
 
 	rt = rt6_get_dflt_router(&skb->nh.ipv6h->saddr, skb->dev);
@@ -1128,6 +1131,8 @@ static void ndisc_router_discovery(struct sk_buff *skb)
 			rt->u.dst.metrics[RTAX_HOPLIMIT-1] = ra_msg->icmph.icmp6_hop_limit;
 	}
 
+skip_defrtr:
+
 	/*
 	 *	Update Reachable Time and Retrans Timer
 	 */