ipv6: Add icmp_echo_ignore_anycast for ICMPv6

In addition to icmp_echo_ignore_multicast, there is a need to also
prevent responding to pings to anycast addresses for security.
Signed-off-by: Stephen Suryaputra <ssuryaextr@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/ip-sysctl.txt

@@ -1923,6 +1923,11 @@ echo_ignore_multicast - BOOLEAN
 	requests sent to it over the IPv6 protocol via multicast.
 	Default: 0
 
+echo_ignore_anycast - BOOLEAN
+	If set non-zero, then the kernel will ignore all ICMP ECHO
+	requests sent to it over the IPv6 protocol destined to anycast address.
+	Default: 0
+
 xfrm6_gc_thresh - INTEGER
 	The threshold at which we will start garbage collecting for IPv6
 	destination cache entries.  At twice this value the system will

include/net/netns/ipv6.h

@@ -34,6 +34,7 @@ struct netns_sysctl_ipv6 {
 	int icmpv6_time;
 	int icmpv6_echo_ignore_all;
 	int icmpv6_echo_ignore_multicast;
+	int icmpv6_echo_ignore_anycast;
 	int anycast_src_echo_reply;
 	int ip_nonlocal_bind;
 	int fwmark_reflect;

net/ipv6/af_inet6.c

@@ -848,6 +848,7 @@ static int __net_init inet6_net_init(struct net *net)
 	net->ipv6.sysctl.icmpv6_time = 1*HZ;
 	net->ipv6.sysctl.icmpv6_echo_ignore_all = 0;
 	net->ipv6.sysctl.icmpv6_echo_ignore_multicast = 0;
+	net->ipv6.sysctl.icmpv6_echo_ignore_anycast = 0;
 	net->ipv6.sysctl.flowlabel_consistency = 1;
 	net->ipv6.sysctl.auto_flowlabels = IP6_DEFAULT_AUTO_FLOW_LABELS;
 	net->ipv6.sysctl.idgen_retries = 3;

net/ipv6/icmp.c

@@ -683,6 +683,7 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
 	struct dst_entry *dst;
 	struct ipcm6_cookie ipc6;
 	u32 mark = IP6_REPLY_MARK(net, skb->mark);
+	bool acast;
 
 	if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr) &&
 	    net->ipv6.sysctl.icmpv6_echo_ignore_multicast)
@@ -690,9 +691,12 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
 
 	saddr = &ipv6_hdr(skb)->daddr;
 
+	acast = ipv6_anycast_destination(skb_dst(skb), saddr);
+	if (acast && net->ipv6.sysctl.icmpv6_echo_ignore_anycast)
+		return;
+
 	if (!ipv6_unicast_destination(skb) &&
-	    !(net->ipv6.sysctl.anycast_src_echo_reply &&
-	      ipv6_anycast_destination(skb_dst(skb), saddr)))
+	    !(net->ipv6.sysctl.anycast_src_echo_reply && acast))
 		saddr = NULL;
 
 	memcpy(&tmp_hdr, icmph, sizeof(tmp_hdr));
@@ -1126,6 +1130,13 @@ static struct ctl_table ipv6_icmp_table_template[] = {
 		.mode		= 0644,
 		.proc_handler = proc_dointvec,
 	},
+	{
+		.procname	= "echo_ignore_anycast",
+		.data		= &init_net.ipv6.sysctl.icmpv6_echo_ignore_anycast,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler = proc_dointvec,
+	},
 	{ },
 };
 
@@ -1141,6 +1152,7 @@ struct ctl_table * __net_init ipv6_icmp_sysctl_init(struct net *net)
 		table[0].data = &net->ipv6.sysctl.icmpv6_time;
 		table[1].data = &net->ipv6.sysctl.icmpv6_echo_ignore_all;
 		table[2].data = &net->ipv6.sysctl.icmpv6_echo_ignore_multicast;
+		table[3].data = &net->ipv6.sysctl.icmpv6_echo_ignore_anycast;
 	}
 	return table;
 }