ipv6: Add icmp_echo_ignore_multicast support for ICMPv6

IPv4 has icmp_echo_ignore_broadcast to prevent responding to broadcast pings.
IPv6 needs a similar mechanism.

v1->v2:
- Remove NET_IPV6_ICMP_ECHO_IGNORE_MULTICAST.
Signed-off-by: Stephen Suryaputra <ssuryaextr@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/ip-sysctl.txt

@@ -1918,6 +1918,11 @@ echo_ignore_all - BOOLEAN
 	requests sent to it over the IPv6 protocol.
 	Default: 0
 
+echo_ignore_multicast - BOOLEAN
+	If set non-zero, then the kernel will ignore all ICMP ECHO
+	requests sent to it over the IPv6 protocol via multicast.
+	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

@@ -33,6 +33,7 @@ struct netns_sysctl_ipv6 {
 	int auto_flowlabels;
 	int icmpv6_time;
 	int icmpv6_echo_ignore_all;
+	int icmpv6_echo_ignore_multicast;
 	int anycast_src_echo_reply;
 	int ip_nonlocal_bind;
 	int fwmark_reflect;

net/ipv6/af_inet6.c

@@ -847,6 +847,7 @@ static int __net_init inet6_net_init(struct net *net)
 	net->ipv6.sysctl.bindv6only = 0;
 	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.flowlabel_consistency = 1;
 	net->ipv6.sysctl.auto_flowlabels = IP6_DEFAULT_AUTO_FLOW_LABELS;
 	net->ipv6.sysctl.idgen_retries = 3;

net/ipv6/icmp.c

@@ -684,6 +684,10 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
 	struct ipcm6_cookie ipc6;
 	u32 mark = IP6_REPLY_MARK(net, skb->mark);
 
+	if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr) &&
+	    net->ipv6.sysctl.icmpv6_echo_ignore_multicast)
+		return;
+
 	saddr = &ipv6_hdr(skb)->daddr;
 
 	if (!ipv6_unicast_destination(skb) &&
@@ -1115,6 +1119,13 @@ static struct ctl_table ipv6_icmp_table_template[] = {
 		.mode		= 0644,
 		.proc_handler = proc_dointvec,
 	},
+	{
+		.procname	= "echo_ignore_multicast",
+		.data		= &init_net.ipv6.sysctl.icmpv6_echo_ignore_multicast,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler = proc_dointvec,
+	},
 	{ },
 };
 
@@ -1129,6 +1140,7 @@ struct ctl_table * __net_init ipv6_icmp_sysctl_init(struct net *net)
 	if (table) {
 		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;
 	}
 	return table;
 }