ipv6: Add icmp_echo_ignore_all support for ICMPv6

Preventing the kernel from responding to ICMP Echo Requests messages
can be useful in several ways. The sysctl parameter
'icmp_echo_ignore_all' can be used to prevent the kernel from
responding to IPv4 ICMP echo requests. For IPv6 pings, such
a sysctl kernel parameter did not exist.

Add the ability to prevent the kernel from responding to IPv6
ICMP echo requests through the use of the following sysctl
parameter : /proc/sys/net/ipv6/icmp/echo_ignore_all.
Update the documentation to reflect this change.
Signed-off-by: Virgile Jarry <virgile@acceis.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/ip-sysctl.txt

@@ -1882,6 +1882,11 @@ ratelimit - INTEGER
 	otherwise the minimal space between responses in milliseconds.
 	Default: 1000
 
+echo_ignore_all - BOOLEAN
+	If set non-zero, then the kernel will ignore all ICMP ECHO
+	requests sent to it over the IPv6 protocol.
+	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

@@ -32,6 +32,7 @@ struct netns_sysctl_ipv6 {
 	int flowlabel_consistency;
 	int auto_flowlabels;
 	int icmpv6_time;
+	int icmpv6_echo_ignore_all;
 	int anycast_src_echo_reply;
 	int ip_nonlocal_bind;
 	int fwmark_reflect;

include/uapi/linux/sysctl.h

@@ -575,7 +575,8 @@ enum {
 
 /* /proc/sys/net/ipv6/icmp */
 enum {
-	NET_IPV6_ICMP_RATELIMIT=1
+	NET_IPV6_ICMP_RATELIMIT = 1,
+	NET_IPV6_ICMP_ECHO_IGNORE_ALL = 2
 };
 
 /* /proc/sys/net/<protocol>/neigh/<dev> */

net/ipv6/af_inet6.c

@@ -832,6 +832,7 @@ 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.flowlabel_consistency = 1;
 	net->ipv6.sysctl.auto_flowlabels = IP6_DEFAULT_AUTO_FLOW_LABELS;
 	net->ipv6.sysctl.idgen_retries = 3;

net/ipv6/icmp.c

@@ -794,6 +794,7 @@ void icmpv6_notify(struct sk_buff *skb, u8 type, u8 code, __be32 info)
 
 static int icmpv6_rcv(struct sk_buff *skb)
 {
+	struct net *net = dev_net(skb->dev);
 	struct net_device *dev = skb->dev;
 	struct inet6_dev *idev = __in6_dev_get(dev);
 	const struct in6_addr *saddr, *daddr;
@@ -843,7 +844,8 @@ static int icmpv6_rcv(struct sk_buff *skb)
 
 	switch (type) {
 	case ICMPV6_ECHO_REQUEST:
-		icmpv6_echo_reply(skb);
+		if (!net->ipv6.sysctl.icmpv6_echo_ignore_all)
+			icmpv6_echo_reply(skb);
 		break;
 
 	case ICMPV6_ECHO_REPLY:
@@ -1104,6 +1106,13 @@ static struct ctl_table ipv6_icmp_table_template[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_ms_jiffies,
 	},
+	{
+		.procname	= "echo_ignore_all",
+		.data		= &init_net.ipv6.sysctl.icmpv6_echo_ignore_all,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler = proc_dointvec,
+	},
 	{ },
 };
 
@@ -1115,9 +1124,10 @@ struct ctl_table * __net_init ipv6_icmp_sysctl_init(struct net *net)
 			sizeof(ipv6_icmp_table_template),
 			GFP_KERNEL);
 
-	if (table)
+	if (table) {
 		table[0].data = &net->ipv6.sysctl.icmpv6_time;
-
+		table[1].data = &net->ipv6.sysctl.icmpv6_echo_ignore_all;
+	}
 	return table;
 }
 #endif