ipv6: Add rate limit mask for ICMPv6 messages

To make ICMPv6 closer to ICMPv4, add ratemask parameter. Since the ICMP
message types use larger numeric values, a simple bitmask doesn't fit.
I use large bitmap. The input and output are the in form of list of
ranges. Set the default to rate limit all error messages but Packet Too
Big. For Packet Too Big, use ratemask instead of hard-coded.

There are functions where icmpv6_xrlim_allow() and icmpv6_global_allow()
aren't called. This patch only adds them to icmpv6_echo_reply().

Rate limiting error messages is mandated by RFC 4443 but RFC 4890 says
that it is also acceptable to rate limit informational messages. Thus,
I removed the current hard-coded behavior of icmpv6_mask_allow() that
doesn't rate limit informational messages.

v2: Add dummy function proc_do_large_bitmap() if CONFIG_PROC_SYSCTL
    isn't defined, expand the description in ip-sysctl.txt and remove
    unnecessary conditional before kfree().
v3: Inline the bitmap instead of dynamically allocated. Still is a
    pointer to it is needed because of the way proc_do_large_bitmap work.

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

1 files changed, 22 insertions, 9 deletions

diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index cc14b9998941..afb915807cd0 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -168,22 +168,21 @@ static bool is_ineligible(const struct sk_buff *skb)
 	return false;
 }
 
-static bool icmpv6_mask_allow(int type)
+static bool icmpv6_mask_allow(struct net *net, int type)
 {
-	/* Informational messages are not limited. */
-	if (type & ICMPV6_INFOMSG_MASK)
+	if (type > ICMPV6_MSG_MAX)
 		return true;
 
-	/* Do not limit pmtu discovery, it would break it. */
-	if (type == ICMPV6_PKT_TOOBIG)
+	/* Limit if icmp type is set in ratemask. */
+	if (!test_bit(type, net->ipv6.sysctl.icmpv6_ratemask))
 		return true;
 
 	return false;
 }
 
-static bool icmpv6_global_allow(int type)
+static bool icmpv6_global_allow(struct net *net, int type)
 {
-	if (icmpv6_mask_allow(type))
+	if (icmpv6_mask_allow(net, type))
 		return true;
 
 	if (icmp_global_allow())
@@ -202,7 +201,7 @@ static bool icmpv6_xrlim_allow(struct sock *sk, u8 type,
 	struct dst_entry *dst;
 	bool res = false;
 
-	if (icmpv6_mask_allow(type))
+	if (icmpv6_mask_allow(net, type))
 		return true;
 
 	/*
@@ -511,7 +510,7 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 	local_bh_disable();
 
 	/* Check global sysctl_icmp_msgs_per_sec ratelimit */
-	if (!(skb->dev->flags&IFF_LOOPBACK) && !icmpv6_global_allow(type))
+	if (!(skb->dev->flags & IFF_LOOPBACK) && !icmpv6_global_allow(net, type))
 		goto out_bh_enable;
 
 	mip6_addr_swap(skb);
@@ -731,6 +730,11 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
 	if (IS_ERR(dst))
 		goto out;
 
+	/* Check the ratelimit */
+	if ((!(skb->dev->flags & IFF_LOOPBACK) && !icmpv6_global_allow(net, ICMPV6_ECHO_REPLY)) ||
+	    !icmpv6_xrlim_allow(sk, ICMPV6_ECHO_REPLY, &fl6))
+		goto out_dst_release;
+
 	idev = __in6_dev_get(skb->dev);
 
 	msg.skb = skb;
@@ -751,6 +755,7 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
 		icmpv6_push_pending_frames(sk, &fl6, &tmp_hdr,
 					   skb->len + sizeof(struct icmp6hdr));
 	}
+out_dst_release:
 	dst_release(dst);
 out:
 	icmpv6_xmit_unlock(sk);
@@ -1137,6 +1142,13 @@ static struct ctl_table ipv6_icmp_table_template[] = {
 		.mode		= 0644,
 		.proc_handler = proc_dointvec,
 	},
+	{
+		.procname	= "ratemask",
+		.data		= &init_net.ipv6.sysctl.icmpv6_ratemask_ptr,
+		.maxlen		= ICMPV6_MSG_MAX + 1,
+		.mode		= 0644,
+		.proc_handler = proc_do_large_bitmap,
+	},
 	{ },
 };
 
@@ -1153,6 +1165,7 @@ struct ctl_table * __net_init ipv6_icmp_sysctl_init(struct net *net)
 		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;
+		table[4].data = &net->ipv6.sysctl.icmpv6_ratemask_ptr;
 	}
 	return table;
 }