[PATCH net-next] icmp: Add counters for rate limits

[Jamie Bainbridge]

There are multiple ICMP rate limiting mechanisms:

* Global limits: net.ipv4.icmp_msgs_burst/icmp_msgs_per_sec
* v4 per-host limits: net.ipv4.icmp_ratelimit/ratemask
* v6 per-host limits: net.ipv6.icmp_ratelimit/ratemask

However, when ICMP output is limited, there is no way to tell
which limit has been hit or even if the limits are responsible
for the lack of ICMP output.

Add counters for each of the cases above. As we are within
local_bh_disable(), use the __INC stats variant.

Example output:

 # nstat -sz "*RateLimit*"
 IcmpOutRateLimitGlobal          134                0.0
 IcmpOutRateLimitHost            770                0.0
 Icmp6OutRateLimitHost           84                 0.0

Signed-off-by: Jamie Bainbridge <jamie.bainbridge@xxxxxxxxx>
Suggested-by: Abhishek Rawal <rawal.abhishek92@xxxxxxxxx>
---
 include/uapi/linux/snmp.h | 3 +++
 net/ipv4/icmp.c           | 3 +++
 net/ipv4/proc.c           | 8 +++++---
 net/ipv6/icmp.c           | 4 ++++
 net/ipv6/proc.c           | 1 +
 5 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 6600cb0164c2beb6f140beaa0bd4ea44e9443b0c..26f33a4c253d75c6661f6606aef9d8fd61baa476 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -95,6 +95,8 @@ enum
 	ICMP_MIB_OUTADDRMASKS,			/* OutAddrMasks */
 	ICMP_MIB_OUTADDRMASKREPS,		/* OutAddrMaskReps */
 	ICMP_MIB_CSUMERRORS,			/* InCsumErrors */
+	ICMP_MIB_RATELIMITGLOBAL,		/* OutRateLimitGlobal */
+	ICMP_MIB_RATELIMITHOST,			/* OutRateLimitHost */
 	__ICMP_MIB_MAX
 };
 
@@ -112,6 +114,7 @@ enum
 	ICMP6_MIB_OUTMSGS,			/* OutMsgs */
 	ICMP6_MIB_OUTERRORS,			/* OutErrors */
 	ICMP6_MIB_CSUMERRORS,			/* InCsumErrors */
+	ICMP6_MIB_RATELIMITHOST,		/* OutRateLimitHost */
 	__ICMP6_MIB_MAX
 };
 
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 46aa2d65e40ab63dc2d343997d13c85fd6a51b7a..8cebb476b3ab1833b4efe073efc57dbdfeffd21d 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -296,6 +296,7 @@ static bool icmpv4_global_allow(struct net *net, int type, int code)
 	if (icmp_global_allow())
 		return true;
 
+	__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITGLOBAL);
 	return false;
 }
 
@@ -325,6 +326,8 @@ static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
 	if (peer)
 		inet_putpeer(peer);
 out:
+	if (!rc)
+		__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITHOST);
 	return rc;
 }
 
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index f88daace9de3e1e747c67710f55a198758243482..eaf1d3113b62f7dc93fdc7b7c4041140ac63bf69 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -353,7 +353,7 @@ static void icmp_put(struct seq_file *seq)
 	seq_puts(seq, "\nIcmp: InMsgs InErrors InCsumErrors");
 	for (i = 0; icmpmibmap[i].name; i++)
 		seq_printf(seq, " In%s", icmpmibmap[i].name);
-	seq_puts(seq, " OutMsgs OutErrors");
+	seq_puts(seq, " OutMsgs OutErrors OutRateLimitGlobal OutRateLimitHost");
 	for (i = 0; icmpmibmap[i].name; i++)
 		seq_printf(seq, " Out%s", icmpmibmap[i].name);
 	seq_printf(seq, "\nIcmp: %lu %lu %lu",
@@ -363,9 +363,11 @@ static void icmp_put(struct seq_file *seq)
 	for (i = 0; icmpmibmap[i].name; i++)
 		seq_printf(seq, " %lu",
 			   atomic_long_read(ptr + icmpmibmap[i].index));
-	seq_printf(seq, " %lu %lu",
+	seq_printf(seq, " %lu %lu %lu %lu",
 		snmp_fold_field(net->mib.icmp_statistics, ICMP_MIB_OUTMSGS),
-		snmp_fold_field(net->mib.icmp_statistics, ICMP_MIB_OUTERRORS));
+		snmp_fold_field(net->mib.icmp_statistics, ICMP_MIB_OUTERRORS),
+		snmp_fold_field(net->mib.icmp_statistics, ICMP_MIB_RATELIMITGLOBAL),
+		snmp_fold_field(net->mib.icmp_statistics, ICMP_MIB_RATELIMITHOST));
 	for (i = 0; icmpmibmap[i].name; i++)
 		seq_printf(seq, " %lu",
 			   atomic_long_read(ptr + (icmpmibmap[i].index | 0x100)));
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 9d92d51c475779f7af72b1c4ea35d4d482874db0..79c769c0d1138de1a73363a58362804657ae83c0 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -183,6 +183,7 @@ static bool icmpv6_global_allow(struct net *net, int type)
 	if (icmp_global_allow())
 		return true;
 
+	__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITGLOBAL);
 	return false;
 }
 
@@ -224,6 +225,9 @@ static bool icmpv6_xrlim_allow(struct sock *sk, u8 type,
 		if (peer)
 			inet_putpeer(peer);
 	}
+	if (!res)
+		__ICMP6_INC_STATS(net, ip6_dst_idev(dst),
+				  ICMP6_MIB_RATELIMITHOST);
 	dst_release(dst);
 	return res;
 }
diff --git a/net/ipv6/proc.c b/net/ipv6/proc.c
index d6306aa46bb1eb768ab77aae6a494640ed462157..e20b3705c2d2accedad4aac75064c33f733a80be 100644
--- a/net/ipv6/proc.c
+++ b/net/ipv6/proc.c
@@ -94,6 +94,7 @@ static const struct snmp_mib snmp6_icmp6_list[] = {
 	SNMP_MIB_ITEM("Icmp6OutMsgs", ICMP6_MIB_OUTMSGS),
 	SNMP_MIB_ITEM("Icmp6OutErrors", ICMP6_MIB_OUTERRORS),
 	SNMP_MIB_ITEM("Icmp6InCsumErrors", ICMP6_MIB_CSUMERRORS),
+	SNMP_MIB_ITEM("Icmp6OutRateLimitHost", ICMP6_MIB_RATELIMITHOST),
 	SNMP_MIB_SENTINEL
 };
 
-- 
2.39.0