[PATCH] ipv4: add documentation of sysctls of error_cost and error_burst

[cgel . zte]

From: xu xin <xu.xin16@xxxxxxxxxx>

The descriptions of error_cost and error_burst sysctls are missing.
So add the descriptions of them in the documentation ip-sysctl.rst.

Signed-off-by: xu xin (CGEL ZTE) <xu.xin16@xxxxxxxxxx>
Reviewed-by: Yunkai Zhang (CGEL ZTE) <zhang.yunkai@xxxxxxxxxx>
---
 Documentation/networking/ip-sysctl.rst | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index a759872a2883..14aaa4cd76c1 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -156,6 +156,23 @@ route/max_size - INTEGER
 	From linux kernel 3.6 onwards, this is deprecated for ipv4
 	as route cache is no longer used.
 
+route/error_cost - INTEGER
+	The minimum time interval between two consecutive ICMP-DEST-
+	UNREACHABLE packets allowed sent to the same peer in the stable
+	period. Basically, The higher its value is, the lower the general
+	frequency of sending ICMP DEST-UNREACHABLE packets.
+
+	Default: HZ (one second)
+
+route/error_burst - INTEGER
+	Together with error_cost, it controls the max number of burstly
+	sent ICMP DEST-UNREACHABLE packets after a long calm time (no
+	sending ICMP DEST-UNREACHABLE). Basically, the higher the rate
+	of error_burst over error_cost is, the more allowed burstly sent
+	ICMP DEST-UNREACHABLE packets after a long calm time.
+
+	Default: 5 * HZ
+
 neigh/default/gc_thresh1 - INTEGER
 	Minimum number of entries to keep.  Garbage collector will not
 	purge entries if there are fewer than this number.
-- 
2.25.1