[PATCH linux-next] Documentation: fix outdated interpretation of ip_no_pmtu_disc

[cgel.zte@gmail.com]

From: xu xin <xu.xin16@zte.com.cn>

The updating way of pmtu has changed, but documentation is still in the
old way. See commit-id 28d35bcdd3925e7293408cdb8aa5f2aac5f0d6e3. So This
patch fix interpretation of ip_no_pmtu_disc.

Besides, min_pmtu seems not to be discoverd, but set.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
---
 Documentation/networking/ip-sysctl.rst | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index c04431144f7a..dd5e53318805 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -25,9 +25,11 @@ ip_default_ttl - INTEGER
 ip_no_pmtu_disc - INTEGER
 	Disable Path MTU Discovery. If enabled in mode 1 and a
 	fragmentation-required ICMP is received, the PMTU to this
-	destination will be set to min_pmtu (see below). You will need
-	to raise min_pmtu to the smallest interface MTU on your system
-	manually if you want to avoid locally generated fragments.
+	destination will be set to the smallest of the old MTU
+        and ip_rt_min_pmtu (see __ip_rt_update_pmtu() in
+        net/ipv4/route.c). You will need to raise min_pmtu to the
+        smallest interface MTU on your system manually if you want to
+        avoid locally generated fragments.
 
 	In mode 2 incoming Path MTU Discovery messages will be
 	discarded. Outgoing frames are handled the same as in mode 1,
@@ -49,7 +51,7 @@ ip_no_pmtu_disc - INTEGER
 	Default: FALSE
 
 min_pmtu - INTEGER
-	default 552 - minimum discovered Path MTU
+	default 552 - minimum set Path MTU
 
 ip_forward_use_pmtu - BOOLEAN
 	By default we don't trust protocol path MTUs while forwarding
-- 
2.25.1