Document new IP_PMTUDISC_PROBE value for IP_MTU_DISCOVERY. (Going into
2.6.22).
Thanks,
-John
diff -rU3 man-pages-2.43-a/man7/ip.7 man-pages-2.43-b/man7/ip.7
--- man-pages-2.43-a/man7/ip.7 2006-09-26 09:54:29.000000000 -0400
+++ man-pages-2.43-b/man7/ip.7 2007-03-27 15:46:18.000000000 -0400
@@ -515,6 +515,7 @@
IP_PMTUDISC_WANT:Use per-route settings.
IP_PMTUDISC_DONT:Never do Path MTU Discovery.
IP_PMTUDISC_DO:Always do Path MTU Discovery.
+IP_PMTUDISC_PROBE:Set DF but ignore Path MTU.
.TE
When PMTU discovery is enabled the kernel automatically keeps track of
@@ -550,6 +551,15 @@
with the
.B IP_MTU
option.
+
+It is possible to implement RFC 4821 MTU probing with
+.B SOCK_DGRAM
+of
+.B SOCK_RAW
+sockets by setting a value of IP_PMTUDISC_PROBE. This is also particularly
+useful for diagnostic tools such as
+.BR tracepath (8)
+that wish to deliberately send probe packets larger than the observed Path MTU.
.TP
.B IP_MTU
Retrieve the current known path MTU of the current socket.
