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Document IP_PMTUDISC_PROBE, which will be in 2.6.22.

This commit is contained in:
Michael Kerrisk 2007-04-05 15:47:26 +00:00
parent 273691af91
commit b59874b963
1 changed files with 17 additions and 0 deletions
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@ -513,6 +513,7 @@ Path MTU discovery flags:Meaning
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
@ -548,6 +549,17 @@ and retrieve the MTU by calling
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
.BR 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.
@ -922,6 +934,11 @@ are new options in Linux 2.2.
They are also all Linux specific and should not be used in
programs intended to be portable.
.PP
.\" FIXME
.\" To be confirmed that IP_PMTUDISC_PROBE makes it into kernel 2.6.22
.I IP_PMTUDISC_PROBE
is new in Linux 2.6.22.
.PP
.I struct ip_mreqn
is new in Linux 2.2. Linux 2.0 only supported
.BR ip_mreq .