.TH IPODUMP 8  "06 June 2000"
.SH NAME
ipodump \- dump IP option packet
.SH SYNOPSIS
.na
.B ipodump 
[
.B \-ix
] [
.B \-c
.I count
] [
.B \-s
.I snaplen
] [
.B \-T
.I expression
]
.br
.ad
.SH DESCRIPTION
.LP
\fIIpodump\fP prints out the IP option headers of packets routing through
a system.

In default operation, \fIipodump\fP captures and displays all passing
IP options packets. \fIIpodump\fP can also print out the option
packets that match the \fIexpression\fP. After a captured packet is printed, 
\fIipodump\fP puts it back onto the wire. The packet can then be forwarded 
to its original destination.

To run this command, ther user needs to have superuser priveleges.
The system needs to have the IPOPTION kernel extension. The kernel
extesnion source code is available at 

\fIhttp://www.cs.columbia.edu/~pingpan/software/netipopt.\fP
 
.SH OPTIONS
.TP
.B \-i
Set the IP_RECVIF option on the socket being used. \fIIpodump\fP
displays the receiving interface index for all captured packets.

.TP
.B \-x
Print each received packet (starting from IP header) in hex. 
The smaller of the entire packet or \fIsnaplen\fP bytes will be
printed.

.TP
.B \-c \fIcount\fP
Stop after receiving \fIcount\fP IP option packets. If this option is not 
specified, \fIipodump\fP will operate until interrupted.

.TP
.B \-s \fIsnaplen\fP
Specify the number of data bytes to display. The default is 128.

.TP
.B \-T \fIexpression\fP
Set the kernel to intercept the packets specified in "\fIexpression\fP. 
Currently known filters are \fBrr\fR (route record), \fBts\fR (timestamp),
\fBsec\fR (security), \fBlsrr\fR (loose source route), \fBssrr\fR
(strict source route), \fBra\fR (router alert), \fBrsvp\fR (RSVP in 
router-alert) and \fBrtcp\fR (RTCP in router-alert).
 
.LP
.ne 3

.SH AVAILABILITY

The \fIipodump\fP command works in FreeBSD 3.3, 3.4 and 4.0.

.SH BUGS
The \fIipodump\fP command takes packets from the kernel. After pasring
and printing, it puts packets back into the kernel. This impacts
packet forwarding performance.

.SH AUTHORS
The \fIipodump\fP command and IPOPTION kernel extension were written
by Ping Pan <pingpan@cs.columbia.edu> while at Bell Labs. The idea 
was cooked up by Ping and Henning Schulzrinne <hgs@cs.columbia.edu>.