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.\" Title: nexp-udp
.\" Author:
.\" Generator: DocBook XSL Stylesheets v1.73.2 <http://docbook.sf.net/>
.\" Date: 26 June 2007
.\" Manual:
.\" Source:
.\"
.TH "NEXP\-UDP" "5" "26 June 2007" "" ""
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.SH "NAME"
nexp-udp \- User Datagram Protocol (UDP) support for Network Expect
.SH "SYNOPSIS"
.PP
PDU definition:
.HP 4
\fBudp\fR( [\fBsrc\fR=\fInum\fR,] [\fBdst\fR=\fInum\fR,] [\fBcksum\fR=\fInum\fR,] [\fBlength\fR=\fInum\fR] )
.PP
PDU decoding:
.PP
\fI$udp(srcport)\fR,
\fI$udp(dstport)\fR,
\fI$udp(length)\fR,
\fI$udperror(srcport)\fR,
\fI$udperror(dstport)\fR,
\fI$udperror(length)\fR
.SH "PDU DEFINITION"
.PP
\fBsrc\fR = \fINUMSPEC\fR
.RS 4
Specifies the source UDP port\&. Default: 1073\&.
.RE
.PP
\fBdst\fR = \fINUMSPEC\fR
.RS 4
Specifies the destination UDP port\&.
.RE
.PP
\fBcksum\fR = \fINUMSPEC\fR
.RS 4
Forces a specific UDP checksum\&. Default: valid, auto\-calculated checksum of the UDP datagram\&.
.RE
.PP
\fBlength\fR = \fINUMSPEC\fR
.RS 4
Forces a specific UDP length\&. Default: valid, auto\-calculated length of the UDP datagram\&.
.RE
.SH "PDU DECODING"
.PP
The following Tcl variables are available to Tcl scripts after any
\fBNetwork Expect\fR
command that reads and decodes packets has decoded a packet\&. Commands that read and decode packets include the
\fBexpect_network\fR
family of commands as well as the
\fBpdu decode\fR
command\&.
.PP
$udp(srcport)
.RS 4
The UDP source port the received UDP datagram\&.
.RE
.PP
$udp(dstport)
.RS 4
The UDP destination port of the received UDP datagram\&.
.RE
.PP
$udp(length)
.RS 4
The 16\-bit
\fIlength\fR
field of the received UDP datagram\&.
.RE
.SH "SEND_EXPECT SUPPORT"
.PP
\fBNetwork Expect\fR
UDP PDUs support the
\fBsend_expect\fR
command\&.
.PP
The hash of an UDP PDU is the bitwise XOR of the source and destination UDP ports, which is a 16\-bit value\&.
.PP
A received UDP PDU is considered to be a response to an injected stimulus if the hash of the received UDP datagram is the same as that of the injected stimulus
\fIand\fR
the following conditions are met:
.sp
.RS 4
\h'-04'\(bu\h'+03'The source port of the injected UDP datagram is the same as the destination port of the received UDP datagram\&.
.RE
.sp
.RS 4
\h'-04'\(bu\h'+03'The destination port of the injected UDP datagram is the same as the source port of the received UDP datagram\&.
.RE
.SH "EXAMPLES"
.sp
.RS 4
\h'-04' 1.\h'+02'A simple UDP datagram:
.sp
.RS 4
.nf
ip(dst = www\&.example\&.com)/udp(src = random, dst = 53)/raw(\'ABCDEFG\')
.fi
.RE
.RE
.sp
.RS 4
\h'-04' 2.\h'+02'A definition for an UDP datagram that forces a bogus length field in the UDP header:
.sp
.RS 4
.nf
ip(dst = www\&.example\&.com)/udp(src = random, dst = 53, \e
length = 5)/raw(\'ABCDEFG\')
.fi
.RE
.RE
.SH "VERSION"
.PP
This man page is correct for version 1\&.0 of
\fBNetwork Expect\fR\&.
.SH "SEE ALSO"
.PP
nexp(1), nexp\-numspec(1)
.SH "AUTHOR"
.PP
UDP support for
\fBNetwork Expect\fR
was written by Eloy Paris <peloy@netexpect\&.org>\&. The "Send and Expect" functionality of the UDP module was borrowed from Scapy, the packet manipulation program written in Python by Philippe Biondi\&.
.PP
This man page was written by Eloy Paris\&.
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