tcpdump get packate, Application get the packete too?

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dhcpdump

DHCPDUMP(1)						      General Commands Manual						       DHCPDUMP(1)

NAME

       dhcpdump - DHCP packet dumper

SYNOPSIS

       dhcpdump [-h regular-expression]

DESCRIPTION

       This command parses the output of tcpdump to display the dhcp-packets for easier checking and debugging.

USAGE

       tcpdump -lenx -s 1500 port bootps or port bootpc | dhcpdump

       If you want to filter a specific Client Hardware Address (CHADDR), then you can specifiy it as a regular expressions:

       tcpdump -lenx -s 1500 port bootps or port bootpc | dhcpdump -h ^00:c0:4f

       This will display only the packets with Client Hardware Addresses which start with 00:c0:4f.

OUTPUT

	 TIME: 15:45:02.084272
	   IP: 0.0.0.0.68 (0:c0:4f:82:ac:7f) > 255.255.255.255.67 (ff:ff:ff:ff:ff:ff)
	   OP: 1 (BOOTPREQUEST)
	HTYPE: 1 (Ethernet)
	 HLEN: 6
	 HOPS: 0
	  XID: 28f61b03
	 SECS: 0
	FLAGS: 0
       CIADDR: 0.0.0.0
       YIADDR: 0.0.0.0
       SIADDR: 0.0.0.0
       GIADDR: 0.0.0.0
       CHADDR: 00:c0:4f:82:ac:7f:00:00:00:00:00:00:00:00:00:00
	SNAME: .
	FNAME: .
       OPTION:	53 (  1) DHCP message type	   3 (DHCPREQUEST)
       OPTION:	54 (  4) Server identifier	   130.139.64.101
       OPTION:	50 (  4) Request IP address	   130.139.64.143
       OPTION:	55 (  7) Parameter Request List      1 (Subnet mask)
						     3 (Routers)
						    58 (T1)
						    59 (T2)

       At the option field, the first field is the value of the option, the second one (between brackets) is the length of the option-datafield,
       the third field is the name of the option, the fourth field is the data of the option.

RETURN VALUES

       Always 0.

NOTES

       Privileged access is often needed for tcpdump.

BUGS

       Not all the parameter options are printed verbose, because of lack of documentation. Not all the options are tested, because of lack of
       clients/servers with these options. If you have a dump of one of them, please send them to me and I'll incorperate them.

THANKS TO

       Ralph Droms and Ted Lemons "The DHCP Handbook", ISBN 1-57870-137-6.

       Peter Apian-Bennewitz <apian@ise.fhg.de> for his Client Hardware Address filtering

AUTHOR

       Edwin Groothuis, edwin@mavetju.org (http://www.mavetju.org)

SEE ALSO

       dhcpd(8), tcpdump(1), RFC2132

November 21, 2003						 November 21, 2003						       DHCPDUMP(1)

Programming