Using tap0 with Tcpreplay

This thread on the Wireshark mailing list brought up the issue of not being able to use Tcpreplay with the loopback interface on FreeBSD, e.g.:

orr:/root# tcpreplay -i lo0 /data/lpc/1.lpc
sending out lo0 
processing file: /data/lpc/1.lpc
Unable to send packet: Address family not supported by protocol family

Here is an alternative: use tap0.

orr:/root# ifconfig tap0
ifconfig: interface tap0 does not exist
orr:/root# dd if=/dev/tap0 of=/dev/null bs=1500 &
[1] 9468
orr:/root# ifconfig tap0 up
orr:/root# ifconfig tap0
tap0: flags=8843 mtu 1500
        inet6 fe80::2bd:1dff:fe2d:4d00%tap0 prefixlen 64 scopeid 0x5 
        ether 00:bd:1d:2d:4d:00
        Opened by PID 9468
orr:/root# tcpreplay -i tap0 /data/lpc/1.lpc
sending out tap0 
processing file: /data/lpc/1.lpc
^C
Actual: 71 packets (6860 bytes) sent in 6.15 seconds
Rated: 1115.0 bps, 0.01 Mbps/sec, 11.54 pps

In a second window, sniff with Tcpdump or whatever program you want:

orr:/root# tcpdump -n -i tap0 -s 1515
tcpdump: WARNING: tap0: no IPv4 address assigned
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on tap0, link-type EN10MB (Ethernet), capture size 1515 bytes
10:25:16.211443 00:0d:28:6c:f5:4f > 01:00:0c:cc:cc:cd sap aa ui/C
10:25:17.567563 IP 192.168.2.5.2882 > 10.20.2.19.22:
 P 1293772727:1293772779(52) ack 478395919 win 64444

I discussed this in my first book and in my network security monitoring class.

Comments

Netfortius said…
Wow! That was fast and comprehensive - thank you, Richard.

Interestingly enough, that does not seem to work on my BSD "flavor" (which is at the basis of MacOSX):

pwrbk:~/scm$ sudo dd if=/dev/tap0 of=/dev/null bs=1500 &
[1] 3398
pwrbk:~/scm$ dd: /dev/tap0: No such file or directory

[1]+ Exit 1 sudo dd if=/dev/tap0 of=/dev/null bs=1500

... thus, consequently:

pwrbk:~/remote-mac scm$ ifconfig tap0 up
ifconfig: interface tap0 does not exist

Do you have a tap0 in your BSD /dev ?

Thanks again,
Stefan
11:13 AM
Richard Bejtlich said…
Hi,

MacOS X is not a BSD "flavor." Mac OS X uses BSD userland tools. The kernel is Mach-based.
11:27 AM
Netfortius said…
... just following up on my own comment ;) Should have googled harder before posting :(

This may work - I will give it a shot right now:

http://www-user.rhrk.uni-kl.de/~nissler/tuntap/

Thanks again, Richard!
Stefan
11:29 AM
Anonymous said…
thanks, it work from my BSD
but how to adding the device imto permanent device
so if my computer reboot not to write the command first
3:01 AM
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