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tcpudpipethernetpacket-injection

tcpreplay: -T option

In tcpreplay there is a very useful feature which, according to the official FAQ's, is called with parameter -T :

The packet length (in this case 8892 bytes) is greater then the maximum transmition unit (MTU) on the outgoing interface. Tcpreplay must skip the packet. Alternatively, you can specify the -T option and tcpreplay will truncate the packet to the MTU size, fix the checksums and send it.

Unfortunately, -T appears to be something different in the man page:

-T string, --timer=string
              Select packet timing mode: select, ioport, rdtsc, gtod, nano, abstime.  This option may appear up to 1 times.  The default string for this option is:
                   gtod
              Allows you to select the packet timing method to use:
              nano - Use nanosleep() API
              select - Use select() API
              ioport - Write to the i386 IO Port 0x80
              rdtsc - Use the x86/x86_64/PPC RDTSC
              gtod [default] - Use a gettimeofday() loop
              abstime - Use OS X's AbsoluteTime API

Has this option been removed in more recent versions of tcpreplay?

Solution

  • Yes, it was separated into tcprewrite (which transforms capture files) and then the options were merged back in the command tcpreplay-edit.

    The FAQ shows tcpreplay-edit --mtu-trunc is now the equivalent of the previous -T option and should imply -C to correct the checksum, but you may need --mtu=n if you aren't dealing with a standard 1500 or need -F if part of the problem is inconsistent header and real length at collection time.