caplen annotation ignored in FromDump element for PCAP files

[bozakov]

Attempting to replay a PCAP trace in which only the first caplen bytes have been recorded and len contains the actual packet length, generates packets which only have a length of caplen.

It seem that the line
SET_EXTRA_LENGTH_ANNO(p, len - caplen);

in elements/userlevel/fromdump.cc does not have any effect.

[kohler]

No, this is the expected behavior. Rather than generate packets with extra, invalid bytes, the element sets an annotation to say “the wire packet had N more bytes than this packet does.”

Not all other elements understand or obey the EXTRA_LENGTH annotation, but many do.

[bozakov]

Sorry for the misunderstanding and thanks a lot for the clarification - the issue can be closed. Is there any element to reverse this type of truncation (e.g., zero padding the packet, replicating the behavior of tcpreplay?). I'm having trouble replaying 10G traces.

[kohler]

Yes, there is. If you update to the latest git, the standard Pad element does what you want.

[bozakov]

Excellent - that works! Thank you for the pointer.