[dpdk-users] Sent a UDP packet, but length is wrong when captured

DoHyung Kim dohyung.kim at fluidic.io
Wed Sep 26 20:28:44 CEST 2018


Hi,

I'm new to DPDK and having trouble in crafting TX packets.

My application receives and caches UDP packets after dropping header part.
When clients request, it sends the cached packets after prepending them 
a new header mbuf
(by chaining), which contains all the headers to UDP's filled correctly 
for targeting the clients.
Though I think I'm doing nothing wrong, I see the transmitted ethernet 
frames are
14 bytes longer than expected.

Please see a capture of such a packet from Wireshark below:





The multi-seg mbuf is 1370 byte long, but weirdly enough, its 1384 when 
captured back.
I'm using libpcap based vdev on loopback interface for testing. And DPDK 
version is 17.11.3 on Ubuntu 18.04.

Any clue?

Thanks in advance.

DoHyung Kim


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