fxp: stalled transfers

Bjoern Koenig bkoenig at alpha-tierchen.de
Thu Apr 9 09:02:07 UTC 2009

pyunyh at gmail.com wrote:

> If you can easily reproduce the issue, can you capture stalled TCP
> session with tcpdump on receiving host?(Make sure to disable Rx
> checksum offload prior to capturing the session.)

I transferred a 256 kiB file and these are the tcpdumps:


Actually the transfer doesn't stall although ftp and scp told me so. It
becomes incredibly slow. It seems like that the chunks are too large and a
smaller packet will be resent. I decreased the MTU from 1500 to 1492 and
it works fine with TSO enabled.

I also captured the traffic on my router:


It reveals a suspect information: "truncated-ip - 8 bytes missing!"

I almost suppose that this is a PPPoE-related configuration issue and the
fxp driver is not necessarily the problem since decreasing the MTU of the
LAN host solves it.


More information about the freebsd-stable mailing list