Re: [REGRESSION, bisect]cxgb4 port failure with TSO traffic after commit 10d3be569243def8("tcp-tso: do not split TSO packets at retransmit time")

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On Fri, Jun 24, 2016 at 4:38 AM, Arjun V. [off-list ref] wrote:

Eric,
We are seeing skb's with length(skb->len) greater than 65536 coming into our ndo_start_xmit() callback routine.
We can add a check in our eth_xmit() routine to skip those packets, but it will be better if you fix this in kernel.


I have attached pcap file obtained from tcpdump. In the pcap file there are 2 such packets(I used tcpdump filter to extract out those packets).

Let us know if you need anything else.

Beats me really.

At retransmit time, we only can eventually reduce packet sizes
(assuming GSO is used, because we might coalesce sub-mss packets in
tcp_retrans_try_collapse())

So why are you seeing too big packets at retransmit, I really have no idea.

MIght be some bug related to MSS computation, overflowing somehow ?