Bug #13475
Updated by Marcel Telka over 1 year ago
Situation:
* tcp connection was closed
* there is more than one mss unsent
* LSO is enabled
In tcp_send() the calculation of bytes to send is done under the assumption that LSO will be used. A value higher than mss is set for lso_usable. Later this 'if' is taken, because we are at the end of the data stream:
<pre>
if (tcp->tcp_valid_bits != 0 &&
(tcp->tcp_valid_bits != TCP_FSS_VALID ||
((*snxt + len) == tcp->tcp_fss))) {
</pre>
This causes cause data with len > mss being sent without LSO setup and due to this with IP segmentation.
I can imagine two fixes:
* the easy one: don't do LSO if any of the VALID bits is set
* more complicated: with TCP_FSS_VALID don't send the complete unsent data with LSO but leave data <=mss for the next loop, which will then automaticaly be without LSO