From: Thomas Falcon <tlfal...@linux.vnet.ibm.com> Date: Thu, 8 Dec 2016 16:40:03 -0600
> This patch is based on an earlier one submitted > by Jon Maxwell with the following commit message: > > "We recently encountered a bug where a few customers using ibmveth on the > same LPAR hit an issue where a TCP session hung when large receive was > enabled. Closer analysis revealed that the session was stuck because the > one side was advertising a zero window repeatedly. > > We narrowed this down to the fact the ibmveth driver did not set gso_size > which is translated by TCP into the MSS later up the stack. The MSS is > used to calculate the TCP window size and as that was abnormally large, > it was calculating a zero window, even although the sockets receive buffer > was completely empty." > > We rely on the Virtual I/O Server partition in a pseries > environment to provide the MSS through the TCP header checksum > field. The stipulation is that users should not disable checksum > offloading if rx packet aggregation is enabled through VIOS. > > Some firmware offerings provide the MSS in the RX buffer. > This is signalled by a bit in the RX queue descriptor. > > Reviewed-by: Brian King <brk...@linux.vnet.ibm.com> > Reviewed-by: Pradeep Satyanarayana <prade...@linux.vnet.ibm.com> > Reviewed-by: Marcelo Ricardo Leitner <marcelo.leit...@gmail.com> > Reviewed-by: Jonathan Maxwell <jmaxwel...@gmail.com> > Reviewed-by: David Dai <z...@us.ibm.com> > Signed-off-by: Thomas Falcon <tlfal...@linux.vnet.ibm.com> Applied, although mis-using the TCP checksum field for this is kind of bogus. I'm surprised there wasn't some other place you could stick this value, which wouldn't modify the packet contents.
