When processing a partial acknowledgment during SACK
loss recovery, the size of the TCP option (in particular,
the timestamp option) was not considered properly.
This would restict the amount of new data to be injected,
but also could lead to the transmission of segments with
little data (a multiple of 12 bytes).
Considering the currently in-use TCP options when
calculating the amount of new data to be injected will
address this issue.
Reported-by: Liang Tian