This bug has been copied from bug #627496 and has been proposed
to be backported to 5.6 z-stream (EUS).
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
When selecting a new window, the tcp_select_window() function tried not to shrink the offered window by using the maximum of the remaining offered window size and the newly calculated window size. The newly calculated window size was always a multiple of the window scaling factor, however, the remaining window size was not since it depended on rcv_wup/rcv_nxt. As a result, a window was shrunk when it was scaled down. With this update, aligning the remaining window to the window scaling factor assures a window is no longer shrunk.