vRouter Extension crashes while scanning fragments table

[Dariusz Sosnowski]

This bug affects Contrail Windows vRouter Extension.

Disabling vRouter Extension on Windows can trigger a bluescreen in fragment assembly module.

vr_delete_timer cancels a timer without waiting for a scheduled
callback. This caused a data race (letter in parenthesis is thread ID):

- (A) disable extension operation starts;
- (A) VrAssemblerExit is called;
- (B) scheduled callback starts executing;
- (A) vr_delete_timer called in vr_assembler_table_scan_exit cancels a timer
      and returns immediately;
- (A) VrAssemblerExit frees VrAssemblerTable;
- (B) memory pointed to by VrAssemblerTable is accessed and extension
      bug checks;

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/46309
Submitter: Dariusz Sosnowski (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/46309
Committed: http://github.com/Juniper/contrail-vrouter/commit/4049fbb1201be4e099c21d921c0829e1907f1c5f
Submitter: Zuul v3 CI (<email address hidden>)
Branch: master

commit 4049fbb1201be4e099c21d921c0829e1907f1c5f
Author: Dariusz Sosnowski <email address hidden>
Date: Wed Sep 19 13:04:43 2018 +0200

windows: Synchronize deleting timers with timer callbacks

vr_delete_timer cancels a timer without waiting for a scheduled
callback. This caused a data race (letter in parenthesis is thread ID):

- (A) disable extension operation starts;
- (A) VrAssemblerExit is called;
- (B) scheduled callback starts executing;
- (A) vr_delete_timer called in vr_assembler_table_scan_exit cancels a timer
and returns immediately;
- (A) VrAssemblerExit frees VrAssemblerTable;
- (B) memory pointed to by VrAssemblerTable is accessed and extension
bug checks;

To fix this we instruct ExDeleteTimer to wait for completion of scheduled
callbacks.

Besides that, this change introduces:

- a few asserts of IRQLs or NULL pointer accesses;
- error value return from vr_assembler_table_scan_init.

Change-Id: I9e8c9d3a7aa9231aba6816ac9a55634a38de16ea
Closes-Bug: #1793299