Comment 35 for bug 1896734

Reviewed: https://review.opendev.org/c/openstack/oslo.privsep/+/819996
Committed: https://opendev.org/openstack/oslo.privsep/commit/c223dbced7d5a8d1920fe764cbce42cf844538e1
Submitter: "Zuul (22348)"
Branch: master

commit c223dbced7d5a8d1920fe764cbce42cf844538e1
Author: Mohammed Naser <email address hidden>
Date: Wed Dec 1 11:19:26 2021 +0400

    Bump max_buffer_size for Deserializer

    Since msgpack 0.6.0, some limits were introduced for the
    deserializer which were put in to avoid any denial of service
    attacks using msgpack. These limits were raised to 100MiB
    in the release of msgpack 1.0.0.

    The default buffer sizes that were implemented were quite low
    and when running certain `privsep` commands, especially for
    Neutron when using linux bridge, where there is a large amount
    of netdevs, privsep would crash since msgpack would fail to
    decode the message since it considers it too big:

      ValueError: 1174941 exceeds max_str_len(1048576)

    In this commit, the `max_buffer_size` is bumped to the value
    that ships with msgpack==1.0.0 to allow for users who don't
    have that to continue to function. Also, since `msgpack` is
    only being used by the internal API, we're not worried about
    a third party coming in and overwhelming the system by
    deserializing calls.

    This fix also addresses some weird behaviour where privsep
    will die and certain OpenStack agents would start to behave
    in a strange way once they hit a certain number of ports (since
    any privsep calls would start to fail).

    Closes-Bug: #1844822
    Closes-Bug: #1896734
    Related-Bug: #1928764
    Closes-Bug: #1952611
    Change-Id: I135917522daff95377d07566317ef0fc0d16e7cb