Hi Ondrej,
yeah, I was kinda expecting "no guarantees", but isn't the plugin_version()
function a good method candidate to enforce compatibility?
I mean, isn't increasing NS_PLUGIN_VERSION when a (plugin visible) data
structure changes, a good way to enforce that only compatible plugins are used?
Thanks,
Marcus
On 15/12/2022 19:32, Ondřej Surý wrote:
Hi Marcus,
I am afraid that we can’t provide any guarantees about the BIND 9 internal
libraries. We made a decision to drop the layers and layers of compatibility
for the sake of maintainability.
That said, once the release is pronounced ESV (roughly a year from initial
release), we try to minimize changes to that branch, but it could still happen
if needed by a security fix.
As for the binary compatibility, there’s no guarantee whatsoever, I think you
need to match the full version to check whether the plug-in should be loaded.
Honestly, the best way how to keep the plug-in that’s useful for wider audience maintained would be to contribute it to the BIND 9 with a promise that the authors will keep helping maintaining the
plug-in. (We would like to avoid the situations where the author just dumps the code on us and don’t care anymore - there’s associated maintenance cost with any new feature.)
Ondrej
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Ondřej Surý — ISC (He/Him)
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On 15. 12. 2022, at 20:10, Marcus Kool <marcus.k...@urlfilterdb.com> wrote:
Hi,
I have written a plugin for named and was wondering what the policy behind the
usage of plugin_version() is and what kind of compatibility check it intends to
perform.
It is common for plugins to use query_ctx_t and its members fname, view, client
(client.message, client.query) etc.
Since these data structures may change between (patch) versions, a plugin
compiled for version A can get a SEGV signal because a data structure changed
and the plugin is used inside named version B.
I have little experience with data structure changes of named and observed only the addition of refresh_rrset in query_ctx (somewhere between 9.16.1 and 9.16.35) which did not cause an issue since
its 1-byte size did not change offsets of most members inside the query_ctx struct.
In our plugin, plugin_register() checks for the major and minor version number in named_g_version so a plugin compiled with 9.16.x refuses to initialize inside a 9.18.y named process and vice
versa. But I have the impression that this might not be a 100% guarantee that all is well.
Because we like to release as few as possible versions of the plugin I have a second question: how can we be sure that a plugin compiled with 9.X.1 will have no issues accessing named data
structures for all patch versions of 9.X?
Thanks,
Marcus
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