Fix for issue #7054 by avoiding recursive calls to websocket_background. #7694
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Is websocket_background a "background callback" created by background_callback_add? This API is intended to provide a guard against recursive calls already. If it is not providing this guard properly, then it would be better to fix that. However, if websocket_background can be called in other contexts than background_callback_run_all, it may be appropriate to add this kind of extra guard. |
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Yes, websocket_background() gets called directly by websocket_available()
and websocket_read_char().
…On Wed, Mar 8, 2023 at 1:26 PM Jeff Epler ***@***.***> wrote:
Is websocket_background a "background callback" created by
background_callback_add? This API is intended to provide a guard against
recursive calls already. If it is not providing this guard properly, then
it would be better to fix that. However, if websocket_background can be
called in other contexts than background_callback_run_all, it may be
appropriate to add this kind of extra guard.
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Thanks! I wasn't able to find that on a quick search in the source code. In that case, I think it's appropriate to add the protection. |
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I think this should go in 8.0.x as well. I can backport it, or if you rebase the PR, it will go in and we can pull it forward to main. |
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@dhalbert ; I'm not sure how to go about rebasing thru github. Do I just create a fork on 8.0.x and commit the change to that? |
Yes, though it can be difficult to get the 8.0.x branch from upstream. I can do a cherry-pick after it's merged -- no problem. |
Issue #7054 was caused by a recursive call to websocket_background(); due to the call to _read_next_payload_byte() in that function. That caused mismatches and overflows in the _incoming_ringbuf ring buffer. This fix will simply return if websocket_background() is already being called.