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Re: [mosquitto-dev] dead loop in mosquitto_loop while connecting to broker
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Hi Arvin,
Thank you for the report and the pull request. I actually looked at
this a few days back and decided to backport the fix from the develop
branch instead of using your PR, which I did but then neglected to
push.
I hope you don't mind, the change is a bit bigger than you suggested
but results in a cleaner overall result.
Regards,
Roger
On Mon, 8 Aug 2022 at 15:10, Stony?Meteorite <icemanpeng@xxxxxxxxxxx> wrote:
>
> Hi Team!
> I'm working with mosquitto and i found: When the TCP connection is complete, but the TLS connection is not complete. If the server disconnects the TCP connection, In this case, SSL_get_error returns the error code SSL_ERROR_SYSCALL.
> In the current implementation, if the error code is SSL_ERROR_SYSCALL, the mosquitto_loop function returns success and continues to invoke SSL_connect in the next mosquitto_loop,
> Because the TCP connection is disconnected, SSL_connect immediately returns the failure error code SSL_ERROR_SYSCALL and invoke the next mosquitto_loop again. As a result, the program enters a dead loop.
> This dead loop causes high CPU usage. In fact, the mosquitto_loop does not return failure until the mqtt keepalive time expires.
> According to https://www.openssl.org/docs/man1.1.1/man3/SSL_get_error.html
>
> SSL_ERROR_SYSCALL
> Some non-recoverable, fatal I/O error occurred. The OpenSSL error queue may contain more information on the error. For socket I/O on Unix systems, consult errno for details. If this error occurs then no further I/O operations should be performed on the connection and SSL_shutdown() must not be called.
>
>
> SSL_ERROR_SYSCALL is fatal error，when SSL_get_error return SSL_ERROR_SYSCALL, we should return an error to the user。
>
> My environment:
> mosquitto version: 1.6.7
> openssl version: 1.1.1k
> platform: linux 4.14
>
> And i think problem still exists in the latest version.
> I submitted a pull request on github to fix this. https://github.com/eclipse/mosquitto/pull/2595
>
> Best regards
> Arvin
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