Add WOLFSSL_FORCE_AUTO_RETRY option: force retrying of network reads

[julek-wolfssl]

Addresses issue #4593

[dgarske]

Is there a specific open source project this fix is being made for?

[dgarske]

So defining this macro forces the network reads to behave as blocking? Is there a reason not to implement runtime support using the SSL_MODE_AUTO_RETRY option? Also can you check review the code comment at ssl.h:2136 for SSL_MODE_AUTO_RETRY? It seems wrong.

SSL_MODE_AUTO_RETRY = 3, /* wolfSSL default is to block with blocking io and auto retry */

[julek-wolfssl]

I wanted to keep this PR minimum but if you would prefer a runtime solution, I can add the necessary API to make that work. Still, I don't think that this is a good default for wolfSSL. If you want me to implement a runtime solution, I'll make the SSL_MODE_AUTO_RETRY option on by default only with OPENSSL_COMPATIBLE_DEFAULTS.

[julek-wolfssl]

I'll update the SSL_MODE_AUTO_RETRY comment to match the real behaviour.

[julek-wolfssl]

Comment fixed.

[dgarske]

This option will force a wolfSSL read to behave as blocking.

[julek-wolfssl]

@dgarske This is being made in response to an issue: #4593. In another issue this user is asking in relation to the fetchmail project so I would guess this issue comes from work on the same project.

[mandree]

@dgarske This is being made in response to an issue: #4593. In another issue this user is asking in relation to the fetchmail project so I would guess this issue comes from work on the same project.

True, but fetchmail no longer requires it after recent updates to its TLS code. To be specific for people who find this thread:

• fetchmail's abfc13c fixes the non-blocking behavior (needed for OpenSSL 1.0.2, too, according to its documentation, although never occurred in practice)
• fetchmail's 8128bea fixes up the old code to work with OpenSSL 1.0.2/1.1.1/3.0 and wolfSSL 5.0.0's OpenSSL compat APIs.

[julek-wolfssl]

I changed this to set SSL_MODE_AUTO_RETRY with OPENSSL_COMPATIBLE_DEFAULTS and added wolfSSL_CTX_clear_mode to allow for clearing this option.