mbedtls_net_set_nonblock / mbedtls_net_set_block doesn't work (IDFGH-2264)

[szmodz]

Latest master (93a8603) using 2019r2 toolchain.

mbedtls_net_set_nonblock / mbedtls_net_set_block doesn't work.

Steps to reproduce: try using mbedtls_net_set_nonblock / mbedtls_net_set_block

Apparently it's because HAVE_FCNTL was not defined when building the C library.

https://github.com/espressif/newlib-esp32/blob/esp_based_on_3_0_0/newlib/libc/syscalls/sysfcntl.c

[szmodz]

I've hacked around the C library problem, and it seems to work, but perhaps there are other issues with nonblocking sockets and that's why fcntl was disabled in the first place?

[szmodz]

This code doesn't work at all with the 2019r2 toolchain:

https://github.com/espressif/esp-aws-iot/blob/0ba1fe942785b2efd553d73124afaef2f0327f41/port/network_mbedtls_wrapper.c#L208

It always fails with

ESP_LOGE(TAG, "failed! net_set_(non)block() returned -0x%x", -ret);

If you need test cases, here they are (Espressif's own code):
https://github.com/espressif/esp-aws-iot/tree/master/examples

The problem also applies to esp-tls:

esp-idf/components/esp-tls/esp_tls.c

Line 191 in 93a8603

int flags = fcntl(fd, F_GETFL, 0);

Basically anything that uses esp-tls in nonblocking mode is broken with the gcc 8.2 based toolchains. It just goes unnoticed because the call is not checked for errors.

[szmodz]

Any ACK on this? I think this problem needs to be fixed, as it affects multiple esp-idf components, but I can keep posting bug reports... ;-)

One of the test cases for esp-idf should include nonblocking sockets. Apparently there's no such test.

This only relates to the gcc 8 based toolchains (including 2019r2).

[szmodz]

This is why it works with gcc 5:

esp-idf/components/vfs/vfs.c

Line 728 in 93a8603

int __attribute__((weak)) fcntl(int fd, int cmd, ...)

(attribute weak)

48d9d50

#1070 (should be reopened)

[mahavirj]

@szmodz

Any ACK on this? I think this problem needs to be fixed, as it affects multiple esp-idf components, but I can keep posting bug reports... ;-)

Thanks for reporting this issue. Fix has been merged for this internally, once ESP-IDF codebase sync with github, this issue will be marked as closed.