io fixes on non-blocking FDs

[rjarry]

These are fixes for problems I encountered with the UNIX transport. Basically, when sending large configurations to netopeer2-server, since the socket fd is non-blocking, we can get EAGAIN errors upon write() if the socket buffer is full and the server does not read fast enough.

These errors are already handled in libnetconf2 but errno is not reset and libyang checks it (since commit CESNET/libyang@609d708). This causes the operation to fail with the following error:

Print error (Resource temporarily unavailable).

Work around the problem by resetting errno to 0 in case of EAGAIN or EINTR.

Also, if the error is EINTR do not wait before trying to read/write again.

I am not sure this is the correct approach, I proposed another (maybe complementary?) solution in CESNET/libyang#903

[codecov-io]

Codecov Report

Merging #175 into master will decrease coverage by 0.05%.
The diff coverage is 17.64%.

@@            Coverage Diff             @@
##           master     #175      +/-   ##
==========================================
- Coverage   38.14%   38.09%   -0.06%     
==========================================
  Files          23       23              
  Lines        9962     9976      +14     
  Branches     1949     1952       +3     
==========================================
  Hits         3800     3800              
- Misses       5217     5226       +9     
- Partials      945      950       +5

Impacted Files	Coverage Δ
src/io.c	44.9% <17.64%> (-0.58%)	⬇️
src/session_server_ssh.c	24.31% <0%> (-0.13%)	⬇️
src/session_server_tls.c	28.24% <0%> (-0.11%)	⬇️

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[brchiu]

@rjarry
Thanks for addressing this issue. I also encountered a similar one for SSH case with Print error (No such file or directory) error message. Can your approach apply to it ?

[michalvasko]

Hi,
depending on how we resolve CESNET/libyang#903, resetting errno may not be needed.

Regards,
Michal

[rjarry]

@rjarry
Thanks for addressing this issue. I also encountered a similar one for SSH case with Print error (No such file or directory) error message. Can your approach apply to it ?

@brchiu I don't think so, I only handle EAGAIN and EINTR, No such file or directory is ENOENT and is a real error.

[rjarry]

depending on how we resolve CESNET/libyang#903, resetting errno may not be needed.

Indeed, I removed the first commit.

[michalvasko]

Hi,
it is fine now, thanks.

Regards,
Michal

[rjarry]

👍