The cause of the error cannot be determined and Data retrieval not guaranteed in read/send functions.

[t-nakagawa-esol]

1. Errors (when errno is -1) except for timeout (when errno is 0) are not output in the return value when executing select in the wait function. It is difficult to identify the cause of the error when debugging.

2. It might not be possible to get the data size of can_frame in one read/send.

So I created a pull request. https://github.com/autowarefoundation/ros2_socketcan/pull/31