ws: handle reads before EAGAIN better

[bagder]

Reported-by: simplerobot on github
Fixes #10831

[simplerobot]

I've found one more issue with this. The packet fragment may not be at the beginning of the buffer. We need to move it there before reading the rest of it. I updated the retry logic (https://github.com/curl/curl/blob/master/lib/ws.c#L451) to:

  if(result == CURLE_AGAIN) {
    /* a packet fragment only, loop and try reading more */
    memmove(data->state.buffer, wsp->stillb, wsp->stillblen);
    continue;
  }

I'd be happy to open a new defect if you want to track this separately.

Thanks,
John

[bagder]

I'd be happy to open a new defect if you want to track this separately.

Please do!

[simplerobot]

Done: #10962