Linux - ioctl with FIONREAD always 0

Question

I\'m trying to get to know how many bytes there are readable at my TCP socket. I am calling ioctl with the Flag \"FIONREAD\" which should actually give me this value. When I ca

Answer 1

For those who are using a docker I had the same issue when I tried to send packets from outside (Ubuntu 16.04 in this case) into the docker's interface (docker0 in this case) using tcpreplay.

The workaround was to run tcpreplay inside the docker.

I do not know if ioctl() is supported in docker or not, so it is not a solution.