Regarding your question, I’ve had trouble multiple times with docker (and other software) that required trying to find out just where a packet was getting stuck. The worst thing is when you open a port in the container to 0.0.0.0, send a request to it (HTTP, telnet, or otherwise) from the host via the container’s IP and the packet doesn’t arrive. Then you have to run through the gamut of:
are the interfaces up?
is it the IP address that’s wrong?
is the the port wrong?
is the network mask correct?
is the gateway IP correct?
is the firewall somehow interfering?
There might be other things I’m missing, but once I get to the firewall stage, most of the time I just give up, put the service into a VM and try accessing it from there - if I really really care. Otherwise, I drop it and move on.
But still, that’s just on my machine. Once things happen on the network and there are routers and other things involved, it’s very difficult for me to debug.
Regarding your question, I’ve had trouble multiple times with docker (and other software) that required trying to find out just where a packet was getting stuck. The worst thing is when you open a port in the container to
0.0.0.0, send a request to it (HTTP, telnet, or otherwise) from the host via the container’s IP and the packet doesn’t arrive. Then you have to run through the gamut of:There might be other things I’m missing, but once I get to the firewall stage, most of the time I just give up, put the service into a VM and try accessing it from there - if I really really care. Otherwise, I drop it and move on.
I did just find this Network address translation part 1 – packet tracing which allows tracing a packet through the firewall via
xtables-monitor. It’s in my notes now, so if I run into the problem again, I might have a place to start next time.But still, that’s just on my machine. Once things happen on the network and there are routers and other things involved, it’s very difficult for me to debug.