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I can definitely maybe do this! (thelemmy.club)
submitted 5 days ago by to c/programmer_humor@programming.dev
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[–] [S] 5 points 5 days ago* (1 child)

I digress. The documentation on iptables alone is an arduous read at best and requires dedication to get through and to understand. With that said, while you "cannot" (loosely said) follow any one singular packet from an iptables listing, using tcpdump will at least let you know wherefrom it connections originate and where they are terminating. Again, it is a hard read, not very beginner friendly, but I think it is also enough for the majority of threat models.

Question: does the person that feels that reading and understand iptables listings and tcpdumps really need to know - through an easy to read/understand UI - what chains and tables any one specific packet has traversed? What scenario/threat model/situation would that be? I'm all for discussing and widening my point of view, so don't hold back! 😊

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  • [–] 2 points 5 days ago

    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.

    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.

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