Oh, just saw this:
Could I instead have told Sonarr qBit is at 172.18…:port(dockers network address)
TL:dr;
No, the host has no idea what happens inside a docker network.
The exception is if the containers are on the same host and joined to the SAME docker network (docker compose does this automatically)
It seems like your home network is on 192.168.something. Youve omitted any details to describe what subnet it is within an entire 182.168.0.0/16 block that is dedicated to local network addresses (rfc1918) but that doesnt matter. And docker uses a different dedicated block of 172.16.0.0/12.
Regardless!
Your host has an ip of 192.168.1.4. A client on 192.168.1.5 knows exactly how to communicate to 192.168.1.4 (provided they are in the same subnet… Which is likely on a standard home DHCP served network. Im glossing over this).
Googles DNS server is 8.8.8.8. Which is outside of your home networks subnet (192.168.1.0/24 in CIDR notation). So client 192.168.1.5 has no idea how to contact 8.8.8.8. So it sends the connection to its default gateway (likely 192.168.1.1) as it is an unknown route. Your router then sends it to the internet appropriately (doing NAT as described elsewhere).
What Im saying is that clients within the 192.168.1.0/24 network know how to talk to eachother. If they dont know how to talk to an IP, they send to the gateway.
Now, docker uses its own internal network: 172.16.0.0/12. To a client on 192.168.1.5/24, an ip inside 172.16.0.0/12 is as strange as 8.8.8.8/32. It has no idea where to send it, so it goes to the default gateway. Which isnt helpful if that network is actually INSIDE the host at 192.168.1.4/24.
What am i getting at? Docker runs its own NAT.
It takes the host’s ip address. When you expose a containers port, you are telling docker to bind a host port and forward it to the specific port of the specific container.
So outside of the host, the network has no idea what 172.16.0.0/12 means, but it does know what 192.168.1.4/24 means.
Inside the docker network, a container has no idea what 192.168.0.0/16 means, but does know 172.16.0.0/12 means. Equally, a docker container will send packets to its default gateway inside that 172.16.0.0/12… Which will then respond aporopriately to the 192.168.1.0/24 client.
Which means a dcoker containers host firewall is going to have no idea whats happening inside a docker network. All it knows is that docker wants to recieve information on port 443, and that the local network is 192.168.1.0/24.
… Ish, there are other configurations
towerful@programming.dev 4 months ago
Basically, what they are getting at is:
Have you allowed internet access TO arr?
A default config ISP router will take the public IP address and drop all incomming connections. It will then NAT internal IP addresses to the public IP addresses.
So when you go to Google, Google responds to the established connection coming from the routers public IP address. Your router then knows to forward that response to the local client that started the connection.
If Google just randomly decided to connect to your public IP address, your router is configured to drop that traffic.
If you set up port forwarding on your router, you are telling it “if you get a new connection on port 443, forward it to this local client”. This is exposing that client to the internet and allowing strangers to connect to it. If Google then tried to connect to your public ip:443, it would get the response from that local client.
If you set up a “dmz” client, the router will forward ALL unknown incoming connections to that client. There is no need to do this. The only exception is for research or as a hunnypot/tarpit.
All other traffic will be on the local network, and wont even touch the routers firewall. A connection from 192.168.0.12 to 192.168.0.200 will go through layer 2 (ie, switches) instead of layer 3 (ie, routing) of the network OSI layers.
So, if you trust your internal home network and you have not exposed anything to the internet (port forwarding on the router, or set up a DMZ client) then you dont really need internal firewalls: the chance of a malicious device being able to even connect to an arr service is vanishingly small - like, your arr service will be the least of your concerns.
When you expose arr to the internet (i wouldnt do it directly, use a VPN or similar as a secure hole through your home firewall).
If you feel you do need them, then go about it for learning purposes and take your time. Do things, break things, learn things, fix things.
TCB13@lemmy.world 4 months ago
I was starting to get annoyed by so much “*arrs” and dancing around the subject that I lost the motivation to type. Thank you for taking the time to type an answer similar to mine. :).
@Fedegenerate@lemmynsfw.com go read this.