83 lines
3.4 KiB
Markdown
83 lines
3.4 KiB
Markdown
# avahi2dns [](https://github.com/LouisBrunner/avahi2dns/actions/workflows/build.yml)
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Small DNS server which interface with avahi (perfect for Alpine Linux and musl)
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## Building
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Requires go 1.16 or later
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```
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go build
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```
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## Usage
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```shell
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$ ./avahi2dns -h
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Usage: avahi2dns [--domains DOMAINS] [--addr ADDR] [--port PORT] [--debug]
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Options:
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--domains DOMAINS, -d DOMAINS
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comma-separated list of domains to resolve
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--addr ADDR, -a ADDR address to bind on [default: localhost]
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--port PORT, -p PORT port to bind on [default: 53]
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--debug, -v also include debug information [default: false]
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--help, -h display this help and exit
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```
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### Examples
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By default the server will bind to port 53 on localhost (not accessible outside the computer) and resolve any domain with the following extensions: `home`, `internal`, `intranet`, `lan`, `local`, `private`, `test`
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```shell
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$ sudo ./avahi2dns
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INFO[0000] starting DNS server addr="localhost:53"
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...
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```
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Settings can be changed through command-line arguments or environment variables:
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```shell
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$ ./avahi2dns -p 5454 -a '0.0.0.0' -d 'local,home'
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or
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$ BIND='0.0.0.0' PORT=5454 ./avahi2dns -d 'local,home'
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```
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You can also use the debug flag if you need more information about what the server is doing (probably overkill):
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```shell
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$ ./avahi2dns -v -p 5454
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DEBU[0000]avahi2dns/server.go:14 main.runServer() connection to dbus...
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DEBU[0000]avahi2dns/server.go:21 main.runServer() connection to avahi through dbus...
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DEBU[0000]avahi2dns/server.go:37 main.runServer() adding dns handler domain=home
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...
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```
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## Using with Alpine and Docker on Linux
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Linux DNS-resolution is done by the standard library (through functions like `getaddrinfo` or `gethostbyname`), unfortunately `musl` used by Alpine Linux doesn't support mdns out-of-the-box.
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However you can easily add this lookup through `avahi2dns`:
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```shell
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$ sudo ./avahi2dns &
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INFO[0000] starting DNS server addr="localhost:53"
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$ docker run --rm --entrypoint ash --net=host alpine -c 'apk add iputils && echo "nameserver 127.0.0.1" >> /etc/resolv.conf && ping your-name-host.local'
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fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/main/armv7/APKINDEX.tar.gz
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fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/community/armv7/APKINDEX.tar.gz
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(1/2) Installing libcap (2.50-r0)
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(2/2) Installing iputils (20210202-r0)
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Executing busybox-1.33.1-r3.trigger
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OK: 4 MiB in 16 packages
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INFO[0006] forwarding query to avahi component=main name=your-name-host.local. protocol=0 type=A
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INFO[0006] forwarding query to avahi component=main name=your-name-host.local. protocol=1 type=AAAA
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PING your-name-host.local (172.16.16.2) 56(84) bytes of data.
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64 bytes from 172.16.16.2 (172.16.16.2): icmp_seq=1 ttl=64 time=0.456 ms
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64 bytes from 172.16.16.2 (172.16.16.2): icmp_seq=2 ttl=64 time=0.426 ms
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64 bytes from 172.16.16.2 (172.16.16.2): icmp_seq=3 ttl=64 time=0.429 ms
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64 bytes from 172.16.16.2 (172.16.16.2): icmp_seq=4 ttl=64 time=0.418 ms
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```
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Note: this requires your Docker container to use `--net=host` instead of the default `--net=bridge`, but that it might be possible without using the latest Docker distributions
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Note: `avahi2dns` is run as a background job for the sake of demonstration, you should really run it through `systemd` or similar
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