Merge pull request #8 from grishy/subdomain

Add subdomain support

.github/workflows/commit.yml

@@ -15,20 +15,20 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-go@v4
         with:
-          go-version: "1.20"
+          go-version: "1.20.7"
           cache: false
 
       - name: golangci-lint
         uses: golangci/golangci-lint-action@v3
         with:
-          version: v1.53
+          version: v1.53.3
   build_test:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-go@v4
         with:
-          go-version: "1.20"
+          go-version: "1.20.7"
           cache: false
 
       - name: Verify dependencies

.github/workflows/release.yml

@@ -19,7 +19,7 @@ jobs:
 
       - uses: actions/setup-go@v4
         with:
-          go-version: "1.20.6"
+          go-version: "1.20.7"
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v2

Dockerfile

@@ -1,7 +1,7 @@
 # syntax=docker/dockerfile:1
 
 # STAGE 1: building the executable
-FROM docker.io/golang:1.20.6-alpine3.18 as builder
+FROM docker.io/golang:1.20.7-alpine3.18 as builder
 WORKDIR /build
 
 COPY go.mod go.sum ./
@@ -15,4 +15,8 @@ RUN go build -ldflags="-w -s" -o /go-avahi-cname
 # STAGE 2: build the container to run
 FROM scratch
 COPY --from=builder /go-avahi-cname /go-avahi-cname
+
+EXPOSE 5353/udp
+
 ENTRYPOINT ["/go-avahi-cname"]
+CMD [ "subdomain" ]

README.md

@@ -1,49 +1,100 @@
-<img src="./docs/logo_x3.png" width="350">
+<p align="center">
+  <img src="./docs/logo_x3.png" width="350">
+</p>
 
-![GitHub tag (with filter)](https://img.shields.io/github/v/tag/grishy/go-avahi-cname)
-[![Go Report Card](https://goreportcard.com/badge/github.com/grishy/go-avahi-cname)](https://goreportcard.com/report/github.com/grishy/go-avahi-cname)
-![Build Status](https://github.com/grishy/go-avahi-cname/actions/workflows/release.yml/badge.svg)
+<p align="center">
+  <img src="https://img.shields.io/github/v/tag/grishy/go-avahi-cname" alt="GitHub tag (with filter)">
+  <img src="https://goreportcard.com/badge/github.com/grishy/go-avahi-cname" alt="Go Report Card">
+  <img src="https://github.com/grishy/go-avahi-cname/actions/workflows/release.yml/badge.svg" alt="Build Status">
+</p>
 
-## What is go-avahi-cname?
+## TL;DR
+
+Forward all subdomains current to machine( `*.hostname.local` -> `hostname.local`)
+
+1. _Binary_ `./go-avahi-cname subdomain`
+2. _Docker_ `docker run -d --network host -v "/var/run/dbus/system_bus_socket:/var/run/dbus/system_bus_socket" ghcr.io/grishy/go-avahi-cname:v2.0.0`
+
+# What is go-avahi-cname?
 
 It is a simple and lightweight project that allows you to publish CNAME records pointing to the local host over multicast DNS using the **Avahi** daemon, which is widely available in most Linux distributions. This means that you can access your local host using different names from any device on the same network, as long as they support Apple’s Bonjour protocol, which is compatible with Avahi.
 
-### Goals
+## Goals
 
 Here are some of the benefits of using go-avahi-cname:
 
-- **✅ No dependencies**   
-   You only need the Avahi daemon running on your host, no other libraries or packages are required.
-- **✅ Small footprint**   
-   The binary size is less than 3MB, and it consumes minimal resources while running.
-- **✅ Support x86_64 and ARM**  
-- **✅ Release binaries and containers**   
+- **✅ No dependencies** - Requires only the Avahi daemon.
+- **✅ Small footprint**
+- **✅ Support x86_64 and ARM**
+- **✅ Install as binaries or containers**
+
+## Modes of Operation
+
+- **Subdomain reply** - _I think you want this._ Listen to the traffic and if someone asks `*.hostname.local` (example: `name1.hostname.local`), we "redirect" to `hostname.local`.
+- **Interval publishing** - Periodically broadcasts CNAME records for various `name1.hostname.local`, `git.any.local`...
+
+---
+
+# How does it work?
+
+The tool communicates with the Avahi daemon via DBus to publish CNAME records.
+
+## Subdomain CNAME reply
+
+![Architecture](./docs/arch_subdomain.excalidraw.svg)
+
+```plain
+> ./go-avahi-cname subdomain -h
+NAME:
+   go-avahi-cname subdomain - Listen for all queries and publish CNAMEs for subdomains
+
+USAGE:
+   go-avahi-cname subdomain [command options] [arguments...]
+
+OPTIONS:
+   --ttl value   TTL of CNAME record in seconds (default: 600) [$TTL]
+   --fqdn value  FQDN which will be used for CNAME. If empty, will be used current FQDN (default: hostname.local.) [$FQDN]
+   --help, -h    show help
+```
 
-### How does it work?
+In this variant, we listen to the traffic with avahi-daemon for all questions with names and if they match ours, we send a command to avahi to answer it (send CNAME). The standard can be run without parameters, then we will resolve all requests that contain our hostname. For example, `git.lab.local` will be redirected to `lab.local`
 
-The following diagram shows the basic architecture of go-avahi-cname:
+## Interval publishing of CNAME records
 
-![Architecture](./docs/arch.excalidraw.svg)
+![Architecture](./docs/arch_cname.excalidraw.svg)
 
-As you can see, _go-avahi-cname_ communicates with the Avahi daemon via DBus, and publishes the CNAME records that you specify as arguments. The Avahi daemon then broadcasts these records over multicast DNS, so that other devices on the same network can resolve them.
+As you can see, _go-avahi-cname_ communicates with the Avahi daemon via DBus, and publishes the CNAME records that you specify as arguments.
 
-## How to use and install?
+```plain
+> ./go-avahi-cname cname -h
+NAME:
+   go-avahi-cname cname - Announce CNAME records for host via avahi-daemon
+
+USAGE:
+   go-avahi-cname cname [command options] [arguments...]
+
+OPTIONS:
+   --ttl value       TTL of CNAME record in seconds. How long they will be valid. (default: 600) [$TTL]
+   --interval value  Interval of publishing CNAME records in seconds. How often to send records to other machines. (default: 300) [$INTERVAL]
+   --fqdn value      Where to redirect. If empty, the Avahi FQDN (current machine) will be used (default: hostname.local.) [$FQDN]
+   --help, -h        show help
+```
 
 You can specify any number of CNAMEs as arguments when running go-avahi-cname, with no length limit.
 You can use either just the name (`name1`), which will create a record as a subdomain for the current machine, or you can write the full FQDN (`name1.hostname.local.` domain with a dot on the end) format.
 
 For example, if your machine’s hostname is lab, you can run:
 
 ```plain
-> ./go-avahi-cname git photo.local. example.lab.local.
-2023/07/27 08:37:14 Creating publisher
-2023/07/27 08:37:14 Formating CNAMEs:
-2023/07/27 08:37:14   > 'git.lab.local.' (added current FQDN)
-2023/07/27 08:37:14   > 'photo.local.'
-2023/07/27 08:37:14   > 'example.lab.local.'
-2023/07/27 08:37:14 Publishing every 5m0s and CNAME TTL=600s.
-^C
-2023/07/27 08:37:16 Closing publisher...
+> ./go-avahi-cname cname git photo.local. example.lab.local.
+2023/08/08 14:51:21 Creating publisher
+2023/08/08 14:51:21 Getting FQDN from Avahi
+2023/08/08 14:51:21 FQDN: lab.local.
+2023/08/08 14:51:21 Formatting CNAMEs:
+2023/08/08 14:51:21   > 'git.lab.local.' (added FQDN)
+2023/08/08 14:51:21   > 'photo.local.'
+2023/08/08 14:51:21   > 'example.lab.local.'
+2023/08/08 14:51:21 Publishing every 300s and CNAME TTL 600s
 ```
 
 This will create three CNAME records pointing to your local host:
@@ -54,31 +105,29 @@ This will create three CNAME records pointing to your local host:
 
 You can then access your local host using any of these names from other devices on the same network.
 
-### Installation options
+## Installation options
 
 There are two ways to install and run go-avahi-cname:
 
-#### Binary
+### Binary
 
 Binary files can be taken as artifacts for [the Release](https://github.com/grishy/go-avahi-cname/releases). In this case, it would be better to create a systemd service.
 
-#### Container
+### Container
 
 The images for each version are in [the Packages section](https://github.com/grishy/go-avahi-cname/pkgs/container/go-avahi-cname).  
 You need to provide the `/var/run/dbus/system_bus_socket` file to the container to be able to communicate with the host's Avahi daemon.
 
-One-liner to run the container `v0.3.1`:
+Docker Composer example:
 
-```bash
-> docker run --restart=unless-stopped -d -v /var/run/dbus/system_bus_socket:/var/run/dbus/system_bus_socket ghcr.io/grishy/go-avahi-cname:v0.3.1 name1 name2.lab.local.
-5a19790e06cca93016af6651d7af4046c24095a6909ace2fe26c3451fb98ceee
-
-> docker logs 5a19790e06cca93016af6651d7af4046c24095a6909ace2fe26c3451fb98ceee
-2023/07/27 08:49:02 Creating publisher
-2023/07/27 08:49:02 Formating CNAMEs:
-2023/07/27 08:49:02   > 'name1.lab.local.' (added current FQDN)
-2023/07/27 08:49:02   > 'name2.lab.local.'
-2023/07/27 08:49:02 Publishing every 5m0s ans CNAME TTL=600s.
+```yaml
+version: "3.3"
+services:
+  go-avahi-cname:
+    network_mode: host
+    volumes:
+      - "/var/run/dbus/system_bus_socket:/var/run/dbus/system_bus_socket"
+    image: "ghcr.io/grishy/go-avahi-cname:v2.0.0"
 ```
 
 Ansible task to run the container:
@@ -87,17 +136,21 @@ Ansible task to run the container:
 - name: go-avahi-cname | Start container
   community.docker.docker_container:
     name: "go-avahi-cname"
-    image: "ghcr.io/grishy/go-avahi-cname:v0.3.1"
+    image: "ghcr.io/grishy/go-avahi-cname:v2.0.0"
     restart_policy: unless-stopped
     volumes:
       - "/var/run/dbus/system_bus_socket:/var/run/dbus/system_bus_socket" # access to avahi-daemon
-    command: "name1 name2 git"
 ```
 
 ## Source of inspiration
 
-- https://web.archive.org/web/20151016190620/http://www.avahi.org/wiki/Examples/PythonPublishAlias
-- https://pypi.org/project/mdns-publisher/
+- [PythonPublishAlias](https://web.archive.org/web/20151016190620/http://www.avahi.org/wiki/Examples/PythonPublishAlias)
+- [mdns-publisher](https://pypi.org/project/mdns-publisher/)
+- [nfam/mdns-subdomain](https://github.com/nfam/mdns-subdomain)
+
+## Logo
+
+Generated by mix of Go Gopher and Avahi logo.
 
 ## License
 

publisher/publisher.go → avahi/publisher.go

@@ -1,4 +1,4 @@
-package publisher
+package avahi
 
 import (
 	"fmt"
@@ -22,20 +22,21 @@ type Publisher struct {
 	rdataField  []byte
 }
 
+// NewPublisher creates a new service for Publisher.
 func NewPublisher() (*Publisher, error) {
 	conn, err := dbus.SystemBus()
 	if err != nil {
-		return nil, fmt.Errorf("can't connect to system bus: %v", err)
+		return nil, fmt.Errorf("failed to connect to system bus: %v", err)
 	}
 
 	server, err := avahi.ServerNew(conn)
 	if err != nil {
-		return nil, fmt.Errorf("can't create Avahi server: %v", err)
+		return nil, fmt.Errorf("failed to create Avahi server: %v", err)
 	}
 
 	avahiFqdn, err := server.GetHostNameFqdn()
 	if err != nil {
-		return nil, fmt.Errorf("can't get FQDN from Avahi: %v", err)
+		return nil, fmt.Errorf("failed to get FQDN from Avahi: %v", err)
 	}
 
 	fqdn := dns.Fqdn(avahiFqdn)
@@ -45,7 +46,7 @@ func NewPublisher() (*Publisher, error) {
 	rdataField := make([]byte, len(fqdn)+1)
 	_, err = dns.PackDomainName(fqdn, rdataField, 0, nil, false)
 	if err != nil {
-		return nil, fmt.Errorf("can't pack FQDN into RDATA: %v", err)
+		return nil, fmt.Errorf("failed to pack FQDN into RDATA: %v", err)
 	}
 
 	return &Publisher{
@@ -56,14 +57,16 @@ func NewPublisher() (*Publisher, error) {
 	}, nil
 }
 
+// Fqdn returns the fully qualified domain name from Avahi.
 func (p *Publisher) Fqdn() string {
 	return p.fqdn
 }
 
+// PublishCNAMES send via Avahi-daemon CNAME records with the provided TTL.
 func (p *Publisher) PublishCNAMES(cnames []string, ttl uint32) error {
 	group, err := p.avahiServer.EntryGroupNew()
 	if err != nil {
-		return fmt.Errorf("can't create entry group: %v", err)
+		return fmt.Errorf("failed to create entry group: %v", err)
 	}
 
 	for _, cname := range cnames {
@@ -78,18 +81,18 @@ func (p *Publisher) PublishCNAMES(cnames []string, ttl uint32) error {
 			p.rdataField,
 		)
 		if err != nil {
-			return fmt.Errorf("can't add record to entry group: %v", err)
+			return fmt.Errorf("failed to add record to entry group: %v", err)
 		}
 	}
 
 	if err := group.Commit(); err != nil {
-		return fmt.Errorf("can't commit entry group: %v", err)
+		return fmt.Errorf("failed to commit entry group: %v", err)
 	}
 
 	return nil
 }
 
-func (p *Publisher) Close() error {
-	p.avahiServer.Close()
-	return p.dbusConn.Close()
+// Close associated resources.
+func (p *Publisher) Close() {
+	p.avahiServer.Close() // It also close the DBus connection
 }