Add support for multi dynamic servers (#5)

* Fix Build badge

* Can now pass multiple dynamic nameservers

* Simplify entry point script

* Finalize entry point script

* Update README

* Fix typo

* Add default dnsmasq config file

README.md

@@ -1,49 +1,61 @@
 # Dnsmasq
 
 [![GitHub Release](https://img.shields.io/github/release/tschaffter/dnsmasq.svg?include_prereleases&color=94398d&labelColor=555555&logoColor=ffffff&style=for-the-badge&logo=github)](https://github.com/tschaffter/dnsmasq/releases)
-[![GitHub CI](https://img.shields.io/github/workflow/status/tschaffter/dnsmasq/ci.svg?color=94398d&labelColor=555555&logoColor=ffffff&style=for-the-badge&logo=github)](https://github.com/tschaffter/dnsmasq/actions)
+[![GitHub CI](https://img.shields.io/github/workflow/status/tschaffter/dnsmasq/CI.svg?color=94398d&labelColor=555555&logoColor=ffffff&style=for-the-badge&logo=github)](https://github.com/tschaffter/dnsmasq/actions)
 [![GitHub License](https://img.shields.io/github/license/tschaffter/dnsmasq.svg?color=94398d&labelColor=555555&logoColor=ffffff&style=for-the-badge&logo=github)](https://github.com/tschaffter/dnsmasq/blob/develop/LICENSE)
 [![Docker Pulls](https://img.shields.io/docker/pulls/tschaffter/dnsmasq.svg?color=94398d&labelColor=555555&logoColor=ffffff&style=for-the-badge&label=pulls&logo=docker)](https://hub.docker.com/r/tschaffter/dnsmasq)
 
 Docker image for Dnsmasq
 
 ## Overview
 
-[Dnsmasq] (short for DNS masquerade) is a lightweight, easy to configure DNS
-forwarder, designed to provide DNS (and optionally DHCP and TFTP) services to a
-small-scale network. It can serve the names of local machines which are not in
-the global DNS.
+[Dnsmasq] is a lightweight, easy to configure DNS forwarder, designed to provide
+DNS (and optionally DHCP and TFTP) services to a small-scale network. It can
+also serve the names of local machines which are not in the global DNS.If you
+own an Asus router, there is a chance that [your Asus router is using Dnsmasq].
 
 ## Features
 
-- Brings the latest release of Dnsmasq to Rapsberry Pi OS and other Debian
-  derivatives.
-- Enables Dnsmasq to resolve the hostname of an upstream server running in a
-  Docker container.
+- Brings the latest release of Dnsmasq (2.84) to Rapsberry Pi OS and other
+  Debian derivatives.
+- Enables Dnsmasq to resolve the hostname of an upstream nameserver running in a
+  Docker container (e.g. Stubby).
 - Provides a Docker image that I can trust until an official image is available
   for Dnsmasq.
 
 ## Usage
 
-### Set upstream nameserver
+### Configuration
 
-There are two ways to specify the address of an upstream nameserver:
+There are three sources of configuration that you can use:
 
-- By specifying `server=` in one of Dnsmasq configuration files
-  - [dnsmasq.conf](dnsmasq.conf) or
-  - [dnsmasq.d/example.com.conf](dnsmasq.d/example.com.conf)
-- By specifying the environment variables `SERVER_HOST` and `SERVER_PORT` in
-  *docker-compose.yml*.
+- Main configuration: [dnsmasq.conf](dnsmasq.conf)
+- Domain-specific configuration(s): [dnsmasq.d/example.com.conf](dnsmasq.d/example.com.conf)
+- Command-line arguments
 
-Both ways can be used to specify a public nameserver like Google Public DNS
-(`8.8.8.8`):
+The file [dnsmasq.conf.example](dnsmasq.conf.example) is the default main
+configuration file provided with the latest release of Dnsmasq available in this
+GitHub repository. The file [dnsmasq.conf](dnsmasq.conf) highlights some options
+of Dnsmasq.
 
-- `server=8.8.8.8` or
-- `SERVER_HOST=8.8.8.8` and `SERVER_PORT=53`
+### Set upstream nameservers
 
-The second method can be used to specify the service name of a dockerized DNS
-server. For example, one could use [Stubby] as a local DNS Privacy stub resolver
-that can be used in addition to Dnsmasq to enable DNS-over-TLS.
+Static nameservers like Cloudflare DNS servers `1.1.1.1` and `1.0.0.1` or Google
+DNS servers `8.8.8.8` and `8.8.4.4` can be specified using any sources of
+configuration.
+
+One of the reason for building this Docker image is because Dnsmasq cannot
+resolve the address from a nameserver that is not an IP address. This is a
+problem when using a nameserver like [Stubby] in a Docker container whose
+address is commonly referenced by its Docker service name. Stubby is a local DNS
+Privacy stub resolver that can be used in addition to Dnsmasq to enable
+DNS-over-TLS.
+
+A solution to the problem mentioned above is implemented in the entrypoint
+script [docker-entrypoint.sh](docker-entrypoint.sh) where the address specified
+for a nameserver is resolved to an IP address using the command `ping`. Thus,
+this solution only applies to server addresses specified as command-line
+arguments.
 
 ### Deploying using Docker
 
@@ -98,7 +110,7 @@ See example specified in
 [dnsmasq.d/example.com.conf](dnsmasq.d/example.com.conf).
 
 ```console
-$ dig @localhost +noall +answer +stats host1.example.com
+$ dig @localhost +noall +answer +stats myhost.example.com
 myhost.example.com.      0       IN      A       192.168.1.10
 ;; Query time: 1 msec
 ;; SERVER: 127.0.0.1#53(127.0.0.1)
@@ -122,9 +134,10 @@ installed.
 <!-- Links -->
 
 [Dnsmasq]: https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=summary
+[your Asus router is using Dnsmasq]: https://unfinishedbitness.info/2015/05/26/asuswrt-finalized-setup/
 [Stubby]: https://github.com/getdnsapi/stubby
 [Dig]: https://en.wikipedia.org/wiki/Dig_(command)
 
 [Stubby server]: https://github.com/tschaffter/stubby
 [How to Do DNS Caching with dnsmasq]: https://netbeez.net/blog/linux-dns-caching-dnsmasq/
-[Apache License 2.0]: https://github.com/nlpsandbox/date-annotator-example/blob/main/LICENSE
+[Apache License 2.0]: https://github.com/nlpsandbox/date-annotator-example/blob/main/LICENSE