DNS Server, Multithreaded

Is a RFC 1035 compatible Domain Name System Server, that implements concurrent query processing and non-blocking cache read access, implemented using std::shared_mutex. File logger that uses lock-free queue to add log messages and a dedicated thread to write to file.

Usage

Binary has 3 positional arguments:

$ dns_server port "hosts_file_path" "forward_server_addr:fwd_srv_port"(optional)

where:

• port - port number for listening
• hosts_file_path - path for initial dns cache, if file does not exist. It will be created and cache will be saved to it on server shutdown. If file exists, entries will be cached and will not timeout, cache file won't be updated
• forward_server_addr:fwd_srv_port - optional external DNS server, to forward queries to, if cache entry is missing, default is Google DNS

Example usage:

$ dns_server 53 "hosts" "127.0.0.1:53"

Features

• Supports Normal Host Address Internet Queries and Responses
• Implements DNS caching. Cache data is updated on timeout(ttl)
• Ability to preload cache from file in format of system hosts example. These entries won't be updated on timeout
• Supports forwarding queries to Forward Server, hence related argument option
• Query processing thread pool with lock-free task queue
• File logging from a dedicated thread with lock-free queue

Dependencies

1. A C++ compiler that supports C++20 standard. The following compilers should work:

• gcc 8+

• clang 9+

2. CMake 3.5+

Build

Target platform is Linux, POSIX is used. You can build main target via CMake.

For example, from build directory call:

 $ cmake "path to the CMakeLists.txt" -DCMAKE_CXX_COMPILER:STRING=/usr/bin/clang++-11 -DCMAKE_BUILD_TYPE:String=Release
 $ make

dns_server target will be built.

Testing

Test server response via "dig" client from local machine. Example:

$ dig @127.0.0.1 www.example.com -p "your_server_port"

Expected output:

$ dig @127.0.0.1 www.example.com  -p 10000

; <<>> DiG 9.16.1-Ubuntu <<>> @127.0.0.1 www.example.com -p 10000
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42801
;; flags: qr rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;www.example.com.		IN	A

;; ANSWER SECTION:
www.example.com.	60	IN	A	93.184.216.34

;; Query time: 27 msec
;; SERVER: 127.0.0.1#10000(127.0.0.1)
;; WHEN: Tue Feb 21 16:04:59 MSK 2023
;; MSG SIZE  rcvd: 49

License

This project is licensed under the MIT License - see the LICENSE file for details.