DNS: A hard to crack nut!

Week 6 :-

Apparently, Linux kernel does not seem to have a DNS resolver! The fundtion gethostbyname() first checks /etc/hosts and if no entries are found, it makes a direct socket connection with the ip address given in resolv.conf and fetches the DNS resolved ip address!

I would do a in-kernel DNS implementation from scratch, but apparently, there are many issues with it. Its not so easy as it originally seemed! Read this response by a certain Josh Graessley in the MAC OS X community who understands Darwin probably. So did the Linux Kernel Hackers actually chose not to have DNS in-kernel for some real-world reasons?

More information we need, but a change of track in the project is apparent. We have decided to move on to the /net/tcp implementation and work with IPs for now.

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March 5, 2009 - Posted by Rahul Murmuria | Glendix, Linux kernel, Networking, TCP/IP

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About

This blog is a project log for the /net virtual filesystem being developed by Rahul Murmuria under the Glendix umbrella. The project will provide Linux users with a more flexsible, powerful and simple alternative to TCP/IP Sockets.

The Glendix project is about bringing the beauty of Plan 9 from Bell Labs to the world of Linux. Some of the work already done by the Glendix project include native Plan9 binary compatibility in Linux and a few new Plan9-like system calls that are missing in Linux. Read more on Glendix on the project website ( http://www.glendix.org ).

UPDATE (5th July, 2009) : slashnet report

Why we chose to do /net ?

When UNIX was originally designed, there were no computer networks. Yes, BSD Sockets were designed first on a UNIX, but that does not imply that UNIX is the best possible design for a networking enabled operating system. Today, all operating systems – including Mac OS X, GNU/Linux, Solaris and Windows – are direct derivatives of the original UNIX first designed over 40 years ago!

So folks at Bell Labs (read Rob Pike, Ken Thompson, Dave Presotto, Phil Winterbottom, Dennis Ritchie, Brian Kernighan, et. al.) designed a new network structure, that exposes the kernel TCP/IP stack in form of filesystems to the user space, instead of the traditional Socket library approach. Plan 9 has been designed from gound up, with networking in mind, and is inherently a distributed operating system. Here’s an extract from Wikipedia:

Plan 9 does not have system calls for the multitude of communication protocols or device driver interfaces. For example /net is the API for all TCP/IP, and it can be used even with scripts or shell tools, writing data to control files to write and read connections. Relevant sub-directories like /net/tcp and /net/udp are used to interface to respective protocols. You can implement a NAT by mounting a /net from a perimeter machine with a public IP, while connecting to it from an internal network of private IP addresses, using the Plan 9 protocol 9P in the internal network. Or you can implement a VPN by mounting a /net directory from a remote gateway, using secured 9P over the public Internet.

Follow the blog to know the current status of this project.

/net in Linux: project log

A Glendix project