Introduction

[Chen Jingpiao]

On 12/25 10:26, Harsha Sharma wrote:
> On Mon, Dec 25, 2017 at 6:51 PM, JingPiao Chen <chenjingpiao at gmail.com> wrote:
> > On 12/25 06:12, Harsha Sharma wrote:
> >> Hello everyone,
> >
> > Hi.
> >
> >> I'm Harsha Sharma, a sophomore student at Indian Institute of
> >> Technology,  Roorkee, India.
> >> I have knowledge of C, git, shell programming, kernel programming, gdb
> >> and parsers and currently working as outreachy intern in Linux-kernel
> >> (project nftables - Network filtration tool).
> >> Strace is one of my favorite tools in linux and want to contribute to
> >> the community.
> >>  I have looked into the mail archives about getting started and
> >> submitted two small patches. I have tried to understand the test
> >> infrastructure and will like to add some tests or fix some of the
> >> existing tests.
> >> It'll be great if someone can suggest either some tests or any other
> >> small bug-fix that I can work upon.
> >> Thanks :)
> >
> > I think write netlink socket parser is suited for you. This is a GSoC 2016
> > and 2017 project. The part of netfilter has not implemented yet.
> > I working on it, but recent I am busy. If you are interested in it, please
> > tell me.
> >
> Yes, definitely. I'm interested.
> How should I start with the project ? (Any guidance will be
> appreciated, meanwhile I'll try to go through your code in strace.)
> Can you assign me a small task in the project ?
> Thanks for your time. :')

300d9f1f: Further decode some attributes.
37dfe8c7: Implement a small protocol.

You can read these commits to get some idea. I recommend you to decode libudev
netlink header (struct udev_monitor_netlink_header).

systemd/src/libudev/libudev-monitor.c: 76
struct udev_monitor_netlink_header {
        /* "libudev" prefix to distinguish libudev and kernel messages */
        char prefix[8];
        /*
         * magic to protect against daemon <-> library message format mismatch
         * used in the kernel from socket filter rules; needs to be stored in network order
         */
        unsigned int magic;
        /* total length of header structure known to the sender */
        unsigned int header_size;
        /* properties string buffer */
        unsigned int properties_off;
        unsigned int properties_len;
        /*
         * hashes of primary device properties strings, to let libudev subscribers
         * use in-kernel socket filters; values need to be stored in network order
         */
        unsigned int filter_subsystem_hash;
        unsigned int filter_devtype_hash;
        unsigned int filter_tag_bloom_hi;
        unsigned int filter_tag_bloom_lo;
};

Netlink overview and its strace parsers:
http://blog.saruta.eu/netlink_strace.html

> 
> > More information:
> >
> > strace GSoC 2017 netlink socket parsers:
> > https://ppiao.github.io/2017/08/22/strace-gsoc-2017-netlink-socket-parser.html
> >
> > My current work of netfilter parser:
> > (Need to fix.)
> > https://github.com/ppiao/strace
> >

--
Chen Jingpiao