viewing source of namespace resolver functions linux fedora

Question

I want to see the source of functions like ns_initparse(), res_search() etc. Where can I look for them?

Answer 1

I am not sure if you are interested in Fedora specific stuff, but I have had good luck with Google Code Search for finding source code for certain functions.

Answer 2

Here's are the steps I take find the source for res_search.

$ man res_search

I see in that man page: Link with -lresolv

$ ls /usr/lib/libresolv*

Oops, nothing there. Where else do we look? How about:

$ ls /lib/libresolv*
/lib/libresolv-2.7.so  /lib/libresolv.so.2

Great. Now what package is that from?

$ rpm -qf /lib/libresolv-2.7.so
glibc-2.7-2

Ah. It's in glibc. Now, there are two choices. I can fetch the source RPMs, and look through those, in order to get the exact version that that my system was built from, but that's a bit complicated to set up.

If you don't need the exact source RPM that you were built from, you can instead look through the upstream source code. Just look around the glibc site to find the source code, and start looking through there.

$ curl -O http://ftp.gnu.org/gnu/glibc/glibc-2.7.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 20.2M  100 20.2M    0     0  12.3M      0  0:00:01  0:00:01 --:--:-- 12.8M
$ tar xzf glibc-2.7.tar.gz
$ cd glibc-2.7
$ find . -name "*.c" | xargs grep res_search
./resolv/res_data.c:res_search(const char *name, /* domain name */
./resolv/res_data.c:# undef res_search
./resolv/res_data.c:weak_alias (__res_search, res_search);

And there you have it!

If you have Git installed, instead of just downloading the tarball, you could clone the git repo, and look through that. That way, you can also look at any past or future version, to see how it's changed over time.

$ git clone git://sourceware.org/git/glibc.git
$ cd glibc
$ git checkout glibc-2.7
$ git grep res_search 
resolv/res_data.c:res_search(const char *name,  /* domain name */
resolv/res_data.c:# undef res_search
resolv/res_data.c:weak_alias (__res_search, res_search);

Answer 3

Once you figure out which package provides the functions you are interested in, all you need to do on Fedora is debuginfo-install glibc-2.7-2. More info here.