Does anyone have idea of how to trace the funtion "gethostbyname"?

Does anyone have idea of how to trace the funtion "gethostbyname"?

[Dongtao Liu]

Hi all:

I recently doing some work to record all DNS lookups in the system.
Could anyone tell me how to trace the function of gethostbyname using
SystemTap?

Thank you very much!

Dongtao

Re: Does anyone have idea of how to trace the funtion "gethostbyname"?

[Breno Leitao]

Dongtao Liu wrote:
> I recently doing some work to record all DNS lookups in the system.
> Could anyone tell me how to trace the function of gethostbyname using
> SystemTap?
Since this is not a kernel function, you might want to probe userspace 
functions. 

Re: Does anyone have idea of how to trace the funtion "gethostbyname"?

[Frank Ch. Eigler]

Breno Leitao <leitao@linux.vnet.ibm.com> writes:

>> Could anyone tell me how to trace the function of gethostbyname using
>> SystemTap?
> Since this is not a kernel function, you might want to probe userspace 
> functions. 

This should work, before long:

  probe process("/libMMM/libc-NNN.so").function("gethostbyname").call { log(user_string($name)) }

In some testing on RHEL5 however, our prologue-searching heuristics
can't outwit gcc's poor debuginfo quality, so that parameter is hidden
at the moment.  There's a systemtap PR about improving the heuristics.

- FChE

Re: Does anyone have idea of how to trace the funtion "gethostbyname"?

[Dongtao Liu]

Is it "/lib/libc-2.7.so" in my system?
probe process("/lib/libc-2.7.so").function("gethostbyname").call {
log(user_string($name)) }

Then how long will SystemTap support to trace this function? Thans a lot!

This is the information about libc in my system.

dliu@dliu-desktop:/lib$ ls -all libc.so.6
lrwxrwxrwx 1 root root 11 2008-10-23 22:02 libc.so.6 -> libc-2.7.so
dliu@dliu-desktop:/lib$ ls -all libc-2.7.so
-rwxr-xr-x 1 root root 1274092 2008-09-12 10:32 libc-2.7.so

dliu@dliu-desktop:/lib$ ls -all libc*.so*
-rwxr-xr-x 1 root root 1274092 2008-09-12 10:32 libc-2.7.so
lrwxrwxrwx 1 root root      11 2008-10-23 22:02 libcap.so -> libcap.so.1
lrwxrwxrwx 1 root root      14 2008-10-23 17:30 libcap.so.1 -> libcap.so.1.10
-rw-r--r-- 1 root root   10316 2007-07-31 15:20 libcap.so.1.10
lrwxrwxrwx 1 root root      17 2008-10-23 17:30 libcfont.so.0 ->
libcfont.so.0.0.0
-rw-r--r-- 1 root root   11512 2008-02-06 17:49 libcfont.so.0.0.0
-rw-r--r-- 1 root root  181724 2008-09-12 10:32 libcidn-2.7.so
lrwxrwxrwx 1 root root      14 2008-10-23 22:02 libcidn.so.1 -> libcidn-2.7.so
lrwxrwxrwx 1 root root      17 2008-10-23 17:30 libcom_err.so.2 ->
libcom_err.so.2.1
-rw-r--r-- 1 root root    7444 2008-03-27 13:25 libcom_err.so.2.1
lrwxrwxrwx 1 root root      19 2008-10-23 17:30 libconsole.so.0 ->
libconsole.so.0.0.0
-rw-r--r-- 1 root root   73312 2008-02-06 17:49 libconsole.so.0.0.0
-rw-r--r-- 1 root root   38300 2008-09-12 10:32 libcrypt-2.7.so
lrwxrwxrwx 1 root root      15 2008-10-23 22:02 libcrypt.so.1 -> libcrypt-2.7.so
lrwxrwxrwx 1 root root      11 2008-10-23 22:02 libc.so.6 -> libc-2.7.so
lrwxrwxrwx 1 root root      19 2008-10-23 17:30 libctutils.so.0 ->
libctutils.so.0.0.0
-rw-r--r-- 1 root root   17424 2008-02-06 17:49 libctutils.so.0.0.0

2008/10/31 Frank Ch. Eigler <fche@redhat.com>:
> Breno Leitao <leitao@linux.vnet.ibm.com> writes:
>
>>> Could anyone tell me how to trace the function of gethostbyname using
>>> SystemTap?
>> Since this is not a kernel function, you might want to probe userspace
>> functions.
>
> This should work, before long:
>
>  probe process("/libMMM/libc-NNN.so").function("gethostbyname").call { log(user_string($name)) }
>
> In some testing on RHEL5 however, our prologue-searching heuristics
> can't outwit gcc's poor debuginfo quality, so that parameter is hidden
> at the moment.  There's a systemtap PR about improving the heuristics.
>
> - FChE
>

Re: Does anyone have idea of how to trace the funtion "gethostbyname"?

[Dongtao Liu]

yes, it is the function in libc. I downloaded the source code of
glibc-2.7.3 and found gethostbyname() function in
/resolv/gethnamaddr.c

dliu@dliu-desktop:/usr/src/glibc/glibc-2.7/resolv$ ls
arpa          gai_misc.c      getaddrinfo_a.c  inet_net_pton.c
netdb.h      ns_samedomain.c  res_debug.c  res_mkquery.c  tst-aton.c
Banner        gai_misc.h      gethnamaddr.c    inet_ntop.c
nsap_addr.c  nss_dns          res_debug.h  resolv.h
tst-inet_ntop.c
base64.c      gai_notify.c    herror.c         inet_pton.c
ns_name.c    ns_ttl.c         res_hconf.c  res_query.c    tst-leaks2.c
Depend        gai_sigqueue.c  inet_addr.c      Makefile
ns_netint.c  README           res_hconf.h  res_send.c     tst-leaks.c
gai_cancel.c  gai_suspend.c   inet_neta.c      mapv4v6addr.h
ns_parse.c   res_comp.c       res_init.c   res-state.c    Versions
gai_error.c   ga_test.c       inet_net_ntop.c  mapv4v6hostent.h
ns_print.c   res_data.c       res_libc.c   sys


2008/10/31 Breno Leitao <leitao@linux.vnet.ibm.com>:
> Dongtao Liu wrote:
>> I recently doing some work to record all DNS lookups in the system.
>> Could anyone tell me how to trace the function of gethostbyname using
>> SystemTap?
> Since this is not a kernel function, you might want to probe userspace
> functions.
>