Re: pcap shared libraries: inconsistencies across Linux machines

[Guy Harris <guy () alum mit edu>]

On Jun 13, 2007, at 9:32 AM, Jonathan Gruenhut wrote:

> To be honest, at this point I’m totally mystified.  My (naive)  
> understanding of shared objects in Linux was that as long as the  
> major version number was the same, the loader should look up  
> whatever is present on the system.

That's how a *sane* shared library mechanism would work, and, as far  
as I know, it's how the SVR4/ELF shared library mechanism was intended  
to work.  That's the shared library mechanism after which the shared  
library mechanisms in Linux and the ELF-based BSDs are modeled, as far  
as I know.

So, if you link with "-lpcap", the executable should be bound to  
libpcap.so.0, *NOT* libpcap.so.0.8.3 or libpcap.so.0.9.4 or whatever.

You *did* link with "-lpcap", not "-lpcap.0.8.3" or something such as  
that, right?

> ldd output:
>
> [jonathan@computer94 ~]$ ldd program83
>        linux-gate.so.1 =>  (0x00422000)
>        libnsl.so.1 => /lib/libnsl.so.1 (0x001f6000)
>        libpcap.so.0.8.3 => /usr/lib/libpcap.so.0.8.3 (0x00195000)
>        libc.so.6 => /lib/libc.so.6 (0x00b47000)
>        /lib/ld-linux.so.2 (0x00178000)

It sounds as if program83 is bound to the right versions of libnsl and  
libc - i.e., it appears to be bound to versions with *ONLY* the major  
version number, *NOT* versions with the full version number.

Are the versions of libpcap on the system the ones that came with the  
system, or did you build and install your own shared libpcap library  
in /usr/lib?

> The so files:
>
> [jonathan@computer94 ~]$ ls -l /usr/lib/*pcap*
> lrwxrwxrwx 1 root root     12 Jun 13 20:27 /usr/lib/libpcap.so ->  
> libpcap.so.0
> lrwxrwxrwx 1 root root     14 Jun 13 21:22 /usr/lib/libpcap.so.0 ->  
> libpcap.so.0.9
> lrwxrwxrwx 1 root root     16 May  3 19:03 /usr/lib/libpcap.so.0.9 - 
> > libpcap.so.0.9.4
> -rwxr-xr-x 1 root root 168544 Jul 13  2006 /usr/lib/libpcap.so.0.9.4

What do "ls -l /usr/lib/libc*" and "/usr/lib/libnsl*" print?

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