Date: Sun, 07 Jun 1998 11:52:38 -0700 From: John Polstra <jdp@polstra.com> To: Brian Somers <brian@Awfulhak.org> Cc: toj@gorillanet.gorilla.net, current@FreeBSD.ORG Subject: Re: IP Packet Aliasing Broke? Message-ID: <199806071852.LAA17184@austin.polstra.com> In-Reply-To: Your message of "Sun, 07 Jun 1998 11:46:30 BST." <199806071046.LAA00965@awfulhak.org>
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> Now all we need is
>
> char *dlfind(const char *, int *major, int *minor)
...
> Has anyone any objections to me implementing dlfind() ?
Yes -- I object for several reasons. I'll save the biggest one
for last.
First, the dlfind() interface is too specific to the object format,
for starters. ELF shared libraries have only major version numbers;
they don't have minor versions.
Second, when loading shared libraries programmatically using dlopen(),
the established convention is that the shared library should simply be
named "foo.so" without any version number. The installation process
should make sure that the library (or a symlink to it) is installed in
a location known to the application ("/usr/libdata/ppp/libalias.so"?).
But really, why does ppp use dlopen to load libalias at all? Why not
simply link it in like other libraries? I've heard the bloat-based
arguments, but they look pretty bogus to me. Consider this:
===============================================================================
$ ldd /usr/sbin/ppp
/usr/sbin/ppp:
-lutil.2 => /usr/lib/aout/libutil.so.2.2 (0x20043000)
-lz.2 => /usr/lib/aout/libz.so.2.0 (0x20049000)
-lcrypt.2 => /usr/lib/aout/libcrypt.so.2.0 (0x20055000)
-ldes.3 => /usr/lib/aout/libdes.so.3.0 (0x2006a000)
-lc.3 => /usr/lib/aout/libc.so.3.1 (0x20073000)
$ size /usr/sbin/ppp /usr/lib/aout/libutil.so.2.2 /usr/lib/aout/libz.so.2.0 \
> /usr/lib/aout/libcrypt.so.2.0 /usr/lib/aout/libdes.so.3.0 \
> /usr/lib/aout/libc.so.3.1
text data bss dec hex
184320 4096 81228 269644 41d4c /usr/sbin/ppp
20480 4096 0 24576 6000 /usr/lib/aout/libutil.so.2.2
40960 4096 256 45312 b100 /usr/lib/aout/libz.so.2.0
12288 4096 68152 84536 14a38 /usr/lib/aout/libcrypt.so.2.0
32768 4096 0 36864 9000 /usr/lib/aout/libdes.so.3.0
425984 16384 53488 495856 790f0 /usr/lib/aout/libc.so.3.1
$ size /usr/lib/aout/libalias.so.2.5
text data bss dec hex
24576 4096 13140 41812 a354
===============================================================================
There's 934K of stuff loaded by ppp no matter what. (Or 518K if you
don't count the text segment of libc, which to be fair would be in
memory whether ppp needed it or not.) Why bother trying to save 41K
for the cases where aliasing isn't needed? It just doesn't seem worth
the bother to me.
One other thing to keep in mind is that this whole /usr/lib/aout
situation is only temporary. As soon as the ELF transition is
finished, the libraries will be back in /usr/lib again.
John
--
John Polstra jdp@polstra.com
John D. Polstra & Co., Inc. Seattle, Washington USA
"Self-knowledge is always bad news." -- John Barth
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