FYI: A Bug In Libc.so.4.6.27 Causing Problem in SLIP Setup

FYI: A Bug In Libc.so.4.6.27 Causing Problem in SLIP Setup

Post by Michael Buchenried » Sat, 20 May 1995 04:00:00




>    After tracing down the problem,  I finally found the libc.so.4.6.27 is
>the culprit.  When gethostbyname() is called, it calls the following
>subroutines
>gethostbyname() --> res_search() --> res_querydomain() --> res_query() -->
>res_mkquery() and res_send().  The res_send() is always return failed when
>called.  The problem can be temparily solved by doing the following:
>    (1) copying libc.so.4.5.26 into /lib directory,
>    (2) moving libc.so.4.6.27 out of /lib, and
>    (3) ln -s /lib/libc.so.4.6.27 /lib/libc.so.4

                            ^^^^^^

This must be 4.5.26 - otherwise you'll be stuck with a non-working
system ! I suppose this was just a typo ?

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1. FYI: A Bug in libc.so.4.6.27 Causing Problem in SLIP Setup

Hi,

I think I found a bug in libc.so.4.6.27, which causes problems whenever the
gethostbyname() is called.  This bug will show up and give a message "Unknown
server error" when I try to use ftp, telnet, or any client programs to connect
to any host other than those specified in my /etc/hosts.  No nameserver can be
used even though /etc/resolv.conf is set up correctly.  

    Here is how I found it, and how the problem can be duplicated and solved.

    I set up SLIP connection early in January when I got a trial licence for
TIA for 14 days.  Everything was working correctly at that time. After my trial
licence expired, I switched to term and have been using term since then.  Since
then I upgraded my kernel, libc, gcc, dip, etc. to the latest version.  Just
recently, I purchased the TIA licence and tried to set up my SLIP connection
again.  But my early SLIP setup no longer worked.  I could only ftp/telnet to
the hosts specified in my /etc/hosts file, if I use hostname as command line
argument.  I could ftp/telnet to any other hosts only if I use IP address as
the command line argument.  However, nslookup did works fine with no problem
in name-to-address translation.

    After tracing down the problem,  I finally found the libc.so.4.6.27 is
the culprit.  When gethostbyname() is called, it calls the following
subroutines gethostbyname() --> res_search() --> res_querydomain() -->
res_query() --> res_mkquery() and res_send().  The res_send() is always
return failed when called.  The problem can be temparily solved by doing
the following:
    (1) copying libc.so.4.5.26 into /lib directory,
    (2) ln -s /lib/libc.so.4.5.26 /lib/libc.so.4
    (3) moving libc.so.4.6.27 out of /lib
The step (3) is necessary.  Otherwise, ftp/telnet will still link to the
libc.so.4.6.27.  You can know this by using "ldd /bin/ftp". The step (2) and
(3) should be changed in sequence.  Otherwise, no command can be
executed without libc.so.4.

    The libc.so.4.5.26 can be found at:
          ftp://tsx-11.mit.edu/pub/linux/distributions/SLS/a4/shlibs.tgz.

    I have not pinned down the exact codes which cause the problem.  I will do
so if I can find the source code for libc.so.4.5.26.  If anybody has the info
please let me know.  

Li

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