From: Jeremy Cooper <j@broder.com>
Subject: Possible bug with BSD/OS 2.1 and 3.5f
Newsgroups: comp.protocols.time.ntp
Date: Fri, 28 Jun 1996 12:27:37 -0700
Organization: Broderbund Software
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I have found what I believe is a possible bug and a patch for it
in the xntpd code.

Description:
------------
During startup, xntpd determines the addresses of all the interfaces
on the system.  In BSD/OS version 2.1 the daemon receives a protection
violation signal while attempting to do this on some systems.

In xntpd/ntp_io.c the new system call, 'getifaddrs', is used to
obtain information about all of the system network interfaces.
The description of this function states that some interfaces may
return a NULL pointer in the 'ifa_addr' member of the interface
structure if no definite address for that interface exists.
ntp_io.c does not check for this.

Symptom:
--------
xntpd core dumps on startup.

Fix:
----
Have the code check to make sure that the 'ifa_addr' member is not NULL
before attempting to determine its address family ('ifa_addr->sa_family').
If it is NULL, skip the interface and move to the next one.

In diff -c format the patch is:

*** ntp_io.c    Fri Jun 28 12:17:41 1996
--- ntp_io.c.new    Fri Jun 28 12:17:46 1996
***************
*** 314,319 ****
--- 314,321 ----
        for (ifap = ifaddrs, lp = ifap + num_if; ifap < lp; ifap++) {
                struct sockaddr_in *sin;
  
+               if (!ifap->ifa_addr)
+                       continue;
                if (ifap->ifa_addr->sa_family != AF_INET)
                        continue;