On Sun, Jul 06, 2008 at 03:09:09PM -0700, Steve Langasek wrote: > Hi folks, > > I've run across an ipv4/ipv6 configuration issue which I think needs to have > light cast on it so we can try to resolve this in time for lenny (whatever > the right resolution actually is), in order to avoid a pile-up of > /etc/hosts-related kludges as has been known to happen before... > > In response to bug #427067, the netbase maintainer made a change that adds > localhost as an alias for ::1 on new installs. In April of this year, the > Debian Installer team followed suit, adding this line in the netcfg udeb. > > The result of these changes is that since July 2007, any new lenny or sid > chroots have had two addresses listed for localhost, and since April of this > year, any new installs of lenny done using d-i have had it as well. > > Now, the problem I ran into is that when I enabled the test suite in the > openldap2.3 package, the build failed mysteriously on a seemingly random set > of architectures. The reason? The test suite configures slapd to run on a > particular port on localhost, and the glibc "files" NSS backend > special-cases the ::1 IPv6 loopback address, so that when you request an > IPv4 address, it will map any ::1 entries to 127.0.0.1 for you. But of > course we already have an entry for localhost as 127.0.0.1, so now we end up > with duplicate addresses returned, and slapd tries to bind twice to the same > address and port!
You don't seem to request ipv4 addresses, you request AF_UNSPEC, which should get you both ipv4 and ipv6. You get 127.0.0.1 twice, and ::1 one time. > A test program showing this behavior is attached - compile and run it on a > system with '::1 localhost' set in /etc/hosts, and you'll see 127.0.0.1 > returned twice. An alternate test case, which also works on systems with > older /etc/hosts and which I think shows the counterintuitiveness of the > nss_files special-casing, is to run "getent ahostsv4 ip6-localhost". > > I don't think it's the responsibility of callers such as slapd to check that > getaddrinfo() hasn't returned duplicate entries, so I see a couple of > solutions here: > > - the ::1 address should *not* be special-cased by nss_files. I really > can't perceive any reason why it should be special-cased in the first > place; i.e., why should the files backend behave differently than the DNS > backend, and why would we want names that were specifically assigned to > ::1, including names like "ip6-loopback", to be automatically mapped to > 127.0.0.1? I can't find any good reason why it should be changing ::1 to 127.0.0.1. So I think that atleast glibc should stop doing that. In any case, it shouldn't return 127.0.0.1 twice when it's not configured to return it twice. > - we should only set up a single 'localhost' entry in /etc/hosts, pointing > at ::1, and let nss_files handle the mapping to 127.0.0.1 automatically. - You could also argue that openldap should get fixed to deal with cases where it tries to bind to the same ip/port twice. On the other hand, I don't think it a normal case, and I think it's unlikely that people would set up dns to have 2 times the same IP address and then try to bind to that hostname. Kurt -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
