Prevent Zypper trying to use IPv6

Question

I'm setting up a box with OpenSUSE 13.1. For reasons beyond my comprehension, Zypper utterly insists on using IPv6 addresses and refuses to use IPv4. Which is a problem, since IPv6 doesn't work on our LAN.

I've tried disabling IPv6 multiple ways:

• I told YaST to disable IPv6.
• I tried poking and prodding /etc/modprobe.
• I tried setting ipv6.disable=1 as a kernel boot parameter.

None of these things had the slightest effect; Zypper still refuses to use real IP addresses and keeps hopelessly trying to use IPv6.

Note that I can ping the download server just fine; the ping command looks up the IPv4 address of the server, and has no problem pinging it. And yet, Zypper still insists on using IPv6, and then giving up because the destination is unreachable. (Which is it - via IPv6.)

I am having the exact problem described in this question. (Even the failing IPv6 address is identical.) That question addresses an older release of OpenSUSE, and the accepted answer just says to disable IPv6, which I already tried.

I have now wasted multiple hours of my life trying to perform the trivial task of installing a few software packages. Does anybody know how I can completely destroy IPv6 and get networking to work again?

Answer 1

It seems like you've done the right things to zap IPv6 from a kernel perspective, but I might also -- assuming you don't care about IPv6 -- delete any IPv6 entries in /etc/hosts. If that still doesn't do the trick (and this is reaching back), I had a problem with Amanda backup once that was very similar to your issue, and was only able to fix it by installing xinetd instead of inetutils-inetd (note that I have no idea what S.u.S.E. installs by default). Lastly (and as a desperation measure) I might suggest using "strace" with something like: strace -s 1024 -f -o /tmp/zypper.log /path/to/zypperexecutable and then go through the log file looking for that IPv6 address, and seeing if there's anything informative that might be helpful. (FYI, "strace" can generate a HUGE file, so you probably want to abort zypper as soon as it fails.)

Answer 2

Following the suggestion by user995746, I tried running strace. Here is what it has to say:

...
1179  socket(PF_INET6, SOCK_DGRAM, IPPROTO_IP) = 5
1179  connect(5, {sa_family=AF_INET6, sin6_port=htons(80), inet_pton(AF_INET6, "2001:67c:2178:8::13", &sin6_addr), sin6_flowinfo=0, sin6_scope_id=0}, 28) = -1 ENETUNREACH (Network is unreachable)
1179  close(5)                          = 0
1179  madvise(0x7ff48750c000, 8368128, MADV_DONTNEED) = 0
1179  _exit(0)                          = ?
1179  +++ exited with 0 +++
1177  <... poll resumed> )              = 0 (Timeout)
1177  socket(PF_INET, SOCK_STREAM|SOCK_CLOEXEC, IPPROTO_TCP) = 5
1177  fcntl(5, F_GETFL)                 = 0x2 (flags O_RDWR)
1177  fcntl(5, F_SETFL, O_RDWR|O_NONBLOCK) = 0
1177  connect(5, {sa_family=AF_INET, sin_port=htons(80), sin_addr=inet_addr("195.135.221.134")}, 16) = -1 EINPROGRESS (Operation now in progress)
1177  poll([{fd=5, events=POLLOUT|POLLWRNORM}], 1, 0) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT}], 1, 1000) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT|POLLWRNORM}], 1, 0) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT}], 1, 1000) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT|POLLWRNORM}], 1, 0) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT}], 1, 1000) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT|POLLWRNORM}], 1, 0) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT}], 1, 1000) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT|POLLWRNORM}], 1, 0) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT}], 1, 1000) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT|POLLWRNORM}], 1, 0) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT}], 1, 1000) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT|POLLWRNORM}], 1, 0) = 0 (Timeout)
1177  poll([{fd=5, events=POLLOUT}], 1, 1000) = ? ERESTART_RESTARTBLOCK (Interrupted by signal)
1177  --- SIGINT {si_signo=SIGINT, si_code=SI_KERNEL} ---
...

It appears, then, that even though the error message from Zypper quite clearly says "Failed to connect to 2001:67c:2178:8::13: Network is unreachable", the program is actually seeing that IPv6 is unreachable, and falling back to IPv4. The question remains why it can't connect via IPv4 - this is probably some sort of firewall issue with our LAN.

In summary, it appears that IPv6 isn't the problem at all, it's just that the error message from Zypper is highly misleading.

Answer 3

Resolving download.opensuse.org (or whatever d/l server you care to use) and then feeding its IPv4 address into the .repo file(s) did it for me. I used sed(1) to search+replace everything in there; worked like a charm.

Not perfect, certainly; and not being able to fall back on a working(!) v4 connection is... less than stellar. Never mind that any other dualstack-capable application is perfectly capable (and able) to access, say, download.opensuse.org when there's a local v6 network that doesn't get routed out (because Mr ISP doesn't play along, for example).

Until that time, just use (numerical) IPv4 addresses.

Note: zypper uses libcurl but doesn't honor $HOME/.curlrc. Maybe it'll honor global curl configuration files or environment variables. curl itself wants -4 / --ipv4 to force ipv4.

Also, if one were to recompile libcurl itself without ipv6 support and then have zypper point there via ld.so.conf or something, I'd imagine things should work as expected as well.