Am 09.02.2013 20:58, schrieb Alan McKinnon: > On 09/02/2013 20:22, Florian Philipp wrote: >> Hi list! >> >> I have an issue with SSH. It's a variation of the old "Set 'UseDNS no' >> to avoid delays with faulty DNS records" theme. >> >> Following setup: >> 1. I have a server with IPv6 compiled into the SSH daemon but no actual >> IPv6 network interface. >> >> 2. The SSH client has no IPv6, neither compiled nor active. >> >> 3. The DNS server doesn't serve or support AAAA records. Apparently it >> drops all such requests. All other records for IP and reverse lookup are >> correct. >> >> Now I'm experiencing the classic, very long delay when connecting to the >> server via SSH because it does DNS lookups. When I look at wireshark >> dumps, I see correctly served A and reverse lookups but the server also >> insists on doing AAAA requests which time out. > > When you say "the server also insists on doing AAAA requests" you mean > the SSH server, right? > >> >> I tried limiting the sshd "AddressFamily" to inet (aka IPv4) but this >> didn't change anything. Is there another workaround or do I really have >> to deactivate DNS lookups? > > Is the server Gentoo and do you really need IPv6 support on it? Did you > consider rebuilding that host with IPv6 disabled in USE? > > IPv6 coexisting with IPv4 is always going to be a tricky problem, and > the recommended defaults you run into all over are usually intended to > force people to hurry IPv6 implementation along :-) > > There's always a way to change defaults, and I found this: > > http://askubuntu.com/questions/32298/prefer-a-ipv4-dns-lookups-before-aaaaipv6-lookups > > The magic file you need to edit appears to be > > /etc/gai.conf >
Okay, I fixed my issue: An intermediate DNS server was misconfigured and recursed on queries for which it is authoritative. Now AAAA queries are properly answered. Regards, Florian Philipp
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