On Wed, 16 Jun 2004, Bernd Eckenfels wrote: > In article <1087370535.24446.2981.camel@segesta.zurich.ibm.com> you wrote: > >> If the application prefers ipv6 it will try to use them, and only on connect > >> it receives an error. Some do then ipv4 fallback (lynx) some dont (mozilla). > > > > Fix your routing as that is the problem. > > No it is not, a Host with only link-local addresses is perfectly well > configured. The application can actually bind to the family and try to > connect to the internet destination, it will just have to deal with the net > not reachable error. And some applications dont. (but this is actually only > the reson why i ave looked at the sysctl options, even if all aplications > are fixed the options still behave wrong) [...] I think we may be having a slightly different problem here (as what the others are discussing). When you have enabled IPv6 but the network does not support IPv6 (i.e., you have link-local addresses), there are certain problems which may lead to longer timeouts. This depends principally on (at least) two things: 1) whether the node has a "on-link assumption", i.e., a default route to your interface. 2) whether TCP implementation aborts connection when it receives a "soft" ICMP error (against the host requirements RFC), These are both described at some length in http://www.ietf.org/internet-drafts/draft-ietf-v6ops-v6onbydefault-02.txt The key point here is that in these cases, even if the application was properly programmed, you might need to wait for a long time (dozens of seconds, even minutes) before the application would fall back to IPv4. IMHO, Linux should do both: 1) remove the IPv6 default routes pointing on each interface when the interface is created, 2) abort TCP connections which are in SYN-SENT state when an ICMP error is received. This would help the robustness a lot in the scenarios where you want to enable IPv6, and make sure it works, even if you didn't have IPv6 connectivity. I.e., this is a critical thing for vendors which might want to ship with IPv6 enabled by default. -- Pekka Savola "You each name yourselves king, yet the Netcore Oy kingdom bleeds." Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
