Date: Sat, 02 Aug 2003 00:47:20 -0700 From: Lev Walkin <vlm@netli.com> To: Luigi Rizzo <rizzo@icir.org> Cc: hackers@freebsd.org Subject: Re: can we disable AAAA queries in the resolver ? Message-ID: <3F2B6C88.5020908@netli.com> In-Reply-To: <20030801235200.A53695@xorpc.icir.org> References: <20030801235200.A53695@xorpc.icir.org>
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Luigi Rizzo wrote: > hi, > recently i have been bitten by a problem which might be already > known, but still... > > quite a few apps (sendmail and ssh among them) seem to always > try an AAAA query if compiled with ipv6 support, and even if > the kernel does not support ipv6, tcpdump shows AAAA queries going out > to the nameserver, and often timing out or otherwise causing my > apps significand delays at startup. > > My understanding is that there are multiple buggy components here: > my ISP's nameserver certainly shouldn't behave so badly on AAAA > requests, and the applications should not bother asking AAAA queries > when the kernel has no ipv6 support. > On the other hand, the resolver code is probably just innocent > because if some application issues an AAAA request, the resolver > has no reason to object. Still, rather than fixing the many > broken applications, or the nameserver (on which i have no control) > i wonder if it is possible to instruct the resolver, perhaps through > some option in resolv.conf, to immediately return some kind > of negative replies on selected queries ? The code does not seem to have this as an option, but it is rather a compile-time stuff. Refer to the /usr/src/lib/libc/net/getaddrinfo.c. Indeed, it would be useful to have it configurable either in resolv.conf (options) or as an environment variable (RES_OPTIONS). -- Lev Walkin vlm@netli.com
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