Max Laier wrote:
On Friday 10 August 2007, JINMEI Tatuya / 神明達哉 wrote:
At Fri, 10 Aug 2007 11:52:09 +0800,
blue <[EMAIL PROTECTED]> wrote:
When looking into kame-20070801-freebsd54-snap, the function,
_dns_getaddrinfo(), defined in getaddrinfo.c, will check if the
device gets any IPv4/global IPv6 address before sending out any
A/AAAA query by calling addrconfig() if the user does not specify the
family type (AF_UNSPEC). However, FreeBSD-CURRENT (known is going to
be FreeBSD7.0), does not do the process.
Do we need to do the same check before sending out the A/AAAA query?
I'm afraid just asking this question without providing a context could
be misleading. I guess this is a continuation of a thread of the
[EMAIL PROTECTED] list:
ftp://ftp.kame.net/pub/mail-list/snap-users/9541
ftp://ftp.kame.net/pub/mail-list/snap-users/9544
If so, we should discuss this with the understanding of why KAME-snap
version behaves that way, specifically referring to Section 3
(especially 3.4.1) of this document:
http://v6fix.net/docs/wide-draft-v6fix.en
We (KAME) thought the behavior was reasonable but we were also afraid
this might be too experimental to incorporate to *BSD release
versions at that time. That's why it's not in the FreeBSD repository.
I'm interested in what others think on this. If others think this
feature is reasonable, too, and want it, I'm happy to commit the
change to the FreeBSD repository.
I agree with the reasoning in the document you reference above.
getaddrinfo is a convenience resolver and thus it's a good thing to
return reasonable defaults. Not returning AAAA when there are no IPv6
addresses around seems reasonable to me. I'm not sure it's a good idea
to go the other way (i.e. not sending A queries when there are no IPv4
addresses), however.
Although DNS resolver may lead to some delay or misbehavior of the upper
application, I think that would be caller's resposibility to decide
which result it would like to use. I am not so sure about the check in
KAME implementation, in getaddrinfo.c:
_dns_getaddrinfo(
void *rv,
void *cb_data,
va_list ap
){
.....
switch (pai->ai_family) {
case AF_UNSPEC:
qp = &q;
buf_current = buf;
/*
* Since queries for AAAA can cause unexpected misbehavior,
* we first send A queries. Note that the query ordering
* is independent from the ordering of the resulting addresses
* returned by getaddrinfo().
*/
if (addrconfig(AF_INET, ac)) {
qp->name = hostname;
qp->qclass = C_IN;
qp->qtype = T_A;
qp->answer = buf_current->buf;
qp->anslen = sizeof(buf_current->buf);
if (addrconfig(AF_INET6, ac)) {
qp->next = &q2;
buf_current = buf2;
qp = &q2;
}
}
if (addrconfig(AF_INET6, ac)) {
qp->name = hostname;
qp->qclass = C_IN;
qp->qtype = T_AAAA;
qp->answer = buf_current->buf;
qp->anslen = sizeof(buf_current->buf);
}
break;
case AF_INET:
q.name = hostname;
q.qclass = C_IN;
q.qtype = T_A;
q.answer = buf->buf;
q.anslen = sizeof(buf->buf);
break;
case AF_INET6:
q.name = hostname;
q.qclass = C_IN;
q.qtype = T_AAAA;
q.answer = buf->buf;
q.anslen = sizeof(buf->buf);
break;
default:
free(buf);
free(buf2);
return NS_UNAVAIL;
}
.....
}
Why the check for avilable IPv4/IPv6 address, addrconfig(), only applies
when the hints' family type is AF_UNSPEC? I think if delaying the upper
application is a concern, the check should be applied no matter what
family type it is.
Thanks.
Best regards,
Yi-Wen
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