CNAME in SRV record RDATA (Target field)

Stefan Puiu stefan.puiu at gmail.com
Mon Apr 18 13:50:04 UTC 2005


Hello, 

according to RFC2782 (section "The format of the SRV RR", on page 4),
the last element in the SRV RDATA section, target, is:

    The domain name of the target host.  *There MUST be one or more
    address records for this name, the name MUST NOT be an alias (in
    the sense of RFC 1034 or RFC 2181).*

So, as far as I understand, target can't be a CNAME - it can't be an
alias and it must own at least one address record.

However, I created a test zone in BIND including the following lines: 

$TTL 1W
@               IN SOA  localhost root (
                                3               ; serial
                                2D              ; refresh
                                4H              ; retry
                                6W              ; expiry
                                1W )            ; minimum

                IN NS   localhost
                IN MX   10 mail

_http._tcp      IN SRV  10 0 80 www
ktulu           IN A    10.0.0.4
www             IN CNAME ktulu

When feeding this zone to BIND 9.2.3 (running on SuSE Linux 9.1),
named starts without reporting any errors or warnings (from
/var/log/messages):

Apr 18 16:11:57 tuxws19 named[16569]: loading configuration from
'/etc/named.conf'
Apr 18 16:11:57 tuxws19 named[16569]: zone varza/IN: loaded serial 3

Is this behaviour intentionally inconsistent with the RFC (it sounds
convenient to be able to use CNAMES in the target field, although this
would make resolution harder for clients) or is it an implementation
error? I've seen an older discussion on this on the list, with various
people pointing out that such a setup would be erroneous:
http://marc.theaimsgroup.com/?l=bind-users&m=102675031813267&w=2.
However, no mention on how BIND handles that. Since there is no
mention of CNAMES and SRVs in the BIND 9.3.1 CHANGES file (in bugs
fixed since 9.2.3 came out), I thought this to be legitimate question.



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