Problem with classless in-addr.arpa DNS entries

[Gabor Kiss <kissg@sztaki.hu>]

I found in 2.99.45 that "bind" type database function "revaddress"
cannot handle classless reverse mapping properly. (See
ftp://ftp.ripe.net/internet-drafts/draft-ietf-dnsind-classless-inaddr-03.txt)

Let's see an example:

% host 2.222.225.193.in-addr.arpa
2.222.225.193.in-addr.arpa	CNAME	2.0.222.225.193.in-addr.arpa
2.0.222.225.193.in-addr.arpa does not exist (Authoritative answer)

This means, that hostmaster of zone 222.225.193.in-addr.arpa
already delegated a small part of 193.225.222 reverse names
but the CNAME points to nothing because the hostmaster of
0.222.225.193.in-addr.arpa zone is not set up yet his name server.

In that case we can experience funny things:
% router -i
...
z$ trace on
z$ gethostbyaddr 193.225.222.2
    gethostbyaddr 193.225.222.2
        revdomain 193.225.222.2
            revdomain 225.222.2
                revdomain 222.2
                    revdomain 2
                        echo 2
                    echo 2.222
                echo 2.222.225
            echo 2.222.225.193
        %dblookup (revaddress 2.222.225.193.in-addr.arpa) <0>
        echo 2.222.225.193.in-addr.arpa
2.222.225.193.in-addr.arpa
        return (return) <0>
?=1
?=1
z$ 

Dblookup should return nothing but it returns 2.222.225.193.in-addr.arpa.

Look what happens in case of a classical nonregistered address:

z$ gethostbyaddr 1.2.3.4
    gethostbyaddr 1.2.3.4
        revdomain 1.2.3.4
            revdomain 2.3.4
                revdomain 3.4
                    revdomain 4
                        echo 4
                    echo 4.3
                echo 4.3.2
            echo 4.3.2.1
        %dblookup (revaddress 4.3.2.1.in-addr.arpa) <0>
?=1
?=1
        echo [1.2.3.4]
[1.2.3.4]
        return (return) <0>
?=1
?=1
z$ 

So one can send mail to user@[1.2.3.4] but not to user@[193.225.222.2].

Fast workaround:
the gethostbyname() function in i-smtp.cf may be hacked in such a way:

gethostbyaddr (ipaddrliteral) {
        local reversed

        reversed=$(revdomain $ipaddrliteral)
        sift $(revaddress $reversed.in-addr.arpa) in
        .*\.in-addr\.arpa echo "[$ipaddrliteral]" ; return ;;     # New line
        .\..*           echo \0 ; return ;;
        .*              echo "[$ipaddrliteral]" ; return ;;
        tfis
}


Gabor