added check.pl and query

dns/GNUmakefile

@@ -1,11 +1,12 @@
 include GNUmakevars
 
-all: gethostbyname fqdn
+all: gethostbyname fqdn query
 install: \
-	$(BINDIR)/gethostbyname \
 	$(BINDIR)/axfr \
 	$(BINDIR)/fqdn \
+	$(BINDIR)/gethostbyname \
 	$(BINDIR)/minnet \
+	$(BINDIR)/query \
 
 
 clean:

dns/check.pl

@@ -0,0 +1,97 @@
+#!/usr/bin/perl -w
+use strict;
+use Net::DNS;
+
+sub usage {
+    print STDERR "Usage: $0 domainname-or-ip-address\n";
+    exit(1);
+}
+
+usage() unless (@ARGV == 1);
+
+my $res = new Net::DNS::Resolver;
+if ($ARGV[0] =~ m/^(\d+)\.(\d+)\.(\d+)\.(\d+)$/) {
+    check_ptr($ARGV[0]);
+} else {
+    check_a($ARGV[0]);
+    # check_ns($ARGV[0]);
+}
+
+exit 0;
+
+my %addr_to_name;
+my %name_to_addr;
+
+sub check_ptr {
+    my ($addr, $name) = @_;
+
+    my @names;
+    if (defined $addr_to_name{$addr}) {
+        @names = @{ $addr_to_name{$addr} };
+    } else {
+        # XXX - ipv6?
+        my $q = join('.', reverse (split(/\./, $addr)), "in-addr", "arpa");
+        my $reply = $res->send($q, 'PTR');
+        for my $ans ($reply->answer) {
+            if ($ans->type eq 'PTR') {
+                push @names, $ans->ptrdname;
+            } else {
+                die "cannot happen";
+            }
+        }
+        if (@names == 0) {
+            print "[$addr] $q has no PTR record\n";
+        }
+        $addr_to_name{$addr} = \@names;
+    }
+    if ($name) {
+        unless (grep { $_ eq $name } @names) {
+            print "$name not found in PTR records of [$addr]\n";
+        }
+        return;
+    }
+    for my $name (@names) {
+        check_a($name, $addr);
+    }
+}
+
+sub check_a {
+    my ($name, $addr) = @_;
+
+    my @addrs;
+    if (defined $name_to_addr{$name}) {
+        @addrs = @{ $name_to_addr{$name} };
+    } else {
+        my $reply = $res->send($name, 'A');
+        for my $ans ($reply->answer) {
+            if ($ans->type eq 'A') {
+                push @addrs, $ans->address;
+            } else {
+                print "unexpected response to A query for $name\n";
+		$ans->print;
+            }
+        }
+        if (@addrs == 0) {
+            print "$name has no A record\n";
+        }
+        $name_to_addr{$name} = \@addrs;
+    }
+    if ($addr) {
+        unless (grep { $_ eq $addr } @addrs) {
+            print "[$addr] not found in A records of $name\n";
+        }
+        return;
+    }
+    for my $addr (@addrs) {
+        check_ptr($addr, $name);
+    }
+}
+
+my $answer = $res->query($ARGV[0], $ARGV[1]);
+if ($answer) {
+    $answer->print;
+} else {
+    print STDERR "query failed: ", $res->errorstring, "\n";
+}
+
+# $res->nameservers($ARGV[2]);

dns/query

@@ -0,0 +1,19 @@
+#!/usr/bin/perl -w
+use strict;
+use Net::DNS;
+
+sub usage {
+    print STDERR "Usage: $0 domainname type nameserver\n" unless (@ARGV == 2);
+    exit(1);
+}
+
+usage() unless (@ARGV == 3);
+
+my $res = new Net::DNS::Resolver;
+$res->nameservers($ARGV[2]);
+my $answer = $res->query($ARGV[0], $ARGV[1]);
+if ($answer) {
+    $answer->print;
+} else {
+    print STDERR "query failed: ", $res->errorstring, "\n";
+}