new file mode 100644
--- /dev/null
+++ b/http_resolver.t
@@ -0,0 +1,338 @@
+#!/usr/bin/perl
+
+# (C) Sergey Kandaurov
+# (C) Nginx, Inc.
+
+# Tests for http resolver.
+
+###############################################################################
+
+use warnings;
+use strict;
+
+use Test::More;
+
+BEGIN { use FindBin; chdir($FindBin::Bin); }
+
+use lib 'lib';
+use Test::Nginx;
+
+###############################################################################
+
+select STDERR; $| = 1;
+select STDOUT; $| = 1;
+
+eval { require Net::DNS::Nameserver; };
+plan(skip_all => "Net::DNS::Nameserver not installed") if $@;
+
+my $t = Test::Nginx->new()->has(qw/http proxy rewrite ipv6/);
+
+$t->write_file_expand('nginx.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    server {
+        listen       127.0.0.1:8080;
+        listen       [::1]:8080;
+        server_name  localhost;
+
+        location / {
+            resolver    127.0.0.1:8081;
+            # to lower resolving delay for unsupported AAAA
+            resolver_timeout 1s;
+            proxy_pass  http://$host:8080/backend;
+        }
+        location /cached {
+            resolver    127.0.0.1:8081 127.0.0.1:8082;
+            proxy_pass  http://$host:8080/backend;
+        }
+        location /two {
+            resolver    127.0.0.1:8081 127.0.0.1:8082;
+            resolver_timeout 2s;
+            proxy_pass  http://$host:8080/backend;
+        }
+        location /valid {
+            resolver    127.0.0.1:8081 127.0.0.1:8082 valid=3s;
+            resolver_timeout 2s;
+            proxy_pass  http://$host:8080/backend;
+        }
+        location /invalid {
+            proxy_pass  http://$host:8080/backend;
+        }
+        location /many {
+            resolver    127.0.0.1:8081 127.0.0.1:8082;
+            resolver_timeout 2s;
+            proxy_pass  http://$host:8080/backend;
+            proxy_next_upstream http_504 timeout error;
+            proxy_intercept_errors on;
+            proxy_connect_timeout 2s;
+            error_page 504 502 /50x;
+        }
+
+        location /backend {
+            return 200;
+        }
+        location /50x {
+            return 200 $upstream_addr;
+        }
+    }
+}
+
+EOF
+
+$t->run_daemon(\&dns_daemon, 8081);
+$t->run_daemon(\&dns_daemon, 8082);
+
+eval {
+	open OLDERR, ">&", \*STDERR; close STDERR;
+	$t->run();
+	open STDERR, ">&", \*OLDERR;
+};
+plan(skip_all => 'no inet6 support') if $@;
+
+$t->waitforsocket('127.0.0.1:8081');
+$t->waitforsocket('127.0.0.1:8082');
+
+$t->plan(27);
+
+###############################################################################
+
+like(http_host_header('a.example.net', '/'), qr/200 OK/, 'A');
+like(http_host_header('short.example.net', '/'), qr/502 Bad/,
+	'A short dns response');
+
+TODO: {
+local $TODO = 'support for AAAA';
+
+like(http_host_header('aaaa.example.net', '/'), qr/200 OK/, 'AAAA');
+
+}
+
+like(http_host_header('nx.example.net', '/'), qr/502 Bad/, 'NXDOMAIN');
+like(http_host_header('cname.example.net', '/cached'), qr/200 OK/, 'CNAME');
+like(http_host_header('cname.example.net', '/cached'), qr/200 OK/,
+	'CNAME cached');
+
+# CNAME refers to non-existing A
+
+like(http_host_header('cname2.example.net', '/'), qr/502 Bad/, 'CNAME bad');
+like(http_host_header('long.example.net', '/'), qr/200 OK/, 'long label');
+like(http_host_header('long2.example.net', '/'), qr/200 OK/, 'long name');
+
+# take into account DNAME
+
+like(http_host_header('alias.example.com', '/'), qr/200 OK/, 'DNAME');
+
+# many A records in round robin
+# nonexisting IPs enumerated with proxy_next_upstream
+
+like(http_host_header('many.example.net', '/many'),
+	qr/^127.0.0.20(1:8080, 127.0.0.202:8080|2:8080, 127.0.0.201:8080)$/m,
+	'A many');
+
+like(http_host_header('many.example.net', '/many'),
+	qr/^127.0.0.20(1:8080, 127.0.0.202:8080|2:8080, 127.0.0.201:8080)$/m,
+	'A many cached');
+
+# several resolver addresses with 1st ns bad
+# query bad ns, negative responses are not cached
+
+like(http_host_header('2.example.net', '/two'), qr/502 Bad/, 'two ns bad');
+
+# query alive ns
+
+like(http_host_header('2.example.net', '/two'), qr/200 OK/, 'two ns good');
+
+# cached response prevents querying the next (bad) ns again
+
+like(http_host_header('2.example.net', '/two'), qr/200 OK/, 'two ns cached');
+
+# ttl tested with 1st ns good and 2nd ns bad
+# query good ns and cache response
+
+like(http_host_header('ttl.example.net', '/two'), qr/200 OK/, 'ttl');
+
+# cached response prevents querying the next (bad) ns
+
+like(http_host_header('ttl.example.net', '/two'), qr/200 OK/, 'ttl cached 1');
+like(http_host_header('ttl.example.net', '/two'), qr/200 OK/, 'ttl cached 2');
+
+sleep 2;
+
+# expired ttl causes nginx to query the next (bad) ns
+
+skip:
+like(http_host_header('ttl.example.net', '/two'), qr/502 Bad/, 'ttl expired');
+
+# zero ttl prohibits response caching
+
+like(http_host_header('ttl0.example.net', '/two'), qr/200 OK/, 'zero ttl');
+
+TODO: {
+local $TODO = 'support for zero ttl';
+
+like(http_host_header('ttl0.example.net', '/two'), qr/502 Bad/,
+	'zero ttl not cached');
+
+}
+
+# "valid" parameter tested with 1st alive ns and 2nd bad ns
+# query alive ns, and cache response
+
+like(http_host_header('ttl.example.net', '/valid'), qr/200 OK/, 'valid');
+
+# cached response prevents querying the next (bad) ns
+
+like(http_host_header('ttl.example.net', '/valid'), qr/200 OK/,
+	'valid cached 1');
+like(http_host_header('ttl.example.net', '/valid'), qr/200 OK/,
+	'valid cached 2');
+
+sleep 2;
+
+# expired ttl is overridden with "valid" parameter
+# response is taken from cache
+
+like(http_host_header('ttl.example.net', '/valid'), qr/200 OK/,
+	'valid overrides ttl');
+
+sleep 2;
+
+# expired "valid" value causes nginx to query the next (bad) ns
+
+like(http_host_header('ttl.example.net', '/valid'), qr/502 Bad/,
+	'valid expired');
+
+like(http_host_header('example.net', '/invalid'), qr/502 Bad/, 'no resolver');
+
+###############################################################################
+
+sub http_host_header {
+	my ($host, $uri) = @_;
+	return http(<<EOF);
+GET $uri HTTP/1.0
+Host: $host
+
+EOF
+}
+
+###############################################################################
+
+sub reply_handler {
+	my ($name, $class, $type, $peerhost, $query, $conn) = @_;
+	my ($rcode, @ans, $ttl, $rdata);
+
+	$rcode = 'NOERROR';
+	$ttl = 3600;
+
+	if (($name eq 'a.example.net') || ($name eq 'alias.example.net')) {
+		($rdata) = ('127.0.0.1');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif (($name eq 'many.example.net')) {
+		if ($conn->{sockport} == 8082) {
+			return 'SERVFAIL';
+		}
+		($rdata) = ('127.0.0.201');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+		($rdata) = ('127.0.0.202');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif (($name eq 'aaaa.example.net')) {
+		($type, $rdata) = ('AAAA', '::1');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif (($name eq 'short.example.net')) {
+		# zero length RDATA in DNS response
+		($name, $rdata) = ($name, '');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif (($name eq 'alias.example.com')) {
+		my $dname = 'example.com';
+		($type, $rdata) = ('DNAME', 'example.net');
+		push @ans, Net::DNS::RR->new("$dname $ttl $class $type $rdata");
+		($type, $rdata) = ('CNAME', 'alias.example.net');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif ($name eq 'cname.example.net') {
+		if ($conn->{sockport} == 8082) {
+			return 'SERVFAIL';
+		}
+		($type, $rdata) = ('CNAME', 'alias.example.net');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif ($name eq 'cname2.example.net') {
+		# points to non-existing A
+		($type, $rdata) = ('CNAME', 'nx.example.net');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif ($name eq 'long.example.net') {
+		($type, $rdata) = ('CNAME', 'a' x 63);
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif (($name eq 'a' x 63)) {
+		($rdata) = ('127.0.0.1');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif ($name eq 'long2.example.net') {
+		($type, $rdata) = ('CNAME', 'a' x 63 . '.' . 'a' x 63 . '.'
+			. 'a' x 63 . '.' . 'a' x 63);
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif (($name eq 'a' x 63 . '.' . 'a' x 63 . '.' . 'a' x 63 . '.'
+			. 'a' x 63))
+	{
+		($rdata) = ('127.0.0.1');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif ($name eq 'ttl.example.net') {
+		if ($conn->{sockport} == 8082) {
+			return 'SERVFAIL';
+		}
+		($ttl, $rdata) = (1, '127.0.0.1');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif ($name eq 'ttl0.example.net') {
+		if ($conn->{sockport} == 8082) {
+			return 'SERVFAIL';
+		}
+		($ttl, $rdata) = (0, '127.0.0.1');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} elsif ($name eq '2.example.net') {
+		if ($conn->{sockport} == 8081) {
+			return 'SERVFAIL';
+		}
+		($rdata) = ('127.0.0.1');
+		push @ans, Net::DNS::RR->new("$name $ttl $class $type $rdata");
+
+	} else {
+		$rcode = 'NXDOMAIN';
+	}
+
+	return ($rcode, \@ans);
+}
+
+sub dns_daemon {
+	my ($port) = @_;
+
+	my $ns = Net::DNS::Nameserver->new(
+		LocalAddr    => '127.0.0.1',
+		LocalPort    => $port,
+		Proto        => 'udp',
+		ReplyHandler => \&reply_handler,
+	)
+		or die "Can't create nameserver object: $!\n";
+
+	$ns->main_loop;
+}
+
+###############################################################################