1 |
=head1 NAME |
2 |
|
3 |
AnyEvent::DNS - fully asynchronous DNS resolution |
4 |
|
5 |
=head1 SYNOPSIS |
6 |
|
7 |
use AnyEvent::DNS; |
8 |
|
9 |
my $cv = AnyEvent->condvar; |
10 |
AnyEvent::DNS::a "www.google.de", $cv; |
11 |
# ... later |
12 |
my @addrs = $cv->recv; |
13 |
|
14 |
=head1 DESCRIPTION |
15 |
|
16 |
This module offers both a number of DNS convenience functions as well |
17 |
as a fully asynchronous and high-performance pure-perl stub resolver. |
18 |
|
19 |
The stub resolver supports DNS over UDP, optional EDNS0 support for up to |
20 |
4kiB datagrams and automatically falls back to virtual circuit mode for |
21 |
large responses. |
22 |
|
23 |
=head2 CONVENIENCE FUNCTIONS |
24 |
|
25 |
=over 4 |
26 |
|
27 |
=cut |
28 |
|
29 |
package AnyEvent::DNS; |
30 |
|
31 |
no warnings; |
32 |
use strict; |
33 |
|
34 |
use Socket qw(AF_INET SOCK_DGRAM SOCK_STREAM); |
35 |
|
36 |
use AnyEvent (); |
37 |
use AnyEvent::Handle (); |
38 |
|
39 |
our @DNS_FALLBACK = (v208.67.220.220, v208.67.222.222); |
40 |
|
41 |
=item AnyEvent::DNS::a $domain, $cb->(@addrs) |
42 |
|
43 |
Tries to resolve the given domain to IPv4 address(es). |
44 |
|
45 |
=item AnyEvent::DNS::aaaa $domain, $cb->(@addrs) |
46 |
|
47 |
Tries to resolve the given domain to IPv6 address(es). |
48 |
|
49 |
=item AnyEvent::DNS::mx $domain, $cb->(@hostnames) |
50 |
|
51 |
Tries to resolve the given domain into a sorted (lower preference value |
52 |
first) list of domain names. |
53 |
|
54 |
=item AnyEvent::DNS::ns $domain, $cb->(@hostnames) |
55 |
|
56 |
Tries to resolve the given domain name into a list of name servers. |
57 |
|
58 |
=item AnyEvent::DNS::txt $domain, $cb->(@hostnames) |
59 |
|
60 |
Tries to resolve the given domain name into a list of text records. |
61 |
|
62 |
=item AnyEvent::DNS::srv $service, $proto, $domain, $cb->(@srv_rr) |
63 |
|
64 |
Tries to resolve the given service, protocol and domain name into a list |
65 |
of service records. |
66 |
|
67 |
Each srv_rr is an array reference with the following contents: |
68 |
C<[$priority, $weight, $transport, $target]>. |
69 |
|
70 |
They will be sorted with lowest priority, highest weight first (TODO: |
71 |
should use the RFC algorithm to reorder same-priority records for weight). |
72 |
|
73 |
Example: |
74 |
|
75 |
AnyEvent::DNS::srv "sip", "udp", "schmorp.de", sub { ... |
76 |
# @_ = ( [10, 10, 5060, "sip1.schmorp.de" ] ) |
77 |
|
78 |
=item AnyEvent::DNS::ptr $ipv4_or_6, $cb->(@hostnames) |
79 |
|
80 |
Tries to reverse-resolve the given IPv4 or IPv6 address (in textual form) |
81 |
into it's hostname(s). |
82 |
|
83 |
Example: |
84 |
|
85 |
AnyEvent::DNS::ptr "2001:500:2f::f", sub { print shift }; |
86 |
# => f.root-servers.net |
87 |
|
88 |
=item AnyEvent::DNS::any $domain, $cb->(@rrs) |
89 |
|
90 |
Tries to resolve the given domain and passes all resource records found to |
91 |
the callback. |
92 |
|
93 |
=cut |
94 |
|
95 |
sub resolver; |
96 |
|
97 |
sub a($$) { |
98 |
my ($domain, $cb) = @_; |
99 |
|
100 |
resolver->resolve ($domain => "a", sub { |
101 |
$cb->(map $_->[3], @_); |
102 |
}); |
103 |
} |
104 |
|
105 |
sub aaaa($$) { |
106 |
my ($domain, $cb) = @_; |
107 |
|
108 |
resolver->resolve ($domain => "aaaa", sub { |
109 |
$cb->(map $_->[3], @_); |
110 |
}); |
111 |
} |
112 |
|
113 |
sub mx($$) { |
114 |
my ($domain, $cb) = @_; |
115 |
|
116 |
resolver->resolve ($domain => "mx", sub { |
117 |
$cb->(map $_->[4], sort { $a->[3] <=> $b->[3] } @_); |
118 |
}); |
119 |
} |
120 |
|
121 |
sub ns($$) { |
122 |
my ($domain, $cb) = @_; |
123 |
|
124 |
resolver->resolve ($domain => "ns", sub { |
125 |
$cb->(map $_->[3], @_); |
126 |
}); |
127 |
} |
128 |
|
129 |
sub txt($$) { |
130 |
my ($domain, $cb) = @_; |
131 |
|
132 |
resolver->resolve ($domain => "txt", sub { |
133 |
$cb->(map $_->[3], @_); |
134 |
}); |
135 |
} |
136 |
|
137 |
sub srv($$$$) { |
138 |
my ($service, $proto, $domain, $cb) = @_; |
139 |
|
140 |
# todo, ask for any and check glue records |
141 |
resolver->resolve ("_$service._$proto.$domain" => "srv", sub { |
142 |
$cb->(map [@$_[3,4,5,6]], sort { $a->[3] <=> $b->[3] || $b->[4] <=> $a->[4] } @_); |
143 |
}); |
144 |
} |
145 |
|
146 |
sub ptr($$) { |
147 |
my ($ip, $cb) = @_; |
148 |
|
149 |
$ip = AnyEvent::Socket::parse_address ($ip) |
150 |
or return $cb->(); |
151 |
|
152 |
if (4 == length $ip) { |
153 |
$ip = join ".", (reverse split /\./, $ip), "in-addr.arpa."; |
154 |
} else { |
155 |
$ip = join ".", (reverse split //, unpack "H*", $ip), "ip6.arpa."; |
156 |
} |
157 |
|
158 |
resolver->resolve ($ip => "ptr", sub { |
159 |
$cb->(map $_->[3], @_); |
160 |
}); |
161 |
} |
162 |
|
163 |
sub any($$) { |
164 |
my ($domain, $cb) = @_; |
165 |
|
166 |
resolver->resolve ($domain => "*", $cb); |
167 |
} |
168 |
|
169 |
################################################################################# |
170 |
|
171 |
=back |
172 |
|
173 |
=head2 LOW-LEVEL DNS EN-/DECODING FUNCTIONS |
174 |
|
175 |
=over 4 |
176 |
|
177 |
=item $AnyEvent::DNS::EDNS0 |
178 |
|
179 |
This variable decides whether dns_pack automatically enables EDNS0 |
180 |
support. By default, this is disabled (C<0>), unless overridden by |
181 |
C<$ENV{PERL_ANYEVENT_EDNS0>), but when set to C<1>, AnyEvent::DNS will use |
182 |
EDNS0 in all requests. |
183 |
|
184 |
=cut |
185 |
|
186 |
our $EDNS0 = $ENV{PERL_ANYEVENT_EDNS0} * 1; # set to 1 to enable (partial) edns0 |
187 |
|
188 |
our %opcode_id = ( |
189 |
query => 0, |
190 |
iquery => 1, |
191 |
status => 2, |
192 |
notify => 4, |
193 |
update => 5, |
194 |
map +($_ => $_), 3, 6..15 |
195 |
); |
196 |
|
197 |
our %opcode_str = reverse %opcode_id; |
198 |
|
199 |
our %rcode_id = ( |
200 |
noerror => 0, |
201 |
formerr => 1, |
202 |
servfail => 2, |
203 |
nxdomain => 3, |
204 |
notimp => 4, |
205 |
refused => 5, |
206 |
yxdomain => 6, # Name Exists when it should not [RFC 2136] |
207 |
yxrrset => 7, # RR Set Exists when it should not [RFC 2136] |
208 |
nxrrset => 8, # RR Set that should exist does not [RFC 2136] |
209 |
notauth => 9, # Server Not Authoritative for zone [RFC 2136] |
210 |
notzone => 10, # Name not contained in zone [RFC 2136] |
211 |
# EDNS0 16 BADVERS Bad OPT Version [RFC 2671] |
212 |
# EDNS0 16 BADSIG TSIG Signature Failure [RFC 2845] |
213 |
# EDNS0 17 BADKEY Key not recognized [RFC 2845] |
214 |
# EDNS0 18 BADTIME Signature out of time window [RFC 2845] |
215 |
# EDNS0 19 BADMODE Bad TKEY Mode [RFC 2930] |
216 |
# EDNS0 20 BADNAME Duplicate key name [RFC 2930] |
217 |
# EDNS0 21 BADALG Algorithm not supported [RFC 2930] |
218 |
map +($_ => $_), 11..15 |
219 |
); |
220 |
|
221 |
our %rcode_str = reverse %rcode_id; |
222 |
|
223 |
our %type_id = ( |
224 |
a => 1, |
225 |
ns => 2, |
226 |
md => 3, |
227 |
mf => 4, |
228 |
cname => 5, |
229 |
soa => 6, |
230 |
mb => 7, |
231 |
mg => 8, |
232 |
mr => 9, |
233 |
null => 10, |
234 |
wks => 11, |
235 |
ptr => 12, |
236 |
hinfo => 13, |
237 |
minfo => 14, |
238 |
mx => 15, |
239 |
txt => 16, |
240 |
aaaa => 28, |
241 |
srv => 33, |
242 |
opt => 41, |
243 |
spf => 99, |
244 |
tkey => 249, |
245 |
tsig => 250, |
246 |
ixfr => 251, |
247 |
axfr => 252, |
248 |
mailb => 253, |
249 |
"*" => 255, |
250 |
); |
251 |
|
252 |
our %type_str = reverse %type_id; |
253 |
|
254 |
our %class_id = ( |
255 |
in => 1, |
256 |
ch => 3, |
257 |
hs => 4, |
258 |
none => 254, |
259 |
"*" => 255, |
260 |
); |
261 |
|
262 |
our %class_str = reverse %class_id; |
263 |
|
264 |
# names MUST have a trailing dot |
265 |
sub _enc_name($) { |
266 |
pack "(C/a*)*", (split /\./, shift), "" |
267 |
} |
268 |
|
269 |
sub _enc_qd() { |
270 |
(_enc_name $_->[0]) . pack "nn", |
271 |
($_->[1] > 0 ? $_->[1] : $type_id {$_->[1]}), |
272 |
($_->[2] > 0 ? $_->[2] : $class_id{$_->[2] || "in"}) |
273 |
} |
274 |
|
275 |
sub _enc_rr() { |
276 |
die "encoding of resource records is not supported"; |
277 |
} |
278 |
|
279 |
=item $pkt = AnyEvent::DNS::dns_pack $dns |
280 |
|
281 |
Packs a perl data structure into a DNS packet. Reading RFC1034 is strongly |
282 |
recommended, then everything will be totally clear. Or maybe not. |
283 |
|
284 |
Resource records are not yet encodable. |
285 |
|
286 |
Examples: |
287 |
|
288 |
# very simple request, using lots of default values: |
289 |
{ rd => 1, qd => [ [ "host.domain", "a"] ] } |
290 |
|
291 |
# more complex example, showing how flags etc. are named: |
292 |
|
293 |
{ |
294 |
id => 10000, |
295 |
op => "query", |
296 |
rc => "nxdomain", |
297 |
|
298 |
# flags |
299 |
qr => 1, |
300 |
aa => 0, |
301 |
tc => 0, |
302 |
rd => 0, |
303 |
ra => 0, |
304 |
ad => 0, |
305 |
cd => 0, |
306 |
|
307 |
qd => [@rr], # query section |
308 |
an => [@rr], # answer section |
309 |
ns => [@rr], # authority section |
310 |
ar => [@rr], # additional records section |
311 |
} |
312 |
|
313 |
=cut |
314 |
|
315 |
sub dns_pack($) { |
316 |
my ($req) = @_; |
317 |
|
318 |
pack "nn nnnn a* a* a* a* a*", |
319 |
$req->{id}, |
320 |
|
321 |
! !$req->{qr} * 0x8000 |
322 |
+ $opcode_id{$req->{op}} * 0x0800 |
323 |
+ ! !$req->{aa} * 0x0400 |
324 |
+ ! !$req->{tc} * 0x0200 |
325 |
+ ! !$req->{rd} * 0x0100 |
326 |
+ ! !$req->{ra} * 0x0080 |
327 |
+ ! !$req->{ad} * 0x0020 |
328 |
+ ! !$req->{cd} * 0x0010 |
329 |
+ $rcode_id{$req->{rc}} * 0x0001, |
330 |
|
331 |
scalar @{ $req->{qd} || [] }, |
332 |
scalar @{ $req->{an} || [] }, |
333 |
scalar @{ $req->{ns} || [] }, |
334 |
$EDNS0 + scalar @{ $req->{ar} || [] }, # include EDNS0 option here |
335 |
|
336 |
(join "", map _enc_qd, @{ $req->{qd} || [] }), |
337 |
(join "", map _enc_rr, @{ $req->{an} || [] }), |
338 |
(join "", map _enc_rr, @{ $req->{ns} || [] }), |
339 |
(join "", map _enc_rr, @{ $req->{ar} || [] }), |
340 |
|
341 |
($EDNS0 ? pack "C nnNn", 0, 41, 4096, 0, 0 : "") # EDNS0, 4kiB udp payload size |
342 |
} |
343 |
|
344 |
our $ofs; |
345 |
our $pkt; |
346 |
|
347 |
# bitches |
348 |
sub _dec_name { |
349 |
my @res; |
350 |
my $redir; |
351 |
my $ptr = $ofs; |
352 |
my $cnt; |
353 |
|
354 |
while () { |
355 |
return undef if ++$cnt >= 256; # to avoid DoS attacks |
356 |
|
357 |
my $len = ord substr $pkt, $ptr++, 1; |
358 |
|
359 |
if ($len >= 0xc0) { |
360 |
$ptr++; |
361 |
$ofs = $ptr if $ptr > $ofs; |
362 |
$ptr = (unpack "n", substr $pkt, $ptr - 2, 2) & 0x3fff; |
363 |
} elsif ($len) { |
364 |
push @res, substr $pkt, $ptr, $len; |
365 |
$ptr += $len; |
366 |
} else { |
367 |
$ofs = $ptr if $ptr > $ofs; |
368 |
return join ".", @res; |
369 |
} |
370 |
} |
371 |
} |
372 |
|
373 |
sub _dec_qd { |
374 |
my $qname = _dec_name; |
375 |
my ($qt, $qc) = unpack "nn", substr $pkt, $ofs; $ofs += 4; |
376 |
[$qname, $type_str{$qt} || $qt, $class_str{$qc} || $qc] |
377 |
} |
378 |
|
379 |
our %dec_rr = ( |
380 |
1 => sub { join ".", unpack "C4", $_ }, # a |
381 |
2 => sub { local $ofs = $ofs - length; _dec_name }, # ns |
382 |
5 => sub { local $ofs = $ofs - length; _dec_name }, # cname |
383 |
6 => sub { |
384 |
local $ofs = $ofs - length; |
385 |
my $mname = _dec_name; |
386 |
my $rname = _dec_name; |
387 |
($mname, $rname, unpack "NNNNN", substr $pkt, $ofs) |
388 |
}, # soa |
389 |
11 => sub { ((join ".", unpack "C4", $_), unpack "C a*", substr $_, 4) }, # wks |
390 |
12 => sub { local $ofs = $ofs - length; _dec_name }, # ptr |
391 |
13 => sub { unpack "C/a* C/a*", $_ }, # hinfo |
392 |
15 => sub { local $ofs = $ofs + 2 - length; ((unpack "n", $_), _dec_name) }, # mx |
393 |
16 => sub { unpack "(C/a*)*", $_ }, # txt |
394 |
28 => sub { AnyEvent::Socket::format_address ($_) }, # aaaa |
395 |
33 => sub { local $ofs = $ofs + 6 - length; ((unpack "nnn", $_), _dec_name) }, # srv |
396 |
99 => sub { unpack "(C/a*)*", $_ }, # spf |
397 |
); |
398 |
|
399 |
sub _dec_rr { |
400 |
my $name = _dec_name; |
401 |
|
402 |
my ($rt, $rc, $ttl, $rdlen) = unpack "nn N n", substr $pkt, $ofs; $ofs += 10; |
403 |
local $_ = substr $pkt, $ofs, $rdlen; $ofs += $rdlen; |
404 |
|
405 |
[ |
406 |
$name, |
407 |
$type_str{$rt} || $rt, |
408 |
$class_str{$rc} || $rc, |
409 |
($dec_rr{$rt} || sub { $_ })->(), |
410 |
] |
411 |
} |
412 |
|
413 |
=item $dns = AnyEvent::DNS::dns_unpack $pkt |
414 |
|
415 |
Unpacks a DNS packet into a perl data structure. |
416 |
|
417 |
Examples: |
418 |
|
419 |
# an unsuccessful reply |
420 |
{ |
421 |
'qd' => [ |
422 |
[ 'ruth.plan9.de.mach.uni-karlsruhe.de', '*', 'in' ] |
423 |
], |
424 |
'rc' => 'nxdomain', |
425 |
'ar' => [], |
426 |
'ns' => [ |
427 |
[ |
428 |
'uni-karlsruhe.de', |
429 |
'soa', |
430 |
'in', |
431 |
'netserv.rz.uni-karlsruhe.de', |
432 |
'hostmaster.rz.uni-karlsruhe.de', |
433 |
2008052201, 10800, 1800, 2592000, 86400 |
434 |
] |
435 |
], |
436 |
'tc' => '', |
437 |
'ra' => 1, |
438 |
'qr' => 1, |
439 |
'id' => 45915, |
440 |
'aa' => '', |
441 |
'an' => [], |
442 |
'rd' => 1, |
443 |
'op' => 'query' |
444 |
} |
445 |
|
446 |
# a successful reply |
447 |
|
448 |
{ |
449 |
'qd' => [ [ 'www.google.de', 'a', 'in' ] ], |
450 |
'rc' => 0, |
451 |
'ar' => [ |
452 |
[ 'a.l.google.com', 'a', 'in', '209.85.139.9' ], |
453 |
[ 'b.l.google.com', 'a', 'in', '64.233.179.9' ], |
454 |
[ 'c.l.google.com', 'a', 'in', '64.233.161.9' ], |
455 |
], |
456 |
'ns' => [ |
457 |
[ 'l.google.com', 'ns', 'in', 'a.l.google.com' ], |
458 |
[ 'l.google.com', 'ns', 'in', 'b.l.google.com' ], |
459 |
], |
460 |
'tc' => '', |
461 |
'ra' => 1, |
462 |
'qr' => 1, |
463 |
'id' => 64265, |
464 |
'aa' => '', |
465 |
'an' => [ |
466 |
[ 'www.google.de', 'cname', 'in', 'www.google.com' ], |
467 |
[ 'www.google.com', 'cname', 'in', 'www.l.google.com' ], |
468 |
[ 'www.l.google.com', 'a', 'in', '66.249.93.104' ], |
469 |
[ 'www.l.google.com', 'a', 'in', '66.249.93.147' ], |
470 |
], |
471 |
'rd' => 1, |
472 |
'op' => 0 |
473 |
} |
474 |
|
475 |
=cut |
476 |
|
477 |
sub dns_unpack($) { |
478 |
local $pkt = shift; |
479 |
my ($id, $flags, $qd, $an, $ns, $ar) |
480 |
= unpack "nn nnnn A*", $pkt; |
481 |
|
482 |
local $ofs = 6 * 2; |
483 |
|
484 |
{ |
485 |
id => $id, |
486 |
qr => ! ! ($flags & 0x8000), |
487 |
aa => ! ! ($flags & 0x0400), |
488 |
tc => ! ! ($flags & 0x0200), |
489 |
rd => ! ! ($flags & 0x0100), |
490 |
ra => ! ! ($flags & 0x0080), |
491 |
ad => ! ! ($flags & 0x0020), |
492 |
cd => ! ! ($flags & 0x0010), |
493 |
op => $opcode_str{($flags & 0x001e) >> 11}, |
494 |
rc => $rcode_str{($flags & 0x000f)}, |
495 |
|
496 |
qd => [map _dec_qd, 1 .. $qd], |
497 |
an => [map _dec_rr, 1 .. $an], |
498 |
ns => [map _dec_rr, 1 .. $ns], |
499 |
ar => [map _dec_rr, 1 .. $ar], |
500 |
} |
501 |
} |
502 |
|
503 |
############################################################################# |
504 |
|
505 |
=back |
506 |
|
507 |
=head2 THE AnyEvent::DNS RESOLVER CLASS |
508 |
|
509 |
This is the class which does the actual protocol work. |
510 |
|
511 |
=over 4 |
512 |
|
513 |
=cut |
514 |
|
515 |
use Carp (); |
516 |
use Scalar::Util (); |
517 |
use Socket (); |
518 |
|
519 |
our $NOW; |
520 |
|
521 |
=item AnyEvent::DNS::resolver |
522 |
|
523 |
This function creates and returns a resolver that is ready to use and |
524 |
should mimic the default resolver for your system as good as possible. |
525 |
|
526 |
It only ever creates one resolver and returns this one on subsequent |
527 |
calls. |
528 |
|
529 |
Unless you have special needs, prefer this function over creating your own |
530 |
resolver object. |
531 |
|
532 |
=cut |
533 |
|
534 |
our $RESOLVER; |
535 |
|
536 |
sub resolver() { |
537 |
$RESOLVER || do { |
538 |
$RESOLVER = new AnyEvent::DNS; |
539 |
$RESOLVER->os_config; |
540 |
$RESOLVER |
541 |
} |
542 |
} |
543 |
|
544 |
=item $resolver = new AnyEvent::DNS key => value... |
545 |
|
546 |
Creates and returns a new resolver. |
547 |
|
548 |
The following options are supported: |
549 |
|
550 |
=over 4 |
551 |
|
552 |
=item server => [...] |
553 |
|
554 |
A list of server addresses (default: C<v127.0.0.1>) in network format (4 |
555 |
octets for IPv4, 16 octets for IPv6 - not yet supported). |
556 |
|
557 |
=item timeout => [...] |
558 |
|
559 |
A list of timeouts to use (also determines the number of retries). To make |
560 |
three retries with individual time-outs of 2, 5 and 5 seconds, use C<[2, |
561 |
5, 5]>, which is also the default. |
562 |
|
563 |
=item search => [...] |
564 |
|
565 |
The default search list of suffixes to append to a domain name (default: none). |
566 |
|
567 |
=item ndots => $integer |
568 |
|
569 |
The number of dots (default: C<1>) that a name must have so that the resolver |
570 |
tries to resolve the name without any suffixes first. |
571 |
|
572 |
=item max_outstanding => $integer |
573 |
|
574 |
Most name servers do not handle many parallel requests very well. This option |
575 |
limits the number of outstanding requests to C<$n> (default: C<10>), that means |
576 |
if you request more than this many requests, then the additional requests will be queued |
577 |
until some other requests have been resolved. |
578 |
|
579 |
=item reuse => $seconds |
580 |
|
581 |
The number of seconds (default: C<300>) that a query id cannot be re-used |
582 |
after a timeout. If there as no time-out then query id's can be reused |
583 |
immediately. |
584 |
|
585 |
=back |
586 |
|
587 |
=cut |
588 |
|
589 |
sub new { |
590 |
my ($class, %arg) = @_; |
591 |
|
592 |
socket my $fh, AF_INET, &Socket::SOCK_DGRAM, 0 |
593 |
or Carp::croak "socket: $!"; |
594 |
|
595 |
AnyEvent::Util::fh_nonblocking $fh, 1; |
596 |
|
597 |
my $self = bless { |
598 |
server => [], |
599 |
timeout => [2, 5, 5], |
600 |
search => [], |
601 |
ndots => 1, |
602 |
max_outstanding => 10, |
603 |
reuse => 300, # reuse id's after 5 minutes only, if possible |
604 |
%arg, |
605 |
fh => $fh, |
606 |
reuse_q => [], |
607 |
}, $class; |
608 |
|
609 |
# search should default to gethostname's domain |
610 |
# but perl lacks a good posix module |
611 |
|
612 |
Scalar::Util::weaken (my $wself = $self); |
613 |
$self->{rw} = AnyEvent->io (fh => $fh, poll => "r", cb => sub { $wself->_recv }); |
614 |
|
615 |
$self->_compile; |
616 |
|
617 |
$self |
618 |
} |
619 |
|
620 |
=item $resolver->parse_resolv_conv ($string) |
621 |
|
622 |
Parses the given string as if it were a F<resolv.conf> file. The following |
623 |
directives are supported (but not necessarily implemented). |
624 |
|
625 |
C<#>-style comments, C<nameserver>, C<domain>, C<search>, C<sortlist>, |
626 |
C<options> (C<timeout>, C<attempts>, C<ndots>). |
627 |
|
628 |
Everything else is silently ignored. |
629 |
|
630 |
=cut |
631 |
|
632 |
sub parse_resolv_conf { |
633 |
my ($self, $resolvconf) = @_; |
634 |
|
635 |
$self->{server} = []; |
636 |
$self->{search} = []; |
637 |
|
638 |
my $attempts; |
639 |
|
640 |
for (split /\n/, $resolvconf) { |
641 |
if (/^\s*#/) { |
642 |
# comment |
643 |
} elsif (/^\s*nameserver\s+(\S+)\s*$/i) { |
644 |
my $ip = $1; |
645 |
if (my $ipn = AnyEvent::Socket::parse_address ($ip)) { |
646 |
push @{ $self->{server} }, $ipn; |
647 |
} else { |
648 |
warn "nameserver $ip invalid and ignored\n"; |
649 |
} |
650 |
} elsif (/^\s*domain\s+(\S*)\s+$/i) { |
651 |
$self->{search} = [$1]; |
652 |
} elsif (/^\s*search\s+(.*?)\s*$/i) { |
653 |
$self->{search} = [split /\s+/, $1]; |
654 |
} elsif (/^\s*sortlist\s+(.*?)\s*$/i) { |
655 |
# ignored, NYI |
656 |
} elsif (/^\s*options\s+(.*?)\s*$/i) { |
657 |
for (split /\s+/, $1) { |
658 |
if (/^timeout:(\d+)$/) { |
659 |
$self->{timeout} = [$1]; |
660 |
} elsif (/^attempts:(\d+)$/) { |
661 |
$attempts = $1; |
662 |
} elsif (/^ndots:(\d+)$/) { |
663 |
$self->{ndots} = $1; |
664 |
} else { |
665 |
# debug, rotate, no-check-names, inet6 |
666 |
} |
667 |
} |
668 |
} |
669 |
} |
670 |
|
671 |
$self->{timeout} = [($self->{timeout}[0]) x $attempts] |
672 |
if $attempts; |
673 |
|
674 |
$self->_compile; |
675 |
} |
676 |
|
677 |
=item $resolver->os_config |
678 |
|
679 |
Tries so load and parse F</etc/resolv.conf> on portable operating systems. Tries various |
680 |
egregious hacks on windows to force the DNS servers and searchlist out of the system. |
681 |
|
682 |
=cut |
683 |
|
684 |
sub os_config { |
685 |
my ($self) = @_; |
686 |
|
687 |
$self->{server} = []; |
688 |
$self->{search} = []; |
689 |
|
690 |
if (AnyEvent::WIN32 || $^O =~ /cygwin/i) { |
691 |
no strict 'refs'; |
692 |
|
693 |
# there are many options to find the current nameservers etc. on windows |
694 |
# all of them don't work consistently: |
695 |
# - the registry thing needs separate code on win32 native vs. cygwin |
696 |
# - the registry layout differs between windows versions |
697 |
# - calling windows api functions doesn't work on cygwin |
698 |
# - ipconfig uses locale-specific messages |
699 |
|
700 |
# we use ipconfig parsing because, despite all it's brokenness, |
701 |
# it seems most stable in practise. |
702 |
# for good measure, we append a fallback nameserver to our list. |
703 |
|
704 |
if (open my $fh, "ipconfig /all |") { |
705 |
# parsing strategy: we go through the output and look for |
706 |
# :-lines with DNS in them. everything in those is regarded as |
707 |
# either a nameserver (if it parses as an ip address), or a suffix |
708 |
# (all else). |
709 |
|
710 |
my $dns; |
711 |
while (<$fh>) { |
712 |
if (s/^\s.*\bdns\b.*://i) { |
713 |
$dns = 1; |
714 |
} elsif (/^\S/ || /^\s[^:]{16,}: /) { |
715 |
$dns = 0; |
716 |
} |
717 |
if ($dns && /^\s*(\S+)\s*$/) { |
718 |
my $s = $1; |
719 |
$s =~ s/%\d+(?!\S)//; # get rid of scope id |
720 |
if (my $ipn = AnyEvent::Socket::parse_address ($s)) { |
721 |
push @{ $self->{server} }, $ipn; |
722 |
} else { |
723 |
push @{ $self->{search} }, $s; |
724 |
} |
725 |
} |
726 |
} |
727 |
|
728 |
# always add one fallback server |
729 |
push @{ $self->{server} }, $DNS_FALLBACK[rand @DNS_FALLBACK]; |
730 |
|
731 |
$self->_compile; |
732 |
} |
733 |
} else { |
734 |
# try resolv.conf everywhere |
735 |
|
736 |
if (open my $fh, "</etc/resolv.conf") { |
737 |
local $/; |
738 |
$self->parse_resolv_conf (<$fh>); |
739 |
} |
740 |
} |
741 |
} |
742 |
|
743 |
sub _compile { |
744 |
my $self = shift; |
745 |
|
746 |
# we currently throw away all ipv6 nameservers, we do not yet support those |
747 |
|
748 |
my %search; $self->{search} = [grep 0 < length, grep !$search{$_}++, @{ $self->{search} }]; |
749 |
my %server; $self->{server} = [grep 4 == length, grep !$server{$_}++, @{ $self->{server} }]; |
750 |
|
751 |
unless (@{ $self->{server} }) { |
752 |
# use 127.0.0.1 by default, and one opendns nameserver as fallback |
753 |
$self->{server} = [v127.0.0.1, $DNS_FALLBACK[rand @DNS_FALLBACK]]; |
754 |
} |
755 |
|
756 |
my @retry; |
757 |
|
758 |
for my $timeout (@{ $self->{timeout} }) { |
759 |
for my $server (@{ $self->{server} }) { |
760 |
push @retry, [$server, $timeout]; |
761 |
} |
762 |
} |
763 |
|
764 |
$self->{retry} = \@retry; |
765 |
} |
766 |
|
767 |
sub _feed { |
768 |
my ($self, $res) = @_; |
769 |
|
770 |
$res = dns_unpack $res |
771 |
or return; |
772 |
|
773 |
my $id = $self->{id}{$res->{id}}; |
774 |
|
775 |
return unless ref $id; |
776 |
|
777 |
$NOW = time; |
778 |
$id->[1]->($res); |
779 |
} |
780 |
|
781 |
sub _recv { |
782 |
my ($self) = @_; |
783 |
|
784 |
# we ignore errors (often one gets port unreachable, but there is |
785 |
# no good way to take advantage of that. |
786 |
while (my $peer = recv $self->{fh}, my $res, 4096, 0) { |
787 |
my ($port, $host) = AnyEvent::Socket::unpack_sockaddr ($peer); |
788 |
|
789 |
return unless $port == 53 && grep $_ eq $host, @{ $self->{server} }; |
790 |
|
791 |
$self->_feed ($res); |
792 |
} |
793 |
} |
794 |
|
795 |
sub _free_id { |
796 |
my ($self, $id, $timeout) = @_; |
797 |
|
798 |
if ($timeout) { |
799 |
# we need to block the id for a while |
800 |
$self->{id}{$id} = 1; |
801 |
push @{ $self->{reuse_q} }, [$NOW + $self->{reuse}, $id]; |
802 |
} else { |
803 |
# we can quickly recycle the id |
804 |
delete $self->{id}{$id}; |
805 |
} |
806 |
|
807 |
--$self->{outstanding}; |
808 |
$self->_scheduler; |
809 |
} |
810 |
|
811 |
# execute a single request, involves sending it with timeouts to multiple servers |
812 |
sub _exec { |
813 |
my ($self, $req) = @_; |
814 |
|
815 |
my $retry; # of retries |
816 |
my $do_retry; |
817 |
|
818 |
$do_retry = sub { |
819 |
my $retry_cfg = $self->{retry}[$retry++] |
820 |
or do { |
821 |
# failure |
822 |
$self->_free_id ($req->[2], $retry > 1); |
823 |
undef $do_retry; return $req->[1]->(); |
824 |
}; |
825 |
|
826 |
my ($server, $timeout) = @$retry_cfg; |
827 |
|
828 |
$self->{id}{$req->[2]} = [AnyEvent->timer (after => $timeout, cb => sub { |
829 |
$NOW = time; |
830 |
|
831 |
# timeout, try next |
832 |
&$do_retry; |
833 |
}), sub { |
834 |
my ($res) = @_; |
835 |
|
836 |
if ($res->{tc}) { |
837 |
# success, but truncated, so use tcp |
838 |
AnyEvent::Socket::tcp_connect ((Socket::inet_ntoa $server), 53, sub { |
839 |
my ($fh) = @_ |
840 |
or return &$do_retry; |
841 |
|
842 |
my $handle = new AnyEvent::Handle |
843 |
fh => $fh, |
844 |
on_error => sub { |
845 |
# failure, try next |
846 |
&$do_retry; |
847 |
}; |
848 |
|
849 |
$handle->push_write (pack "n/a", $req->[0]); |
850 |
$handle->push_read (chunk => 2, sub { |
851 |
$handle->unshift_read (chunk => (unpack "n", $_[1]), sub { |
852 |
$self->_feed ($_[1]); |
853 |
}); |
854 |
}); |
855 |
shutdown $fh, 1; |
856 |
|
857 |
}, sub { $timeout }); |
858 |
|
859 |
} else { |
860 |
# success |
861 |
$self->_free_id ($req->[2], $retry > 1); |
862 |
undef $do_retry; return $req->[1]->($res); |
863 |
} |
864 |
}]; |
865 |
|
866 |
send $self->{fh}, $req->[0], 0, AnyEvent::Socket::pack_sockaddr (53, $server); |
867 |
}; |
868 |
|
869 |
&$do_retry; |
870 |
} |
871 |
|
872 |
sub _scheduler { |
873 |
my ($self) = @_; |
874 |
|
875 |
$NOW = time; |
876 |
|
877 |
# first clear id reuse queue |
878 |
delete $self->{id}{ (shift @{ $self->{reuse_q} })->[1] } |
879 |
while @{ $self->{reuse_q} } && $self->{reuse_q}[0][0] <= $NOW; |
880 |
|
881 |
while ($self->{outstanding} < $self->{max_outstanding}) { |
882 |
|
883 |
if (@{ $self->{reuse_q} } >= 30000) { |
884 |
# we ran out of ID's, wait a bit |
885 |
$self->{reuse_to} ||= AnyEvent->timer (after => $self->{reuse_q}[0][0] - $NOW, cb => sub { |
886 |
delete $self->{reuse_to}; |
887 |
$self->_scheduler; |
888 |
}); |
889 |
last; |
890 |
} |
891 |
|
892 |
my $req = shift @{ $self->{queue} } |
893 |
or last; |
894 |
|
895 |
while () { |
896 |
$req->[2] = int rand 65536; |
897 |
last unless exists $self->{id}{$req->[2]}; |
898 |
} |
899 |
|
900 |
++$self->{outstanding}; |
901 |
$self->{id}{$req->[2]} = 1; |
902 |
substr $req->[0], 0, 2, pack "n", $req->[2]; |
903 |
|
904 |
$self->_exec ($req); |
905 |
} |
906 |
} |
907 |
|
908 |
=item $resolver->request ($req, $cb->($res)) |
909 |
|
910 |
Sends a single request (a hash-ref formated as specified for |
911 |
C<dns_pack>) to the configured nameservers including |
912 |
retries. Calls the callback with the decoded response packet if a reply |
913 |
was received, or no arguments on timeout. |
914 |
|
915 |
=cut |
916 |
|
917 |
sub request($$) { |
918 |
my ($self, $req, $cb) = @_; |
919 |
|
920 |
push @{ $self->{queue} }, [dns_pack $req, $cb]; |
921 |
$self->_scheduler; |
922 |
} |
923 |
|
924 |
=item $resolver->resolve ($qname, $qtype, %options, $cb->($rcode, @rr)) |
925 |
|
926 |
Queries the DNS for the given domain name C<$qname> of type C<$qtype> (a |
927 |
qtype of "*" is supported and means "any"). |
928 |
|
929 |
The callback will be invoked with a list of matching result records or |
930 |
none on any error or if the name could not be found. |
931 |
|
932 |
CNAME chains (although illegal) are followed up to a length of 8. |
933 |
|
934 |
Note that this resolver is just a stub resolver: it requires a name server |
935 |
supporting recursive queries, will not do any recursive queries itself and |
936 |
is not secure when used against an untrusted name server. |
937 |
|
938 |
The following options are supported: |
939 |
|
940 |
=over 4 |
941 |
|
942 |
=item search => [$suffix...] |
943 |
|
944 |
Use the given search list (which might be empty), by appending each one |
945 |
in turn to the C<$qname>. If this option is missing then the configured |
946 |
C<ndots> and C<search> define its value. If the C<$qname> ends in a dot, |
947 |
then the searchlist will be ignored. |
948 |
|
949 |
=item accept => [$type...] |
950 |
|
951 |
Lists the acceptable result types: only result types in this set will be |
952 |
accepted and returned. The default includes the C<$qtype> and nothing |
953 |
else. |
954 |
|
955 |
=item class => "class" |
956 |
|
957 |
Specify the query class ("in" for internet, "ch" for chaosnet and "hs" for |
958 |
hesiod are the only ones making sense). The default is "in", of course. |
959 |
|
960 |
=back |
961 |
|
962 |
Examples: |
963 |
|
964 |
$res->resolve ("ruth.plan9.de", "a", sub { |
965 |
warn Dumper [@_]; |
966 |
}); |
967 |
|
968 |
[ |
969 |
[ |
970 |
'ruth.schmorp.de', |
971 |
'a', |
972 |
'in', |
973 |
'129.13.162.95' |
974 |
] |
975 |
] |
976 |
|
977 |
$res->resolve ("test1.laendle", "*", |
978 |
accept => ["a", "aaaa"], |
979 |
sub { |
980 |
warn Dumper [@_]; |
981 |
} |
982 |
); |
983 |
|
984 |
[ |
985 |
[ |
986 |
'test1.laendle', |
987 |
'a', |
988 |
'in', |
989 |
'10.0.0.255' |
990 |
], |
991 |
[ |
992 |
'test1.laendle', |
993 |
'aaaa', |
994 |
'in', |
995 |
'3ffe:1900:4545:0002:0240:0000:0000:f7e1' |
996 |
] |
997 |
] |
998 |
|
999 |
=cut |
1000 |
|
1001 |
sub resolve($%) { |
1002 |
my $cb = pop; |
1003 |
my ($self, $qname, $qtype, %opt) = @_; |
1004 |
|
1005 |
my @search = $qname =~ s/\.$// |
1006 |
? "" |
1007 |
: $opt{search} |
1008 |
? @{ $opt{search} } |
1009 |
: ($qname =~ y/.//) >= $self->{ndots} |
1010 |
? ("", @{ $self->{search} }) |
1011 |
: (@{ $self->{search} }, ""); |
1012 |
|
1013 |
my $class = $opt{class} || "in"; |
1014 |
|
1015 |
my %atype = $opt{accept} |
1016 |
? map +($_ => 1), @{ $opt{accept} } |
1017 |
: ($qtype => 1); |
1018 |
|
1019 |
# advance in searchlist |
1020 |
my ($do_search, $do_req); |
1021 |
|
1022 |
$do_search = sub { |
1023 |
@search |
1024 |
or (undef $do_search), (undef $do_req), return $cb->(); |
1025 |
|
1026 |
(my $name = lc "$qname." . shift @search) =~ s/\.$//; |
1027 |
my $depth = 2; |
1028 |
|
1029 |
# advance in cname-chain |
1030 |
$do_req = sub { |
1031 |
$self->request ({ |
1032 |
rd => 1, |
1033 |
qd => [[$name, $qtype, $class]], |
1034 |
}, sub { |
1035 |
my ($res) = @_ |
1036 |
or return $do_search->(); |
1037 |
|
1038 |
my $cname; |
1039 |
|
1040 |
while () { |
1041 |
# results found? |
1042 |
my @rr = grep $name eq lc $_->[0] && ($atype{"*"} || $atype{$_->[1]}), @{ $res->{an} }; |
1043 |
|
1044 |
(undef $do_search), (undef $do_req), return $cb->(@rr) |
1045 |
if @rr; |
1046 |
|
1047 |
# see if there is a cname we can follow |
1048 |
my @rr = grep $name eq lc $_->[0] && $_->[1] eq "cname", @{ $res->{an} }; |
1049 |
|
1050 |
if (@rr) { |
1051 |
$depth-- |
1052 |
or return $do_search->(); # cname chain too long |
1053 |
|
1054 |
$cname = 1; |
1055 |
$name = $rr[0][3]; |
1056 |
|
1057 |
} elsif ($cname) { |
1058 |
# follow the cname |
1059 |
return $do_req->(); |
1060 |
|
1061 |
} else { |
1062 |
# no, not found anything |
1063 |
return $do_search->(); |
1064 |
} |
1065 |
} |
1066 |
}); |
1067 |
}; |
1068 |
|
1069 |
$do_req->(); |
1070 |
}; |
1071 |
|
1072 |
$do_search->(); |
1073 |
} |
1074 |
|
1075 |
use AnyEvent::Socket (); # circular dependency, so do not import anything and do it at the end |
1076 |
|
1077 |
1; |
1078 |
|
1079 |
=back |
1080 |
|
1081 |
=head1 AUTHOR |
1082 |
|
1083 |
Marc Lehmann <schmorp@schmorp.de> |
1084 |
http://home.schmorp.de/ |
1085 |
|
1086 |
=cut |
1087 |
|