net/dns.lua

   1 -- Prosody IM
   2 -- This file is included with Prosody IM. It has modifications,
   3 -- which are hereby placed in the public domain.
   4
   5
   6 -- todo: quick (default) header generation
   7 -- todo: nxdomain, error handling
   8 -- todo: cache results of encodeName
   9
  10
  11 -- reference: http://tools.ietf.org/html/rfc1035
  12 -- reference: http://tools.ietf.org/html/rfc1876 (LOC)
  13
  14
  15 local socket = require "socket";
  16 local timer = require "util.timer";
  17
  18 local _, windows = pcall(require, "util.windows");
  19 local is_windows = (_ and windows) or os.getenv("WINDIR");
  20
  21 local coroutine, io, math, string, table =
  22       coroutine, io, math, string, table;
  23
  24 local ipairs, next, pairs, print, setmetatable, tostring, assert, error, unpack, select =
  25       ipairs, next, pairs, print, setmetatable, tostring, assert, error, unpack, select;
  26
  27 local ztact = { -- public domain 20080404 lua@ztact.com
  28         get = function(parent, ...)
  29                 local len = select('#', ...);
  30                 for i=1,len do
  31                         parent = parent[select(i, ...)];
  32                         if parent == nil then break; end
  33                 end
  34                 return parent;
  35         end;
  36         set = function(parent, ...)
  37                 local len = select('#', ...);
  38                 local key, value = select(len-1, ...);
  39                 local cutpoint, cutkey;
  40
  41                 for i=1,len-2 do
  42                         local key = select (i, ...)
  43                         local child = parent[key]
  44
  45                         if value == nil then
  46                                 if child == nil then
  47                                         return;
  48                                 elseif next(child, next(child)) then
  49                                         cutpoint = nil; cutkey = nil;
  50                                 elseif cutpoint == nil then
  51                                         cutpoint = parent; cutkey = key;
  52                                 end
  53                         elseif child == nil then
  54                                 child = {};
  55                                 parent[key] = child;
  56                         end
  57                         parent = child
  58                 end
  59
  60                 if value == nil and cutpoint then
  61                         cutpoint[cutkey] = nil;
  62                 else
  63                         parent[key] = value;
  64                         return value;
  65                 end
  66         end;
  67 };
  68 local get, set = ztact.get, ztact.set;
  69
  70 local default_timeout = 15;
  71
  72 -------------------------------------------------- module dns
  73 module('dns')
  74 local dns = _M;
  75
  76
  77 -- dns type & class codes ------------------------------ dns type & class codes
  78
  79
  80 local append = table.insert
  81
  82
  83 local function highbyte(i)    -- - - - - - - - - - - - - - - - - - -  highbyte
  84         return (i-(i%0x100))/0x100;
  85 end
  86
  87
  88 local function augment (t)    -- - - - - - - - - - - - - - - - - - - -  augment
  89         local a = {};
  90         for i,s in pairs(t) do
  91                 a[i] = s;
  92                 a[s] = s;
  93                 a[string.lower(s)] = s;
  94         end
  95         return a;
  96 end
  97
  98
  99 local function encode (t)    -- - - - - - - - - - - - - - - - - - - - -  encode
 100         local code = {};
 101         for i,s in pairs(t) do
 102                 local word = string.char(highbyte(i), i%0x100);
 103                 code[i] = word;
 104                 code[s] = word;
 105                 code[string.lower(s)] = word;
 106         end
 107         return code;
 108 end
 109
 110
 111 dns.types = {
 112         'A', 'NS', 'MD', 'MF', 'CNAME', 'SOA', 'MB', 'MG', 'MR', 'NULL', 'WKS',
 113         'PTR', 'HINFO', 'MINFO', 'MX', 'TXT',
 114         [ 28] = 'AAAA', [ 29] = 'LOC',   [ 33] = 'SRV',
 115         [252] = 'AXFR', [253] = 'MAILB', [254] = 'MAILA', [255] = '*' };
 116
 117
 118 dns.classes = { 'IN', 'CS', 'CH', 'HS', [255] = '*' };
 119
 120
 121 dns.type      = augment (dns.types);
 122 dns.class     = augment (dns.classes);
 123 dns.typecode  = encode  (dns.types);
 124 dns.classcode = encode  (dns.classes);
 125
 126
 127
 128 local function standardize(qname, qtype, qclass)    -- - - - - - - standardize
 129         if string.byte(qname, -1) ~= 0x2E then qname = qname..'.';  end
 130         qname = string.lower(qname);
 131         return qname, dns.type[qtype or 'A'], dns.class[qclass or 'IN'];
 132 end
 133
 134
 135 local function prune(rrs, time, soft)    -- - - - - - - - - - - - - - -  prune
 136         time = time or socket.gettime();
 137         for i,rr in pairs(rrs) do
 138                 if rr.tod then
 139                         -- rr.tod = rr.tod - 50    -- accelerated decripitude
 140                         rr.ttl = math.floor(rr.tod - time);
 141                         if rr.ttl <= 0 then
 142                                 table.remove(rrs, i);
 143                                 return prune(rrs, time, soft); -- Re-iterate
 144                         end
 145                 elseif soft == 'soft' then    -- What is this?  I forget!
 146                         assert(rr.ttl == 0);
 147                         rrs[i] = nil;
 148                 end
 149         end
 150 end
 151
 152
 153 -- metatables & co. ------------------------------------------ metatables & co.
 154
 155
 156 local resolver = {};
 157 resolver.__index = resolver;
 158
 159 resolver.timeout = default_timeout;
 160
 161 local SRV_tostring;
 162
 163
 164 local rr_metatable = {};   -- - - - - - - - - - - - - - - - - - -  rr_metatable
 165 function rr_metatable.__tostring(rr)
 166         local s0 = string.format('%2s %-5s %6i %-28s', rr.class, rr.type, rr.ttl, rr.name);
 167         local s1 = '';
 168         if rr.type == 'A' then
 169                 s1 = ' '..rr.a;
 170         elseif rr.type == 'MX' then
 171                 s1 = string.format(' %2i %s', rr.pref, rr.mx);
 172         elseif rr.type == 'CNAME' then
 173                 s1 = ' '..rr.cname;
 174         elseif rr.type == 'LOC' then
 175                 s1 = ' '..resolver.LOC_tostring(rr);
 176         elseif rr.type == 'NS' then
 177                 s1 = ' '..rr.ns;
 178         elseif rr.type == 'SRV' then
 179                 s1 = ' '..SRV_tostring(rr);
 180         elseif rr.type == 'TXT' then
 181                 s1 = ' '..rr.txt;
 182         else
 183                 s1 = ' <UNKNOWN RDATA TYPE>';
 184         end
 185         return s0..s1;
 186 end
 187
 188
 189 local rrs_metatable = {};    -- - - - - - - - - - - - - - - - - -  rrs_metatable
 190 function rrs_metatable.__tostring(rrs)
 191         local t = {};
 192         for i,rr in pairs(rrs) do
 193                 append(t, tostring(rr)..'\n');
 194         end
 195         return table.concat(t);
 196 end
 197
 198
 199 local cache_metatable = {};    -- - - - - - - - - - - - - - - -  cache_metatable
 200 function cache_metatable.__tostring(cache)
 201         local time = socket.gettime();
 202         local t = {};
 203         for class,types in pairs(cache) do
 204                 for type,names in pairs(types) do
 205                         for name,rrs in pairs(names) do
 206                                 prune(rrs, time);
 207                                 append(t, tostring(rrs));
 208                         end
 209                 end
 210         end
 211         return table.concat(t);
 212 end
 213
 214
 215 function resolver:new()    -- - - - - - - - - - - - - - - - - - - - - resolver
 216         local r = { active = {}, cache = {}, unsorted = {} };
 217         setmetatable(r, resolver);
 218         setmetatable(r.cache, cache_metatable);
 219         setmetatable(r.unsorted, { __mode = 'kv' });
 220         return r;
 221 end
 222
 223
 224 -- packet layer -------------------------------------------------- packet layer
 225
 226
 227 function dns.random(...)    -- - - - - - - - - - - - - - - - - - -  dns.random
 228         math.randomseed(math.floor(10000*socket.gettime()));
 229         dns.random = math.random;
 230         return dns.random(...);
 231 end
 232
 233
 234 local function encodeHeader(o)    -- - - - - - - - - - - - - - -  encodeHeader
 235         o = o or {};
 236         o.id = o.id or dns.random(0, 0xffff); -- 16b    (random) id
 237
 238         o.rd = o.rd or 1;               --  1b  1 recursion desired
 239         o.tc = o.tc or 0;               --  1b  1 truncated response
 240         o.aa = o.aa or 0;               --  1b  1 authoritative response
 241         o.opcode = o.opcode or 0;       --  4b  0 query
 242                                 --  1 inverse query
 243                                 --      2 server status request
 244                                 --      3-15 reserved
 245         o.qr = o.qr or 0;               --  1b  0 query, 1 response
 246
 247         o.rcode = o.rcode or 0; --  4b  0 no error
 248                                 --      1 format error
 249                                 --      2 server failure
 250                                 --      3 name error
 251                                 --      4 not implemented
 252                                 --      5 refused
 253                                 --      6-15 reserved
 254         o.z = o.z  or 0;                --  3b  0 resvered
 255         o.ra = o.ra or 0;               --  1b  1 recursion available
 256
 257         o.qdcount = o.qdcount or 1;     -- 16b  number of question RRs
 258         o.ancount = o.ancount or 0;     -- 16b  number of answers RRs
 259         o.nscount = o.nscount or 0;     -- 16b  number of nameservers RRs
 260         o.arcount = o.arcount or 0;     -- 16b  number of additional RRs
 261
 262         -- string.char() rounds, so prevent roundup with -0.4999
 263         local header = string.char(
 264                 highbyte(o.id), o.id %0x100,
 265                 o.rd + 2*o.tc + 4*o.aa + 8*o.opcode + 128*o.qr,
 266                 o.rcode + 16*o.z + 128*o.ra,
 267                 highbyte(o.qdcount),  o.qdcount %0x100,
 268                 highbyte(o.ancount),  o.ancount %0x100,
 269                 highbyte(o.nscount),  o.nscount %0x100,
 270                 highbyte(o.arcount),  o.arcount %0x100
 271         );
 272
 273         return header, o.id;
 274 end
 275
 276
 277 local function encodeName(name)    -- - - - - - - - - - - - - - - - encodeName
 278         local t = {};
 279         for part in string.gmatch(name, '[^.]+') do
 280                 append(t, string.char(string.len(part)));
 281                 append(t, part);
 282         end
 283         append(t, string.char(0));
 284         return table.concat(t);
 285 end
 286
 287
 288 local function encodeQuestion(qname, qtype, qclass)    -- - - - encodeQuestion
 289         qname  = encodeName(qname);
 290         qtype  = dns.typecode[qtype or 'a'];
 291         qclass = dns.classcode[qclass or 'in'];
 292         return qname..qtype..qclass;
 293 end
 294
 295
 296 function resolver:byte(len)    -- - - - - - - - - - - - - - - - - - - - - byte
 297         len = len or 1;
 298         local offset = self.offset;
 299         local last = offset + len - 1;
 300         if last > #self.packet then
 301                 error(string.format('out of bounds: %i>%i', last, #self.packet));
 302         end
 303         self.offset = offset + len;
 304         return string.byte(self.packet, offset, last);
 305 end
 306
 307
 308 function resolver:word()    -- - - - - - - - - - - - - - - - - - - - - -  word
 309         local b1, b2 = self:byte(2);
 310         return 0x100*b1 + b2;
 311 end
 312
 313
 314 function resolver:dword ()    -- - - - - - - - - - - - - - - - - - - - -  dword
 315         local b1, b2, b3, b4 = self:byte(4);
 316         --print('dword', b1, b2, b3, b4);
 317         return 0x1000000*b1 + 0x10000*b2 + 0x100*b3 + b4;
 318 end
 319
 320
 321 function resolver:sub(len)    -- - - - - - - - - - - - - - - - - - - - - - sub
 322         len = len or 1;
 323         local s = string.sub(self.packet, self.offset, self.offset + len - 1);
 324         self.offset = self.offset + len;
 325         return s;
 326 end
 327
 328
 329 function resolver:header(force)    -- - - - - - - - - - - - - - - - - - header
 330         local id = self:word();
 331         --print(string.format(':header  id  %x', id));
 332         if not self.active[id] and not force then return nil; end
 333
 334         local h = { id = id };
 335
 336         local b1, b2 = self:byte(2);
 337
 338         h.rd      = b1 %2;
 339         h.tc      = b1 /2%2;
 340         h.aa      = b1 /4%2;
 341         h.opcode  = b1 /8%16;
 342         h.qr      = b1 /128;
 343
 344         h.rcode   = b2 %16;
 345         h.z       = b2 /16%8;
 346         h.ra      = b2 /128;
 347
 348         h.qdcount = self:word();
 349         h.ancount = self:word();
 350         h.nscount = self:word();
 351         h.arcount = self:word();
 352
 353         for k,v in pairs(h) do h[k] = v-v%1; end
 354
 355         return h;
 356 end
 357
 358
 359 function resolver:name()    -- - - - - - - - - - - - - - - - - - - - - -  name
 360         local remember, pointers = nil, 0;
 361         local len = self:byte();
 362         local n = {};
 363         while len > 0 do
 364                 if len >= 0xc0 then    -- name is "compressed"
 365                         pointers = pointers + 1;
 366                         if pointers >= 20 then error('dns error: 20 pointers'); end;
 367                         local offset = ((len-0xc0)*0x100) + self:byte();
 368                         remember = remember or self.offset;
 369                         self.offset = offset + 1;    -- +1 for lua
 370                 else    -- name is not compressed
 371                         append(n, self:sub(len)..'.');
 372                 end
 373                 len = self:byte();
 374         end
 375         self.offset = remember or self.offset;
 376         return table.concat(n);
 377 end
 378
 379
 380 function resolver:question()    -- - - - - - - - - - - - - - - - - -  question
 381         local q = {};
 382         q.name  = self:name();
 383         q.type  = dns.type[self:word()];
 384         q.class = dns.class[self:word()];
 385         return q;
 386 end
 387
 388
 389 function resolver:A(rr)    -- - - - - - - - - - - - - - - - - - - - - - - -  A
 390         local b1, b2, b3, b4 = self:byte(4);
 391         rr.a = string.format('%i.%i.%i.%i', b1, b2, b3, b4);
 392 end
 393
 394
 395 function resolver:CNAME(rr)    -- - - - - - - - - - - - - - - - - - - -  CNAME
 396         rr.cname = self:name();
 397 end
 398
 399
 400 function resolver:MX(rr)    -- - - - - - - - - - - - - - - - - - - - - - -  MX
 401         rr.pref = self:word();
 402         rr.mx   = self:name();
 403 end
 404
 405
 406 function resolver:LOC_nibble_power()    -- - - - - - - - - -  LOC_nibble_power
 407         local b = self:byte();
 408         --print('nibbles', ((b-(b%0x10))/0x10), (b%0x10));
 409         return ((b-(b%0x10))/0x10) * (10^(b%0x10));
 410 end
 411
 412
 413 function resolver:LOC(rr)    -- - - - - - - - - - - - - - - - - - - - - -  LOC
 414         rr.version = self:byte();
 415         if rr.version == 0 then
 416                 rr.loc           = rr.loc or {};
 417                 rr.loc.size      = self:LOC_nibble_power();
 418                 rr.loc.horiz_pre = self:LOC_nibble_power();
 419                 rr.loc.vert_pre  = self:LOC_nibble_power();
 420                 rr.loc.latitude  = self:dword();
 421                 rr.loc.longitude = self:dword();
 422                 rr.loc.altitude  = self:dword();
 423         end
 424 end
 425
 426
 427 local function LOC_tostring_degrees(f, pos, neg)    -- - - - - - - - - - - - -
 428         f = f - 0x80000000;
 429         if f < 0 then pos = neg; f = -f; end
 430         local deg, min, msec;
 431         msec = f%60000;
 432         f    = (f-msec)/60000;
 433         min  = f%60;
 434         deg = (f-min)/60;
 435         return string.format('%3d %2d %2.3f %s', deg, min, msec/1000, pos);
 436 end
 437
 438
 439 function resolver.LOC_tostring(rr)    -- - - - - - - - - - - - -  LOC_tostring
 440         local t = {};
 441
 442         --[[
 443         for k,name in pairs { 'size', 'horiz_pre', 'vert_pre', 'latitude', 'longitude', 'altitude' } do
 444                 append(t, string.format('%4s%-10s: %12.0f\n', '', name, rr.loc[name]));
 445         end
 446         --]]
 447
 448         append(t, string.format(
 449                 '%s    %s    %.2fm %.2fm %.2fm %.2fm',
 450                 LOC_tostring_degrees (rr.loc.latitude, 'N', 'S'),
 451                 LOC_tostring_degrees (rr.loc.longitude, 'E', 'W'),
 452                 (rr.loc.altitude - 10000000) / 100,
 453                 rr.loc.size / 100,
 454                 rr.loc.horiz_pre / 100,
 455                 rr.loc.vert_pre / 100
 456         ));
 457
 458         return table.concat(t);
 459 end
 460
 461
 462 function resolver:NS(rr)    -- - - - - - - - - - - - - - - - - - - - - - -  NS
 463         rr.ns = self:name();
 464 end
 465
 466
 467 function resolver:SOA(rr)    -- - - - - - - - - - - - - - - - - - - - - -  SOA
 468 end
 469
 470
 471 function resolver:SRV(rr)    -- - - - - - - - - - - - - - - - - - - - - -  SRV
 472           rr.srv = {};
 473           rr.srv.priority = self:word();
 474           rr.srv.weight   = self:word();
 475           rr.srv.port     = self:word();
 476           rr.srv.target   = self:name();
 477 end
 478
 479 function resolver:PTR(rr)
 480         rr.ptr = self:name();
 481 end
 482
 483 function SRV_tostring(rr)    -- - - - - - - - - - - - - - - - - - SRV_tostring
 484         local s = rr.srv;
 485         return string.format( '%5d %5d %5d %s', s.priority, s.weight, s.port, s.target );
 486 end
 487
 488
 489 function resolver:TXT(rr)    -- - - - - - - - - - - - - - - - - - - - - -  TXT
 490         rr.txt = self:sub (rr.rdlength);
 491 end
 492
 493
 494 function resolver:rr()    -- - - - - - - - - - - - - - - - - - - - - - - -  rr
 495         local rr = {};
 496         setmetatable(rr, rr_metatable);
 497         rr.name     = self:name(self);
 498         rr.type     = dns.type[self:word()] or rr.type;
 499         rr.class    = dns.class[self:word()] or rr.class;
 500         rr.ttl      = 0x10000*self:word() + self:word();
 501         rr.rdlength = self:word();
 502
 503         if rr.ttl <= 0 then
 504                 rr.tod = self.time + 30;
 505         else
 506                 rr.tod = self.time + rr.ttl;
 507         end
 508
 509         local remember = self.offset;
 510         local rr_parser = self[dns.type[rr.type]];
 511         if rr_parser then rr_parser(self, rr); end
 512         self.offset = remember;
 513         rr.rdata = self:sub(rr.rdlength);
 514         return rr;
 515 end
 516
 517
 518 function resolver:rrs (count)    -- - - - - - - - - - - - - - - - - - - - - rrs
 519         local rrs = {};
 520         for i = 1,count do append(rrs, self:rr()); end
 521         return rrs;
 522 end
 523
 524
 525 function resolver:decode(packet, force)    -- - - - - - - - - - - - - - decode
 526         self.packet, self.offset = packet, 1;
 527         local header = self:header(force);
 528         if not header then return nil; end
 529         local response = { header = header };
 530
 531         response.question = {};
 532         local offset = self.offset;
 533         for i = 1,response.header.qdcount do
 534                 append(response.question, self:question());
 535         end
 536         response.question.raw = string.sub(self.packet, offset, self.offset - 1);
 537
 538         if not force then
 539                 if not self.active[response.header.id] or not self.active[response.header.id][response.question.raw] then
 540                         return nil;
 541                 end
 542         end
 543
 544         response.answer     = self:rrs(response.header.ancount);
 545         response.authority  = self:rrs(response.header.nscount);
 546         response.additional = self:rrs(response.header.arcount);
 547
 548         return response;
 549 end
 550
 551
 552 -- socket layer -------------------------------------------------- socket layer
 553
 554
 555 resolver.delays = { 1, 3 };
 556
 557
 558 function resolver:addnameserver(address)    -- - - - - - - - - - addnameserver
 559         self.server = self.server or {};
 560         append(self.server, address);
 561 end
 562
 563
 564 function resolver:setnameserver(address)    -- - - - - - - - - - setnameserver
 565         self.server = {};
 566         self:addnameserver(address);
 567 end
 568
 569
 570 function resolver:adddefaultnameservers()    -- - - - -  adddefaultnameservers
 571         if is_windows then
 572                 if windows and windows.get_nameservers then
 573                         for _, server in ipairs(windows.get_nameservers()) do
 574                                 self:addnameserver(server);
 575                         end
 576                 end
 577                 if not self.server or #self.server == 0 then
 578                         -- TODO log warning about no nameservers, adding opendns servers as fallback
 579                         self:addnameserver("208.67.222.222");
 580                         self:addnameserver("208.67.220.220");
 581                 end
 582         else -- posix
 583                 local resolv_conf = io.open("/etc/resolv.conf");
 584                 if resolv_conf then
 585                         for line in resolv_conf:lines() do
 586                                 line = line:gsub("#.*$", "")
 587                                         :match('^%s*nameserver%s+(.*)%s*$');
 588                                 if line then
 589                                         line:gsub("%f[%d.](%d+%.%d+%.%d+%.%d+)%f[^%d.]", function (address)
 590                                                 self:addnameserver(address)
 591                                         end);
 592                                 end
 593                         end
 594                 end
 595                 if not self.server or #self.server == 0 then
 596                         -- TODO log warning about no nameservers, adding localhost as the default nameserver
 597                         self:addnameserver("127.0.0.1");
 598                 end
 599         end
 600 end
 601
 602
 603 function resolver:getsocket(servernum)    -- - - - - - - - - - - - - getsocket
 604         self.socket = self.socket or {};
 605         self.socketset = self.socketset or {};
 606
 607         local sock = self.socket[servernum];
 608         if sock then return sock; end
 609
 610         sock = socket.udp();
 611         if self.socket_wrapper then sock = self.socket_wrapper(sock, self); end
 612         sock:settimeout(0);
 613         -- todo: attempt to use a random port, fallback to 0
 614         sock:setsockname('*', 0);
 615         sock:setpeername(self.server[servernum], 53);
 616         self.socket[servernum] = sock;
 617         self.socketset[sock] = servernum;
 618         return sock;
 619 end
 620
 621 function resolver:voidsocket(sock)
 622         if self.socket[sock] then
 623                 self.socketset[self.socket[sock]] = nil;
 624                 self.socket[sock] = nil;
 625         elseif self.socketset[sock] then
 626                 self.socket[self.socketset[sock]] = nil;
 627                 self.socketset[sock] = nil;
 628         end
 629 end
 630
 631 function resolver:socket_wrapper_set(func)  -- - - - - - - socket_wrapper_set
 632         self.socket_wrapper = func;
 633 end
 634
 635
 636 function resolver:closeall ()    -- - - - - - - - - - - - - - - - - -  closeall
 637         for i,sock in ipairs(self.socket) do
 638                 self.socket[i] = nil;
 639                 self.socketset[sock] = nil;
 640                 sock:close();
 641         end
 642 end
 643
 644
 645 function resolver:remember(rr, type)    -- - - - - - - - - - - - - -  remember
 646         --print ('remember', type, rr.class, rr.type, rr.name)
 647         local qname, qtype, qclass = standardize(rr.name, rr.type, rr.class);
 648
 649         if type ~= '*' then
 650                 type = qtype;
 651                 local all = get(self.cache, qclass, '*', qname);
 652                 --print('remember all', all);
 653                 if all then append(all, rr); end
 654         end
 655
 656         self.cache = self.cache or setmetatable({}, cache_metatable);
 657         local rrs = get(self.cache, qclass, type, qname) or
 658                 set(self.cache, qclass, type, qname, setmetatable({}, rrs_metatable));
 659         append(rrs, rr);
 660
 661         if type == 'MX' then self.unsorted[rrs] = true; end
 662 end
 663
 664
 665 local function comp_mx(a, b)    -- - - - - - - - - - - - - - - - - - - comp_mx
 666         return (a.pref == b.pref) and (a.mx < b.mx) or (a.pref < b.pref);
 667 end
 668
 669
 670 function resolver:peek (qname, qtype, qclass)    -- - - - - - - - - - - -  peek
 671         qname, qtype, qclass = standardize(qname, qtype, qclass);
 672         local rrs = get(self.cache, qclass, qtype, qname);
 673         if not rrs then return nil; end
 674         if prune(rrs, socket.gettime()) and qtype == '*' or not next(rrs) then
 675                 set(self.cache, qclass, qtype, qname, nil);
 676                 return nil;
 677         end
 678         if self.unsorted[rrs] then table.sort (rrs, comp_mx); end
 679         return rrs;
 680 end
 681
 682
 683 function resolver:purge(soft)    -- - - - - - - - - - - - - - - - - - -  purge
 684         if soft == 'soft' then
 685                 self.time = socket.gettime();
 686                 for class,types in pairs(self.cache or {}) do
 687                         for type,names in pairs(types) do
 688                                 for name,rrs in pairs(names) do
 689                                         prune(rrs, self.time, 'soft')
 690                                 end
 691                         end
 692                 end
 693         else self.cache = {}; end
 694 end
 695
 696
 697 function resolver:query(qname, qtype, qclass)    -- - - - - - - - - - -- query
 698         qname, qtype, qclass = standardize(qname, qtype, qclass)
 699
 700         if not self.server then self:adddefaultnameservers(); end
 701
 702         local question = encodeQuestion(qname, qtype, qclass);
 703         local peek = self:peek (qname, qtype, qclass);
 704         if peek then return peek; end
 705
 706         local header, id = encodeHeader();
 707         --print ('query  id', id, qclass, qtype, qname)
 708         local o = {
 709                 packet = header..question,
 710                 server = self.best_server,
 711                 delay  = 1,
 712                 retry  = socket.gettime() + self.delays[1]
 713         };
 714
 715         -- remember the query
 716         self.active[id] = self.active[id] or {};
 717         self.active[id][question] = o;
 718
 719         -- remember which coroutine wants the answer
 720         local co = coroutine.running();
 721         if co then
 722                 set(self.wanted, qclass, qtype, qname, co, true);
 723                 --set(self.yielded, co, qclass, qtype, qname, true);
 724         end
 725
 726         local conn = self:getsocket(o.server)
 727         conn:send (o.packet)
 728
 729         if timer and self.timeout then
 730                 local num_servers = #self.server;
 731                 local i = 1;
 732                 timer.add_task(self.timeout, function ()
 733                         if get(self.wanted, qclass, qtype, qname, co) then
 734                                 if i < num_servers then
 735                                         i = i + 1;
 736                                         self:servfail(conn);
 737                                         o.server = self.best_server;
 738                                         conn = self:getsocket(o.server);
 739                                         conn:send(o.packet);
 740                                         return self.timeout;
 741                                 else
 742                                         -- Tried everything, failed
 743                                         self:cancel(qclass, qtype, qname, co, true);
 744                                 end
 745                         end
 746                 end)
 747         end
 748 end
 749
 750 function resolver:servfail(sock)
 751         -- Resend all queries for this server
 752
 753         local num = self.socketset[sock]
 754
 755         -- Socket is dead now
 756         self:voidsocket(sock);
 757
 758         -- Find all requests to the down server, and retry on the next server
 759         self.time = socket.gettime();
 760         for id,queries in pairs(self.active) do
 761                 for question,o in pairs(queries) do
 762                         if o.server == num then -- This request was to the broken server
 763                                 o.server = o.server + 1 -- Use next server
 764                                 if o.server > #self.server then
 765                                         o.server = 1;
 766                                 end
 767
 768                                 o.retries = (o.retries or 0) + 1;
 769                                 if o.retries >= #self.server then
 770                                         --print('timeout');
 771                                         queries[question] = nil;
 772                                 else
 773                                         local _a = self:getsocket(o.server);
 774                                         if _a then _a:send(o.packet); end
 775                                 end
 776                         end
 777                 end
 778         end
 779
 780         if num == self.best_server then
 781                 self.best_server = self.best_server + 1;
 782                 if self.best_server > #self.server then
 783                         -- Exhausted all servers, try first again
 784                         self.best_server = 1;
 785                 end
 786         end
 787 end
 788
 789 function resolver:settimeout(seconds)
 790         self.timeout = seconds;
 791 end
 792
 793 function resolver:receive(rset)    -- - - - - - - - - - - - - - - - -  receive
 794         --print('receive');  print(self.socket);
 795         self.time = socket.gettime();
 796         rset = rset or self.socket;
 797
 798         local response;
 799         for i,sock in pairs(rset) do
 800
 801                 if self.socketset[sock] then
 802                         local packet = sock:receive();
 803                         if packet then
 804                                 response = self:decode(packet);
 805                                 if response and self.active[response.header.id]
 806                                         and self.active[response.header.id][response.question.raw] then
 807                                         --print('received response');
 808                                         --self.print(response);
 809
 810                                         for j,rr in pairs(response.answer) do
 811                                                 if rr.name:sub(-#response.question[1].name, -1) == response.question[1].name then
 812                                                         self:remember(rr, response.question[1].type)
 813                                                 end
 814                                         end
 815
 816                                         -- retire the query
 817                                         local queries = self.active[response.header.id];
 818                                         queries[response.question.raw] = nil;
 819
 820                                         if not next(queries) then self.active[response.header.id] = nil; end
 821                                         if not next(self.active) then self:closeall(); end
 822
 823                                         -- was the query on the wanted list?
 824                                         local q = response.question[1];
 825                                         local cos = get(self.wanted, q.class, q.type, q.name);
 826                                         if cos then
 827                                                 for co in pairs(cos) do
 828                                                         set(self.yielded, co, q.class, q.type, q.name, nil);
 829                                                         if coroutine.status(co) == "suspended" then coroutine.resume(co); end
 830                                                 end
 831                                                 set(self.wanted, q.class, q.type, q.name, nil);
 832                                         end
 833                                 end
 834                         end
 835                 end
 836         end
 837
 838         return response;
 839 end
 840
 841
 842 function resolver:feed(sock, packet, force)
 843         --print('receive'); print(self.socket);
 844         self.time = socket.gettime();
 845
 846         local response = self:decode(packet, force);
 847         if response and self.active[response.header.id]
 848                 and self.active[response.header.id][response.question.raw] then
 849                 --print('received response');
 850                 --self.print(response);
 851
 852                 for j,rr in pairs(response.answer) do
 853                         self:remember(rr, response.question[1].type);
 854                 end
 855
 856                 -- retire the query
 857                 local queries = self.active[response.header.id];
 858                 queries[response.question.raw] = nil;
 859                 if not next(queries) then self.active[response.header.id] = nil; end
 860                 if not next(self.active) then self:closeall(); end
 861
 862                 -- was the query on the wanted list?
 863                 local q = response.question[1];
 864                 if q then
 865                         local cos = get(self.wanted, q.class, q.type, q.name);
 866                         if cos then
 867                                 for co in pairs(cos) do
 868                                         set(self.yielded, co, q.class, q.type, q.name, nil);
 869                                         if coroutine.status(co) == "suspended" then coroutine.resume(co); end
 870                                 end
 871                                 set(self.wanted, q.class, q.type, q.name, nil);
 872                         end
 873                 end
 874         end
 875
 876         return response;
 877 end
 878
 879 function resolver:cancel(qclass, qtype, qname, co, call_handler)
 880         local cos = get(self.wanted, qclass, qtype, qname);
 881         if cos then
 882                 if call_handler then
 883                         coroutine.resume(co);
 884                 end
 885                 cos[co] = nil;
 886         end
 887 end
 888
 889 function resolver:pulse()    -- - - - - - - - - - - - - - - - - - - - -  pulse
 890         --print(':pulse');
 891         while self:receive() do end
 892         if not next(self.active) then return nil; end
 893
 894         self.time = socket.gettime();
 895         for id,queries in pairs(self.active) do
 896                 for question,o in pairs(queries) do
 897                         if self.time >= o.retry then
 898
 899                                 o.server = o.server + 1;
 900                                 if o.server > #self.server then
 901                                         o.server = 1;
 902                                         o.delay = o.delay + 1;
 903                                 end
 904
 905                                 if o.delay > #self.delays then
 906                                         --print('timeout');
 907                                         queries[question] = nil;
 908                                         if not next(queries) then self.active[id] = nil; end
 909                                         if not next(self.active) then return nil; end
 910                                 else
 911                                         --print('retry', o.server, o.delay);
 912                                         local _a = self.socket[o.server];
 913                                         if _a then _a:send(o.packet); end
 914                                         o.retry = self.time + self.delays[o.delay];
 915                                 end
 916                         end
 917                 end
 918         end
 919
 920         if next(self.active) then return true; end
 921         return nil;
 922 end
 923
 924
 925 function resolver:lookup(qname, qtype, qclass)    -- - - - - - - - - -  lookup
 926         self:query (qname, qtype, qclass)
 927         while self:pulse() do
 928                 local recvt = {}
 929                 for i, s in ipairs(self.socket) do
 930                         recvt[i] = s
 931                 end
 932                 socket.select(recvt, nil, 4)
 933         end
 934         --print(self.cache);
 935         return self:peek(qname, qtype, qclass);
 936 end
 937
 938 function resolver:lookupex(handler, qname, qtype, qclass)    -- - - - - - - - - -  lookup
 939         return self:peek(qname, qtype, qclass) or self:query(qname, qtype, qclass);
 940 end
 941
 942
 943 --print ---------------------------------------------------------------- print
 944
 945
 946 local hints = {    -- - - - - - - - - - - - - - - - - - - - - - - - - - - hints
 947         qr = { [0]='query', 'response' },
 948         opcode = { [0]='query', 'inverse query', 'server status request' },
 949         aa = { [0]='non-authoritative', 'authoritative' },
 950         tc = { [0]='complete', 'truncated' },
 951         rd = { [0]='recursion not desired', 'recursion desired' },
 952         ra = { [0]='recursion not available', 'recursion available' },
 953         z  = { [0]='(reserved)' },
 954         rcode = { [0]='no error', 'format error', 'server failure', 'name error', 'not implemented' },
 955
 956         type = dns.type,
 957         class = dns.class
 958 };
 959
 960
 961 local function hint(p, s)    -- - - - - - - - - - - - - - - - - - - - - - hint
 962         return (hints[s] and hints[s][p[s]]) or '';
 963 end
 964
 965
 966 function resolver.print(response)    -- - - - - - - - - - - - - resolver.print
 967         for s,s in pairs { 'id', 'qr', 'opcode', 'aa', 'tc', 'rd', 'ra', 'z',
 968                                                 'rcode', 'qdcount', 'ancount', 'nscount', 'arcount' } do
 969                 print( string.format('%-30s', 'header.'..s), response.header[s], hint(response.header, s) );
 970         end
 971
 972         for i,question in ipairs(response.question) do
 973                 print(string.format ('question[%i].name         ', i), question.name);
 974                 print(string.format ('question[%i].type         ', i), question.type);
 975                 print(string.format ('question[%i].class        ', i), question.class);
 976         end
 977
 978         local common = { name=1, type=1, class=1, ttl=1, rdlength=1, rdata=1 };
 979         local tmp;
 980         for s,s in pairs({'answer', 'authority', 'additional'}) do
 981                 for i,rr in pairs(response[s]) do
 982                         for j,t in pairs({ 'name', 'type', 'class', 'ttl', 'rdlength' }) do
 983                                 tmp = string.format('%s[%i].%s', s, i, t);
 984                                 print(string.format('%-30s', tmp), rr[t], hint(rr, t));
 985                         end
 986                         for j,t in pairs(rr) do
 987                                 if not common[j] then
 988                                         tmp = string.format('%s[%i].%s', s, i, j);
 989                                         print(string.format('%-30s  %s', tostring(tmp), tostring(t)));
 990                                 end
 991                         end
 992                 end
 993         end
 994 end
 995
 996
 997 -- module api ------------------------------------------------------ module api
 998
 999
1000 function dns.resolver ()    -- - - - - - - - - - - - - - - - - - - - - resolver
1001         -- this function seems to be redundant with resolver.new ()
1002
1003         local r = { active = {}, cache = {}, unsorted = {}, wanted = {}, yielded = {}, best_server = 1 };
1004         setmetatable (r, resolver);
1005         setmetatable (r.cache, cache_metatable);
1006         setmetatable (r.unsorted, { __mode = 'kv' });
1007         return r;
1008 end
1009
1010 local _resolver = dns.resolver();
1011 dns._resolver = _resolver;
1012
1013 function dns.lookup(...)    -- - - - - - - - - - - - - - - - - - - - -  lookup
1014         return _resolver:lookup(...);
1015 end
1016
1017 function dns.purge(...)    -- - - - - - - - - - - - - - - - - - - - - -  purge
1018         return _resolver:purge(...);
1019 end
1020
1021 function dns.peek(...)    -- - - - - - - - - - - - - - - - - - - - - - -  peek
1022         return _resolver:peek(...);
1023 end
1024
1025 function dns.query(...)    -- - - - - - - - - - - - - - - - - - - - - -  query
1026         return _resolver:query(...);
1027 end
1028
1029 function dns.feed(...)    -- - - - - - - - - - - - - - - - - - - - - - -  feed
1030         return _resolver:feed(...);
1031 end
1032
1033 function dns.cancel(...)  -- - - - - - - - - - - - - - - - - - - - - -  cancel
1034         return _resolver:cancel(...);
1035 end
1036
1037 function dns.settimeout(...)
1038         return _resolver:settimeout(...);
1039 end
1040
1041 function dns.socket_wrapper_set(...)    -- - - - - - - - -  socket_wrapper_set
1042         return _resolver:socket_wrapper_set(...);
1043 end
1044
1045 return dns;