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, type=
  25       ipairs, next, pairs, print, setmetatable, tostring, assert, error, unpack, select, type;
  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 local function default_rr_tostring(rr)
 164         local rr_val = rr.type and rr[rr.type:lower()];
 165         if type(rr_val) ~= "string" then
 166                 return "<UNKNOWN RDATA TYPE>";
 167         end
 168         return rr_val;
 169 end
 170
 171 local special_tostrings = {
 172         LOC = resolver.LOC_tostring;
 173         MX = function (rr) return string.format('%2i %s', rr.pref, rr.mx); end;
 174         SRV = SRV_tostring;
 175 };
 176
 177 local rr_metatable = {};   -- - - - - - - - - - - - - - - - - - -  rr_metatable
 178 function rr_metatable.__tostring(rr)
 179         local rr_string = (special_tostrings[rr.type] or default_rr_tostring)(rr);
 180         return string.format('%2s %-5s %6i %-28s %s', rr.class, rr.type, rr.ttl, rr.name, rr_string);
 181 end
 182
 183
 184 local rrs_metatable = {};    -- - - - - - - - - - - - - - - - - -  rrs_metatable
 185 function rrs_metatable.__tostring(rrs)
 186         local t = {};
 187         for i,rr in pairs(rrs) do
 188                 append(t, tostring(rr)..'\n');
 189         end
 190         return table.concat(t);
 191 end
 192
 193
 194 local cache_metatable = {};    -- - - - - - - - - - - - - - - -  cache_metatable
 195 function cache_metatable.__tostring(cache)
 196         local time = socket.gettime();
 197         local t = {};
 198         for class,types in pairs(cache) do
 199                 for type,names in pairs(types) do
 200                         for name,rrs in pairs(names) do
 201                                 prune(rrs, time);
 202                                 append(t, tostring(rrs));
 203                         end
 204                 end
 205         end
 206         return table.concat(t);
 207 end
 208
 209
 210 function resolver:new()    -- - - - - - - - - - - - - - - - - - - - - resolver
 211         local r = { active = {}, cache = {}, unsorted = {} };
 212         setmetatable(r, resolver);
 213         setmetatable(r.cache, cache_metatable);
 214         setmetatable(r.unsorted, { __mode = 'kv' });
 215         return r;
 216 end
 217
 218
 219 -- packet layer -------------------------------------------------- packet layer
 220
 221
 222 function dns.random(...)    -- - - - - - - - - - - - - - - - - - -  dns.random
 223         math.randomseed(math.floor(10000*socket.gettime()));
 224         dns.random = math.random;
 225         return dns.random(...);
 226 end
 227
 228
 229 local function encodeHeader(o)    -- - - - - - - - - - - - - - -  encodeHeader
 230         o = o or {};
 231         o.id = o.id or dns.random(0, 0xffff); -- 16b    (random) id
 232
 233         o.rd = o.rd or 1;               --  1b  1 recursion desired
 234         o.tc = o.tc or 0;               --  1b  1 truncated response
 235         o.aa = o.aa or 0;               --  1b  1 authoritative response
 236         o.opcode = o.opcode or 0;       --  4b  0 query
 237                                 --  1 inverse query
 238                                 --      2 server status request
 239                                 --      3-15 reserved
 240         o.qr = o.qr or 0;               --  1b  0 query, 1 response
 241
 242         o.rcode = o.rcode or 0; --  4b  0 no error
 243                                 --      1 format error
 244                                 --      2 server failure
 245                                 --      3 name error
 246                                 --      4 not implemented
 247                                 --      5 refused
 248                                 --      6-15 reserved
 249         o.z = o.z  or 0;                --  3b  0 resvered
 250         o.ra = o.ra or 0;               --  1b  1 recursion available
 251
 252         o.qdcount = o.qdcount or 1;     -- 16b  number of question RRs
 253         o.ancount = o.ancount or 0;     -- 16b  number of answers RRs
 254         o.nscount = o.nscount or 0;     -- 16b  number of nameservers RRs
 255         o.arcount = o.arcount or 0;     -- 16b  number of additional RRs
 256
 257         -- string.char() rounds, so prevent roundup with -0.4999
 258         local header = string.char(
 259                 highbyte(o.id), o.id %0x100,
 260                 o.rd + 2*o.tc + 4*o.aa + 8*o.opcode + 128*o.qr,
 261                 o.rcode + 16*o.z + 128*o.ra,
 262                 highbyte(o.qdcount),  o.qdcount %0x100,
 263                 highbyte(o.ancount),  o.ancount %0x100,
 264                 highbyte(o.nscount),  o.nscount %0x100,
 265                 highbyte(o.arcount),  o.arcount %0x100
 266         );
 267
 268         return header, o.id;
 269 end
 270
 271
 272 local function encodeName(name)    -- - - - - - - - - - - - - - - - encodeName
 273         local t = {};
 274         for part in string.gmatch(name, '[^.]+') do
 275                 append(t, string.char(string.len(part)));
 276                 append(t, part);
 277         end
 278         append(t, string.char(0));
 279         return table.concat(t);
 280 end
 281
 282
 283 local function encodeQuestion(qname, qtype, qclass)    -- - - - encodeQuestion
 284         qname  = encodeName(qname);
 285         qtype  = dns.typecode[qtype or 'a'];
 286         qclass = dns.classcode[qclass or 'in'];
 287         return qname..qtype..qclass;
 288 end
 289
 290
 291 function resolver:byte(len)    -- - - - - - - - - - - - - - - - - - - - - byte
 292         len = len or 1;
 293         local offset = self.offset;
 294         local last = offset + len - 1;
 295         if last > #self.packet then
 296                 error(string.format('out of bounds: %i>%i', last, #self.packet));
 297         end
 298         self.offset = offset + len;
 299         return string.byte(self.packet, offset, last);
 300 end
 301
 302
 303 function resolver:word()    -- - - - - - - - - - - - - - - - - - - - - -  word
 304         local b1, b2 = self:byte(2);
 305         return 0x100*b1 + b2;
 306 end
 307
 308
 309 function resolver:dword ()    -- - - - - - - - - - - - - - - - - - - - -  dword
 310         local b1, b2, b3, b4 = self:byte(4);
 311         --print('dword', b1, b2, b3, b4);
 312         return 0x1000000*b1 + 0x10000*b2 + 0x100*b3 + b4;
 313 end
 314
 315
 316 function resolver:sub(len)    -- - - - - - - - - - - - - - - - - - - - - - sub
 317         len = len or 1;
 318         local s = string.sub(self.packet, self.offset, self.offset + len - 1);
 319         self.offset = self.offset + len;
 320         return s;
 321 end
 322
 323
 324 function resolver:header(force)    -- - - - - - - - - - - - - - - - - - header
 325         local id = self:word();
 326         --print(string.format(':header  id  %x', id));
 327         if not self.active[id] and not force then return nil; end
 328
 329         local h = { id = id };
 330
 331         local b1, b2 = self:byte(2);
 332
 333         h.rd      = b1 %2;
 334         h.tc      = b1 /2%2;
 335         h.aa      = b1 /4%2;
 336         h.opcode  = b1 /8%16;
 337         h.qr      = b1 /128;
 338
 339         h.rcode   = b2 %16;
 340         h.z       = b2 /16%8;
 341         h.ra      = b2 /128;
 342
 343         h.qdcount = self:word();
 344         h.ancount = self:word();
 345         h.nscount = self:word();
 346         h.arcount = self:word();
 347
 348         for k,v in pairs(h) do h[k] = v-v%1; end
 349
 350         return h;
 351 end
 352
 353
 354 function resolver:name()    -- - - - - - - - - - - - - - - - - - - - - -  name
 355         local remember, pointers = nil, 0;
 356         local len = self:byte();
 357         local n = {};
 358         while len > 0 do
 359                 if len >= 0xc0 then    -- name is "compressed"
 360                         pointers = pointers + 1;
 361                         if pointers >= 20 then error('dns error: 20 pointers'); end;
 362                         local offset = ((len-0xc0)*0x100) + self:byte();
 363                         remember = remember or self.offset;
 364                         self.offset = offset + 1;    -- +1 for lua
 365                 else    -- name is not compressed
 366                         append(n, self:sub(len)..'.');
 367                 end
 368                 len = self:byte();
 369         end
 370         self.offset = remember or self.offset;
 371         return table.concat(n);
 372 end
 373
 374
 375 function resolver:question()    -- - - - - - - - - - - - - - - - - -  question
 376         local q = {};
 377         q.name  = self:name();
 378         q.type  = dns.type[self:word()];
 379         q.class = dns.class[self:word()];
 380         return q;
 381 end
 382
 383
 384 function resolver:A(rr)    -- - - - - - - - - - - - - - - - - - - - - - - -  A
 385         local b1, b2, b3, b4 = self:byte(4);
 386         rr.a = string.format('%i.%i.%i.%i', b1, b2, b3, b4);
 387 end
 388
 389
 390 function resolver:CNAME(rr)    -- - - - - - - - - - - - - - - - - - - -  CNAME
 391         rr.cname = self:name();
 392 end
 393
 394
 395 function resolver:MX(rr)    -- - - - - - - - - - - - - - - - - - - - - - -  MX
 396         rr.pref = self:word();
 397         rr.mx   = self:name();
 398 end
 399
 400
 401 function resolver:LOC_nibble_power()    -- - - - - - - - - -  LOC_nibble_power
 402         local b = self:byte();
 403         --print('nibbles', ((b-(b%0x10))/0x10), (b%0x10));
 404         return ((b-(b%0x10))/0x10) * (10^(b%0x10));
 405 end
 406
 407
 408 function resolver:LOC(rr)    -- - - - - - - - - - - - - - - - - - - - - -  LOC
 409         rr.version = self:byte();
 410         if rr.version == 0 then
 411                 rr.loc           = rr.loc or {};
 412                 rr.loc.size      = self:LOC_nibble_power();
 413                 rr.loc.horiz_pre = self:LOC_nibble_power();
 414                 rr.loc.vert_pre  = self:LOC_nibble_power();
 415                 rr.loc.latitude  = self:dword();
 416                 rr.loc.longitude = self:dword();
 417                 rr.loc.altitude  = self:dword();
 418         end
 419 end
 420
 421
 422 local function LOC_tostring_degrees(f, pos, neg)    -- - - - - - - - - - - - -
 423         f = f - 0x80000000;
 424         if f < 0 then pos = neg; f = -f; end
 425         local deg, min, msec;
 426         msec = f%60000;
 427         f    = (f-msec)/60000;
 428         min  = f%60;
 429         deg = (f-min)/60;
 430         return string.format('%3d %2d %2.3f %s', deg, min, msec/1000, pos);
 431 end
 432
 433
 434 function resolver.LOC_tostring(rr)    -- - - - - - - - - - - - -  LOC_tostring
 435         local t = {};
 436
 437         --[[
 438         for k,name in pairs { 'size', 'horiz_pre', 'vert_pre', 'latitude', 'longitude', 'altitude' } do
 439                 append(t, string.format('%4s%-10s: %12.0f\n', '', name, rr.loc[name]));
 440         end
 441         --]]
 442
 443         append(t, string.format(
 444                 '%s    %s    %.2fm %.2fm %.2fm %.2fm',
 445                 LOC_tostring_degrees (rr.loc.latitude, 'N', 'S'),
 446                 LOC_tostring_degrees (rr.loc.longitude, 'E', 'W'),
 447                 (rr.loc.altitude - 10000000) / 100,
 448                 rr.loc.size / 100,
 449                 rr.loc.horiz_pre / 100,
 450                 rr.loc.vert_pre / 100
 451         ));
 452
 453         return table.concat(t);
 454 end
 455
 456
 457 function resolver:NS(rr)    -- - - - - - - - - - - - - - - - - - - - - - -  NS
 458         rr.ns = self:name();
 459 end
 460
 461
 462 function resolver:SOA(rr)    -- - - - - - - - - - - - - - - - - - - - - -  SOA
 463 end
 464
 465
 466 function resolver:SRV(rr)    -- - - - - - - - - - - - - - - - - - - - - -  SRV
 467           rr.srv = {};
 468           rr.srv.priority = self:word();
 469           rr.srv.weight   = self:word();
 470           rr.srv.port     = self:word();
 471           rr.srv.target   = self:name();
 472 end
 473
 474 function resolver:PTR(rr)
 475         rr.ptr = self:name();
 476 end
 477
 478 function SRV_tostring(rr)    -- - - - - - - - - - - - - - - - - - SRV_tostring
 479         local s = rr.srv;
 480         return string.format( '%5d %5d %5d %s', s.priority, s.weight, s.port, s.target );
 481 end
 482
 483
 484 function resolver:TXT(rr)    -- - - - - - - - - - - - - - - - - - - - - -  TXT
 485         rr.txt = self:sub (rr.rdlength);
 486 end
 487
 488
 489 function resolver:rr()    -- - - - - - - - - - - - - - - - - - - - - - - -  rr
 490         local rr = {};
 491         setmetatable(rr, rr_metatable);
 492         rr.name     = self:name(self);
 493         rr.type     = dns.type[self:word()] or rr.type;
 494         rr.class    = dns.class[self:word()] or rr.class;
 495         rr.ttl      = 0x10000*self:word() + self:word();
 496         rr.rdlength = self:word();
 497
 498         if rr.ttl <= 0 then
 499                 rr.tod = self.time + 30;
 500         else
 501                 rr.tod = self.time + rr.ttl;
 502         end
 503
 504         local remember = self.offset;
 505         local rr_parser = self[dns.type[rr.type]];
 506         if rr_parser then rr_parser(self, rr); end
 507         self.offset = remember;
 508         rr.rdata = self:sub(rr.rdlength);
 509         return rr;
 510 end
 511
 512
 513 function resolver:rrs (count)    -- - - - - - - - - - - - - - - - - - - - - rrs
 514         local rrs = {};
 515         for i = 1,count do append(rrs, self:rr()); end
 516         return rrs;
 517 end
 518
 519
 520 function resolver:decode(packet, force)    -- - - - - - - - - - - - - - decode
 521         self.packet, self.offset = packet, 1;
 522         local header = self:header(force);
 523         if not header then return nil; end
 524         local response = { header = header };
 525
 526         response.question = {};
 527         local offset = self.offset;
 528         for i = 1,response.header.qdcount do
 529                 append(response.question, self:question());
 530         end
 531         response.question.raw = string.sub(self.packet, offset, self.offset - 1);
 532
 533         if not force then
 534                 if not self.active[response.header.id] or not self.active[response.header.id][response.question.raw] then
 535                         return nil;
 536                 end
 537         end
 538
 539         response.answer     = self:rrs(response.header.ancount);
 540         response.authority  = self:rrs(response.header.nscount);
 541         response.additional = self:rrs(response.header.arcount);
 542
 543         return response;
 544 end
 545
 546
 547 -- socket layer -------------------------------------------------- socket layer
 548
 549
 550 resolver.delays = { 1, 3 };
 551
 552
 553 function resolver:addnameserver(address)    -- - - - - - - - - - addnameserver
 554         self.server = self.server or {};
 555         append(self.server, address);
 556 end
 557
 558
 559 function resolver:setnameserver(address)    -- - - - - - - - - - setnameserver
 560         self.server = {};
 561         self:addnameserver(address);
 562 end
 563
 564
 565 function resolver:adddefaultnameservers()    -- - - - -  adddefaultnameservers
 566         if is_windows then
 567                 if windows and windows.get_nameservers then
 568                         for _, server in ipairs(windows.get_nameservers()) do
 569                                 self:addnameserver(server);
 570                         end
 571                 end
 572                 if not self.server or #self.server == 0 then
 573                         -- TODO log warning about no nameservers, adding opendns servers as fallback
 574                         self:addnameserver("208.67.222.222");
 575                         self:addnameserver("208.67.220.220");
 576                 end
 577         else -- posix
 578                 local resolv_conf = io.open("/etc/resolv.conf");
 579                 if resolv_conf then
 580                         for line in resolv_conf:lines() do
 581                                 line = line:gsub("#.*$", "")
 582                                         :match('^%s*nameserver%s+(.*)%s*$');
 583                                 if line then
 584                                         line:gsub("%f[%d.](%d+%.%d+%.%d+%.%d+)%f[^%d.]", function (address)
 585                                                 self:addnameserver(address)
 586                                         end);
 587                                 end
 588                         end
 589                 end
 590                 if not self.server or #self.server == 0 then
 591                         -- TODO log warning about no nameservers, adding localhost as the default nameserver
 592                         self:addnameserver("127.0.0.1");
 593                 end
 594         end
 595 end
 596
 597
 598 function resolver:getsocket(servernum)    -- - - - - - - - - - - - - getsocket
 599         self.socket = self.socket or {};
 600         self.socketset = self.socketset or {};
 601
 602         local sock = self.socket[servernum];
 603         if sock then return sock; end
 604
 605         local err;
 606         sock, err = socket.udp();
 607         if not sock then
 608                 return nil, err;
 609         end
 610         if self.socket_wrapper then sock = self.socket_wrapper(sock, self); end
 611         sock:settimeout(0);
 612         -- todo: attempt to use a random port, fallback to 0
 613         sock:setsockname('*', 0);
 614         sock:setpeername(self.server[servernum], 53);
 615         self.socket[servernum] = sock;
 616         self.socketset[sock] = servernum;
 617         return sock;
 618 end
 619
 620 function resolver:voidsocket(sock)
 621         if self.socket[sock] then
 622                 self.socketset[self.socket[sock]] = nil;
 623                 self.socket[sock] = nil;
 624         elseif self.socketset[sock] then
 625                 self.socket[self.socketset[sock]] = nil;
 626                 self.socketset[sock] = nil;
 627         end
 628 end
 629
 630 function resolver:socket_wrapper_set(func)  -- - - - - - - socket_wrapper_set
 631         self.socket_wrapper = func;
 632 end
 633
 634
 635 function resolver:closeall ()    -- - - - - - - - - - - - - - - - - -  closeall
 636         for i,sock in ipairs(self.socket) do
 637                 self.socket[i] = nil;
 638                 self.socketset[sock] = nil;
 639                 sock:close();
 640         end
 641 end
 642
 643
 644 function resolver:remember(rr, type)    -- - - - - - - - - - - - - -  remember
 645         --print ('remember', type, rr.class, rr.type, rr.name)
 646         local qname, qtype, qclass = standardize(rr.name, rr.type, rr.class);
 647
 648         if type ~= '*' then
 649                 type = qtype;
 650                 local all = get(self.cache, qclass, '*', qname);
 651                 --print('remember all', all);
 652                 if all then append(all, rr); end
 653         end
 654
 655         self.cache = self.cache or setmetatable({}, cache_metatable);
 656         local rrs = get(self.cache, qclass, type, qname) or
 657                 set(self.cache, qclass, type, qname, setmetatable({}, rrs_metatable));
 658         append(rrs, rr);
 659
 660         if type == 'MX' then self.unsorted[rrs] = true; end
 661 end
 662
 663
 664 local function comp_mx(a, b)    -- - - - - - - - - - - - - - - - - - - comp_mx
 665         return (a.pref == b.pref) and (a.mx < b.mx) or (a.pref < b.pref);
 666 end
 667
 668
 669 function resolver:peek (qname, qtype, qclass)    -- - - - - - - - - - - -  peek
 670         qname, qtype, qclass = standardize(qname, qtype, qclass);
 671         local rrs = get(self.cache, qclass, qtype, qname);
 672         if not rrs then return nil; end
 673         if prune(rrs, socket.gettime()) and qtype == '*' or not next(rrs) then
 674                 set(self.cache, qclass, qtype, qname, nil);
 675                 return nil;
 676         end
 677         if self.unsorted[rrs] then table.sort (rrs, comp_mx); end
 678         return rrs;
 679 end
 680
 681
 682 function resolver:purge(soft)    -- - - - - - - - - - - - - - - - - - -  purge
 683         if soft == 'soft' then
 684                 self.time = socket.gettime();
 685                 for class,types in pairs(self.cache or {}) do
 686                         for type,names in pairs(types) do
 687                                 for name,rrs in pairs(names) do
 688                                         prune(rrs, self.time, 'soft')
 689                                 end
 690                         end
 691                 end
 692         else self.cache = {}; end
 693 end
 694
 695
 696 function resolver:query(qname, qtype, qclass)    -- - - - - - - - - - -- query
 697         qname, qtype, qclass = standardize(qname, qtype, qclass)
 698
 699         if not self.server then self:adddefaultnameservers(); end
 700
 701         local question = encodeQuestion(qname, qtype, qclass);
 702         local peek = self:peek (qname, qtype, qclass);
 703         if peek then return peek; end
 704
 705         local header, id = encodeHeader();
 706         --print ('query  id', id, qclass, qtype, qname)
 707         local o = {
 708                 packet = header..question,
 709                 server = self.best_server,
 710                 delay  = 1,
 711                 retry  = socket.gettime() + self.delays[1]
 712         };
 713
 714         -- remember the query
 715         self.active[id] = self.active[id] or {};
 716         self.active[id][question] = o;
 717
 718         -- remember which coroutine wants the answer
 719         local co = coroutine.running();
 720         if co then
 721                 set(self.wanted, qclass, qtype, qname, co, true);
 722                 --set(self.yielded, co, qclass, qtype, qname, true);
 723         end
 724
 725         local conn, err = self:getsocket(o.server)
 726         if not conn then
 727                 return nil, err;
 728         end
 729         conn:send (o.packet)
 730
 731         if timer and self.timeout then
 732                 local num_servers = #self.server;
 733                 local i = 1;
 734                 timer.add_task(self.timeout, function ()
 735                         if get(self.wanted, qclass, qtype, qname, co) then
 736                                 if i < num_servers then
 737                                         i = i + 1;
 738                                         self:servfail(conn);
 739                                         o.server = self.best_server;
 740                                         conn, err = self:getsocket(o.server);
 741                                         if conn then
 742                                                 conn:send(o.packet);
 743                                                 return self.timeout;
 744                                         end
 745                                 end
 746                                 -- Tried everything, failed
 747                                 self:cancel(qclass, qtype, qname, co, true);
 748                         end
 749                 end)
 750         end
 751         return true;
 752 end
 753
 754 function resolver:servfail(sock)
 755         -- Resend all queries for this server
 756
 757         local num = self.socketset[sock]
 758
 759         -- Socket is dead now
 760         self:voidsocket(sock);
 761
 762         -- Find all requests to the down server, and retry on the next server
 763         self.time = socket.gettime();
 764         for id,queries in pairs(self.active) do
 765                 for question,o in pairs(queries) do
 766                         if o.server == num then -- This request was to the broken server
 767                                 o.server = o.server + 1 -- Use next server
 768                                 if o.server > #self.server then
 769                                         o.server = 1;
 770                                 end
 771
 772                                 o.retries = (o.retries or 0) + 1;
 773                                 if o.retries >= #self.server then
 774                                         --print('timeout');
 775                                         queries[question] = nil;
 776                                 else
 777                                         local _a = self:getsocket(o.server);
 778                                         if _a then _a:send(o.packet); end
 779                                 end
 780                         end
 781                 end
 782         end
 783
 784         if num == self.best_server then
 785                 self.best_server = self.best_server + 1;
 786                 if self.best_server > #self.server then
 787                         -- Exhausted all servers, try first again
 788                         self.best_server = 1;
 789                 end
 790         end
 791 end
 792
 793 function resolver:settimeout(seconds)
 794         self.timeout = seconds;
 795 end
 796
 797 function resolver:receive(rset)    -- - - - - - - - - - - - - - - - -  receive
 798         --print('receive');  print(self.socket);
 799         self.time = socket.gettime();
 800         rset = rset or self.socket;
 801
 802         local response;
 803         for i,sock in pairs(rset) do
 804
 805                 if self.socketset[sock] then
 806                         local packet = sock:receive();
 807                         if packet then
 808                                 response = self:decode(packet);
 809                                 if response and self.active[response.header.id]
 810                                         and self.active[response.header.id][response.question.raw] then
 811                                         --print('received response');
 812                                         --self.print(response);
 813
 814                                         for j,rr in pairs(response.answer) do
 815                                                 if rr.name:sub(-#response.question[1].name, -1) == response.question[1].name then
 816                                                         self:remember(rr, response.question[1].type)
 817                                                 end
 818                                         end
 819
 820                                         -- retire the query
 821                                         local queries = self.active[response.header.id];
 822                                         queries[response.question.raw] = nil;
 823
 824                                         if not next(queries) then self.active[response.header.id] = nil; end
 825                                         if not next(self.active) then self:closeall(); end
 826
 827                                         -- was the query on the wanted list?
 828                                         local q = response.question[1];
 829                                         local cos = get(self.wanted, q.class, q.type, q.name);
 830                                         if cos then
 831                                                 for co in pairs(cos) do
 832                                                         set(self.yielded, co, q.class, q.type, q.name, nil);
 833                                                         if coroutine.status(co) == "suspended" then coroutine.resume(co); end
 834                                                 end
 835                                                 set(self.wanted, q.class, q.type, q.name, nil);
 836                                         end
 837                                 end
 838                         end
 839                 end
 840         end
 841
 842         return response;
 843 end
 844
 845
 846 function resolver:feed(sock, packet, force)
 847         --print('receive'); print(self.socket);
 848         self.time = socket.gettime();
 849
 850         local response = self:decode(packet, force);
 851         if response and self.active[response.header.id]
 852                 and self.active[response.header.id][response.question.raw] then
 853                 --print('received response');
 854                 --self.print(response);
 855
 856                 for j,rr in pairs(response.answer) do
 857                         self:remember(rr, response.question[1].type);
 858                 end
 859
 860                 -- retire the query
 861                 local queries = self.active[response.header.id];
 862                 queries[response.question.raw] = nil;
 863                 if not next(queries) then self.active[response.header.id] = nil; end
 864                 if not next(self.active) then self:closeall(); end
 865
 866                 -- was the query on the wanted list?
 867                 local q = response.question[1];
 868                 if q then
 869                         local cos = get(self.wanted, q.class, q.type, q.name);
 870                         if cos then
 871                                 for co in pairs(cos) do
 872                                         set(self.yielded, co, q.class, q.type, q.name, nil);
 873                                         if coroutine.status(co) == "suspended" then coroutine.resume(co); end
 874                                 end
 875                                 set(self.wanted, q.class, q.type, q.name, nil);
 876                         end
 877                 end
 878         end
 879
 880         return response;
 881 end
 882
 883 function resolver:cancel(qclass, qtype, qname, co, call_handler)
 884         local cos = get(self.wanted, qclass, qtype, qname);
 885         if cos then
 886                 if call_handler then
 887                         coroutine.resume(co);
 888                 end
 889                 cos[co] = nil;
 890         end
 891 end
 892
 893 function resolver:pulse()    -- - - - - - - - - - - - - - - - - - - - -  pulse
 894         --print(':pulse');
 895         while self:receive() do end
 896         if not next(self.active) then return nil; end
 897
 898         self.time = socket.gettime();
 899         for id,queries in pairs(self.active) do
 900                 for question,o in pairs(queries) do
 901                         if self.time >= o.retry then
 902
 903                                 o.server = o.server + 1;
 904                                 if o.server > #self.server then
 905                                         o.server = 1;
 906                                         o.delay = o.delay + 1;
 907                                 end
 908
 909                                 if o.delay > #self.delays then
 910                                         --print('timeout');
 911                                         queries[question] = nil;
 912                                         if not next(queries) then self.active[id] = nil; end
 913                                         if not next(self.active) then return nil; end
 914                                 else
 915                                         --print('retry', o.server, o.delay);
 916                                         local _a = self.socket[o.server];
 917                                         if _a then _a:send(o.packet); end
 918                                         o.retry = self.time + self.delays[o.delay];
 919                                 end
 920                         end
 921                 end
 922         end
 923
 924         if next(self.active) then return true; end
 925         return nil;
 926 end
 927
 928
 929 function resolver:lookup(qname, qtype, qclass)    -- - - - - - - - - -  lookup
 930         self:query (qname, qtype, qclass)
 931         while self:pulse() do
 932                 local recvt = {}
 933                 for i, s in ipairs(self.socket) do
 934                         recvt[i] = s
 935                 end
 936                 socket.select(recvt, nil, 4)
 937         end
 938         --print(self.cache);
 939         return self:peek(qname, qtype, qclass);
 940 end
 941
 942 function resolver:lookupex(handler, qname, qtype, qclass)    -- - - - - - - - - -  lookup
 943         return self:peek(qname, qtype, qclass) or self:query(qname, qtype, qclass);
 944 end
 945
 946 function resolver:tohostname(ip)
 947         return dns.lookup(ip:gsub("(%d+)%.(%d+)%.(%d+)%.(%d+)", "%4.%3.%2.%1.in-addr.arpa."), "PTR");
 948 end
 949
 950 --print ---------------------------------------------------------------- print
 951
 952
 953 local hints = {    -- - - - - - - - - - - - - - - - - - - - - - - - - - - hints
 954         qr = { [0]='query', 'response' },
 955         opcode = { [0]='query', 'inverse query', 'server status request' },
 956         aa = { [0]='non-authoritative', 'authoritative' },
 957         tc = { [0]='complete', 'truncated' },
 958         rd = { [0]='recursion not desired', 'recursion desired' },
 959         ra = { [0]='recursion not available', 'recursion available' },
 960         z  = { [0]='(reserved)' },
 961         rcode = { [0]='no error', 'format error', 'server failure', 'name error', 'not implemented' },
 962
 963         type = dns.type,
 964         class = dns.class
 965 };
 966
 967
 968 local function hint(p, s)    -- - - - - - - - - - - - - - - - - - - - - - hint
 969         return (hints[s] and hints[s][p[s]]) or '';
 970 end
 971
 972
 973 function resolver.print(response)    -- - - - - - - - - - - - - resolver.print
 974         for s,s in pairs { 'id', 'qr', 'opcode', 'aa', 'tc', 'rd', 'ra', 'z',
 975                                                 'rcode', 'qdcount', 'ancount', 'nscount', 'arcount' } do
 976                 print( string.format('%-30s', 'header.'..s), response.header[s], hint(response.header, s) );
 977         end
 978
 979         for i,question in ipairs(response.question) do
 980                 print(string.format ('question[%i].name         ', i), question.name);
 981                 print(string.format ('question[%i].type         ', i), question.type);
 982                 print(string.format ('question[%i].class        ', i), question.class);
 983         end
 984
 985         local common = { name=1, type=1, class=1, ttl=1, rdlength=1, rdata=1 };
 986         local tmp;
 987         for s,s in pairs({'answer', 'authority', 'additional'}) do
 988                 for i,rr in pairs(response[s]) do
 989                         for j,t in pairs({ 'name', 'type', 'class', 'ttl', 'rdlength' }) do
 990                                 tmp = string.format('%s[%i].%s', s, i, t);
 991                                 print(string.format('%-30s', tmp), rr[t], hint(rr, t));
 992                         end
 993                         for j,t in pairs(rr) do
 994                                 if not common[j] then
 995                                         tmp = string.format('%s[%i].%s', s, i, j);
 996                                         print(string.format('%-30s  %s', tostring(tmp), tostring(t)));
 997                                 end
 998                         end
 999                 end
1000         end
1001 end
1002
1003
1004 -- module api ------------------------------------------------------ module api
1005
1006
1007 function dns.resolver ()    -- - - - - - - - - - - - - - - - - - - - - resolver
1008         -- this function seems to be redundant with resolver.new ()
1009
1010         local r = { active = {}, cache = {}, unsorted = {}, wanted = {}, yielded = {}, best_server = 1 };
1011         setmetatable (r, resolver);
1012         setmetatable (r.cache, cache_metatable);
1013         setmetatable (r.unsorted, { __mode = 'kv' });
1014         return r;
1015 end
1016
1017 local _resolver = dns.resolver();
1018 dns._resolver = _resolver;
1019
1020 function dns.lookup(...)    -- - - - - - - - - - - - - - - - - - - - -  lookup
1021         return _resolver:lookup(...);
1022 end
1023
1024 function dns.tohostname(...)
1025         return _resolver:tohostname(...);
1026 end
1027
1028 function dns.purge(...)    -- - - - - - - - - - - - - - - - - - - - - -  purge
1029         return _resolver:purge(...);
1030 end
1031
1032 function dns.peek(...)    -- - - - - - - - - - - - - - - - - - - - - - -  peek
1033         return _resolver:peek(...);
1034 end
1035
1036 function dns.query(...)    -- - - - - - - - - - - - - - - - - - - - - -  query
1037         return _resolver:query(...);
1038 end
1039
1040 function dns.feed(...)    -- - - - - - - - - - - - - - - - - - - - - - -  feed
1041         return _resolver:feed(...);
1042 end
1043
1044 function dns.cancel(...)  -- - - - - - - - - - - - - - - - - - - - - -  cancel
1045         return _resolver:cancel(...);
1046 end
1047
1048 function dns.settimeout(...)
1049         return _resolver:settimeout(...);
1050 end
1051
1052 function dns.socket_wrapper_set(...)    -- - - - - - - - -  socket_wrapper_set
1053         return _resolver:socket_wrapper_set(...);
1054 end
1055
1056 return dns;