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