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 local new_ip = require "util.ip".new_ip;
  18
  19 local _, windows = pcall(require, "util.windows");
  20 local is_windows = (_ and windows) or os.getenv("WINDIR");
  21
  22 local coroutine, io, math, string, table =
  23       coroutine, io, math, string, table;
  24
  25 local ipairs, next, pairs, print, setmetatable, tostring, assert, error, unpack, select, type=
  26       ipairs, next, pairs, print, setmetatable, tostring, assert, error, unpack, select, type;
  27
  28 local ztact = { -- public domain 20080404 lua@ztact.com
  29         get = function(parent, ...)
  30                 local len = select('#', ...);
  31                 for i=1,len do
  32                         parent = parent[select(i, ...)];
  33                         if parent == nil then break; end
  34                 end
  35                 return parent;
  36         end;
  37         set = function(parent, ...)
  38                 local len = select('#', ...);
  39                 local key, value = select(len-1, ...);
  40                 local cutpoint, cutkey;
  41
  42                 for i=1,len-2 do
  43                         local key = select (i, ...)
  44                         local child = parent[key]
  45
  46                         if value == nil then
  47                                 if child == nil then
  48                                         return;
  49                                 elseif next(child, next(child)) then
  50                                         cutpoint = nil; cutkey = nil;
  51                                 elseif cutpoint == nil then
  52                                         cutpoint = parent; cutkey = key;
  53                                 end
  54                         elseif child == nil then
  55                                 child = {};
  56                                 parent[key] = child;
  57                         end
  58                         parent = child
  59                 end
  60
  61                 if value == nil and cutpoint then
  62                         cutpoint[cutkey] = nil;
  63                 else
  64                         parent[key] = value;
  65                         return value;
  66                 end
  67         end;
  68 };
  69 local get, set = ztact.get, ztact.set;
  70
  71 local default_timeout = 15;
  72
  73 -------------------------------------------------- module dns
  74 module('dns')
  75 local dns = _M;
  76
  77
  78 -- dns type & class codes ------------------------------ dns type & class codes
  79
  80
  81 local append = table.insert
  82
  83
  84 local function highbyte(i)    -- - - - - - - - - - - - - - - - - - -  highbyte
  85         return (i-(i%0x100))/0x100;
  86 end
  87
  88
  89 local function augment (t)    -- - - - - - - - - - - - - - - - - - - -  augment
  90         local a = {};
  91         for i,s in pairs(t) do
  92                 a[i] = s;
  93                 a[s] = s;
  94                 a[string.lower(s)] = s;
  95         end
  96         return a;
  97 end
  98
  99
 100 local function encode (t)    -- - - - - - - - - - - - - - - - - - - - -  encode
 101         local code = {};
 102         for i,s in pairs(t) do
 103                 local word = string.char(highbyte(i), i%0x100);
 104                 code[i] = word;
 105                 code[s] = word;
 106                 code[string.lower(s)] = word;
 107         end
 108         return code;
 109 end
 110
 111
 112 dns.types = {
 113         'A', 'NS', 'MD', 'MF', 'CNAME', 'SOA', 'MB', 'MG', 'MR', 'NULL', 'WKS',
 114         'PTR', 'HINFO', 'MINFO', 'MX', 'TXT',
 115         [ 28] = 'AAAA', [ 29] = 'LOC',   [ 33] = 'SRV',
 116         [252] = 'AXFR', [253] = 'MAILB', [254] = 'MAILA', [255] = '*' };
 117
 118
 119 dns.classes = { 'IN', 'CS', 'CH', 'HS', [255] = '*' };
 120
 121
 122 dns.type      = augment (dns.types);
 123 dns.class     = augment (dns.classes);
 124 dns.typecode  = encode  (dns.types);
 125 dns.classcode = encode  (dns.classes);
 126
 127
 128
 129 local function standardize(qname, qtype, qclass)    -- - - - - - - standardize
 130         if string.byte(qname, -1) ~= 0x2E then qname = qname..'.';  end
 131         qname = string.lower(qname);
 132         return qname, dns.type[qtype or 'A'], dns.class[qclass or 'IN'];
 133 end
 134
 135
 136 local function prune(rrs, time, soft)    -- - - - - - - - - - - - - - -  prune
 137         time = time or socket.gettime();
 138         for i,rr in pairs(rrs) do
 139                 if rr.tod then
 140                         -- rr.tod = rr.tod - 50    -- accelerated decripitude
 141                         rr.ttl = math.floor(rr.tod - time);
 142                         if rr.ttl <= 0 then
 143                                 table.remove(rrs, i);
 144                                 return prune(rrs, time, soft); -- Re-iterate
 145                         end
 146                 elseif soft == 'soft' then    -- What is this?  I forget!
 147                         assert(rr.ttl == 0);
 148                         rrs[i] = nil;
 149                 end
 150         end
 151 end
 152
 153
 154 -- metatables & co. ------------------------------------------ metatables & co.
 155
 156
 157 local resolver = {};
 158 resolver.__index = resolver;
 159
 160 resolver.timeout = default_timeout;
 161
 162 local function default_rr_tostring(rr)
 163         local rr_val = rr.type and rr[rr.type:lower()];
 164         if type(rr_val) ~= "string" then
 165                 return "<UNKNOWN RDATA TYPE>";
 166         end
 167         return rr_val;
 168 end
 169
 170 local special_tostrings = {
 171         LOC = resolver.LOC_tostring;
 172         MX  = function (rr)
 173                 return string.format('%2i %s', rr.pref, rr.mx);
 174         end;
 175         SRV = function (rr)
 176                 local s = rr.srv;
 177                 return string.format('%5d %5d %5d %s', s.priority, s.weight, s.port, s.target);
 178         end;
 179 };
 180
 181 local rr_metatable = {};   -- - - - - - - - - - - - - - - - - - -  rr_metatable
 182 function rr_metatable.__tostring(rr)
 183         local rr_string = (special_tostrings[rr.type] or default_rr_tostring)(rr);
 184         return string.format('%2s %-5s %6i %-28s %s', rr.class, rr.type, rr.ttl, rr.name, rr_string);
 185 end
 186
 187
 188 local rrs_metatable = {};    -- - - - - - - - - - - - - - - - - -  rrs_metatable
 189 function rrs_metatable.__tostring(rrs)
 190         local t = {};
 191         for i,rr in pairs(rrs) do
 192                 append(t, tostring(rr)..'\n');
 193         end
 194         return table.concat(t);
 195 end
 196
 197
 198 local cache_metatable = {};    -- - - - - - - - - - - - - - - -  cache_metatable
 199 function cache_metatable.__tostring(cache)
 200         local time = socket.gettime();
 201         local t = {};
 202         for class,types in pairs(cache) do
 203                 for type,names in pairs(types) do
 204                         for name,rrs in pairs(names) do
 205                                 prune(rrs, time);
 206                                 append(t, tostring(rrs));
 207                         end
 208                 end
 209         end
 210         return table.concat(t);
 211 end
 212
 213
 214 function resolver:new()    -- - - - - - - - - - - - - - - - - - - - - resolver
 215         local r = { active = {}, cache = {}, unsorted = {} };
 216         setmetatable(r, resolver);
 217         setmetatable(r.cache, cache_metatable);
 218         setmetatable(r.unsorted, { __mode = 'kv' });
 219         return r;
 220 end
 221
 222
 223 -- packet layer -------------------------------------------------- packet layer
 224
 225
 226 function dns.random(...)    -- - - - - - - - - - - - - - - - - - -  dns.random
 227         math.randomseed(math.floor(10000*socket.gettime()) % 0x100000000);
 228         dns.random = math.random;
 229         return dns.random(...);
 230 end
 231
 232
 233 local function encodeHeader(o)    -- - - - - - - - - - - - - - -  encodeHeader
 234         o = o or {};
 235         o.id = o.id or dns.random(0, 0xffff); -- 16b    (random) id
 236
 237         o.rd = o.rd or 1;               --  1b  1 recursion desired
 238         o.tc = o.tc or 0;               --  1b  1 truncated response
 239         o.aa = o.aa or 0;               --  1b  1 authoritative response
 240         o.opcode = o.opcode or 0;       --  4b  0 query
 241                                 --  1 inverse query
 242                                 --      2 server status request
 243                                 --      3-15 reserved
 244         o.qr = o.qr or 0;               --  1b  0 query, 1 response
 245
 246         o.rcode = o.rcode or 0; --  4b  0 no error
 247                                 --      1 format error
 248                                 --      2 server failure
 249                                 --      3 name error
 250                                 --      4 not implemented
 251                                 --      5 refused
 252                                 --      6-15 reserved
 253         o.z = o.z  or 0;                --  3b  0 resvered
 254         o.ra = o.ra or 0;               --  1b  1 recursion available
 255
 256         o.qdcount = o.qdcount or 1;     -- 16b  number of question RRs
 257         o.ancount = o.ancount or 0;     -- 16b  number of answers RRs
 258         o.nscount = o.nscount or 0;     -- 16b  number of nameservers RRs
 259         o.arcount = o.arcount or 0;     -- 16b  number of additional RRs
 260
 261         -- string.char() rounds, so prevent roundup with -0.4999
 262         local header = string.char(
 263                 highbyte(o.id), o.id %0x100,
 264                 o.rd + 2*o.tc + 4*o.aa + 8*o.opcode + 128*o.qr,
 265                 o.rcode + 16*o.z + 128*o.ra,
 266                 highbyte(o.qdcount),  o.qdcount %0x100,
 267                 highbyte(o.ancount),  o.ancount %0x100,
 268                 highbyte(o.nscount),  o.nscount %0x100,
 269                 highbyte(o.arcount),  o.arcount %0x100
 270         );
 271
 272         return header, o.id;
 273 end
 274
 275
 276 local function encodeName(name)    -- - - - - - - - - - - - - - - - encodeName
 277         local t = {};
 278         for part in string.gmatch(name, '[^.]+') do
 279                 append(t, string.char(string.len(part)));
 280                 append(t, part);
 281         end
 282         append(t, string.char(0));
 283         return table.concat(t);
 284 end
 285
 286
 287 local function encodeQuestion(qname, qtype, qclass)    -- - - - encodeQuestion
 288         qname  = encodeName(qname);
 289         qtype  = dns.typecode[qtype or 'a'];
 290         qclass = dns.classcode[qclass or 'in'];
 291         return qname..qtype..qclass;
 292 end
 293
 294
 295 function resolver:byte(len)    -- - - - - - - - - - - - - - - - - - - - - byte
 296         len = len or 1;
 297         local offset = self.offset;
 298         local last = offset + len - 1;
 299         if last > #self.packet then
 300                 error(string.format('out of bounds: %i>%i', last, #self.packet));
 301         end
 302         self.offset = offset + len;
 303         return string.byte(self.packet, offset, last);
 304 end
 305
 306
 307 function resolver:word()    -- - - - - - - - - - - - - - - - - - - - - -  word
 308         local b1, b2 = self:byte(2);
 309         return 0x100*b1 + b2;
 310 end
 311
 312
 313 function resolver:dword ()    -- - - - - - - - - - - - - - - - - - - - -  dword
 314         local b1, b2, b3, b4 = self:byte(4);
 315         --print('dword', b1, b2, b3, b4);
 316         return 0x1000000*b1 + 0x10000*b2 + 0x100*b3 + b4;
 317 end
 318
 319
 320 function resolver:sub(len)    -- - - - - - - - - - - - - - - - - - - - - - sub
 321         len = len or 1;
 322         local s = string.sub(self.packet, self.offset, self.offset + len - 1);
 323         self.offset = self.offset + len;
 324         return s;
 325 end
 326
 327
 328 function resolver:header(force)    -- - - - - - - - - - - - - - - - - - header
 329         local id = self:word();
 330         --print(string.format(':header  id  %x', id));
 331         if not self.active[id] and not force then return nil; end
 332
 333         local h = { id = id };
 334
 335         local b1, b2 = self:byte(2);
 336
 337         h.rd      = b1 %2;
 338         h.tc      = b1 /2%2;
 339         h.aa      = b1 /4%2;
 340         h.opcode  = b1 /8%16;
 341         h.qr      = b1 /128;
 342
 343         h.rcode   = b2 %16;
 344         h.z       = b2 /16%8;
 345         h.ra      = b2 /128;
 346
 347         h.qdcount = self:word();
 348         h.ancount = self:word();
 349         h.nscount = self:word();
 350         h.arcount = self:word();
 351
 352         for k,v in pairs(h) do h[k] = v-v%1; end
 353
 354         return h;
 355 end
 356
 357
 358 function resolver:name()    -- - - - - - - - - - - - - - - - - - - - - -  name
 359         local remember, pointers = nil, 0;
 360         local len = self:byte();
 361         local n = {};
 362         if len == 0 then return "." end -- Root label
 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 function resolver:AAAA(rr)
 395         local addr = {};
 396         for i = 1, rr.rdlength, 2 do
 397                 local b1, b2 = self:byte(2);
 398                 table.insert(addr, ("%02x%02x"):format(b1, b2));
 399         end
 400         addr = table.concat(addr, ":"):gsub("%f[%x]0+(%x)","%1");
 401         local zeros = {};
 402         for item in addr:gmatch(":[0:]+:") do
 403                 table.insert(zeros, item)
 404         end
 405         if #zeros == 0 then
 406                 rr.aaaa = addr;
 407                 return
 408         elseif #zeros > 1 then
 409                 table.sort(zeros, function(a, b) return #a > #b end);
 410         end
 411         rr.aaaa = addr:gsub(zeros[1], "::", 1):gsub("^0::", "::"):gsub("::0$", "::");
 412 end
 413
 414 function resolver:CNAME(rr)    -- - - - - - - - - - - - - - - - - - - -  CNAME
 415         rr.cname = self:name();
 416 end
 417
 418
 419 function resolver:MX(rr)    -- - - - - - - - - - - - - - - - - - - - - - -  MX
 420         rr.pref = self:word();
 421         rr.mx   = self:name();
 422 end
 423
 424
 425 function resolver:LOC_nibble_power()    -- - - - - - - - - -  LOC_nibble_power
 426         local b = self:byte();
 427         --print('nibbles', ((b-(b%0x10))/0x10), (b%0x10));
 428         return ((b-(b%0x10))/0x10) * (10^(b%0x10));
 429 end
 430
 431
 432 function resolver:LOC(rr)    -- - - - - - - - - - - - - - - - - - - - - -  LOC
 433         rr.version = self:byte();
 434         if rr.version == 0 then
 435                 rr.loc           = rr.loc or {};
 436                 rr.loc.size      = self:LOC_nibble_power();
 437                 rr.loc.horiz_pre = self:LOC_nibble_power();
 438                 rr.loc.vert_pre  = self:LOC_nibble_power();
 439                 rr.loc.latitude  = self:dword();
 440                 rr.loc.longitude = self:dword();
 441                 rr.loc.altitude  = self:dword();
 442         end
 443 end
 444
 445
 446 local function LOC_tostring_degrees(f, pos, neg)    -- - - - - - - - - - - - -
 447         f = f - 0x80000000;
 448         if f < 0 then pos = neg; f = -f; end
 449         local deg, min, msec;
 450         msec = f%60000;
 451         f    = (f-msec)/60000;
 452         min  = f%60;
 453         deg = (f-min)/60;
 454         return string.format('%3d %2d %2.3f %s', deg, min, msec/1000, pos);
 455 end
 456
 457
 458 function resolver.LOC_tostring(rr)    -- - - - - - - - - - - - -  LOC_tostring
 459         local t = {};
 460
 461         --[[
 462         for k,name in pairs { 'size', 'horiz_pre', 'vert_pre', 'latitude', 'longitude', 'altitude' } do
 463                 append(t, string.format('%4s%-10s: %12.0f\n', '', name, rr.loc[name]));
 464         end
 465         --]]
 466
 467         append(t, string.format(
 468                 '%s    %s    %.2fm %.2fm %.2fm %.2fm',
 469                 LOC_tostring_degrees (rr.loc.latitude, 'N', 'S'),
 470                 LOC_tostring_degrees (rr.loc.longitude, 'E', 'W'),
 471                 (rr.loc.altitude - 10000000) / 100,
 472                 rr.loc.size / 100,
 473                 rr.loc.horiz_pre / 100,
 474                 rr.loc.vert_pre / 100
 475         ));
 476
 477         return table.concat(t);
 478 end
 479
 480
 481 function resolver:NS(rr)    -- - - - - - - - - - - - - - - - - - - - - - -  NS
 482         rr.ns = self:name();
 483 end
 484
 485
 486 function resolver:SOA(rr)    -- - - - - - - - - - - - - - - - - - - - - -  SOA
 487 end
 488
 489
 490 function resolver:SRV(rr)    -- - - - - - - - - - - - - - - - - - - - - -  SRV
 491           rr.srv = {};
 492           rr.srv.priority = self:word();
 493           rr.srv.weight   = self:word();
 494           rr.srv.port     = self:word();
 495           rr.srv.target   = self:name();
 496 end
 497
 498 function resolver:PTR(rr)
 499         rr.ptr = self:name();
 500 end
 501
 502 function resolver:TXT(rr)    -- - - - - - - - - - - - - - - - - - - - - -  TXT
 503         rr.txt = self:sub (self:byte());
 504 end
 505
 506
 507 function resolver:rr()    -- - - - - - - - - - - - - - - - - - - - - - - -  rr
 508         local rr = {};
 509         setmetatable(rr, rr_metatable);
 510         rr.name     = self:name(self);
 511         rr.type     = dns.type[self:word()] or rr.type;
 512         rr.class    = dns.class[self:word()] or rr.class;
 513         rr.ttl      = 0x10000*self:word() + self:word();
 514         rr.rdlength = self:word();
 515
 516         if rr.ttl <= 0 then
 517                 rr.tod = self.time + 30;
 518         else
 519                 rr.tod = self.time + rr.ttl;
 520         end
 521
 522         local remember = self.offset;
 523         local rr_parser = self[dns.type[rr.type]];
 524         if rr_parser then rr_parser(self, rr); end
 525         self.offset = remember;
 526         rr.rdata = self:sub(rr.rdlength);
 527         return rr;
 528 end
 529
 530
 531 function resolver:rrs (count)    -- - - - - - - - - - - - - - - - - - - - - rrs
 532         local rrs = {};
 533         for i = 1,count do append(rrs, self:rr()); end
 534         return rrs;
 535 end
 536
 537
 538 function resolver:decode(packet, force)    -- - - - - - - - - - - - - - decode
 539         self.packet, self.offset = packet, 1;
 540         local header = self:header(force);
 541         if not header then return nil; end
 542         local response = { header = header };
 543
 544         response.question = {};
 545         local offset = self.offset;
 546         for i = 1,response.header.qdcount do
 547                 append(response.question, self:question());
 548         end
 549         response.question.raw = string.sub(self.packet, offset, self.offset - 1);
 550
 551         if not force then
 552                 if not self.active[response.header.id] or not self.active[response.header.id][response.question.raw] then
 553                         self.active[response.header.id] = nil;
 554                         return nil;
 555                 end
 556         end
 557
 558         response.answer     = self:rrs(response.header.ancount);
 559         response.authority  = self:rrs(response.header.nscount);
 560         response.additional = self:rrs(response.header.arcount);
 561
 562         return response;
 563 end
 564
 565
 566 -- socket layer -------------------------------------------------- socket layer
 567
 568
 569 resolver.delays = { 1, 3 };
 570
 571
 572 function resolver:addnameserver(address)    -- - - - - - - - - - addnameserver
 573         self.server = self.server or {};
 574         append(self.server, address);
 575 end
 576
 577
 578 function resolver:setnameserver(address)    -- - - - - - - - - - setnameserver
 579         self.server = {};
 580         self:addnameserver(address);
 581 end
 582
 583
 584 function resolver:adddefaultnameservers()    -- - - - -  adddefaultnameservers
 585         if is_windows then
 586                 if windows and windows.get_nameservers then
 587                         for _, server in ipairs(windows.get_nameservers()) do
 588                                 self:addnameserver(server);
 589                         end
 590                 end
 591                 if not self.server or #self.server == 0 then
 592                         -- TODO log warning about no nameservers, adding opendns servers as fallback
 593                         self:addnameserver("208.67.222.222");
 594                         self:addnameserver("208.67.220.220");
 595                 end
 596         else -- posix
 597                 local resolv_conf = io.open("/etc/resolv.conf");
 598                 if resolv_conf then
 599                         for line in resolv_conf:lines() do
 600                                 line = line:gsub("#.*$", "")
 601                                         :match('^%s*nameserver%s+([%x:%.]*)%s*$');
 602                                 if line then
 603                                         local ip = new_ip(line);
 604                                         if ip then
 605                                                 self:addnameserver(ip.addr);
 606                                         end
 607                                 end
 608                         end
 609                 end
 610                 if not self.server or #self.server == 0 then
 611                         -- TODO log warning about no nameservers, adding localhost as the default nameserver
 612                         self:addnameserver("127.0.0.1");
 613                 end
 614         end
 615 end
 616
 617
 618 function resolver:getsocket(servernum)    -- - - - - - - - - - - - - getsocket
 619         self.socket = self.socket or {};
 620         self.socketset = self.socketset or {};
 621
 622         local sock = self.socket[servernum];
 623         if sock then return sock; end
 624
 625         local err;
 626         local peer = self.server[servernum];
 627         if peer:find(":") then
 628                 sock, err = socket.udp6();
 629         else
 630                 sock, err = socket.udp();
 631         end
 632         if sock and self.socket_wrapper then sock, err = self.socket_wrapper(sock, self); end
 633         if not sock then
 634                 return nil, err;
 635         end
 636         sock:settimeout(0);
 637         -- todo: attempt to use a random port, fallback to 0
 638         sock:setsockname('*', 0);
 639         sock:setpeername(peer, 53);
 640         self.socket[servernum] = sock;
 641         self.socketset[sock] = servernum;
 642         return sock;
 643 end
 644
 645 function resolver:voidsocket(sock)
 646         if self.socket[sock] then
 647                 self.socketset[self.socket[sock]] = nil;
 648                 self.socket[sock] = nil;
 649         elseif self.socketset[sock] then
 650                 self.socket[self.socketset[sock]] = nil;
 651                 self.socketset[sock] = nil;
 652         end
 653         sock:close();
 654 end
 655
 656 function resolver:socket_wrapper_set(func)  -- - - - - - - socket_wrapper_set
 657         self.socket_wrapper = func;
 658 end
 659
 660
 661 function resolver:closeall ()    -- - - - - - - - - - - - - - - - - -  closeall
 662         for i,sock in ipairs(self.socket) do
 663                 self.socket[i] = nil;
 664                 self.socketset[sock] = nil;
 665                 sock:close();
 666         end
 667 end
 668
 669
 670 function resolver:remember(rr, type)    -- - - - - - - - - - - - - -  remember
 671         --print ('remember', type, rr.class, rr.type, rr.name)
 672         local qname, qtype, qclass = standardize(rr.name, rr.type, rr.class);
 673
 674         if type ~= '*' then
 675                 type = qtype;
 676                 local all = get(self.cache, qclass, '*', qname);
 677                 --print('remember all', all);
 678                 if all then append(all, rr); end
 679         end
 680
 681         self.cache = self.cache or setmetatable({}, cache_metatable);
 682         local rrs = get(self.cache, qclass, type, qname) or
 683                 set(self.cache, qclass, type, qname, setmetatable({}, rrs_metatable));
 684         append(rrs, rr);
 685
 686         if type == 'MX' then self.unsorted[rrs] = true; end
 687 end
 688
 689
 690 local function comp_mx(a, b)    -- - - - - - - - - - - - - - - - - - - comp_mx
 691         return (a.pref == b.pref) and (a.mx < b.mx) or (a.pref < b.pref);
 692 end
 693
 694
 695 function resolver:peek (qname, qtype, qclass)    -- - - - - - - - - - - -  peek
 696         qname, qtype, qclass = standardize(qname, qtype, qclass);
 697         local rrs = get(self.cache, qclass, qtype, qname);
 698         if not rrs then return nil; end
 699         if prune(rrs, socket.gettime()) and qtype == '*' or not next(rrs) then
 700                 set(self.cache, qclass, qtype, qname, nil);
 701                 return nil;
 702         end
 703         if self.unsorted[rrs] then table.sort (rrs, comp_mx); end
 704         return rrs;
 705 end
 706
 707
 708 function resolver:purge(soft)    -- - - - - - - - - - - - - - - - - - -  purge
 709         if soft == 'soft' then
 710                 self.time = socket.gettime();
 711                 for class,types in pairs(self.cache or {}) do
 712                         for type,names in pairs(types) do
 713                                 for name,rrs in pairs(names) do
 714                                         prune(rrs, self.time, 'soft')
 715                                 end
 716                         end
 717                 end
 718         else self.cache = setmetatable({}, cache_metatable); end
 719 end
 720
 721
 722 function resolver:query(qname, qtype, qclass)    -- - - - - - - - - - -- query
 723         qname, qtype, qclass = standardize(qname, qtype, qclass)
 724
 725         if not self.server then self:adddefaultnameservers(); end
 726
 727         local question = encodeQuestion(qname, qtype, qclass);
 728         local peek = self:peek (qname, qtype, qclass);
 729         if peek then return peek; end
 730
 731         local header, id = encodeHeader();
 732         --print ('query  id', id, qclass, qtype, qname)
 733         local o = {
 734                 packet = header..question,
 735                 server = self.best_server,
 736                 delay  = 1,
 737                 retry  = socket.gettime() + self.delays[1]
 738         };
 739
 740         -- remember the query
 741         self.active[id] = self.active[id] or {};
 742         self.active[id][question] = o;
 743
 744         -- remember which coroutine wants the answer
 745         local co = coroutine.running();
 746         if co then
 747                 set(self.wanted, qclass, qtype, qname, co, true);
 748                 --set(self.yielded, co, qclass, qtype, qname, true);
 749         end
 750
 751         local conn, err = self:getsocket(o.server)
 752         if not conn then
 753                 return nil, err;
 754         end
 755         conn:send (o.packet)
 756
 757         if timer and self.timeout then
 758                 local num_servers = #self.server;
 759                 local i = 1;
 760                 timer.add_task(self.timeout, function ()
 761                         if get(self.wanted, qclass, qtype, qname, co) then
 762                                 if i < num_servers then
 763                                         i = i + 1;
 764                                         self:servfail(conn);
 765                                         o.server = self.best_server;
 766                                         conn, err = self:getsocket(o.server);
 767                                         if conn then
 768                                                 conn:send(o.packet);
 769                                                 return self.timeout;
 770                                         end
 771                                 end
 772                                 -- Tried everything, failed
 773                                 self:cancel(qclass, qtype, qname, co, true);
 774                         end
 775                 end)
 776         end
 777         return true;
 778 end
 779
 780 function resolver:servfail(sock)
 781         -- Resend all queries for this server
 782
 783         local num = self.socketset[sock]
 784
 785         -- Socket is dead now
 786         self:voidsocket(sock);
 787
 788         -- Find all requests to the down server, and retry on the next server
 789         self.time = socket.gettime();
 790         for id,queries in pairs(self.active) do
 791                 for question,o in pairs(queries) do
 792                         if o.server == num then -- This request was to the broken server
 793                                 o.server = o.server + 1 -- Use next server
 794                                 if o.server > #self.server then
 795                                         o.server = 1;
 796                                 end
 797
 798                                 o.retries = (o.retries or 0) + 1;
 799                                 if o.retries >= #self.server then
 800                                         --print('timeout');
 801                                         queries[question] = nil;
 802                                 else
 803                                         local _a = self:getsocket(o.server);
 804                                         if _a then _a:send(o.packet); end
 805                                 end
 806                         end
 807                 end
 808                 if next(queries) == nil then
 809                         self.active[id] = nil;
 810                 end
 811         end
 812
 813         if num == self.best_server then
 814                 self.best_server = self.best_server + 1;
 815                 if self.best_server > #self.server then
 816                         -- Exhausted all servers, try first again
 817                         self.best_server = 1;
 818                 end
 819         end
 820 end
 821
 822 function resolver:settimeout(seconds)
 823         self.timeout = seconds;
 824 end
 825
 826 function resolver:receive(rset)    -- - - - - - - - - - - - - - - - -  receive
 827         --print('receive');  print(self.socket);
 828         self.time = socket.gettime();
 829         rset = rset or self.socket;
 830
 831         local response;
 832         for i,sock in pairs(rset) do
 833
 834                 if self.socketset[sock] then
 835                         local packet = sock:receive();
 836                         if packet then
 837                                 response = self:decode(packet);
 838                                 if response and self.active[response.header.id]
 839                                         and self.active[response.header.id][response.question.raw] then
 840                                         --print('received response');
 841                                         --self.print(response);
 842
 843                                         for j,rr in pairs(response.answer) do
 844                                                 if rr.name:sub(-#response.question[1].name, -1) == response.question[1].name then
 845                                                         self:remember(rr, response.question[1].type)
 846                                                 end
 847                                         end
 848
 849                                         -- retire the query
 850                                         local queries = self.active[response.header.id];
 851                                         queries[response.question.raw] = nil;
 852
 853                                         if not next(queries) then self.active[response.header.id] = nil; end
 854                                         if not next(self.active) then self:closeall(); end
 855
 856                                         -- was the query on the wanted list?
 857                                         local q = response.question[1];
 858                                         local cos = get(self.wanted, q.class, q.type, q.name);
 859                                         if cos then
 860                                                 for co in pairs(cos) do
 861                                                         set(self.yielded, co, q.class, q.type, q.name, nil);
 862                                                         if coroutine.status(co) == "suspended" then coroutine.resume(co); end
 863                                                 end
 864                                                 set(self.wanted, q.class, q.type, q.name, nil);
 865                                         end
 866                                 end
 867
 868                         end
 869                 end
 870         end
 871
 872         return response;
 873 end
 874
 875
 876 function resolver:feed(sock, packet, force)
 877         --print('receive'); print(self.socket);
 878         self.time = socket.gettime();
 879
 880         local response = self:decode(packet, force);
 881         if response and self.active[response.header.id]
 882                 and self.active[response.header.id][response.question.raw] then
 883                 --print('received response');
 884                 --self.print(response);
 885
 886                 for j,rr in pairs(response.answer) do
 887                         self:remember(rr, response.question[1].type);
 888                 end
 889
 890                 -- retire the query
 891                 local queries = self.active[response.header.id];
 892                 queries[response.question.raw] = nil;
 893                 if not next(queries) then self.active[response.header.id] = nil; end
 894                 if not next(self.active) then self:closeall(); end
 895
 896                 -- was the query on the wanted list?
 897                 local q = response.question[1];
 898                 if q then
 899                         local cos = get(self.wanted, q.class, q.type, q.name);
 900                         if cos then
 901                                 for co in pairs(cos) do
 902                                         set(self.yielded, co, q.class, q.type, q.name, nil);
 903                                         if coroutine.status(co) == "suspended" then coroutine.resume(co); end
 904                                 end
 905                                 set(self.wanted, q.class, q.type, q.name, nil);
 906                         end
 907                 end
 908         end
 909
 910         return response;
 911 end
 912
 913 function resolver:cancel(qclass, qtype, qname, co, call_handler)
 914         local cos = get(self.wanted, qclass, qtype, qname);
 915         if cos then
 916                 if call_handler then
 917                         coroutine.resume(co);
 918                 end
 919                 cos[co] = nil;
 920         end
 921 end
 922
 923 function resolver:pulse()    -- - - - - - - - - - - - - - - - - - - - -  pulse
 924         --print(':pulse');
 925         while self:receive() do end
 926         if not next(self.active) then return nil; end
 927
 928         self.time = socket.gettime();
 929         for id,queries in pairs(self.active) do
 930                 for question,o in pairs(queries) do
 931                         if self.time >= o.retry then
 932
 933                                 o.server = o.server + 1;
 934                                 if o.server > #self.server then
 935                                         o.server = 1;
 936                                         o.delay = o.delay + 1;
 937                                 end
 938
 939                                 if o.delay > #self.delays then
 940                                         --print('timeout');
 941                                         queries[question] = nil;
 942                                         if not next(queries) then self.active[id] = nil; end
 943                                         if not next(self.active) then return nil; end
 944                                 else
 945                                         --print('retry', o.server, o.delay);
 946                                         local _a = self.socket[o.server];
 947                                         if _a then _a:send(o.packet); end
 948                                         o.retry = self.time + self.delays[o.delay];
 949                                 end
 950                         end
 951                 end
 952         end
 953
 954         if next(self.active) then return true; end
 955         return nil;
 956 end
 957
 958
 959 function resolver:lookup(qname, qtype, qclass)    -- - - - - - - - - -  lookup
 960         self:query (qname, qtype, qclass)
 961         while self:pulse() do
 962                 local recvt = {}
 963                 for i, s in ipairs(self.socket) do
 964                         recvt[i] = s
 965                 end
 966                 socket.select(recvt, nil, 4)
 967         end
 968         --print(self.cache);
 969         return self:peek(qname, qtype, qclass);
 970 end
 971
 972 function resolver:lookupex(handler, qname, qtype, qclass)    -- - - - - - - - - -  lookup
 973         return self:peek(qname, qtype, qclass) or self:query(qname, qtype, qclass);
 974 end
 975
 976 function resolver:tohostname(ip)
 977         return dns.lookup(ip:gsub("(%d+)%.(%d+)%.(%d+)%.(%d+)", "%4.%3.%2.%1.in-addr.arpa."), "PTR");
 978 end
 979
 980 --print ---------------------------------------------------------------- print
 981
 982
 983 local hints = {    -- - - - - - - - - - - - - - - - - - - - - - - - - - - hints
 984         qr = { [0]='query', 'response' },
 985         opcode = { [0]='query', 'inverse query', 'server status request' },
 986         aa = { [0]='non-authoritative', 'authoritative' },
 987         tc = { [0]='complete', 'truncated' },
 988         rd = { [0]='recursion not desired', 'recursion desired' },
 989         ra = { [0]='recursion not available', 'recursion available' },
 990         z  = { [0]='(reserved)' },
 991         rcode = { [0]='no error', 'format error', 'server failure', 'name error', 'not implemented' },
 992
 993         type = dns.type,
 994         class = dns.class
 995 };
 996
 997
 998 local function hint(p, s)    -- - - - - - - - - - - - - - - - - - - - - - hint
 999         return (hints[s] and hints[s][p[s]]) or '';
1000 end
1001
1002
1003 function resolver.print(response)    -- - - - - - - - - - - - - resolver.print
1004         for s,s in pairs { 'id', 'qr', 'opcode', 'aa', 'tc', 'rd', 'ra', 'z',
1005                                                 'rcode', 'qdcount', 'ancount', 'nscount', 'arcount' } do
1006                 print( string.format('%-30s', 'header.'..s), response.header[s], hint(response.header, s) );
1007         end
1008
1009         for i,question in ipairs(response.question) do
1010                 print(string.format ('question[%i].name         ', i), question.name);
1011                 print(string.format ('question[%i].type         ', i), question.type);
1012                 print(string.format ('question[%i].class        ', i), question.class);
1013         end
1014
1015         local common = { name=1, type=1, class=1, ttl=1, rdlength=1, rdata=1 };
1016         local tmp;
1017         for s,s in pairs({'answer', 'authority', 'additional'}) do
1018                 for i,rr in pairs(response[s]) do
1019                         for j,t in pairs({ 'name', 'type', 'class', 'ttl', 'rdlength' }) do
1020                                 tmp = string.format('%s[%i].%s', s, i, t);
1021                                 print(string.format('%-30s', tmp), rr[t], hint(rr, t));
1022                         end
1023                         for j,t in pairs(rr) do
1024                                 if not common[j] then
1025                                         tmp = string.format('%s[%i].%s', s, i, j);
1026                                         print(string.format('%-30s  %s', tostring(tmp), tostring(t)));
1027                                 end
1028                         end
1029                 end
1030         end
1031 end
1032
1033
1034 -- module api ------------------------------------------------------ module api
1035
1036
1037 function dns.resolver ()    -- - - - - - - - - - - - - - - - - - - - - resolver
1038         -- this function seems to be redundant with resolver.new ()
1039
1040         local r = { active = {}, cache = {}, unsorted = {}, wanted = {}, yielded = {}, best_server = 1 };
1041         setmetatable (r, resolver);
1042         setmetatable (r.cache, cache_metatable);
1043         setmetatable (r.unsorted, { __mode = 'kv' });
1044         return r;
1045 end
1046
1047 local _resolver = dns.resolver();
1048 dns._resolver = _resolver;
1049
1050 function dns.lookup(...)    -- - - - - - - - - - - - - - - - - - - - -  lookup
1051         return _resolver:lookup(...);
1052 end
1053
1054 function dns.tohostname(...)
1055         return _resolver:tohostname(...);
1056 end
1057
1058 function dns.purge(...)    -- - - - - - - - - - - - - - - - - - - - - -  purge
1059         return _resolver:purge(...);
1060 end
1061
1062 function dns.peek(...)    -- - - - - - - - - - - - - - - - - - - - - - -  peek
1063         return _resolver:peek(...);
1064 end
1065
1066 function dns.query(...)    -- - - - - - - - - - - - - - - - - - - - - -  query
1067         return _resolver:query(...);
1068 end
1069
1070 function dns.feed(...)    -- - - - - - - - - - - - - - - - - - - - - - -  feed
1071         return _resolver:feed(...);
1072 end
1073
1074 function dns.cancel(...)  -- - - - - - - - - - - - - - - - - - - - - -  cancel
1075         return _resolver:cancel(...);
1076 end
1077
1078 function dns.settimeout(...)
1079         return _resolver:settimeout(...);
1080 end
1081
1082 function dns.cache()
1083         return _resolver.cache;
1084 end
1085
1086 function dns.socket_wrapper_set(...)    -- - - - - - - - -  socket_wrapper_set
1087         return _resolver:socket_wrapper_set(...);
1088 end
1089
1090 return dns;