util/rfc3484.lua

   1 -- Prosody IM
   2 -- Copyright (C) 2008-2011 Florian Zeitz
   3 --
   4 -- This project is MIT/X11 licensed. Please see the
   5 -- COPYING file in the source package for more information.
   6 --
   7
   8 local commonPrefixLength = require"util.ip".commonPrefixLength
   9 local new_ip = require"util.ip".new_ip;
  10
  11 local function t_sort(t, comp)
  12         for i = 1, (#t - 1) do
  13                 for j = (i + 1), #t do
  14                         local a, b = t[i], t[j];
  15                         if not comp(a,b) then
  16                                 t[i], t[j] = b, a;
  17                         end
  18                 end
  19         end
  20 end
  21
  22 local function source(dest, candidates)
  23         local function comp(ipA, ipB)
  24                 -- Rule 1: Prefer same address
  25                 if dest == ipA then
  26                         return true;
  27                 elseif dest == ipB then
  28                         return false;
  29                 end
  30
  31                 -- Rule 2: Prefer appropriate scope
  32                 if ipA.scope < ipB.scope then
  33                         if ipA.scope < dest.scope then
  34                                 return false;
  35                         else
  36                                 return true;
  37                         end
  38                 elseif ipA.scope > ipB.scope then
  39                         if ipB.scope < dest.scope then
  40                                 return true;
  41                         else
  42                                 return false;
  43                         end
  44                 end
  45
  46                 -- Rule 3: Avoid deprecated addresses
  47                 -- XXX: No way to determine this
  48                 -- Rule 4: Prefer home addresses
  49                 -- XXX: Mobility Address related, no way to determine this
  50                 -- Rule 5: Prefer outgoing interface
  51                 -- XXX: Interface to address relation. No way to determine this
  52                 -- Rule 6: Prefer matching label
  53                 if ipA.label == dest.label and ipB.label ~= dest.label then
  54                         return true;
  55                 elseif ipB.label == dest.label and ipA.label ~= dest.label then
  56                         return false;
  57                 end
  58
  59                 -- Rule 7: Prefer public addresses (over temporary ones)
  60                 -- XXX: No way to determine this
  61                 -- Rule 8: Use longest matching prefix
  62                 if commonPrefixLength(ipA, dest) > commonPrefixLength(ipB, dest) then
  63                         return true;
  64                 else
  65                         return false;
  66                 end
  67         end
  68
  69         t_sort(candidates, comp);
  70         return candidates[1];
  71 end
  72
  73 local function destination(candidates, sources)
  74         local sourceAddrs = {};
  75         local function comp(ipA, ipB)
  76                 local ipAsource = sourceAddrs[ipA];
  77                 local ipBsource = sourceAddrs[ipB];
  78                 -- Rule 1: Avoid unusable destinations
  79                 -- XXX: No such information
  80                 -- Rule 2: Prefer matching scope
  81                 if ipA.scope == ipAsource.scope and ipB.scope ~= ipBsource.scope then
  82                         return true;
  83                 elseif ipA.scope ~= ipAsource.scope and ipB.scope == ipBsource.scope then
  84                         return false;
  85                 end
  86
  87                 -- Rule 3: Avoid deprecated addresses
  88                 -- XXX: No way to determine this
  89                 -- Rule 4: Prefer home addresses
  90                 -- XXX: Mobility Address related, no way to determine this
  91                 -- Rule 5: Prefer matching label
  92                 if ipAsource.label == ipA.label and ipBsource.label ~= ipB.label then
  93                         return true;
  94                 elseif ipBsource.label == ipB.label and ipAsource.label ~= ipA.label then
  95                         return false;
  96                 end
  97
  98                 -- Rule 6: Prefer higher precedence
  99                 if ipA.precedence > ipB.precedence then
 100                         return true;
 101                 elseif ipA.precedence < ipB.precedence then
 102                         return false;
 103                 end
 104
 105                 -- Rule 7: Prefer native transport
 106                 -- XXX: No way to determine this
 107                 -- Rule 8: Prefer smaller scope
 108                 if ipA.scope < ipB.scope then
 109                         return true;
 110                 elseif ipA.scope > ipB.scope then
 111                         return false;
 112                 end
 113
 114                 -- Rule 9: Use longest matching prefix
 115                 if commonPrefixLength(ipA, ipAsource) > commonPrefixLength(ipB, ipBsource) then
 116                         return true;
 117                 elseif commonPrefixLength(ipA, ipAsource) < commonPrefixLength(ipB, ipBsource) then
 118                         return false;
 119                 end
 120
 121                 -- Rule 10: Otherwise, leave order unchanged
 122                 return true;
 123         end
 124         for _, ip in ipairs(candidates) do
 125                 sourceAddrs[ip] = source(ip, sources);
 126         end
 127
 128         t_sort(candidates, comp);
 129         return candidates;
 130 end
 131
 132 return {source = source,
 133         destination = destination};