src/src/routers/rf_lookup_hostlist.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2015 */
   6 /* See the file NOTICE for conditions of use and distribution. */
   7
   8
   9 #include "../exim.h"
  10 #include "rf_functions.h"
  11
  12
  13
  14 /*************************************************
  15 *     Look up IP addresses for a set of hosts    *
  16 *************************************************/
  17
  18 /* This function is called by a router to fill in the IP addresses for a set of
  19 hosts that are attached to an address. Each host has its name and MX value set;
  20 and those that need processing have their address fields set NULL. Multihomed
  21 hosts cause additional blocks to be inserted into the chain.
  22
  23 This function also supports pseudo-hosts whose names end with "/MX". In this
  24 case, MX records are looked up for the name, and the list of hosts obtained
  25 replaces the incoming "host". In other words, "x/MX" is shorthand for "those
  26 hosts pointed to by x's MX records".
  27
  28 It is also possible for a port to be specified along with the host name or IP
  29 address. The syntax is to add ":port" on to the end. This doesn't work with
  30 IPv6 addresses, so we allow IP addresses to be enclosed in [] in order to make
  31 this work. The specification of the port must come last, that is, after "/MX"
  32 if that is present.
  33
  34 Arguments:
  35   rblock               the router block
  36   addr                 the address being routed
  37   ignore_target_hosts  list of hosts to ignore
  38   lookup_type          LK_DEFAULT or LK_BYNAME or LK_BYDNS,
  39                        plus LK_IPV4_{ONLY,PREFER}
  40   hff_code             what to do for host find failed
  41   addr_new             passed to rf_self_action for self=reroute
  42
  43 Returns:               OK
  44                        DEFER host lookup defer
  45                        PASS  timeout etc and pass_on_timeout set
  46                        self_action: PASS, DECLINE, DEFER, FAIL, FREEZE
  47                        hff_code after host find failed
  48 */
  49
  50 int
  51 rf_lookup_hostlist(router_instance *rblock, address_item *addr,
  52   uschar *ignore_target_hosts, int lookup_type, int hff_code,
  53   address_item **addr_new)
  54 {
  55 BOOL self_send = FALSE;
  56
  57 /* Look up each host address. A lookup may add additional items into the chain
  58 if there are multiple addresses. Hence the use of next_h to start each cycle of
  59 the loop at the next original host. If any host is identified as being the local
  60 host, omit it and any subsequent hosts - i.e. treat the list like an ordered
  61 list of MX hosts. If the first host is the local host, act according to the
  62 "self" option in the configuration. */
  63
  64 for (host_item * prev = NULL, * h = addr->host_list, *next_h; h; h = next_h)
  65   {
  66   const uschar *canonical_name;
  67   int rc, len, port, mx, sort_key;
  68
  69   next_h = h->next;
  70   if (h->address) { prev = h; continue; }
  71
  72   DEBUG(D_route|D_host_lookup)
  73     debug_printf("finding IP address for %s\n", h->name);
  74
  75   /* Handle any port setting that may be on the name; it will be removed
  76   from the end of the name. */
  77
  78   port = host_item_get_port(h);
  79
  80   /* Store the previous mx and sort_key values, which were assigned in
  81   host_build_hostlist and will be overwritten by host_find_bydns. */
  82
  83   mx = h->mx;
  84   sort_key = h->sort_key;
  85
  86   /* If the name ends with "/MX", we interpret it to mean "the list of hosts
  87   pointed to by MX records with this name", and the MX record values override
  88   the ordering from host_build_hostlist. */
  89
  90   len = Ustrlen(h->name);
  91   if (len > 3 && strcmpic(h->name + len - 3, US"/mx") == 0)
  92     {
  93     int whichrrs = lookup_type & LK_IPV4_ONLY
  94       ? HOST_FIND_BY_MX | HOST_FIND_IPV4_ONLY
  95       : lookup_type & LK_IPV4_PREFER
  96       ? HOST_FIND_BY_MX | HOST_FIND_IPV4_FIRST
  97       : HOST_FIND_BY_MX;
  98
  99     DEBUG(D_route|D_host_lookup)
 100       debug_printf("doing DNS MX lookup for %s\n", h->name);
 101
 102     mx = MX_NONE;
 103     h->name = string_copyn(h->name, len - 3);
 104     rc = host_find_bydns(h,
 105         ignore_target_hosts,
 106         whichrrs,                       /* look only for MX records */
 107         NULL,                           /* SRV service not relevant */
 108         NULL,                           /* failing srv domains not relevant */
 109         NULL,                           /* no special mx failing domains */
 110         &rblock->dnssec,                /* dnssec request/require */
 111         NULL,                           /* fully_qualified_name */
 112         NULL);                          /* indicate local host removed */
 113     }
 114
 115   /* If explicitly configured to look up by name, or if the "host name" is
 116   actually an IP address, do a byname lookup. */
 117
 118   else if (lookup_type & LK_BYNAME || string_is_ip_address(h->name, NULL) != 0)
 119     {
 120     DEBUG(D_route|D_host_lookup) debug_printf("calling host_find_byname\n");
 121     rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE,
 122       &canonical_name, TRUE);
 123     }
 124
 125   /* Otherwise, do a DNS lookup. If that yields "host not found", and the
 126   lookup type is the default (i.e. "bydns" is not explicitly configured),
 127   follow up with a byname lookup, just in case. */
 128
 129   else
 130     {
 131     BOOL removed;
 132     int whichrrs = lookup_type & LK_IPV4_ONLY
 133       ? HOST_FIND_BY_A
 134       : lookup_type & LK_IPV4_PREFER
 135       ? HOST_FIND_BY_A | HOST_FIND_BY_AAAA | HOST_FIND_IPV4_FIRST
 136       : HOST_FIND_BY_A | HOST_FIND_BY_AAAA;
 137
 138     DEBUG(D_route|D_host_lookup) debug_printf("doing DNS lookup\n");
 139     switch (rc = host_find_bydns(h, ignore_target_hosts, whichrrs, NULL,
 140         NULL, NULL,
 141         &rblock->dnssec,                        /* domains for request/require */
 142         &canonical_name, &removed))
 143       {
 144       case HOST_FOUND:
 145         if (removed) setflag(addr, af_local_host_removed);
 146         break;
 147       case HOST_FIND_FAILED:
 148         if (lookup_type & LK_DEFAULT)
 149           {
 150           DEBUG(D_route|D_host_lookup)
 151             debug_printf("DNS lookup failed: trying getipnodebyname\n");
 152           rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE,
 153             &canonical_name, TRUE);
 154           }
 155         break;
 156       }
 157     }
 158
 159   /* Temporary failure defers, unless pass_on_timeout is set */
 160
 161   if (rc == HOST_FIND_SECURITY)
 162     {
 163     addr->message = string_sprintf("host lookup for %s done insecurely" , h->name);
 164     addr->basic_errno = ERRNO_DNSDEFER;
 165     return DEFER;
 166     }
 167   if (rc == HOST_FIND_AGAIN)
 168     {
 169     if (rblock->pass_on_timeout)
 170       {
 171       DEBUG(D_route)
 172         debug_printf("%s router timed out and pass_on_timeout set\n",
 173           rblock->name);
 174       return PASS;
 175       }
 176     addr->message = string_sprintf("host lookup for %s did not complete "
 177       "(DNS timeout?)", h->name);
 178     addr->basic_errno = ERRNO_DNSDEFER;
 179     return DEFER;
 180     }
 181
 182   /* Permanent failure is controlled by host_find_failed */
 183
 184   if (rc == HOST_FIND_FAILED)
 185     {
 186     if (hff_code == hff_ignore)
 187       {
 188       if (prev == NULL) addr->host_list = next_h; else prev->next = next_h;
 189       continue;   /* With the next host, leave prev unchanged */
 190       }
 191
 192     if (hff_code == hff_pass) return PASS;
 193     if (hff_code == hff_decline) return DECLINE;
 194
 195     addr->basic_errno = ERRNO_UNKNOWNHOST;
 196     addr->message =
 197       string_sprintf("lookup of host \"%s\" failed in %s router%s",
 198         h->name, rblock->name,
 199         f.host_find_failed_syntax? ": syntax error in name" : "");
 200
 201     if (hff_code == hff_defer) return DEFER;
 202     if (hff_code == hff_fail) return FAIL;
 203
 204     addr->special_action = SPECIAL_FREEZE;
 205     return DEFER;
 206     }
 207
 208   /* Deal with the settings that were previously cleared:
 209   port, mx and sort_key. */
 210
 211   if (port != PORT_NONE)
 212     for (host_item * hh = h; hh != next_h; hh = hh->next)
 213       hh->port = port;
 214
 215   if (mx != MX_NONE)
 216     for (host_item * hh = h; hh != next_h; hh = hh->next)
 217       {
 218       hh->mx = mx;
 219       hh->sort_key = sort_key;
 220       }
 221
 222   /* A local host gets chopped, with its successors, if there are previous
 223   hosts. Otherwise the self option is used. If it is set to "send", any
 224   subsequent hosts that are also the local host do NOT get chopped. */
 225
 226   if (rc == HOST_FOUND_LOCAL && !self_send)
 227     {
 228     if (prev)
 229       {
 230       DEBUG(D_route)
 231         {
 232         debug_printf("Removed from host list:\n");
 233         for (; h; h = h->next) debug_printf("  %s\n", h->name);
 234         }
 235       prev->next = NULL;
 236       setflag(addr, af_local_host_removed);
 237       break;
 238       }
 239     rc = rf_self_action(addr, h, rblock->self_code, rblock->self_rewrite,
 240       rblock->self, addr_new);
 241     if (rc != OK)
 242       {
 243       addr->host_list = NULL;   /* Kill the host list for */
 244       return rc;                /* anything other than "send" */
 245       }
 246     self_send = TRUE;
 247     }
 248
 249   /* Ensure that prev is the host before next_h; this will not be h if a lookup
 250   found multiple addresses or multiple MX records. */
 251
 252   prev = h;
 253   while (prev->next != next_h) prev = prev->next;
 254   }
 255
 256 return OK;
 257 }
 258
 259 /* End of rf_lookup_hostlist.c */