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   hff_code             what to do for host find failed
  40   addr_new             passed to rf_self_action for self=reroute
  41
  42 Returns:               OK
  43                        DEFER host lookup defer
  44                        PASS  timeout etc and pass_on_timeout set
  45                        self_action: PASS, DECLINE, DEFER, FAIL, FREEZE
  46                        hff_code after host find failed
  47 */
  48
  49 int
  50 rf_lookup_hostlist(router_instance *rblock, address_item *addr,
  51   uschar *ignore_target_hosts, int lookup_type, int hff_code,
  52   address_item **addr_new)
  53 {
  54 BOOL self_send = FALSE;
  55 host_item *h, *next_h, *prev;
  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 (prev = NULL, h = addr->host_list; 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     DEBUG(D_route|D_host_lookup)
  94       debug_printf("doing DNS MX lookup for %s\n", h->name);
  95
  96     mx = MX_NONE;
  97     h->name = string_copyn(h->name, len - 3);
  98     rc = host_find_bydns(h,
  99         ignore_target_hosts,
 100         HOST_FIND_BY_MX,                /* look only for MX records */
 101         NULL,                           /* SRV service not relevant */
 102         NULL,                           /* failing srv domains not relevant */
 103         NULL,                           /* no special mx failing domains */
 104         &rblock->dnssec,                /* dnssec request/require */
 105         NULL,                           /* fully_qualified_name */
 106         NULL);                          /* indicate local host removed */
 107     }
 108
 109   /* If explicitly configured to look up by name, or if the "host name" is
 110   actually an IP address, do a byname lookup. */
 111
 112   else if (lookup_type == lk_byname || string_is_ip_address(h->name, NULL) != 0)
 113     {
 114     DEBUG(D_route|D_host_lookup) debug_printf("calling host_find_byname\n");
 115     rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE,
 116       &canonical_name, TRUE);
 117     }
 118
 119   /* Otherwise, do a DNS lookup. If that yields "host not found", and the
 120   lookup type is the default (i.e. "bydns" is not explicitly configured),
 121   follow up with a byname lookup, just in case. */
 122
 123   else
 124     {
 125     BOOL removed;
 126     DEBUG(D_route|D_host_lookup) debug_printf("doing DNS lookup\n");
 127     switch (rc = host_find_bydns(h, ignore_target_hosts, HOST_FIND_BY_A, NULL,
 128         NULL, NULL,
 129         &rblock->dnssec,                        /* domains for request/require */
 130         &canonical_name, &removed))
 131       {
 132       case HOST_FOUND:
 133         if (removed) setflag(addr, af_local_host_removed);
 134         break;
 135       case HOST_FIND_FAILED:
 136         if (lookup_type == lk_default)
 137           {
 138           DEBUG(D_route|D_host_lookup)
 139             debug_printf("DNS lookup failed: trying getipnodebyname\n");
 140           rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE,
 141             &canonical_name, TRUE);
 142           }
 143         break;
 144       }
 145     }
 146
 147   /* Temporary failure defers, unless pass_on_timeout is set */
 148
 149   if (rc == HOST_FIND_AGAIN)
 150     {
 151     if (rblock->pass_on_timeout)
 152       {
 153       DEBUG(D_route)
 154         debug_printf("%s router timed out and pass_on_timeout set\n",
 155           rblock->name);
 156       return PASS;
 157       }
 158     addr->message = string_sprintf("host lookup for %s did not complete "
 159       "(DNS timeout?)", h->name);
 160     addr->basic_errno = ERRNO_DNSDEFER;
 161     return DEFER;
 162     }
 163
 164   /* Permanent failure is controlled by host_find_failed */
 165
 166   if (rc == HOST_FIND_FAILED)
 167     {
 168     if (hff_code == hff_ignore)
 169       {
 170       if (prev == NULL) addr->host_list = next_h; else prev->next = next_h;
 171       continue;   /* With the next host, leave prev unchanged */
 172       }
 173
 174     if (hff_code == hff_pass) return PASS;
 175     if (hff_code == hff_decline) return DECLINE;
 176
 177     addr->basic_errno = ERRNO_UNKNOWNHOST;
 178     addr->message =
 179       string_sprintf("lookup of host \"%s\" failed in %s router%s",
 180         h->name, rblock->name,
 181         host_find_failed_syntax? ": syntax error in name" : "");
 182
 183     if (hff_code == hff_defer) return DEFER;
 184     if (hff_code == hff_fail) return FAIL;
 185
 186     addr->special_action = SPECIAL_FREEZE;
 187     return DEFER;
 188     }
 189
 190   /* Deal with the settings that were previously cleared:
 191   port, mx and sort_key. */
 192
 193   if (port != PORT_NONE)
 194     {
 195     host_item *hh;
 196     for (hh = h; hh != next_h; hh = hh->next) hh->port = port;
 197     }
 198
 199   if (mx != MX_NONE)
 200     {
 201     host_item *hh;
 202     for (hh = h; hh != next_h; hh = hh->next)
 203       {
 204       hh->mx = mx;
 205       hh->sort_key = sort_key;
 206       }
 207     }
 208
 209   /* A local host gets chopped, with its successors, if there are previous
 210   hosts. Otherwise the self option is used. If it is set to "send", any
 211   subsequent hosts that are also the local host do NOT get chopped. */
 212
 213   if (rc == HOST_FOUND_LOCAL && !self_send)
 214     {
 215     if (prev)
 216       {
 217       DEBUG(D_route)
 218         {
 219         debug_printf("Removed from host list:\n");
 220         for (; h != NULL; h = h->next) debug_printf("  %s\n", h->name);
 221         }
 222       prev->next = NULL;
 223       setflag(addr, af_local_host_removed);
 224       break;
 225       }
 226     rc = rf_self_action(addr, h, rblock->self_code, rblock->self_rewrite,
 227       rblock->self, addr_new);
 228     if (rc != OK)
 229       {
 230       addr->host_list = NULL;   /* Kill the host list for */
 231       return rc;                /* anything other than "send" */
 232       }
 233     self_send = TRUE;
 234     }
 235
 236   /* Ensure that prev is the host before next_h; this will not be h if a lookup
 237   found multiple addresses or multiple MX records. */
 238
 239   prev = h;
 240   while (prev->next != next_h) prev = prev->next;
 241   }
 242
 243 return OK;
 244 }
 245
 246 /* End of rf_lookup_hostlist.c */