src/src/routers/rf_lookup_hostlist.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2009 */
   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 prev = NULL;
  65 for (h = addr->host_list; h != NULL; h = next_h)
  66   {
  67   uschar *canonical_name;
  68   int rc, len, port;
  69
  70   next_h = h->next;
  71   if (h->address != NULL) { prev = h; continue; }
  72
  73   DEBUG(D_route|D_host_lookup)
  74     debug_printf("finding IP address for %s\n", h->name);
  75
  76   /* Handle any port setting that may be on the name; it will be removed
  77   from the end of the name. */
  78
  79   port = host_item_get_port(h);
  80
  81   /* If the name ends with "/MX", we interpret it to mean "the list of hosts
  82   pointed to by MX records with this name". */
  83
  84   len = Ustrlen(h->name);
  85   if (len > 3 && strcmpic(h->name + len - 3, US"/mx") == 0)
  86     {
  87     DEBUG(D_route|D_host_lookup)
  88       debug_printf("doing DNS MX lookup for %s\n", h->name);
  89
  90     h->name = string_copyn(h->name, len - 3);
  91     rc = host_find_bydns(h,
  92         ignore_target_hosts,
  93         HOST_FIND_BY_MX,                /* look only for MX records */
  94         NULL,                           /* SRV service not relevant */
  95         NULL,                           /* failing srv domains not relevant */
  96         NULL,                           /* no special mx failing domains */
  97         NULL,                           /* fully_qualified_name */
  98         NULL);                          /* indicate local host removed */
  99     }
 100
 101   /* If explicitly configured to look up by name, or if the "host name" is
 102   actually an IP address, do a byname lookup. */
 103
 104   else if (lookup_type == lk_byname || string_is_ip_address(h->name, NULL) != 0)
 105     {
 106     DEBUG(D_route|D_host_lookup) debug_printf("calling host_find_byname\n");
 107     rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE,
 108       &canonical_name, TRUE);
 109     }
 110
 111   /* Otherwise, do a DNS lookup. If that yields "host not found", and the
 112   lookup type is the default (i.e. "bydns" is not explicitly configured),
 113   follow up with a byname lookup, just in case. */
 114
 115   else
 116     {
 117     BOOL removed;
 118     DEBUG(D_route|D_host_lookup) debug_printf("doing DNS lookup\n");
 119     rc = host_find_bydns(h, ignore_target_hosts, HOST_FIND_BY_A, NULL, NULL,
 120       NULL, &canonical_name, &removed);
 121     if (rc == HOST_FOUND)
 122       {
 123       if (removed) setflag(addr, af_local_host_removed);
 124       }
 125     else if (rc == HOST_FIND_FAILED)
 126       {
 127       if (lookup_type == lk_default)
 128         {
 129         DEBUG(D_route|D_host_lookup)
 130           debug_printf("DNS lookup failed: trying getipnodebyname\n");
 131         rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE,
 132           &canonical_name, TRUE);
 133         }
 134       }
 135     }
 136
 137   /* Temporary failure defers, unless pass_on_timeout is set */
 138
 139   if (rc == HOST_FIND_AGAIN)
 140     {
 141     if (rblock->pass_on_timeout)
 142       {
 143       DEBUG(D_route)
 144         debug_printf("%s router timed out and pass_on_timeout set\n",
 145           rblock->name);
 146       return PASS;
 147       }
 148     addr->message = string_sprintf("host lookup for %s did not complete "
 149       "(DNS timeout?)", h->name);
 150     addr->basic_errno = ERRNO_DNSDEFER;
 151     return DEFER;
 152     }
 153
 154   /* Permanent failure is controlled by host_find_failed */
 155
 156   if (rc == HOST_FIND_FAILED)
 157     {
 158     if (hff_code == hff_ignore)
 159       {
 160       if (prev == NULL) addr->host_list = next_h; else prev->next = next_h;
 161       continue;   /* With the next host, leave prev unchanged */
 162       }
 163
 164     if (hff_code == hff_pass) return PASS;
 165     if (hff_code == hff_decline) return DECLINE;
 166
 167     addr->message =
 168       string_sprintf("lookup of host \"%s\" failed in %s router%s",
 169         h->name, rblock->name,
 170         host_find_failed_syntax? ": syntax error in name" : "");
 171
 172     if (hff_code == hff_defer) return DEFER;
 173     if (hff_code == hff_fail) return FAIL;
 174
 175     addr->special_action = SPECIAL_FREEZE;
 176     return DEFER;
 177     }
 178
 179   /* Deal with a port setting */
 180
 181   if (port != PORT_NONE)
 182     {
 183     host_item *hh;
 184     for (hh = h; hh != next_h; hh = hh->next) hh->port = port;
 185     }
 186
 187   /* A local host gets chopped, with its successors, if there are previous
 188   hosts. Otherwise the self option is used. If it is set to "send", any
 189   subsequent hosts that are also the local host do NOT get chopped. */
 190
 191   if (rc == HOST_FOUND_LOCAL && !self_send)
 192     {
 193     if (prev != NULL)
 194       {
 195       DEBUG(D_route)
 196         {
 197         debug_printf("Removed from host list:\n");
 198         for (; h != NULL; h = h->next) debug_printf("  %s\n", h->name);
 199         }
 200       prev->next = NULL;
 201       setflag(addr, af_local_host_removed);
 202       break;
 203       }
 204     rc = rf_self_action(addr, h, rblock->self_code, rblock->self_rewrite,
 205       rblock->self, addr_new);
 206     if (rc != OK)
 207       {
 208       addr->host_list = NULL;   /* Kill the host list for */
 209       return rc;                /* anything other than "send" */
 210       }
 211     self_send = TRUE;
 212     }
 213
 214   /* Ensure that prev is the host before next_h; this will not be h if a lookup
 215   found multiple addresses or multiple MX records. */
 216
 217   prev = h;
 218   while (prev->next != next_h) prev = prev->next;
 219   }
 220
 221 return OK;
 222 }
 223
 224 /* End of rf_lookup_hostlist.c */