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