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 host_item *h, *next_h, *prev;
  57
  58 /* Look up each host address. A lookup may add additional items into the chain
  59 if there are multiple addresses. Hence the use of next_h to start each cycle of
  60 the loop at the next original host. If any host is identified as being the local
  61 host, omit it and any subsequent hosts - i.e. treat the list like an ordered
  62 list of MX hosts. If the first host is the local host, act according to the
  63 "self" option in the configuration. */
  64
  65 for (prev = NULL, h = addr->host_list; h; h = next_h)
  66   {
  67   const uschar *canonical_name;
  68   int rc, len, port, mx, sort_key;
  69
  70   next_h = h->next;
  71   if (h->address) { 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   /* Store the previous mx and sort_key values, which were assigned in
  82   host_build_hostlist and will be overwritten by host_find_bydns. */
  83
  84   mx = h->mx;
  85   sort_key = h->sort_key;
  86
  87   /* If the name ends with "/MX", we interpret it to mean "the list of hosts
  88   pointed to by MX records with this name", and the MX record values override
  89   the ordering from host_build_hostlist. */
  90
  91   len = Ustrlen(h->name);
  92   if (len > 3 && strcmpic(h->name + len - 3, US"/mx") == 0)
  93     {
  94     int whichrrs = lookup_type & LK_IPV4_ONLY
  95       ? HOST_FIND_BY_MX | HOST_FIND_IPV4_ONLY
  96       : lookup_type & LK_IPV4_PREFER
  97       ? HOST_FIND_BY_MX | HOST_FIND_IPV4_FIRST
  98       : HOST_FIND_BY_MX;
  99
 100     DEBUG(D_route|D_host_lookup)
 101       debug_printf("doing DNS MX lookup for %s\n", h->name);
 102
 103     mx = MX_NONE;
 104     h->name = string_copyn(h->name, len - 3);
 105     rc = host_find_bydns(h,
 106         ignore_target_hosts,
 107         whichrrs,                       /* look only for MX records */
 108         NULL,                           /* SRV service not relevant */
 109         NULL,                           /* failing srv domains not relevant */
 110         NULL,                           /* no special mx failing domains */
 111         &rblock->dnssec,                /* dnssec request/require */
 112         NULL,                           /* fully_qualified_name */
 113         NULL);                          /* indicate local host removed */
 114     }
 115
 116   /* If explicitly configured to look up by name, or if the "host name" is
 117   actually an IP address, do a byname lookup. */
 118
 119   else if (lookup_type & LK_BYNAME || string_is_ip_address(h->name, NULL) != 0)
 120     {
 121     DEBUG(D_route|D_host_lookup) debug_printf("calling host_find_byname\n");
 122     rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE,
 123       &canonical_name, TRUE);
 124     }
 125
 126   /* Otherwise, do a DNS lookup. If that yields "host not found", and the
 127   lookup type is the default (i.e. "bydns" is not explicitly configured),
 128   follow up with a byname lookup, just in case. */
 129
 130   else
 131     {
 132     BOOL removed;
 133     int whichrrs = lookup_type & LK_IPV4_ONLY
 134       ? HOST_FIND_BY_A
 135       : lookup_type & LK_IPV4_PREFER
 136       ? HOST_FIND_BY_A | HOST_FIND_BY_AAAA | HOST_FIND_IPV4_FIRST
 137       : HOST_FIND_BY_A | HOST_FIND_BY_AAAA;
 138
 139     DEBUG(D_route|D_host_lookup) debug_printf("doing DNS lookup\n");
 140     switch (rc = host_find_bydns(h, ignore_target_hosts, whichrrs, NULL,
 141         NULL, NULL,
 142         &rblock->dnssec,                        /* domains for request/require */
 143         &canonical_name, &removed))
 144       {
 145       case HOST_FOUND:
 146         if (removed) setflag(addr, af_local_host_removed);
 147         break;
 148       case HOST_FIND_FAILED:
 149         if (lookup_type & LK_DEFAULT)
 150           {
 151           DEBUG(D_route|D_host_lookup)
 152             debug_printf("DNS lookup failed: trying getipnodebyname\n");
 153           rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE,
 154             &canonical_name, TRUE);
 155           }
 156         break;
 157       }
 158     }
 159
 160   /* Temporary failure defers, unless pass_on_timeout is set */
 161
 162   if (rc == HOST_FIND_SECURITY)
 163     {
 164     addr->message = string_sprintf("host lookup for %s done insecurely" , h->name);
 165     addr->basic_errno = ERRNO_DNSDEFER;
 166     return DEFER;
 167     }
 168   if (rc == HOST_FIND_AGAIN)
 169     {
 170     if (rblock->pass_on_timeout)
 171       {
 172       DEBUG(D_route)
 173         debug_printf("%s router timed out and pass_on_timeout set\n",
 174           rblock->name);
 175       return PASS;
 176       }
 177     addr->message = string_sprintf("host lookup for %s did not complete "
 178       "(DNS timeout?)", h->name);
 179     addr->basic_errno = ERRNO_DNSDEFER;
 180     return DEFER;
 181     }
 182
 183   /* Permanent failure is controlled by host_find_failed */
 184
 185   if (rc == HOST_FIND_FAILED)
 186     {
 187     if (hff_code == hff_ignore)
 188       {
 189       if (prev == NULL) addr->host_list = next_h; else prev->next = next_h;
 190       continue;   /* With the next host, leave prev unchanged */
 191       }
 192
 193     if (hff_code == hff_pass) return PASS;
 194     if (hff_code == hff_decline) return DECLINE;
 195
 196     addr->basic_errno = ERRNO_UNKNOWNHOST;
 197     addr->message =
 198       string_sprintf("lookup of host \"%s\" failed in %s router%s",
 199         h->name, rblock->name,
 200         f.host_find_failed_syntax? ": syntax error in name" : "");
 201
 202     if (hff_code == hff_defer) return DEFER;
 203     if (hff_code == hff_fail) return FAIL;
 204
 205     addr->special_action = SPECIAL_FREEZE;
 206     return DEFER;
 207     }
 208
 209   /* Deal with the settings that were previously cleared:
 210   port, mx and sort_key. */
 211
 212   if (port != PORT_NONE)
 213     {
 214     host_item *hh;
 215     for (hh = h; hh != next_h; hh = hh->next) hh->port = port;
 216     }
 217
 218   if (mx != MX_NONE)
 219     {
 220     host_item *hh;
 221     for (hh = h; hh != next_h; hh = hh->next)
 222       {
 223       hh->mx = mx;
 224       hh->sort_key = sort_key;
 225       }
 226     }
 227
 228   /* A local host gets chopped, with its successors, if there are previous
 229   hosts. Otherwise the self option is used. If it is set to "send", any
 230   subsequent hosts that are also the local host do NOT get chopped. */
 231
 232   if (rc == HOST_FOUND_LOCAL && !self_send)
 233     {
 234     if (prev)
 235       {
 236       DEBUG(D_route)
 237         {
 238         debug_printf("Removed from host list:\n");
 239         for (; h != NULL; h = h->next) debug_printf("  %s\n", h->name);
 240         }
 241       prev->next = NULL;
 242       setflag(addr, af_local_host_removed);
 243       break;
 244       }
 245     rc = rf_self_action(addr, h, rblock->self_code, rblock->self_rewrite,
 246       rblock->self, addr_new);
 247     if (rc != OK)
 248       {
 249       addr->host_list = NULL;   /* Kill the host list for */
 250       return rc;                /* anything other than "send" */
 251       }
 252     self_send = TRUE;
 253     }
 254
 255   /* Ensure that prev is the host before next_h; this will not be h if a lookup
 256   found multiple addresses or multiple MX records. */
 257
 258   prev = h;
 259   while (prev->next != next_h) prev = prev->next;
 260   }
 261
 262 return OK;
 263 }
 264
 265 /* End of rf_lookup_hostlist.c */