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 /* Copyright (c) The Exim Maintainers 2020 */
   7 /* See the file NOTICE for conditions of use and distribution. */
   8
   9
  10 #include "../exim.h"
  11 #include "rf_functions.h"
  12
  13
  14
  15 /*************************************************
  16 *     Look up IP addresses for a set of hosts    *
  17 *************************************************/
  18
  19 /* This function is called by a router to fill in the IP addresses for a set of
  20 hosts that are attached to an address. Each host has its name and MX value set;
  21 and those that need processing have their address fields set NULL. Multihomed
  22 hosts cause additional blocks to be inserted into the chain.
  23
  24 This function also supports pseudo-hosts whose names end with "/MX". In this
  25 case, MX records are looked up for the name, and the list of hosts obtained
  26 replaces the incoming "host". In other words, "x/MX" is shorthand for "those
  27 hosts pointed to by x's MX records".
  28
  29 It is also possible for a port to be specified along with the host name or IP
  30 address. The syntax is to add ":port" on to the end. This doesn't work with
  31 IPv6 addresses, so we allow IP addresses to be enclosed in [] in order to make
  32 this work. The specification of the port must come last, that is, after "/MX"
  33 if that is present.
  34
  35 Arguments:
  36   rblock               the router block
  37   addr                 the address being routed
  38   ignore_target_hosts  list of hosts to ignore
  39   lookup_type          LK_DEFAULT or LK_BYNAME or LK_BYDNS,
  40                        plus LK_IPV4_{ONLY,PREFER}
  41   hff_code             what to do for host find failed
  42   addr_new             passed to rf_self_action for self=reroute
  43
  44 Returns:               OK
  45                        DEFER host lookup defer
  46                        PASS  timeout etc and pass_on_timeout set
  47                        self_action: PASS, DECLINE, DEFER, FAIL, FREEZE
  48                        hff_code after host find failed
  49 */
  50
  51 int
  52 rf_lookup_hostlist(router_instance *rblock, address_item *addr,
  53   uschar *ignore_target_hosts, int lookup_type, int hff_code,
  54   address_item **addr_new)
  55 {
  56 BOOL self_send = FALSE;
  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 (host_item * prev = NULL, * h = addr->host_list, *next_h; 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 %s\n",
 153               f.running_in_test_harness
 154               ? "host_fake_gethostbyname" : "getipnodebyname");
 155           rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE,
 156             &canonical_name, TRUE);
 157           }
 158         break;
 159       }
 160     }
 161
 162   /* Temporary failure defers, unless pass_on_timeout is set */
 163
 164   if (rc == HOST_FIND_SECURITY)
 165     {
 166     addr->message = string_sprintf("host lookup for %s done insecurely" , h->name);
 167     addr->basic_errno = ERRNO_DNSDEFER;
 168     return DEFER;
 169     }
 170   if (rc == HOST_FIND_AGAIN)
 171     {
 172     if (rblock->pass_on_timeout)
 173       {
 174       DEBUG(D_route)
 175         debug_printf("%s router timed out and pass_on_timeout set\n",
 176           rblock->name);
 177       return PASS;
 178       }
 179     addr->message = string_sprintf("host lookup for %s did not complete "
 180       "(DNS timeout?)", h->name);
 181     addr->basic_errno = ERRNO_DNSDEFER;
 182     return DEFER;
 183     }
 184
 185   /* Permanent failure is controlled by host_find_failed */
 186
 187   if (rc == HOST_FIND_FAILED)
 188     {
 189     if (hff_code == hff_ignore)
 190       {
 191       if (prev == NULL) addr->host_list = next_h; else prev->next = next_h;
 192       continue;   /* With the next host, leave prev unchanged */
 193       }
 194
 195     if (hff_code == hff_pass) return PASS;
 196     if (hff_code == hff_decline) return DECLINE;
 197
 198     addr->basic_errno = ERRNO_UNKNOWNHOST;
 199     addr->message =
 200       string_sprintf("lookup of host \"%s\" failed in %s router%s",
 201         h->name, rblock->name,
 202         f.host_find_failed_syntax? ": syntax error in name" : "");
 203
 204     if (hff_code == hff_defer) return DEFER;
 205     if (hff_code == hff_fail) return FAIL;
 206
 207     addr->special_action = SPECIAL_FREEZE;
 208     return DEFER;
 209     }
 210
 211   /* Deal with the settings that were previously cleared:
 212   port, mx and sort_key. */
 213
 214   if (port != PORT_NONE)
 215     for (host_item * hh = h; hh != next_h; hh = hh->next)
 216       hh->port = port;
 217
 218   if (mx != MX_NONE)
 219     for (host_item * hh = h; hh != next_h; hh = hh->next)
 220       {
 221       hh->mx = mx;
 222       hh->sort_key = sort_key;
 223       }
 224
 225   /* A local host gets chopped, with its successors, if there are previous
 226   hosts. Otherwise the self option is used. If it is set to "send", any
 227   subsequent hosts that are also the local host do NOT get chopped. */
 228
 229   if (rc == HOST_FOUND_LOCAL && !self_send)
 230     {
 231     if (prev)
 232       {
 233       DEBUG(D_route)
 234         {
 235         debug_printf("Removed from host list:\n");
 236         for (; h; h = h->next) debug_printf("  %s\n", h->name);
 237         }
 238       prev->next = NULL;
 239       setflag(addr, af_local_host_removed);
 240       break;
 241       }
 242     rc = rf_self_action(addr, h, rblock->self_code, rblock->self_rewrite,
 243       rblock->self, addr_new);
 244     if (rc != OK)
 245       {
 246       addr->host_list = NULL;   /* Kill the host list for */
 247       return rc;                /* anything other than "send" */
 248       }
 249     self_send = TRUE;
 250     }
 251
 252   /* Ensure that prev is the host before next_h; this will not be h if a lookup
 253   found multiple addresses or multiple MX records. */
 254
 255   prev = h;
 256   while (prev->next != next_h) prev = prev->next;
 257   }
 258
 259 return OK;
 260 }
 261
 262 /* End of rf_lookup_hostlist.c */