/************************************************* * Exim - an Internet mail transport agent * *************************************************/ /* Copyright (c) University of Cambridge 1995 - 2015 */ /* Copyright (c) The Exim Maintainers 2020 */ /* See the file NOTICE for conditions of use and distribution. */ #include "../exim.h" #include "rf_functions.h" /************************************************* * Look up IP addresses for a set of hosts * *************************************************/ /* This function is called by a router to fill in the IP addresses for a set of hosts that are attached to an address. Each host has its name and MX value set; and those that need processing have their address fields set NULL. Multihomed hosts cause additional blocks to be inserted into the chain. This function also supports pseudo-hosts whose names end with "/MX". In this case, MX records are looked up for the name, and the list of hosts obtained replaces the incoming "host". In other words, "x/MX" is shorthand for "those hosts pointed to by x's MX records". It is also possible for a port to be specified along with the host name or IP address. The syntax is to add ":port" on to the end. This doesn't work with IPv6 addresses, so we allow IP addresses to be enclosed in [] in order to make this work. The specification of the port must come last, that is, after "/MX" if that is present. Arguments: rblock the router block addr the address being routed ignore_target_hosts list of hosts to ignore lookup_type LK_DEFAULT or LK_BYNAME or LK_BYDNS, plus LK_IPV4_{ONLY,PREFER} hff_code what to do for host find failed addr_new passed to rf_self_action for self=reroute Returns: OK DEFER host lookup defer PASS timeout etc and pass_on_timeout set self_action: PASS, DECLINE, DEFER, FAIL, FREEZE hff_code after host find failed */ int rf_lookup_hostlist(router_instance *rblock, address_item *addr, uschar *ignore_target_hosts, int lookup_type, int hff_code, address_item **addr_new) { BOOL self_send = FALSE; /* Look up each host address. A lookup may add additional items into the chain if there are multiple addresses. Hence the use of next_h to start each cycle of the loop at the next original host. If any host is identified as being the local host, omit it and any subsequent hosts - i.e. treat the list like an ordered list of MX hosts. If the first host is the local host, act according to the "self" option in the configuration. */ for (host_item * prev = NULL, * h = addr->host_list, *next_h; h; h = next_h) { const uschar *canonical_name; int rc, len, port, mx, sort_key; next_h = h->next; if (h->address) { prev = h; continue; } DEBUG(D_route|D_host_lookup) debug_printf("finding IP address for %s\n", h->name); /* Handle any port setting that may be on the name; it will be removed from the end of the name. */ port = host_item_get_port(h); /* Store the previous mx and sort_key values, which were assigned in host_build_hostlist and will be overwritten by host_find_bydns. */ mx = h->mx; sort_key = h->sort_key; /* If the name ends with "/MX", we interpret it to mean "the list of hosts pointed to by MX records with this name", and the MX record values override the ordering from host_build_hostlist. */ len = Ustrlen(h->name); if (len > 3 && strcmpic(h->name + len - 3, US"/mx") == 0) { int whichrrs = lookup_type & LK_IPV4_ONLY ? HOST_FIND_BY_MX | HOST_FIND_IPV4_ONLY : lookup_type & LK_IPV4_PREFER ? HOST_FIND_BY_MX | HOST_FIND_IPV4_FIRST : HOST_FIND_BY_MX; DEBUG(D_route|D_host_lookup) debug_printf("doing DNS MX lookup for %s\n", h->name); mx = MX_NONE; h->name = string_copyn(h->name, len - 3); rc = host_find_bydns(h, ignore_target_hosts, whichrrs, /* look only for MX records */ NULL, /* SRV service not relevant */ NULL, /* failing srv domains not relevant */ NULL, /* no special mx failing domains */ &rblock->dnssec, /* dnssec request/require */ NULL, /* fully_qualified_name */ NULL); /* indicate local host removed */ } /* If explicitly configured to look up by name, or if the "host name" is actually an IP address, do a byname lookup. */ else if (lookup_type & LK_BYNAME || string_is_ip_address(h->name, NULL) != 0) { DEBUG(D_route|D_host_lookup) debug_printf("calling host_find_byname\n"); rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE, &canonical_name, TRUE); } /* Otherwise, do a DNS lookup. If that yields "host not found", and the lookup type is the default (i.e. "bydns" is not explicitly configured), follow up with a byname lookup, just in case. */ else { BOOL removed; int whichrrs = lookup_type & LK_IPV4_ONLY ? HOST_FIND_BY_A : lookup_type & LK_IPV4_PREFER ? HOST_FIND_BY_A | HOST_FIND_BY_AAAA | HOST_FIND_IPV4_FIRST : HOST_FIND_BY_A | HOST_FIND_BY_AAAA; DEBUG(D_route|D_host_lookup) debug_printf("doing DNS lookup\n"); switch (rc = host_find_bydns(h, ignore_target_hosts, whichrrs, NULL, NULL, NULL, &rblock->dnssec, /* domains for request/require */ &canonical_name, &removed)) { case HOST_FOUND: if (removed) setflag(addr, af_local_host_removed); break; case HOST_FIND_FAILED: if (lookup_type & LK_DEFAULT) { DEBUG(D_route|D_host_lookup) debug_printf("DNS lookup failed: trying %s\n", f.running_in_test_harness ? "host_fake_gethostbyname" : "getipnodebyname"); rc = host_find_byname(h, ignore_target_hosts, HOST_FIND_QUALIFY_SINGLE, &canonical_name, TRUE); } break; } } /* Temporary failure defers, unless pass_on_timeout is set */ if (rc == HOST_FIND_SECURITY) { addr->message = string_sprintf("host lookup for %s done insecurely" , h->name); addr->basic_errno = ERRNO_DNSDEFER; return DEFER; } if (rc == HOST_FIND_AGAIN) { if (rblock->pass_on_timeout) { DEBUG(D_route) debug_printf("%s router timed out and pass_on_timeout set\n", rblock->name); return PASS; } addr->message = string_sprintf("host lookup for %s did not complete " "(DNS timeout?)", h->name); addr->basic_errno = ERRNO_DNSDEFER; return DEFER; } /* Permanent failure is controlled by host_find_failed */ if (rc == HOST_FIND_FAILED) { if (hff_code == hff_ignore) { if (prev == NULL) addr->host_list = next_h; else prev->next = next_h; continue; /* With the next host, leave prev unchanged */ } if (hff_code == hff_pass) return PASS; if (hff_code == hff_decline) return DECLINE; addr->basic_errno = ERRNO_UNKNOWNHOST; addr->message = string_sprintf("lookup of host \"%s\" failed in %s router%s", h->name, rblock->name, f.host_find_failed_syntax? ": syntax error in name" : ""); if (hff_code == hff_defer) return DEFER; if (hff_code == hff_fail) return FAIL; addr->special_action = SPECIAL_FREEZE; return DEFER; } /* Deal with the settings that were previously cleared: port, mx and sort_key. */ if (port != PORT_NONE) for (host_item * hh = h; hh != next_h; hh = hh->next) hh->port = port; if (mx != MX_NONE) for (host_item * hh = h; hh != next_h; hh = hh->next) { hh->mx = mx; hh->sort_key = sort_key; } /* A local host gets chopped, with its successors, if there are previous hosts. Otherwise the self option is used. If it is set to "send", any subsequent hosts that are also the local host do NOT get chopped. */ if (rc == HOST_FOUND_LOCAL && !self_send) { if (prev) { DEBUG(D_route) { debug_printf("Removed from host list:\n"); for (; h; h = h->next) debug_printf(" %s\n", h->name); } prev->next = NULL; setflag(addr, af_local_host_removed); break; } rc = rf_self_action(addr, h, rblock->self_code, rblock->self_rewrite, rblock->self, addr_new); if (rc != OK) { addr->host_list = NULL; /* Kill the host list for */ return rc; /* anything other than "send" */ } self_send = TRUE; } /* Ensure that prev is the host before next_h; this will not be h if a lookup found multiple addresses or multiple MX records. */ prev = h; while (prev->next != next_h) prev = prev->next; } return OK; } /* End of rf_lookup_hostlist.c */