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Diffstat (limited to 'src/routers/rf_lookup_hostlist.c')
| -rw-r--r-- | src/routers/rf_lookup_hostlist.c | 262 |
1 files changed, 262 insertions, 0 deletions
diff --git a/src/routers/rf_lookup_hostlist.c b/src/routers/rf_lookup_hostlist.c new file mode 100644 index 0000000..79a7799 --- /dev/null +++ b/src/routers/rf_lookup_hostlist.c @@ -0,0 +1,262 @@ +/************************************************* +* 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 */ |