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/* $Cambridge: exim/exim-src/src/lookups/dnsdb.c,v 1.19 2009/11/16 19:50:38 nm4 Exp $ */
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/*************************************************
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* Exim - an Internet mail transport agent *
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*************************************************/
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/* Copyright (c) University of Cambridge 1995 - 2009 */
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/* See the file NOTICE for conditions of use and distribution. */
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#include "lf_functions.h"
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/* Ancient systems (e.g. SunOS4) don't appear to have T_TXT defined in their
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/* Table of recognized DNS record types and their integer values. */
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static char *type_names[] = {
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static int type_values[] = {
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T_CSA, /* Private type for "Client SMTP Authorization". */
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T_MXH, /* Private type for "MX hostnames" */
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T_ZNS /* Private type for "zone nameservers" */
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/*************************************************
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*************************************************/
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/* See local README for interface description. */
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dnsdb_open(uschar *filename, uschar **errmsg)
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filename = filename; /* Keep picky compilers happy */
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errmsg = errmsg; /* Ditto */
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return (void *)(-1); /* Any non-0 value */
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/*************************************************
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* Find entry point for dnsdb *
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*************************************************/
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/* See local README for interface description. The query in the "keystring" may
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consist of a number of parts.
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(a) If the first significant character is '>' then the next character is the
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separator character that is used when multiple records are found. The default
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(b) If the next sequence of characters is 'defer_FOO' followed by a comma,
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the defer behaviour is set to FOO. The possible behaviours are: 'strict', where
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any defer causes the whole lookup to defer; 'lax', where a defer causes the
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whole lookup to defer only if none of the DNS queries succeeds; and 'never',
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where all defers are as if the lookup failed. The default is 'lax'.
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(c) If the next sequence of characters is a sequence of letters and digits
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followed by '=', it is interpreted as the name of the DNS record type. The
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(d) Then there follows list of domain names. This is a generalized Exim list,
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which may start with '<' in order to set a specific separator. The default
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separator, as always, is colon. */
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dnsdb_find(void *handle, uschar *filename, uschar *keystring, int length,
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uschar **result, uschar **errmsg, BOOL *do_cache)
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int defer_mode = PASS;
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uschar *outsep = US"\n";
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uschar *equals, *domain, *found;
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/* Because we're the working in the search pool, we try to reclaim as much
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store as possible later, so we preallocate the result here */
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uschar *yield = store_get(size);
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handle = handle; /* Keep picky compilers happy */
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/* If the string starts with '>' we change the output separator */
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while (isspace(*keystring)) keystring++;
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if (*keystring == '>')
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outsep = keystring + 1;
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while (isspace(*keystring)) keystring++;
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/* Check for a defer behaviour keyword. */
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if (strncmpic(keystring, US"defer_", 6) == 0)
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if (strncmpic(keystring, US"strict", 6) == 0)
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else if (strncmpic(keystring, US"lax", 3) == 0)
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else if (strncmpic(keystring, US"never", 5) == 0)
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*errmsg = US"unsupported dnsdb defer behaviour";
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while (isspace(*keystring)) keystring++;
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if (*keystring++ != ',')
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*errmsg = US"dnsdb defer behaviour syntax error";
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while (isspace(*keystring)) keystring++;
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/* If the keystring contains an = this must be preceded by a valid type name. */
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if ((equals = Ustrchr(keystring, '=')) != NULL)
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uschar *tend = equals;
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while (tend > keystring && isspace(tend[-1])) tend--;
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len = tend - keystring;
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for (i = 0; i < sizeof(type_names)/sizeof(uschar *); i++)
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if (len == Ustrlen(type_names[i]) &&
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strncmpic(keystring, US type_names[i], len) == 0)
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type = type_values[i];
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if (i >= sizeof(type_names)/sizeof(uschar *))
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*errmsg = US"unsupported DNS record type";
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keystring = equals + 1;
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while (isspace(*keystring)) keystring++;
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/* Initialize the resolver in case this is the first time it has been used. */
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dns_init(FALSE, FALSE);
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/* The remainder of the string must be a list of domains. As long as the lookup
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for at least one of them succeeds, we return success. Failure means that none
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The original implementation did not support a list of domains. Adding the list
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feature is compatible, except in one case: when PTR records are being looked up
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for a single IPv6 address. Fortunately, we can hack in a compatibility feature
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here: If the type is PTR and no list separator is specified, and the entire
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remaining string is valid as an IP address, set an impossible separator so that
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it is treated as one item. */
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if (type == T_PTR && keystring[0] != '<' &&
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string_is_ip_address(keystring, NULL) != 0)
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/* Now scan the list and do a lookup for each item */
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while ((domain = string_nextinlist(&keystring, &sep, buffer, sizeof(buffer)))
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int searchtype = (type == T_CSA)? T_SRV : /* record type we want */
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(type == T_MXH)? T_MX :
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(type == T_ZNS)? T_NS : type;
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/* If the type is PTR or CSA, we have to construct the relevant magic lookup
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key if the original is an IP address (some experimental protocols are using
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PTR records for different purposes where the key string is a host name, and
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Exim's extended CSA can be keyed by domains or IP addresses). This code for
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doing the reversal is now in a separate function. */
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if ((type == T_PTR || type == T_CSA) &&
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string_is_ip_address(domain, NULL) != 0)
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dns_build_reverse(domain, rbuffer);
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DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", domain);
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/* Do the lookup and sort out the result. There are three special types that
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are handled specially: T_CSA, T_ZNS and T_MXH. The former two are handled in
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a special lookup function so that the facility could be used from other
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parts of the Exim code. The latter affects only what happens later on in
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this function, but for tidiness it is handled in a similar way. If the
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lookup fails, continue with the next domain. In the case of DEFER, adjust
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the final "nothing found" result, but carry on to the next domain. */
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rc = dns_special_lookup(&dnsa, domain, type, &found);
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if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue;
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if (rc != DNS_SUCCEED)
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if (defer_mode == DEFER) return DEFER; /* always defer */
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else if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */
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continue; /* treat defer as fail */
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/* Search the returned records */
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for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
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rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
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if (rr->type != searchtype) continue;
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/* There may be several addresses from an A6 record. Put the configured
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separator between them, just as for between several records. However, A6
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support is not normally configured these days. */
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for (da = dns_address_from_rr(&dnsa, rr); da != NULL; da = da->next)
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if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
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yield = string_cat(yield, &size, &ptr, da->address,
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Ustrlen(da->address));
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/* Other kinds of record just have one piece of data each, but there may be
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several of them, of course. */
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if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
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while (data_offset < rr->size)
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uschar chunk_len = (rr->data)[data_offset++];
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yield = string_cat(yield, &size, &ptr,
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(uschar *)((rr->data)+data_offset), chunk_len);
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data_offset += chunk_len;
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else /* T_CNAME, T_CSA, T_MX, T_MXH, T_NS, T_PTR, T_SRV */
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int priority, weight, port;
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uschar *p = (uschar *)(rr->data);
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/* mxh ignores the priority number and includes only the hostnames */
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GETSHORT(priority, p);
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else if (type == T_MX)
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GETSHORT(priority, p);
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sprintf(CS s, "%d ", priority);
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yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
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else if (type == T_SRV)
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GETSHORT(priority, p);
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sprintf(CS s, "%d %d %d ", priority, weight, port);
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yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
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else if (type == T_CSA)
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/* See acl_verify_csa() for more comments about CSA. */
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GETSHORT(priority, p);
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if (priority != 1) continue; /* CSA version must be 1 */
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/* If the CSA record we found is not the one we asked for, analyse
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the subdomain assertions in the port field, else analyse the direct
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authorization status in the weight field. */
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if (port & 1) *s = 'X'; /* explicit authorization required */
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else *s = '?'; /* no subdomain assertions here */
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if (weight < 2) *s = 'N'; /* not authorized */
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else if (weight == 2) *s = 'Y'; /* authorized */
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else if (weight == 3) *s = '?'; /* unauthorizable */
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else continue; /* invalid */
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yield = string_cat(yield, &size, &ptr, s, 2);
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/* GETSHORT() has advanced the pointer to the target domain. */
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rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
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(DN_EXPAND_ARG4_TYPE)(s), sizeof(s));
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/* If an overlong response was received, the data will have been
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truncated and dn_expand may fail. */
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log_write(0, LOG_MAIN, "host name alias list truncated: type=%s "
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"domain=%s", dns_text_type(type), domain);
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else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
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} /* Loop for list of returned records */
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} /* Loop for list of domains */
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/* Reclaim unused memory */
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store_reset(yield + ptr + 1);
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/* If ptr == 0 we have not found anything. Otherwise, insert the terminating
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zero and return the result. */
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if (ptr == 0) return failrc;
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/* End of lookups/dnsdb.c */
added
removed
src/lookups/dnsdb.c
