dns_special_lookup(dns_answer *dnsa, const uschar *name, int type,
const uschar **fully_qualified_name)
{
-if (type >= 0) return dns_lookup(dnsa, name, type, fully_qualified_name);
-
-/* The "mx hosts only" type doesn't require any special action here */
-
-if (type == T_MXH) return dns_lookup(dnsa, name, T_MX, fully_qualified_name);
-
-/* Find nameservers for the domain or the nearest enclosing zone, excluding the
-root servers. */
-
-if (type == T_ZNS)
- {
- const uschar *d = name;
- while (d != 0)
- {
- int rc = dns_lookup(dnsa, d, T_NS, fully_qualified_name);
- if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc;
- while (*d != 0 && *d != '.') d++;
- if (*d++ == 0) break;
- }
- return DNS_NOMATCH;
- }
-
-/* Try to look up the Client SMTP Authorization SRV record for the name. If
-there isn't one, search from the top downwards for a CSA record in a parent
-domain, which might be making assertions about subdomains. If we find a record
-we set fully_qualified_name to whichever lookup succeeded, so that the caller
-can tell whether to look at the explicit authorization field or the subdomain
-assertion field. */
-
-if (type == T_CSA)
+switch (type)
{
- uschar *srvname, *namesuff, *tld, *p;
- int priority, weight, port;
- int limit, rc, i;
- BOOL ipv6;
- dns_record *rr;
- dns_scan dnss;
-
- DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name);
-
- srvname = string_sprintf("_client._smtp.%s", name);
- rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
- if (rc == DNS_SUCCEED || rc == DNS_AGAIN)
- {
- if (rc == DNS_SUCCEED) *fully_qualified_name = string_copy(name);
- return rc;
- }
-
- /* Search for CSA subdomain assertion SRV records from the top downwards,
- starting with the 2nd level domain. This order maximizes cache-friendliness.
- We skip the top level domains to avoid loading their nameservers and because
- we know they'll never have CSA SRV records. */
-
- namesuff = Ustrrchr(name, '.');
- if (namesuff == NULL) return DNS_NOMATCH;
- tld = namesuff + 1;
- ipv6 = FALSE;
- limit = dns_csa_search_limit;
-
- /* Use more appropriate search parameters if we are in the reverse DNS. */
-
- if (strcmpic(namesuff, US".arpa") == 0)
- {
- if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0)
- {
- namesuff -= 8;
- tld = namesuff + 1;
- limit = 3;
- }
- else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0)
- {
- namesuff -= 4;
- tld = namesuff + 1;
- ipv6 = TRUE;
- limit = 3;
- }
- }
-
- DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld);
-
- /* Do not perform the search if the top level or 2nd level domains do not
- exist. This is quite common, and when it occurs all the search queries would
- go to the root or TLD name servers, which is not friendly. So we check the
- AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then
- the TLD or the 2LD (respectively) doesn't exist and we can skip the search.
- If the TLD and the 2LD exist but the explicit CSA record lookup failed, then
- the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */
-
- if (rc == DNS_NOMATCH)
- {
- /* This is really gross. The successful return value from res_search() is
- the packet length, which is stored in dnsa->answerlen. If we get a
- negative DNS reply then res_search() returns -1, which causes the bounds
- checks for name decompression to fail when it is treated as a packet
- length, which in turn causes the authority search to fail. The correct
- packet length has been lost inside libresolv, so we have to guess a
- replacement value. (The only way to fix this properly would be to
- re-implement res_search() and res_query() so that they don't muddle their
- success and packet length return values.) For added safety we only reset
- the packet length if the packet header looks plausible. */
-
- HEADER *h = (HEADER *)dnsa->answer;
- if (h->qr == 1 && h->opcode == QUERY && h->tc == 0
- && (h->rcode == NOERROR || h->rcode == NXDOMAIN)
- && ntohs(h->qdcount) == 1 && ntohs(h->ancount) == 0
- && ntohs(h->nscount) >= 1)
- dnsa->answerlen = MAXPACKET;
-
- for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
- rr != NULL;
- rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
- if (rr->type != T_SOA) continue;
- else if (strcmpic(rr->name, US"") == 0 ||
- strcmpic(rr->name, tld) == 0) return DNS_NOMATCH;
- else break;
- }
-
- for (i = 0; i < limit; i++)
- {
- if (ipv6)
- {
- /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP
- address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */
- namesuff -= 8;
- if (namesuff <= name) return DNS_NOMATCH;
- }
- else
- /* Find the start of the preceding domain name label. */
- do
- if (--namesuff <= name) return DNS_NOMATCH;
- while (*namesuff != '.');
-
- DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1);
-
- srvname = string_sprintf("_client._smtp.%s", namesuff + 1);
- rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
- if (rc == DNS_AGAIN) return rc;
- if (rc != DNS_SUCCEED) continue;
-
- /* Check that the SRV record we have found is worth returning. We don't
- just return the first one we find, because some lower level SRV record
- might make stricter assertions than its parent domain. */
+ /* The "mx hosts only" type doesn't require any special action here */
+ case T_MXH:
+ return dns_lookup(dnsa, name, T_MX, fully_qualified_name);
+
+ /* Find nameservers for the domain or the nearest enclosing zone, excluding
+ the root servers. */
+ case T_ZNS:
+ type = T_NS;
+ /* FALLTHROUGH */
+ case T_SOA:
+ {
+ const uschar *d = name;
+ while (d != 0)
+ {
+ int rc = dns_lookup(dnsa, d, type, fully_qualified_name);
+ if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc;
+ while (*d != 0 && *d != '.') d++;
+ if (*d++ == 0) break;
+ }
+ return DNS_NOMATCH;
+ }
+
+ /* Try to look up the Client SMTP Authorization SRV record for the name. If
+ there isn't one, search from the top downwards for a CSA record in a parent
+ domain, which might be making assertions about subdomains. If we find a record
+ we set fully_qualified_name to whichever lookup succeeded, so that the caller
+ can tell whether to look at the explicit authorization field or the subdomain
+ assertion field. */
+ case T_CSA:
+ {
+ uschar *srvname, *namesuff, *tld, *p;
+ int priority, weight, port;
+ int limit, rc, i;
+ BOOL ipv6;
+ dns_record *rr;
+ dns_scan dnss;
+
+ DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name);
+
+ srvname = string_sprintf("_client._smtp.%s", name);
+ rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
+ if (rc == DNS_SUCCEED || rc == DNS_AGAIN)
+ {
+ if (rc == DNS_SUCCEED) *fully_qualified_name = string_copy(name);
+ return rc;
+ }
+
+ /* Search for CSA subdomain assertion SRV records from the top downwards,
+ starting with the 2nd level domain. This order maximizes cache-friendliness.
+ We skip the top level domains to avoid loading their nameservers and because
+ we know they'll never have CSA SRV records. */
+
+ namesuff = Ustrrchr(name, '.');
+ if (namesuff == NULL) return DNS_NOMATCH;
+ tld = namesuff + 1;
+ ipv6 = FALSE;
+ limit = dns_csa_search_limit;
+
+ /* Use more appropriate search parameters if we are in the reverse DNS. */
+
+ if (strcmpic(namesuff, US".arpa") == 0)
+ {
+ if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0)
+ {
+ namesuff -= 8;
+ tld = namesuff + 1;
+ limit = 3;
+ }
+ else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0)
+ {
+ namesuff -= 4;
+ tld = namesuff + 1;
+ ipv6 = TRUE;
+ limit = 3;
+ }
+ }
+
+ DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld);
+
+ /* Do not perform the search if the top level or 2nd level domains do not
+ exist. This is quite common, and when it occurs all the search queries would
+ go to the root or TLD name servers, which is not friendly. So we check the
+ AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then
+ the TLD or the 2LD (respectively) doesn't exist and we can skip the search.
+ If the TLD and the 2LD exist but the explicit CSA record lookup failed, then
+ the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */
+
+ if (rc == DNS_NOMATCH)
+ {
+ /* This is really gross. The successful return value from res_search() is
+ the packet length, which is stored in dnsa->answerlen. If we get a
+ negative DNS reply then res_search() returns -1, which causes the bounds
+ checks for name decompression to fail when it is treated as a packet
+ length, which in turn causes the authority search to fail. The correct
+ packet length has been lost inside libresolv, so we have to guess a
+ replacement value. (The only way to fix this properly would be to
+ re-implement res_search() and res_query() so that they don't muddle their
+ success and packet length return values.) For added safety we only reset
+ the packet length if the packet header looks plausible. */
+
+ HEADER *h = (HEADER *)dnsa->answer;
+ if (h->qr == 1 && h->opcode == QUERY && h->tc == 0
+ && (h->rcode == NOERROR || h->rcode == NXDOMAIN)
+ && ntohs(h->qdcount) == 1 && ntohs(h->ancount) == 0
+ && ntohs(h->nscount) >= 1)
+ dnsa->answerlen = MAXPACKET;
+
+ for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
+ rr != NULL;
+ rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
+ if (rr->type != T_SOA) continue;
+ else if (strcmpic(rr->name, US"") == 0 ||
+ strcmpic(rr->name, tld) == 0) return DNS_NOMATCH;
+ else break;
+ }
+
+ for (i = 0; i < limit; i++)
+ {
+ if (ipv6)
+ {
+ /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP
+ address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */
+ namesuff -= 8;
+ if (namesuff <= name) return DNS_NOMATCH;
+ }
+ else
+ /* Find the start of the preceding domain name label. */
+ do
+ if (--namesuff <= name) return DNS_NOMATCH;
+ while (*namesuff != '.');
+
+ DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1);
+
+ srvname = string_sprintf("_client._smtp.%s", namesuff + 1);
+ rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
+ if (rc == DNS_AGAIN) return rc;
+ if (rc != DNS_SUCCEED) continue;
+
+ /* Check that the SRV record we have found is worth returning. We don't
+ just return the first one we find, because some lower level SRV record
+ might make stricter assertions than its parent domain. */
+
+ for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
+ rr != NULL;
+ rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
+ {
+ if (rr->type != T_SRV) continue;
+
+ /* Extract the numerical SRV fields (p is incremented) */
+ p = rr->data;
+ GETSHORT(priority, p);
+ GETSHORT(weight, p); weight = weight; /* compiler quietening */
+ GETSHORT(port, p);
+
+ /* Check the CSA version number */
+ if (priority != 1) continue;
+
+ /* If it's making an interesting assertion, return this response. */
+ if (port & 1)
+ {
+ *fully_qualified_name = namesuff + 1;
+ return DNS_SUCCEED;
+ }
+ }
+ }
+ return DNS_NOMATCH;
+ }
- for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
- rr != NULL;
- rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
- {
- if (rr->type != T_SRV) continue;
-
- /* Extract the numerical SRV fields (p is incremented) */
- p = rr->data;
- GETSHORT(priority, p);
- GETSHORT(weight, p); weight = weight; /* compiler quietening */
- GETSHORT(port, p);
-
- /* Check the CSA version number */
- if (priority != 1) continue;
-
- /* If it's making an interesting assertion, return this response. */
- if (port & 1)
- {
- *fully_qualified_name = namesuff + 1;
- return DNS_SUCCEED;
- }
- }
- }
- return DNS_NOMATCH;
+ default:
+ if (type >= 0)
+ return dns_lookup(dnsa, name, type, fully_qualified_name);
}
/* Control should never reach here */
*************************************************/
/* The record type is either T_A for an IPv4 address or T_AAAA (or T_A6 when
-supported) for an IPv6 address. In the A6 case, there may be several addresses,
-generated by following chains. A recursive function does all the hard work. A6
-records now look like passing into history, so the code is only included when
-explicitly asked for.
+supported) for an IPv6 address.
Argument:
dnsa the DNS answer block
rr the RR
-Returns: pointer a chain of dns_address items
+Returns: pointer to a chain of dns_address items
*/
dns_address *
if (rr->type == T_A)
{
- uschar *p = (uschar *)(rr->data);
+ uschar *p = US rr->data;
yield = store_get(sizeof(dns_address) + 20);
(void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]);
yield->next = NULL;
else
{
yield = store_get(sizeof(dns_address) + 50);
- inet_ntop(AF_INET6, (uschar *)(rr->data), CS yield->address, 50);
+ inet_ntop(AF_INET6, US rr->data, CS yield->address, 50);
yield->next = NULL;
}
#endif /* HAVE_IPV6 */
projects / exim.git / blobdiff