defined. AAAA records (analogous to A records for IPv4) are in use, and are
currently seen as the mainstream. Another record type called A6 was proposed
as better than AAAA because it had more flexibility. However, it was felt to be
-over-complex, and its status was reduced to &"experimental"&. It is not known
-if anyone is actually using A6 records. Exim has support for A6 records, but
-this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The
-support has not been tested for some time.
+over-complex, and its status was reduced to &"experimental"&. Exim used to
+have a compile option for including A6 record support but this has now been
+withdrawn.
&<<SECTforexpfai>>& for an explanation of what this means.
The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, TLSA and TXT,
-and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
-configured). If no type is given, TXT is assumed. When the type is PTR,
+and, when Exim is compiled with IPv6 support, AAAA.
+If no type is given, TXT is assumed. When the type is PTR,
the data can be an IP address, written as normal; inversion and the addition of
&%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
.code
If the data for a PTR record is not a syntactically valid IP address, it is not
altered and nothing is added.
-For any record type, if multiple records are found (or, for A6 lookups, if a
-single record leads to multiple addresses), the data is returned as a
+For any record type, if multiple records are found, the data is returned as a
concatenation, with newline as the default separator. The order, of course,
depends on the DNS resolver. You can specify a different separator character
between multiple records by putting a right angle-bracket followed immediately
authorization required but absent, or &"?"& for unknown.
.cindex "A+" "in &(dnsdb)& lookup"
-The pseudo-type A+ performs an A6 lookup (if configured) followed by an AAAA
+The pseudo-type A+ performs an AAAA
and then an A lookup. All results are returned; defer processing
(see below) is handled separately for each lookup. Example:
.code
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_request_domains%& will be done with
the dnssec request bit set.
-This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
+This applies to all of the SRV, MX, AAAA, A lookup sequence.
DNS lookups for domains matching &%dnssec_request_domains%& will be done with
the dnssec request bit set. Any returns not having the Authenticated Data bit
(AD bit) set wil be ignored and logged as a host-lookup failure.
-This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
+This applies to all of the SRV, MX, AAAA, A lookup sequence.
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_request_domains%& will be done with
the dnssec request bit set.
-This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
+This applies to all of the SRV, MX, AAAA, A lookup sequence.
DNS lookups for domains matching &%dnssec_request_domains%& will be done with
the dnssec request bit set. Any returns not having the Authenticated Data bit
(AD bit) set wil be ignored and logged as a host-lookup failure.
-This applies to all of the SRV, MX A6, AAAA, A lookup sequence.
+This applies to all of the SRV, MX, AAAA, A lookup sequence.
#include "exim.h"
-/* Function declaration needed for mutual recursion when A6 records
-are supported. */
-
-#if HAVE_IPV6
-#ifdef SUPPORT_A6
-static void dns_complete_a6(dns_address ***, dns_answer *, dns_record *,
- int, uschar *);
-#endif
-#endif
-
/*************************************************
* Fake DNS resolver *
nameservers are also believed to do this. It is, of course, contrary to the
specification of the DNS, so we lock it out. */
-if ((
- #ifdef SUPPORT_A6
- type == T_A6 ||
- #endif
- type == T_A || type == T_AAAA) &&
- string_is_ip_address(name, NULL) != 0)
+if ((type == T_A || type == T_AAAA) && string_is_ip_address(name, NULL) != 0)
return DNS_NOMATCH;
/* If we are running in the test harness, instead of calling the normal resolver
(res_search), we call fakens_search(), which recognizes certain special
domains, and interfaces to a fake nameserver for certain special zones. */
-if (running_in_test_harness)
- dnsa->answerlen = fakens_search(name, type, dnsa->answer, MAXPACKET);
-else
- dnsa->answerlen = res_search(CCS name, C_IN, type, dnsa->answer, MAXPACKET);
+dnsa->answerlen = running_in_test_harness
+ ? fakens_search(name, type, dnsa->answer, MAXPACKET)
+ : res_search(CCS name, C_IN, type, dnsa->answer, MAXPACKET);
if (dnsa->answerlen > MAXPACKET)
{
-/* Support for A6 records has been commented out since they were demoted to
-experimental status at IETF 51. */
-
-#if HAVE_IPV6 && defined(SUPPORT_A6)
-
-/*************************************************
-* Search DNS block for prefix RRs *
-*************************************************/
-
-/* Called from dns_complete_a6() to search an additional section or a main
-answer section for required prefix records to complete an IPv6 address obtained
-from an A6 record. For each prefix record, a recursive call to dns_complete_a6
-is made, with a new copy of the address so far.
-
-Arguments:
- dnsa the DNS answer block
- which RESET_ADDITIONAL or RESET_ANSWERS
- name name of prefix record
- yptrptr pointer to the pointer that points to where to hang the next
- dns_address structure
- bits number of bits we have already got
- bitvec the bits we have already got
-
-Returns: TRUE if any records were found
-*/
-
-static BOOL
-dns_find_prefix(dns_answer *dnsa, int which, uschar *name, dns_address
- ***yptrptr, int bits, uschar *bitvec)
-{
-BOOL yield = FALSE;
-dns_record *rr;
-dns_scan dnss;
-
-for (rr = dns_next_rr(dnsa, &dnss, which);
- rr != NULL;
- rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
- {
- uschar cbitvec[16];
- if (rr->type != T_A6 || strcmpic(rr->name, name) != 0) continue;
- yield = TRUE;
- memcpy(cbitvec, bitvec, sizeof(cbitvec));
- dns_complete_a6(yptrptr, dnsa, rr, bits, cbitvec);
- }
-
-return yield;
-}
-
-
-
-/*************************************************
-* Follow chains of A6 records *
-*************************************************/
-
-/* A6 records may be incomplete, with pointers to other records containing more
-bits of the address. There can be a tree structure, leading to a number of
-addresses originating from a single initial A6 record.
-
-Arguments:
- yptrptr pointer to the pointer that points to where to hang the next
- dns_address structure
- dnsa the current DNS answer block
- rr the RR we have at present
- bits number of bits we have already got
- bitvec the bits we have already got
-
-Returns: nothing
-*/
-
-static void
-dns_complete_a6(dns_address ***yptrptr, dns_answer *dnsa, dns_record *rr,
- int bits, uschar *bitvec)
-{
-static uschar bitmask[] = { 0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80 };
-uschar *p = (uschar *)(rr->data);
-int prefix_len, suffix_len;
-int i, j, k;
-uschar *chainptr;
-uschar chain[264];
-dns_answer cdnsa;
-
-/* The prefix length is the first byte. It defines the prefix which is missing
-from the data in this record as a number of bits. Zero means this is the end of
-a chain. The suffix is the data in this record; only sufficient bytes to hold
-it are supplied. There may be zero bytes. We have to ignore trailing bits that
-we have already obtained from earlier RRs in the chain. */
-
-prefix_len = *p++; /* bits */
-suffix_len = (128 - prefix_len + 7)/8; /* bytes */
-
-/* If the prefix in this record is greater than the prefix in the previous
-record in the chain, we have to ignore the record (RFC 2874). */
-
-if (prefix_len > 128 - bits) return;
-
-/* In this little loop, the number of bits up to and including the current byte
-is held in k. If we have none of the bits in this byte, we can just or it into
-the current data. If we have all of the bits in this byte, we skip it.
-Otherwise, some masking has to be done. */
-
-for (i = suffix_len - 1, j = 15, k = 8; i >= 0; i--)
- {
- int required = k - bits;
- if (required >= 8) bitvec[j] |= p[i];
- else if (required > 0) bitvec[j] |= p[i] & bitmask[required];
- j--; /* I tried putting these in the "for" statement, but gcc muttered */
- k += 8; /* about computed values not being used. */
- }
-
-/* If the prefix_length is zero, we are at the end of a chain. Build a
-dns_address item with the current data, hang it onto the end of the chain,
-adjust the hanging pointer, and we are done. */
-
-if (prefix_len == 0)
- {
- dns_address *new = store_get(sizeof(dns_address) + 50);
- inet_ntop(AF_INET6, bitvec, CS new->address, 50);
- new->next = NULL;
- **yptrptr = new;
- *yptrptr = &(new->next);
- return;
- }
-
-/* Prefix length is not zero. Reset the number of bits that we have collected
-so far, and extract the chain name. */
-
-bits = 128 - prefix_len;
-p += suffix_len;
-
-chainptr = chain;
-while ((i = *p++) != 0)
- {
- if (chainptr != chain) *chainptr++ = '.';
- memcpy(chainptr, p, i);
- chainptr += i;
- p += i;
- }
-*chainptr = 0;
-chainptr = chain;
-
-/* Now scan the current DNS response record to see if the additional section
-contains the records we want. This processing can be cut out for testing
-purposes. */
-
-if (dns_find_prefix(dnsa, RESET_ADDITIONAL, chainptr, yptrptr, bits, bitvec))
- return;
-
-/* No chain records were found in the current DNS response block. Do a new DNS
-lookup to try to find these records. This opens up the possibility of DNS
-failures. We ignore them at this point; if all branches of the tree fail, there
-will be no addresses at the end. */
-
-if (dns_lookup(&cdnsa, chainptr, T_A6, NULL) == DNS_SUCCEED)
- (void)dns_find_prefix(&cdnsa, RESET_ANSWERS, chainptr, yptrptr, bits, bitvec);
-}
-#endif /* HAVE_IPV6 && defined(SUPPORT_A6) */
-
-
/*************************************************
{
dns_address *yield = NULL;
-#if HAVE_IPV6 && defined(SUPPORT_A6)
-dns_address **yieldptr = &yield;
-uschar bitvec[16];
-#else
dnsa = dnsa; /* Stop picky compilers warning */
-#endif
if (rr->type == T_A)
{
#if HAVE_IPV6
-#ifdef SUPPORT_A6
-else if (rr->type == T_A6)
- {
- memset(bitvec, 0, sizeof(bitvec));
- dns_complete_a6(&yieldptr, dnsa, rr, 0, bitvec);
- }
-#endif /* SUPPORT_A6 */
-
else
{
yield = store_get(sizeof(dns_address) + 50);
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