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Don't return NXDOMAIN to empty non-terminals.

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When a record is defined locally, eg an A record for one.two.example then
we already know that if we forward, eg an AAAA query for one.two.example,
and get back NXDOMAIN, then we need to alter that to NODATA. This is handled
by  check_for_local_domain(). But, if we forward two.example, because
one.two.example exists, then the answer to two.example should also be
a NODATA.

For most local records this is easy, just to substring matching.
for A, AAAA and CNAME records that are in the cache, it's more difficult.
The cache has no efficient way to find such records. The fix is to
insert empty (none of F_IPV4, F_IPV6 F_CNAME set) records for each
non-terminal.

The same considerations apply in auth mode, and the same basic mechanism
is used there too.
This commit is contained in:
Simon Kelley
2018-08-21 17:46:52 +01:00
parent c822620967
commit b6f926fbef
5 changed files with 179 additions and 28 deletions
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23
src/rfc1035.c
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@@ -986,40 +986,35 @@ size_t setup_reply(struct dns_header *header, size_t qlen,
/* check if name matches local names ie from /etc/hosts or DHCP or local mx names. */
int check_for_local_domain(char *name, time_t now)
{
struct crec *crecp;
struct mx_srv_record *mx;
struct txt_record *txt;
struct interface_name *intr;
struct ptr_record *ptr;
struct naptr *naptr;
/* Note: the call to cache_find_by_name is intended to find any record which matches
ie A, AAAA, CNAME. */
if ((crecp = cache_find_by_name(NULL, name, now, F_IPV4 | F_IPV6 | F_CNAME | F_NO_RR)) &&
(crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)))
return 1;
for (naptr = daemon->naptr; naptr; naptr = naptr->next)
if (hostname_isequal(name, naptr->name))
if (hostname_issubdomain(name, naptr->name))
return 1;
for (mx = daemon->mxnames; mx; mx = mx->next)
if (hostname_isequal(name, mx->name))
if (hostname_issubdomain(name, mx->name))
return 1;
for (txt = daemon->txt; txt; txt = txt->next)
if (hostname_isequal(name, txt->name))
if (hostname_issubdomain(name, txt->name))
return 1;
for (intr = daemon->int_names; intr; intr = intr->next)
if (hostname_isequal(name, intr->name))
if (hostname_issubdomain(name, intr->name))
return 1;
for (ptr = daemon->ptr; ptr; ptr = ptr->next)
if (hostname_isequal(name, ptr->name))
if (hostname_issubdomain(name, ptr->name))
return 1;
if (cache_find_non_terminal(name, now))
return 1;
return 0;
}