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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
Download Patch File Download Diff File Expand all files Collapse all files

116
src/cache.c
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@@ -25,6 +25,8 @@ static int insert_error;
static union bigname *big_free = NULL;
static int bignames_left, hash_size;
static void make_non_terminals(struct crec *source);
/* type->string mapping: this is also used by the name-hash function as a mixing table. */
static const struct {
unsigned int type;
@@ -648,6 +650,20 @@ void cache_end_insert(void)
new_chain = NULL;
}
int cache_find_non_terminal(char *name, time_t now)
{
struct crec *crecp;
for (crecp = *hash_bucket(name); crecp; crecp = crecp->hash_next)
if (!is_outdated_cname_pointer(crecp) &&
!is_expired(now, crecp) &&
(crecp->flags & F_FORWARD) &&
hostname_isequal(name, cache_get_name(crecp)))
return 1;
return 0;
}
struct crec *cache_find_by_name(struct crec *crecp, char *name, time_t now, unsigned int prot)
{
struct crec *ans;
@@ -818,6 +834,8 @@ static void add_hosts_cname(struct crec *target)
crec->addr.cname.uid = target->uid;
crec->uid = UID_NONE;
cache_hash(crec);
make_non_terminals(crec);
add_hosts_cname(crec); /* handle chains */
}
}
@@ -889,6 +907,7 @@ static void add_hosts_entry(struct crec *cache, struct all_addr *addr, int addrl
cache->uid = index;
memcpy(&cache->addr.addr, addr, addrlen);
cache_hash(cache);
make_non_terminals(cache);
/* don't need to do alias stuff for second and subsequent addresses. */
if (!nameexists)
@@ -1102,6 +1121,7 @@ void cache_reload(void)
cache->addr.cname.uid = SRC_INTERFACE;
cache->uid = UID_NONE;
cache_hash(cache);
make_non_terminals(cache);
add_hosts_cname(cache); /* handle chains */
}
@@ -1119,6 +1139,7 @@ void cache_reload(void)
cache->addr.ds.digest = ds->digest_type;
cache->uid = ds->class;
cache_hash(cache);
make_non_terminals(cache);
}
#endif
@@ -1234,6 +1255,7 @@ static void add_dhcp_cname(struct crec *target, time_t ttd)
aliasc->addr.cname.uid = target->uid;
aliasc->uid = UID_NONE;
cache_hash(aliasc);
make_non_terminals(aliasc);
add_dhcp_cname(aliasc, ttd);
}
}
@@ -1322,12 +1344,104 @@ void cache_add_dhcp_entry(char *host_name, int prot,
crec->name.namep = host_name;
crec->uid = UID_NONE;
cache_hash(crec);
make_non_terminals(crec);
add_dhcp_cname(crec, ttd);
}
}
#endif
/* Called when we put a local or DHCP name into the cache.
Creates empty cache entries for subnames (ie,
for three.two.one, for two.one and one), without
F_IPV4 or F_IPV6 or F_CNAME set. These convert
NXDOMAIN answers to NoData ones. */
static void make_non_terminals(struct crec *source)
{
char *name = cache_get_name(source);
struct crec* crecp, *tmp, **up;
int type = F_HOSTS | F_CONFIG;
#ifdef HAVE_DHCP
if (source->flags & F_DHCP)
type = F_DHCP;
#endif
/* First delete any empty entries for our new real name. Note that
we only delete empty entries deriving from DHCP for a new DHCP-derived
entry and vice-versa for HOSTS and CONFIG. This ensures that
non-terminals from DHCP go when we reload DHCP and
for HOSTS/CONFIG when we re-read. */
for (up = hash_bucket(name), crecp = *up; crecp; crecp = tmp)
{
tmp = crecp->hash_next;
if (!is_outdated_cname_pointer(crecp) &&
(crecp->flags & F_FORWARD) &&
(crecp->flags & type) &&
!(crecp->flags & (F_IPV4 | F_IPV6 | F_CNAME)) &&
hostname_isequal(name, cache_get_name(crecp)))
{
*up = crecp->hash_next;
#ifdef HAVE_DHCP
if (type & F_DHCP)
{
crecp->next = dhcp_spare;
dhcp_spare = crecp;
}
else
#endif
free(crecp);
break;
}
else
up = &crecp->hash_next;
}
while ((name = strchr(name, '.')))
{
name++;
/* Look for one existing, don't need another */
for (crecp = *hash_bucket(name); crecp; crecp = crecp->hash_next)
if (!is_outdated_cname_pointer(crecp) &&
(crecp->flags & F_FORWARD) &&
(crecp->flags & type) &&
hostname_isequal(name, cache_get_name(crecp)))
break;
if (crecp)
{
/* If the new name expires later, transfer that time to
empty non-terminal entry. */
if (!(crecp->flags & F_IMMORTAL))
{
if (source->flags & F_IMMORTAL)
crecp->flags |= F_IMMORTAL;
else if (difftime(crecp->ttd, source->ttd) < 0)
crecp->ttd = source->ttd;
}
continue;
}
#ifdef HAVE_DHCP
if ((source->flags & F_DHCP) && dhcp_spare)
{
crecp = dhcp_spare;
dhcp_spare = dhcp_spare->next;
}
else
#endif
crecp = whine_malloc(sizeof(struct crec));
*crecp = *source;
crecp->flags &= ~(F_IPV4 | F_IPV6 | F_CNAME | F_REVERSE);
crecp->flags |= F_NAMEP;
crecp->name.namep = name;
cache_hash(crecp);
}
}
#ifndef NO_ID
int cache_make_stat(struct txt_record *t)
{
@@ -1443,7 +1557,6 @@ static char *sanitise(char *name)
void dump_cache(time_t now)
{
struct server *serv, *serv1;
char *t = "";
my_syslog(LOG_INFO, _("time %lu"), (unsigned long)now);
my_syslog(LOG_INFO, _("cache size %d, %d/%d cache insertions re-used unexpired cache entries."),
@@ -1489,6 +1602,7 @@ void dump_cache(time_t now)
for (i=0; i<hash_size; i++)
for (cache = hash_table[i]; cache; cache = cache->hash_next)
{
char *t = " ";
char *a = daemon->addrbuff, *p = daemon->namebuff, *n = cache_get_name(cache);
*a = 0;
if (strlen(n) == 0 && !(cache->flags & F_REVERSE))