Make caching work for CNAMEs pointing to A/AAAA records shadowed in /etc/hosts
If the answer to an upstream query is a CNAME which points to an
A/AAAA record which also exists in /etc/hosts and friends, then
caching is suppressed, to avoid inconsistent answers. This is
now modified to allow caching when the upstream and local A/AAAA
records have the same value.
diff --git a/src/cache.c b/src/cache.c
index f9e1d31..ff1ca6f 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -322,7 +322,7 @@
return 1;
}
-static int cache_scan_free(char *name, struct all_addr *addr, time_t now, unsigned short flags)
+static struct crec *cache_scan_free(char *name, struct all_addr *addr, time_t now, unsigned short flags)
{
/* Scan and remove old entries.
If (flags & F_FORWARD) then remove any forward entries for name and any expired
@@ -331,8 +331,8 @@
entries in the whole cache.
If (flags == 0) remove any expired entries in the whole cache.
- In the flags & F_FORWARD case, the return code is valid, and returns zero if the
- name exists in the cache as a HOSTS or DHCP entry (these are never deleted)
+ In the flags & F_FORWARD case, the return code is valid, and returns a non-NULL pointer
+ to a cache entry if the name exists in the cache as a HOSTS or DHCP entry (these are never deleted)
We take advantage of the fact that hash chains have stuff in the order <reverse>,<other>,<immortal>
so that when we hit an entry which isn't reverse and is immortal, we're done. */
@@ -361,7 +361,7 @@
(((crecp->flags | flags) & F_CNAME) && !(crecp->flags & (F_DNSKEY | F_DS))))
{
if (crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG))
- return 0;
+ return crecp;
*up = crecp->hash_next;
cache_unlink(crecp);
cache_free(crecp);
@@ -378,7 +378,7 @@
crecp->addr.sig.type_covered == addr->addr.dnssec.type))
{
if (crecp->flags & F_CONFIG)
- return 0;
+ return crecp;
*up = crecp->hash_next;
cache_unlink(crecp);
cache_free(crecp);
@@ -423,7 +423,7 @@
up = &crecp->hash_next;
}
- return 1;
+ return NULL;
}
/* Note: The normal calling sequence is
@@ -471,10 +471,26 @@
return NULL;
/* First remove any expired entries and entries for the name/address we
- are currently inserting. Fail if we attempt to delete a name from
- /etc/hosts or DHCP. */
- if (!cache_scan_free(name, addr, now, flags))
+ are currently inserting. */
+ if ((new = cache_scan_free(name, addr, now, flags)))
{
+ /* We're trying to insert a record over one from
+ /etc/hosts or DHCP, or other config. If the
+ existing record is for an A or AAAA and
+ the record we're trying to insert is the same,
+ just drop the insert, but don't error the whole process. */
+ if ((flags & (F_IPV4 | F_IPV6)) && (flags & F_FORWARD))
+ {
+ if ((flags & F_IPV4) && (new->flags & F_IPV4) &&
+ new->addr.addr.addr.addr4.s_addr == addr->addr.addr4.s_addr)
+ return new;
+#ifdef HAVE_IPV6
+ else if ((flags & F_IPV6) && (new->flags & F_IPV6) &&
+ IN6_ARE_ADDR_EQUAL(&new->addr.addr.addr.addr6, &addr->addr.addr6))
+ return new;
+#endif
+ }
+
insert_error = 1;
return NULL;
}
