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authorTom Gundersen <teg@jklm.no>2015-08-17 07:56:57 +0200
committerTom Gundersen <teg@jklm.no>2015-09-16 17:03:17 +0200
commit5643c00afe29eae4b2e3575277038e60e6967d09 (patch)
treef3196293051dc93ee58eb06421df9367dc794f17
parent8e427d9be93e1289eba2a3055bbc632babc75b81 (diff)
resolved: cache - handle CNAME redirection
CNAME records are special in the way they are treated by DNS servers, and our cache should mimic that behavior: In case a domain name has an alias, its CNAME record is returned in place of any other. Our cache was not doing this despite caching the CNAME records, this entailed needless lookups to re-resolve the CNAME.
-rw-r--r--src/resolve/resolved-bus.c2
-rw-r--r--src/resolve/resolved-dns-cache.c25
2 files changed, 24 insertions, 3 deletions
diff --git a/src/resolve/resolved-bus.c b/src/resolve/resolved-bus.c
index 19db781ac4..bf1b7c8ab4 100644
--- a/src/resolve/resolved-bus.c
+++ b/src/resolve/resolved-bus.c
@@ -220,8 +220,6 @@ static void bus_method_resolve_hostname_complete(DnsQuery *q) {
added++;
}
- // what about the cache?
-
/* If we didn't find anything, then let's restart the
* query, this time with the cname */
if (added <= 0) {
diff --git a/src/resolve/resolved-dns-cache.c b/src/resolve/resolved-dns-cache.c
index 478ad29bbf..93b98f3727 100644
--- a/src/resolve/resolved-dns-cache.c
+++ b/src/resolve/resolved-dns-cache.c
@@ -493,6 +493,29 @@ fail:
return r;
}
+static DnsCacheItem *dns_cache_get_by_key_follow_cname(DnsCache *c, DnsResourceKey *k) {
+ _cleanup_(dns_resource_key_unrefp) DnsResourceKey *cname_key = NULL;
+ DnsCacheItem *i, *j;
+
+ assert(c);
+ assert(k);
+
+ i = hashmap_get(c->by_key, k);
+ if (i || k->type == DNS_TYPE_CNAME)
+ return i;
+
+ /* check if we have a CNAME record instead */
+ cname_key = dns_resource_key_new_cname(k);
+ if (!cname_key)
+ return NULL;
+
+ j = hashmap_get(c->by_key, cname_key);
+ if (j)
+ return j;
+
+ return i;
+}
+
int dns_cache_lookup(DnsCache *c, DnsResourceKey *key, int *rcode, DnsAnswer **ret) {
_cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
unsigned n = 0;
@@ -522,7 +545,7 @@ int dns_cache_lookup(DnsCache *c, DnsResourceKey *key, int *rcode, DnsAnswer **r
return 0;
}
- first = hashmap_get(c->by_key, key);
+ first = dns_cache_get_by_key_follow_cname(c, key);
if (!first) {
/* If one question cannot be answered we need to refresh */