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resolved: cache - handle CNAME redirection

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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.
This commit is contained in:
Tom Gundersen 2015-08-17 07:56:57 +02:00
parent 8e427d9be9
commit 5643c00afe
2 changed files with 24 additions and 3 deletions
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2
src/resolve/resolved-bus.c
View File

@ -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) {

25
src/resolve/resolved-dns-cache.c
View File

@ -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 */