From 5643c00afe29eae4b2e3575277038e60e6967d09 Mon Sep 17 00:00:00 2001 From: Tom Gundersen Date: Mon, 17 Aug 2015 07:56:57 +0200 Subject: 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. --- src/resolve/resolved-dns-cache.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) (limited to 'src/resolve/resolved-dns-cache.c') 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 */ -- cgit v1.2.3-54-g00ecf