diff options
Diffstat (limited to 'src/resolve/resolved-dns-cache.c')
| -rw-r--r-- | src/resolve/resolved-dns-cache.c | 119 |
1 files changed, 81 insertions, 38 deletions
diff --git a/src/resolve/resolved-dns-cache.c b/src/resolve/resolved-dns-cache.c index cbbbed8c8a..ab13636bc1 100644 --- a/src/resolve/resolved-dns-cache.c +++ b/src/resolve/resolved-dns-cache.c @@ -277,13 +277,14 @@ static int dns_cache_put_positive( /* New TTL is 0? Delete the entry... */ if (rr->ttl <= 0) { - if (dns_cache_remove(c, rr->key)) { - r = dns_resource_key_to_string(rr->key, &key_str); - if (r < 0) - return r; + r = dns_resource_key_to_string(rr->key, &key_str); + if (r < 0) + return r; + if (dns_cache_remove(c, rr->key)) log_debug("Removed zero TTL entry from cache: %s", key_str); - } + else + log_debug("Not caching zero TTL cache entry: %s", key_str); return 0; } @@ -361,7 +362,7 @@ static int dns_cache_put_negative( if (r < 0) return r; - log_debug("Ignored negative cache entry with zero SOA TTL: %s", key_str); + log_debug("Not caching negative entry with zero SOA TTL: %s", key_str); return 0; } @@ -402,7 +403,7 @@ static int dns_cache_put_negative( int dns_cache_put( DnsCache *c, - DnsQuestion *q, + DnsResourceKey *key, int rcode, DnsAnswer *answer, unsigned max_rrs, @@ -410,16 +411,16 @@ int dns_cache_put( int owner_family, const union in_addr_union *owner_address) { + DnsResourceRecord *soa = NULL; unsigned cache_keys, i; int r; assert(c); - if (q) { - /* First, if we were passed a question, delete all matching old RRs, + if (key) { + /* First, if we were passed a key, delete all matching old RRs, * so that we only keep complete by_key in place. */ - for (i = 0; i < q->n_keys; i++) - dns_cache_remove(c, q->keys[i]); + dns_cache_remove(c, key); } if (!answer) @@ -437,8 +438,8 @@ int dns_cache_put( cache_keys = answer->n_rrs; - if (q) - cache_keys += q->n_keys; + if (key) + cache_keys ++; /* Make some space for our new entries */ dns_cache_make_space(c, cache_keys); @@ -453,44 +454,63 @@ int dns_cache_put( goto fail; } - if (!q) + if (!key) return 0; - /* Third, add in negative entries for all keys with no RR */ - for (i = 0; i < q->n_keys; i++) { - DnsResourceRecord *soa = NULL; + /* Third, add in negative entries if the key has no RR */ + r = dns_answer_contains(answer, key); + if (r < 0) + goto fail; + if (r > 0) + return 0; - r = dns_answer_contains(answer, q->keys[i]); - if (r < 0) - goto fail; - if (r > 0) - continue; + /* See https://tools.ietf.org/html/rfc2308, which + * say that a matching SOA record in the packet + * is used to to enable negative caching. */ - /* See https://tools.ietf.org/html/rfc2308, which - * say that a matching SOA record in the packet - * is used to to enable negative caching. */ + r = dns_answer_find_soa(answer, key, &soa); + if (r < 0) + goto fail; + if (r == 0) + return 0; - r = dns_answer_find_soa(answer, q->keys[i], &soa); - if (r < 0) - goto fail; - if (r == 0) - continue; + /* Also, if the requested key is an alias, the negative response should + be cached for each name in the redirect chain. Any CNAME record in + the response is from the redirection chain, though only the final one + is guaranteed to be included. This means that we cannot verify the + chain and that we need to cache them all as it may be incomplete. */ + for (i = 0; i < answer->n_rrs; i++) { + DnsResourceRecord *answer_rr = answer->items[i].rr; - r = dns_cache_put_negative(c, q->keys[i], rcode, timestamp, MIN(soa->soa.minimum, soa->ttl), owner_family, owner_address); - if (r < 0) - goto fail; + if (answer_rr->key->type == DNS_TYPE_CNAME) { + _cleanup_(dns_resource_key_unrefp) DnsResourceKey *canonical_key = NULL; + + canonical_key = dns_resource_key_new_redirect(key, answer_rr); + if (!canonical_key) + goto fail; + + /* Let's not add negative cache entries for records outside the current zone. */ + if (!dns_answer_match_soa(canonical_key, soa->key)) + continue; + + r = dns_cache_put_negative(c, canonical_key, rcode, timestamp, MIN(soa->soa.minimum, soa->ttl), owner_family, owner_address); + if (r < 0) + goto fail; + } } + r = dns_cache_put_negative(c, key, rcode, timestamp, MIN(soa->soa.minimum, soa->ttl), owner_family, owner_address); + if (r < 0) + goto fail; + return 0; fail: /* Adding all RRs failed. Let's clean up what we already * added, just in case */ - if (q) { - for (i = 0; i < q->n_keys; i++) - dns_cache_remove(c, q->keys[i]); - } + if (key) + dns_cache_remove(c, key); for (i = 0; i < answer->n_rrs; i++) dns_cache_remove(c, answer->items[i].rr->key); @@ -498,6 +518,29 @@ 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; @@ -527,7 +570,7 @@ 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 */ |