diff options
Diffstat (limited to 'src/resolve/resolved-dns-answer.c')
| -rw-r--r-- | src/resolve/resolved-dns-answer.c | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/src/resolve/resolved-dns-answer.c b/src/resolve/resolved-dns-answer.c index 3d42b0d..bf023a7 100644 --- a/src/resolve/resolved-dns-answer.c +++ b/src/resolve/resolved-dns-answer.c @@ -181,11 +181,23 @@ int dns_answer_add( exist = ordered_set_get(a->items, &tmp); if (exist) { - /* There's already an RR of the same RRset in place! Let's see if the TTLs more or less - * match. We don't really care if they match precisely, but we do care whether one is 0 and - * the other is not. See RFC 2181, Section 5.2. */ - if ((rr->ttl == 0) != (exist->rr->ttl == 0)) - return -EINVAL; + /* There's already an RR of the same RRset in place! Let's see if the TTLs more or + * less match. RFC 2181, Section 5.2 suggests clients should reject RRsets + * containing RRs with differing TTLs. We are more tolerant of this situation except + * if one RR has a zero TTL and the other a nonzero TTL. In mDNS, zero TTLs are + * special, so we must error in that case. */ + if ((rr->ttl == 0) != (exist->rr->ttl == 0)) { + if ((exist->flags | flags) & DNS_ANSWER_REFUSE_TTL_NO_MATCH) + return log_debug_errno( + SYNTHETIC_ERRNO(EINVAL), + "Refusing to merge RRs with zero TTL and non-zero TTL: %s vs. %s", + dns_resource_record_to_string(rr), + dns_resource_record_to_string(exist->rr)); + + log_debug("Merging RRs with zero TTL and non-zero TTL (not RFC 2181/5.2 compliant): %s vs. %s", + dns_resource_record_to_string(rr), + dns_resource_record_to_string(exist->rr)); + } /* Entry already exists, keep the entry with the higher TTL. */ if (rr->ttl > exist->rr->ttl) { |