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resolved: set cache-flush bit on mDNS responses

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From RFC 6762, Section 10.2
"They (the rules about when to set the cache-flush bit) apply to
startup announcements as described in Section 8.3, "Announcing",
and to responses generated as a result of receiving query messages."

So, set the cache-flush bit for mDNS answers except for DNS-SD
service enumerattion PTRs described in RFC 6763, Section 4.1.
This commit is contained in:
Dmitry Rozhkov 2017-10-31 10:34:58 +02:00
parent 008d4ab7a2
commit 748a548e1b
1 changed files with 20 additions and 2 deletions
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22
src/resolve/resolved-dns-zone.c
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@ -305,6 +305,24 @@ int dns_zone_put(DnsZone *z, DnsScope *s, DnsResourceRecord *rr, bool probe) {
return 0;
}
static int dns_zone_add_authenticated_answer(DnsAnswer *a, DnsZoneItem *i, int ifindex) {
DnsAnswerFlags flags;
/* From RFC 6762, Section 10.2
* "They (the rules about when to set the cache-flush bit) apply to
* startup announcements as described in Section 8.3, "Announcing",
* and to responses generated as a result of receiving query messages."
* So, set the cache-flush bit for mDNS answers except for DNS-SD
* service enumeration PTRs described in RFC 6763, Section 4.1. */
if (i->scope->protocol == DNS_PROTOCOL_MDNS &&
!dns_resource_key_is_dnssd_ptr(i->rr->key))
flags = DNS_ANSWER_AUTHENTICATED|DNS_ANSWER_CACHE_FLUSH;
else
flags = DNS_ANSWER_AUTHENTICATED;
return dns_answer_add(a, i->rr, ifindex, flags);
}
int dns_zone_lookup(DnsZone *z, DnsResourceKey *key, int ifindex, DnsAnswer **ret_answer, DnsAnswer **ret_soa, bool *ret_tentative) {
_cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL, *soa = NULL;
unsigned n_answer = 0;
@ -410,7 +428,7 @@ int dns_zone_lookup(DnsZone *z, DnsResourceKey *key, int ifindex, DnsAnswer **re
if (k < 0)
return k;
if (k > 0) {
r = dns_answer_add(answer, j->rr, ifindex, DNS_ANSWER_AUTHENTICATED);
r = dns_zone_add_authenticated_answer(answer, j, ifindex);
if (r < 0)
return r;
@ -436,7 +454,7 @@ int dns_zone_lookup(DnsZone *z, DnsResourceKey *key, int ifindex, DnsAnswer **re
if (j->state != DNS_ZONE_ITEM_PROBING)
tentative = false;
r = dns_answer_add(answer, j->rr, ifindex, DNS_ANSWER_AUTHENTICATED);
r = dns_zone_add_authenticated_answer(answer, j, ifindex);
if (r < 0)
return r;
}