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resolved: add authority section to mDNS probing queries 

According to RFC 6762 Section 8.2 "Simultaneous Probe Tiebreaking"
probing queries' Authority Section is populated with proposed
resource records in order to resolve possible race conditions.
This commit is contained in:
Dmitry Rozhkov 2017-10-16 17:25:17 +03:00
parent 748a548e1b
commit 0d5ee47dfd
1 changed files with 40 additions and 0 deletions
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40
src/resolve/resolved-dns-transaction.c
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@ -1377,7 +1377,11 @@ static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
bool add_known_answers = false;
DnsTransaction *other;
Iterator i;
DnsResourceKey *tkey;
_cleanup_set_free_ Set *keys = NULL;
unsigned qdcount;
unsigned nscount = 0;
usec_t ts;
int r;
@ -1400,6 +1404,16 @@ static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
if (dns_key_is_shared(t->key))
add_known_answers = true;
if (t->key->type == DNS_TYPE_ANY) {
r = set_ensure_allocated(&keys, &dns_resource_key_hash_ops);
if (r < 0)
return r;
r = set_put(keys, t->key);
if (r < 0)
return r;
}
/*
* For mDNS, we want to coalesce as many open queries in pending transactions into one single
* query packet on the wire as possible. To achieve that, we iterate through all pending transactions
@ -1459,6 +1473,16 @@ static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
if (dns_key_is_shared(other->key))
add_known_answers = true;
if (other->key->type == DNS_TYPE_ANY) {
r = set_ensure_allocated(&keys, &dns_resource_key_hash_ops);
if (r < 0)
return r;
r = set_put(keys, other->key);
if (r < 0)
return r;
}
}
DNS_PACKET_HEADER(p)->qdcount = htobe16(qdcount);
@ -1470,6 +1494,22 @@ static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
return r;
}
SET_FOREACH(tkey, keys, i) {
_cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
bool tentative;
r = dns_zone_lookup(&t->scope->zone, tkey, t->scope->link->ifindex, &answer, NULL, &tentative);
if (r < 0)
return r;
r = dns_packet_append_answer(p, answer);
if (r < 0)
return r;
nscount += dns_answer_size(answer);
}
DNS_PACKET_HEADER(p)->nscount = htobe16(nscount);
t->sent = p;
p = NULL;