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RFC 6762 section 7.1: a Multicast DNS querier SHOULD NOT include records in the

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Known-Answer list whose remaining TTL is less than half of their original TTL
This commit is contained in:
Vishal Chillara Srinivas 2022-06-15 18:16:06 +05:30 committed by Yu Watanabe
parent 82af03c223
commit f941c12427
1 changed files with 8 additions and 0 deletions
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8
src/resolve/resolved-dns-cache.c
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@ -1245,11 +1245,14 @@ int dns_cache_check_conflicts(DnsCache *cache, DnsResourceRecord *rr, int owner_
int dns_cache_export_shared_to_packet(DnsCache *cache, DnsPacket *p) {
unsigned ancount = 0;
DnsCacheItem *i;
usec_t t;
int r;
assert(cache);
assert(p);
t = now(CLOCK_BOOTTIME);
HASHMAP_FOREACH(i, cache->by_key)
LIST_FOREACH(by_key, j, i) {
if (!j->rr)
@ -1258,6 +1261,11 @@ int dns_cache_export_shared_to_packet(DnsCache *cache, DnsPacket *p) {
if (!j->shared_owner)
continue;
/* RFC6762 7.1: Don't append records with less than half the TTL remaining
* as known answers. */
if (usec_sub_unsigned(j->until, t) < j->rr->ttl * USEC_PER_SEC / 2)
continue;
r = dns_packet_append_rr(p, j->rr, 0, NULL, NULL);
if (r == -EMSGSIZE && p->protocol == DNS_PROTOCOL_MDNS) {
/* For mDNS, if we're unable to stuff all known answers into the given packet,