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| author | Vishal Chillara Srinivas <vishal.chillarasrinivas@philips.com> | 2022-06-15 14:46:06 +0200 |
|---|---|---|
| committer | Yu Watanabe <watanabe.yu+github@gmail.com> | 2022-06-16 03:44:25 +0200 |
| commit | f941c124273ac1b3bce0029f69f9664ba6f01f7f (patch) | |
| tree | 06725c962ace43d3186763bbfa7c310577066bad /src/resolve/resolved-dns-cache.c | |
| parent | resolve: mark mDNS RRs in the Additional Records section as cacheable (diff) | |
| download | systemd-f941c124273ac1b3bce0029f69f9664ba6f01f7f.tar.xz systemd-f941c124273ac1b3bce0029f69f9664ba6f01f7f.zip | |
RFC 6762 section 7.1: a Multicast DNS querier SHOULD NOT include records in the
Known-Answer list whose remaining TTL is less than half of their original TTL
Diffstat (limited to '')
| -rw-r--r-- | src/resolve/resolved-dns-cache.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/src/resolve/resolved-dns-cache.c b/src/resolve/resolved-dns-cache.c index 395109dcb2..0856976d3e 100644 --- a/src/resolve/resolved-dns-cache.c +++ b/src/resolve/resolved-dns-cache.c @@ -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, |