diff options
| author | Daniel Mack <daniel@zonque.org> | 2015-08-25 14:08:29 +0200 |
|---|---|---|
| committer | Daniel Mack <daniel@zonque.org> | 2015-12-08 16:41:45 +0100 |
| commit | ea12bcc78911fd3531955a799dbf6c5ac33bf567 (patch) | |
| tree | ceba1d11e5edcec63119badd465d785786379309 | |
| parent | b4f1862df2e45aba90386887d685b8bf3c840e10 (diff) | |
resolved: add mDNS initial jitter
The logic is to kick off mDNS packets in a delayed way is mostly identical
to what LLMNR needs, except that the constants are different.
| -rw-r--r-- | src/resolve/resolved-dns-transaction.c | 26 | ||||
| -rw-r--r-- | src/resolve/resolved-dns-transaction.h | 4 |
2 files changed, 24 insertions, 6 deletions
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c index f77931ed53..2cf9417a4b 100644 --- a/src/resolve/resolved-dns-transaction.c +++ b/src/resolve/resolved-dns-transaction.c @@ -751,8 +751,10 @@ int dns_transaction_go(DnsTransaction *t) { } } - if (t->scope->protocol == DNS_PROTOCOL_LLMNR && !t->initial_jitter) { - usec_t jitter; + if (!t->initial_jitter && + (t->scope->protocol == DNS_PROTOCOL_LLMNR || + t->scope->protocol == DNS_PROTOCOL_MDNS)) { + usec_t jitter, accuracy; /* RFC 4795 Section 2.7 suggests all queries should be * delayed by a random time from 0 to JITTER_INTERVAL. */ @@ -760,14 +762,26 @@ int dns_transaction_go(DnsTransaction *t) { t->initial_jitter = true; random_bytes(&jitter, sizeof(jitter)); - jitter %= LLMNR_JITTER_INTERVAL_USEC; + + switch (t->scope->protocol) { + case DNS_PROTOCOL_LLMNR: + jitter %= LLMNR_JITTER_INTERVAL_USEC; + accuracy = LLMNR_JITTER_INTERVAL_USEC; + break; + case DNS_PROTOCOL_MDNS: + jitter %= MDNS_JITTER_RANGE_USEC; + jitter += MDNS_JITTER_MIN_USEC; + accuracy = MDNS_JITTER_RANGE_USEC; + break; + default: + assert_not_reached("bad protocol"); + } r = sd_event_add_time( t->scope->manager->event, &t->timeout_event_source, clock_boottime_or_monotonic(), - ts + jitter, - LLMNR_JITTER_INTERVAL_USEC, + ts + jitter, accuracy, on_transaction_timeout, t); if (r < 0) return r; @@ -775,7 +789,7 @@ int dns_transaction_go(DnsTransaction *t) { t->n_attempts = 0; t->state = DNS_TRANSACTION_PENDING; - log_debug("Delaying LLMNR transaction for " USEC_FMT "us.", jitter); + log_debug("Delaying %s transaction for " USEC_FMT "us.", dns_protocol_to_string(t->scope->protocol), jitter); return 0; } diff --git a/src/resolve/resolved-dns-transaction.h b/src/resolve/resolved-dns-transaction.h index a3058ce6e8..1d445ffee7 100644 --- a/src/resolve/resolved-dns-transaction.h +++ b/src/resolve/resolved-dns-transaction.h @@ -119,6 +119,10 @@ DnsTransactionSource dns_transaction_source_from_string(const char *s) _pure_; /* LLMNR Jitter interval, see RFC 4795 Section 7 */ #define LLMNR_JITTER_INTERVAL_USEC (100 * USEC_PER_MSEC) +/* mDNS Jitter interval, see RFC 6762 Section 5.2 */ +#define MDNS_JITTER_MIN_USEC (20 * USEC_PER_MSEC) +#define MDNS_JITTER_RANGE_USEC (100 * USEC_PER_MSEC) + /* Maximum attempts to send DNS requests, across all DNS servers */ #define DNS_TRANSACTION_ATTEMPTS_MAX 16 |