Vishal Chillara SrinivasandVishwanath Chandapur
6ccc2b24f5
Prepare for upcoming mDNS browse services. Prevent continuous queries from being attempted thrice. Co-authored-by: Vishwanath Chandapur <vishwanath.chandapur@philips.com>
63 lines
2.4 KiB
C
63 lines
2.4 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#pragma once
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#include "resolved-def.h"
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#include "time-util.h"
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/* LLMNR Jitter interval, see RFC 4795 Section 7 */
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#define LLMNR_JITTER_INTERVAL_USEC (100 * USEC_PER_MSEC)
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/* mDNS probing interval, see RFC 6762 Section 8.1 */
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#define MDNS_PROBING_INTERVAL_USEC (250 * USEC_PER_MSEC)
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/* Maximum attempts to send DNS requests, across all DNS servers */
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#define DNS_TRANSACTION_ATTEMPTS_MAX 24
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/* Maximum attempts to send LLMNR requests, see RFC 4795 Section 2.7 */
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#define LLMNR_TRANSACTION_ATTEMPTS_MAX 3
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/* Maximum attempts to send MDNS requests, see RFC 6762 Section 8.1 */
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#define MDNS_TRANSACTION_ATTEMPTS_MAX 3
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/* Maximum attempts to send an mDNS continuous query.
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*
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* RFC 6762 Section 5.2 does not specify a maximum number of attempts directly.
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* However, it outlines two important guidelines:
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*
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* 1. The interval between the first two queries MUST be at least one second.
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* 2. The intervals between successive queries MUST increase by at least a factor of two.
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*
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* To adhere to these timing requirements for continuous queries,
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* the maximum number of attempts should be set to 1.
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*/
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#define MDNS_TRANSACTION_CONTINUOUS_QUERY_MAX 1U
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static inline unsigned dns_transaction_attempts_max(DnsProtocol p, uint64_t query_flags) {
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switch (p) {
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case DNS_PROTOCOL_LLMNR:
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return LLMNR_TRANSACTION_ATTEMPTS_MAX;
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case DNS_PROTOCOL_MDNS:
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if (FLAGS_SET(query_flags, SD_RESOLVED_QUERY_CONTINUOUS))
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return MDNS_TRANSACTION_CONTINUOUS_QUERY_MAX;
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else
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return MDNS_TRANSACTION_ATTEMPTS_MAX;
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default:
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return DNS_TRANSACTION_ATTEMPTS_MAX;
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}
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}
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/* After how much time to repeat classic DNS requests */
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#define TRANSACTION_UDP_TIMEOUT_USEC (SD_RESOLVED_QUERY_TIMEOUT_USEC / DNS_TRANSACTION_ATTEMPTS_MAX)
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/* When we do TCP, grant a much longer timeout, as in this case there's no need for us to quickly
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* resend, as the kernel does that anyway for us, and we really don't want to interrupt it in that
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* needlessly. */
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#define TRANSACTION_TCP_TIMEOUT_USEC (10 * USEC_PER_SEC)
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/* Should be longer than transaction timeout for a single UDP transaction, so we get at least
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* one transaction retry before timeouting the whole candidate */
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#define CANDIDATE_EXPEDITED_TIMEOUT_USEC (TRANSACTION_UDP_TIMEOUT_USEC + 1 * USEC_PER_SEC)
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