9df3ba6c6c
Rather than fixing this to 5s for unicast DNS and 1s for LLMNR, start at a tenth of those values and increase exponentially until the old values are reached. For LLMNR the recommended timeout for IEEE802 networks (which basically means all of the ones we care about) is 100ms, so that should be uncontroversial. For unicast DNS I have found no recommended value. However, it seems vastly more likely that hitting a 500ms timeout is casued by a packet loss, rather than the RTT genuinely being greater than 500ms, so taking this as a startnig value seems reasonable to me. In the common case this greatly reduces the latency due to normal packet loss. Moreover, once we get support for probing for features, this means that we can send more packets before degrading the feature level whilst still allowing us to settle on the correct feature level in a reasonable timeframe. The timeouts are tracked per server (or per scope for the multicast protocols), and once a server (or scope) receives a successfull package the timeout is reset. We also track the largest RTT for the given server/scope, and always start our timouts at twice the largest observed RTT.
74 lines
1.9 KiB
C
74 lines
1.9 KiB
C
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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#pragma once
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/***
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This file is part of systemd.
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Copyright 2014 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include "in-addr-util.h"
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typedef struct DnsServer DnsServer;
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typedef enum DnsServerSource DnsServerSource;
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typedef enum DnsServerType {
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DNS_SERVER_SYSTEM,
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DNS_SERVER_FALLBACK,
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DNS_SERVER_LINK,
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} DnsServerType;
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#include "resolved-link.h"
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struct DnsServer {
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Manager *manager;
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unsigned n_ref;
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DnsServerType type;
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Link *link;
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int family;
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union in_addr_union address;
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usec_t resend_timeout;
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usec_t max_rtt;
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bool marked:1;
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LIST_FIELDS(DnsServer, servers);
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};
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int dns_server_new(
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Manager *m,
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DnsServer **s,
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DnsServerType type,
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Link *l,
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int family,
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const union in_addr_union *address);
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DnsServer* dns_server_ref(DnsServer *s);
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DnsServer* dns_server_unref(DnsServer *s);
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void dns_server_packet_received(DnsServer *s, usec_t rtt);
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void dns_server_packet_lost(DnsServer *s, usec_t usec);
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DEFINE_TRIVIAL_CLEANUP_FUNC(DnsServer*, dns_server_unref);
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extern const struct hash_ops dns_server_hash_ops;
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