6bb2c08597
This changes the DnsServer logic to count failed UDP and TCP failures separately. This is useful so that we don't end up downgrading the feature level from one UDP level to a lower UDP level just because a TCP connection we did because of a TC response failed. This also adds accounting of truncated packets. If we detect incoming truncated packets, and count too many failed TCP connections (which is the normal fall back if we get a trucnated UDP packet) we downgrade the feature level, given that the responses at the current levels don't get through, and we somehow need to make sure they become smaller, which they will do if we don't request DNSSEC or EDNS support. This makes resolved work much better with crappy DNS servers that do not implement TCP and only limited UDP packet sizes, but otherwise support DNSSEC RRs. They end up choking on the generally larger DNSSEC RRs and there's no way to retrieve the full data.
130 lines
4.2 KiB
C
130 lines
4.2 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 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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typedef enum DnsServerFeatureLevel {
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DNS_SERVER_FEATURE_LEVEL_TCP,
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DNS_SERVER_FEATURE_LEVEL_UDP,
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DNS_SERVER_FEATURE_LEVEL_EDNS0,
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DNS_SERVER_FEATURE_LEVEL_DO,
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DNS_SERVER_FEATURE_LEVEL_LARGE,
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_DNS_SERVER_FEATURE_LEVEL_MAX,
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_DNS_SERVER_FEATURE_LEVEL_INVALID = -1
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} DnsServerFeatureLevel;
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#define DNS_SERVER_FEATURE_LEVEL_WORST 0
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#define DNS_SERVER_FEATURE_LEVEL_BEST (_DNS_SERVER_FEATURE_LEVEL_MAX - 1)
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const char* dns_server_feature_level_to_string(int i) _const_;
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int dns_server_feature_level_from_string(const char *s) _pure_;
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#include "resolved-link.h"
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#include "resolved-manager.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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DnsServerFeatureLevel verified_feature_level;
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DnsServerFeatureLevel possible_feature_level;
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size_t received_udp_packet_max;
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unsigned n_failed_udp;
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unsigned n_failed_tcp;
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bool packet_failed:1;
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bool packet_truncated:1;
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usec_t verified_usec;
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usec_t features_grace_period_usec;
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/* Indicates whether responses are augmented with RRSIG by
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* server or not. Note that this is orthogonal to the feature
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* level stuff, as it's only information describing responses,
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* and has no effect on how the questions are asked. */
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bool rrsig_missing:1;
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/* Used when GC'ing old DNS servers when configuration changes. */
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bool marked:1;
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/* If linked is set, then this server appears in the servers linked list */
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bool linked: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 **ret,
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DnsServerType type,
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Link *link,
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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_unlink(DnsServer *s);
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void dns_server_move_back_and_unmark(DnsServer *s);
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void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t rtt, size_t size);
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void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t usec);
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void dns_server_packet_failed(DnsServer *s, DnsServerFeatureLevel level);
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void dns_server_packet_truncated(DnsServer *s, DnsServerFeatureLevel level);
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void dns_server_packet_rrsig_missing(DnsServer *s);
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DnsServerFeatureLevel dns_server_possible_feature_level(DnsServer *s);
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int dns_server_adjust_opt(DnsServer *server, DnsPacket *packet, DnsServerFeatureLevel level);
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DnsServer *dns_server_find(DnsServer *first, int family, const union in_addr_union *in_addr);
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void dns_server_unlink_all(DnsServer *first);
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void dns_server_unlink_marked(DnsServer *first);
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void dns_server_mark_all(DnsServer *first);
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DnsServer *manager_get_first_dns_server(Manager *m, DnsServerType t);
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DnsServer *manager_set_dns_server(Manager *m, DnsServer *s);
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DnsServer *manager_get_dns_server(Manager *m);
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void manager_next_dns_server(Manager *m);
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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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