2
0
mirror of https://gitlab.isc.org/isc-projects/bind9 synced 2025-08-22 18:19:42 +00:00
bind/lib/ns/server.c
Ondřej Surý bb990030d3 Simplify the EDNS buffer size logic for DNS Flag Day 2020
The DNS Flag Day 2020 aims to remove the IP fragmentation problem from
the UDP DNS communication.  In this commit, we implement the required
changes and simplify the logic for picking the EDNS Buffer Size.

1. The defaults for `edns-udp-size`, `max-udp-size` and
   `nocookie-udp-size` have been changed to `1232` (the value picked by
   DNS Flag Day 2020).

2. The probing heuristics that would try 512->4096->1432->1232 buffer
   sizes has been removed and the resolver will always use just the
   `edns-udp-size` value.

3. Instead of just disabling the PMTUD mechanism on the UDP sockets, we
   now set IP_DONTFRAG (IPV6_DONTFRAG) flag.  That means that the UDP
   packets won't get ever fragmented.  If the ICMP packets are lost the
   UDP will just timeout and eventually be retried over TCP.
2020-10-05 16:21:21 +02:00

230 lines
5.4 KiB
C

/*
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, you can obtain one at https://mozilla.org/MPL/2.0/.
*
* See the COPYRIGHT file distributed with this work for additional
* information regarding copyright ownership.
*/
/*! \file */
#include <stdbool.h>
#include <isc/mem.h>
#include <isc/stats.h>
#include <isc/util.h>
#include <dns/stats.h>
#include <dns/tkey.h>
#include <ns/query.h>
#include <ns/server.h>
#include <ns/stats.h>
#define SCTX_MAGIC ISC_MAGIC('S', 'c', 't', 'x')
#define SCTX_VALID(s) ISC_MAGIC_VALID(s, SCTX_MAGIC)
#define CHECKFATAL(op) \
do { \
result = (op); \
RUNTIME_CHECK(result == ISC_R_SUCCESS); \
} while (0)
isc_result_t
ns_server_create(isc_mem_t *mctx, ns_matchview_t matchingview,
ns_server_t **sctxp) {
ns_server_t *sctx;
isc_result_t result;
REQUIRE(sctxp != NULL && *sctxp == NULL);
sctx = isc_mem_get(mctx, sizeof(*sctx));
memset(sctx, 0, sizeof(*sctx));
isc_mem_attach(mctx, &sctx->mctx);
isc_refcount_init(&sctx->references, 1);
isc_quota_init(&sctx->xfroutquota, 10);
isc_quota_init(&sctx->tcpquota, 10);
isc_quota_init(&sctx->recursionquota, 100);
CHECKFATAL(dns_tkeyctx_create(mctx, &sctx->tkeyctx));
CHECKFATAL(ns_stats_create(mctx, ns_statscounter_max, &sctx->nsstats));
CHECKFATAL(dns_rdatatypestats_create(mctx, &sctx->rcvquerystats));
CHECKFATAL(dns_opcodestats_create(mctx, &sctx->opcodestats));
CHECKFATAL(dns_rcodestats_create(mctx, &sctx->rcodestats));
CHECKFATAL(isc_stats_create(mctx, &sctx->udpinstats4,
dns_sizecounter_in_max));
CHECKFATAL(isc_stats_create(mctx, &sctx->udpoutstats4,
dns_sizecounter_out_max));
CHECKFATAL(isc_stats_create(mctx, &sctx->udpinstats6,
dns_sizecounter_in_max));
CHECKFATAL(isc_stats_create(mctx, &sctx->udpoutstats6,
dns_sizecounter_out_max));
CHECKFATAL(isc_stats_create(mctx, &sctx->tcpinstats4,
dns_sizecounter_in_max));
CHECKFATAL(isc_stats_create(mctx, &sctx->tcpoutstats4,
dns_sizecounter_out_max));
CHECKFATAL(isc_stats_create(mctx, &sctx->tcpinstats6,
dns_sizecounter_in_max));
CHECKFATAL(isc_stats_create(mctx, &sctx->tcpoutstats6,
dns_sizecounter_out_max));
sctx->udpsize = 1232;
sctx->transfer_tcp_message_size = 20480;
sctx->fuzztype = isc_fuzz_none;
sctx->fuzznotify = NULL;
sctx->gethostname = NULL;
sctx->matchingview = matchingview;
sctx->answercookie = true;
ISC_LIST_INIT(sctx->altsecrets);
sctx->magic = SCTX_MAGIC;
*sctxp = sctx;
return (ISC_R_SUCCESS);
}
void
ns_server_attach(ns_server_t *src, ns_server_t **dest) {
REQUIRE(SCTX_VALID(src));
REQUIRE(dest != NULL && *dest == NULL);
isc_refcount_increment(&src->references);
*dest = src;
}
void
ns_server_detach(ns_server_t **sctxp) {
ns_server_t *sctx;
REQUIRE(sctxp != NULL && SCTX_VALID(*sctxp));
sctx = *sctxp;
*sctxp = NULL;
if (isc_refcount_decrement(&sctx->references) == 1) {
ns_altsecret_t *altsecret;
while ((altsecret = ISC_LIST_HEAD(sctx->altsecrets)) != NULL) {
ISC_LIST_UNLINK(sctx->altsecrets, altsecret, link);
isc_mem_put(sctx->mctx, altsecret, sizeof(*altsecret));
}
isc_quota_destroy(&sctx->recursionquota);
isc_quota_destroy(&sctx->tcpquota);
isc_quota_destroy(&sctx->xfroutquota);
if (sctx->server_id != NULL) {
isc_mem_free(sctx->mctx, sctx->server_id);
}
if (sctx->blackholeacl != NULL) {
dns_acl_detach(&sctx->blackholeacl);
}
if (sctx->keepresporder != NULL) {
dns_acl_detach(&sctx->keepresporder);
}
if (sctx->tkeyctx != NULL) {
dns_tkeyctx_destroy(&sctx->tkeyctx);
}
if (sctx->nsstats != NULL) {
ns_stats_detach(&sctx->nsstats);
}
if (sctx->rcvquerystats != NULL) {
dns_stats_detach(&sctx->rcvquerystats);
}
if (sctx->opcodestats != NULL) {
dns_stats_detach(&sctx->opcodestats);
}
if (sctx->rcodestats != NULL) {
dns_stats_detach(&sctx->rcodestats);
}
if (sctx->udpinstats4 != NULL) {
isc_stats_detach(&sctx->udpinstats4);
}
if (sctx->tcpinstats4 != NULL) {
isc_stats_detach(&sctx->tcpinstats4);
}
if (sctx->udpoutstats4 != NULL) {
isc_stats_detach(&sctx->udpoutstats4);
}
if (sctx->tcpoutstats4 != NULL) {
isc_stats_detach(&sctx->tcpoutstats4);
}
if (sctx->udpinstats6 != NULL) {
isc_stats_detach(&sctx->udpinstats6);
}
if (sctx->tcpinstats6 != NULL) {
isc_stats_detach(&sctx->tcpinstats6);
}
if (sctx->udpoutstats6 != NULL) {
isc_stats_detach(&sctx->udpoutstats6);
}
if (sctx->tcpoutstats6 != NULL) {
isc_stats_detach(&sctx->tcpoutstats6);
}
sctx->magic = 0;
isc_mem_putanddetach(&sctx->mctx, sctx, sizeof(*sctx));
}
}
isc_result_t
ns_server_setserverid(ns_server_t *sctx, const char *serverid) {
REQUIRE(SCTX_VALID(sctx));
if (sctx->server_id != NULL) {
isc_mem_free(sctx->mctx, sctx->server_id);
sctx->server_id = NULL;
}
if (serverid != NULL) {
sctx->server_id = isc_mem_strdup(sctx->mctx, serverid);
}
return (ISC_R_SUCCESS);
}
void
ns_server_setoption(ns_server_t *sctx, unsigned int option, bool value) {
REQUIRE(SCTX_VALID(sctx));
if (value) {
sctx->options |= option;
} else {
sctx->options &= ~option;
}
}
bool
ns_server_getoption(ns_server_t *sctx, unsigned int option) {
REQUIRE(SCTX_VALID(sctx));
return ((sctx->options & option) != 0);
}