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/*
* 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.
*/
#ifndef DNS_RRL_H
#define DNS_RRL_H 1
/*
* Rate limit DNS responses.
*/
#include <inttypes.h>
#include <stdbool.h>
#include <isc/lang.h>
#include <dns/fixedname.h>
#include <dns/rdata.h>
#include <dns/types.h>
ISC_LANG_BEGINDECLS
/*
* Memory allocation or other failures.
*/
#define DNS_RRL_LOG_FAIL ISC_LOG_WARNING
/*
* dropped or slipped responses.
*/
#define DNS_RRL_LOG_DROP ISC_LOG_INFO
/*
* Major events in dropping or slipping.
*/
#define DNS_RRL_LOG_DEBUG1 ISC_LOG_DEBUG(3)
/*
* Limit computations.
*/
#define DNS_RRL_LOG_DEBUG2 ISC_LOG_DEBUG(4)
/*
* Even less interesting.
*/
#define DNS_RRL_LOG_DEBUG3 ISC_LOG_DEBUG(9)
#define DNS_RRL_LOG_ERR_LEN 64
#define DNS_RRL_LOG_BUF_LEN (sizeof("would continue limiting") + \
DNS_RRL_LOG_ERR_LEN + \
sizeof(" responses to ") + \
ISC_NETADDR_FORMATSIZE + \
sizeof("/128 for IN ") + \
DNS_RDATATYPE_FORMATSIZE + \
DNS_NAME_FORMATSIZE)
typedef struct dns_rrl_hash dns_rrl_hash_t;
/*
* Response types.
*/
typedef enum {
DNS_RRL_RTYPE_FREE = 0,
DNS_RRL_RTYPE_QUERY,
DNS_RRL_RTYPE_REFERRAL,
DNS_RRL_RTYPE_NODATA,
DNS_RRL_RTYPE_NXDOMAIN,
DNS_RRL_RTYPE_ERROR,
DNS_RRL_RTYPE_ALL,
DNS_RRL_RTYPE_TCP,
} dns_rrl_rtype_t;
/*
* A rate limit bucket key.
* This should be small to limit the total size of the database.
* The hash of the qname should be wide enough to make the probability
* of collisions among requests from a single IP address block less than 50%.
* We need a 32-bit hash value for 10000 qps (e.g. random qnames forged
* by attacker) to collide with legitimate qnames from the target with
* probability at most 1%.
*/
#define DNS_RRL_MAX_PREFIX 64
typedef union dns_rrl_key dns_rrl_key_t;
struct dns__rrl_key {
uint32_t ip[DNS_RRL_MAX_PREFIX/32];
uint32_t qname_hash;
dns_rdatatype_t qtype;
uint8_t qclass;
unsigned int rtype :4; /* dns_rrl_rtype_t */
unsigned int ipv6 :1;
};
union dns_rrl_key {
struct dns__rrl_key s;
uint16_t w[sizeof(struct dns__rrl_key)/sizeof(uint16_t)];
};
/*
* A rate-limit entry.
* This should be small to limit the total size of the table of entries.
*/
typedef struct dns_rrl_entry dns_rrl_entry_t;
typedef ISC_LIST(dns_rrl_entry_t) dns_rrl_bin_t;
struct dns_rrl_entry {
ISC_LINK(dns_rrl_entry_t) lru;
ISC_LINK(dns_rrl_entry_t) hlink;
dns_rrl_key_t key;
# define DNS_RRL_RESPONSE_BITS 24
signed int responses :DNS_RRL_RESPONSE_BITS;
# define DNS_RRL_QNAMES_BITS 8
unsigned int log_qname :DNS_RRL_QNAMES_BITS;
# define DNS_RRL_TS_GEN_BITS 2
unsigned int ts_gen :DNS_RRL_TS_GEN_BITS;
unsigned int ts_valid :1;
# define DNS_RRL_HASH_GEN_BITS 1
unsigned int hash_gen :DNS_RRL_HASH_GEN_BITS;
unsigned int logged :1;
# define DNS_RRL_LOG_BITS 11
unsigned int log_secs :DNS_RRL_LOG_BITS;
# define DNS_RRL_TS_BITS 12
unsigned int ts :DNS_RRL_TS_BITS;
# define DNS_RRL_MAX_SLIP 10
unsigned int slip_cnt :4;
};
#define DNS_RRL_MAX_TIME_TRAVEL 5
#define DNS_RRL_FOREVER (1<<DNS_RRL_TS_BITS)
#define DNS_RRL_MAX_TS (DNS_RRL_FOREVER - 1)
#define DNS_RRL_MAX_RESPONSES ((1<<(DNS_RRL_RESPONSE_BITS-1))-1)
#define DNS_RRL_MAX_WINDOW 3600
#if DNS_RRL_MAX_WINDOW >= DNS_RRL_MAX_TS
#error "DNS_RRL_MAX_WINDOW is too large"
#endif
#define DNS_RRL_MAX_RATE 1000
#if DNS_RRL_MAX_RATE >= (DNS_RRL_MAX_RESPONSES / DNS_RRL_MAX_WINDOW)
#error "DNS_RRL_MAX_rate is too large"
#endif
#if (1<<DNS_RRL_LOG_BITS) >= DNS_RRL_FOREVER
#error DNS_RRL_LOG_BITS is too big
#endif
#define DNS_RRL_MAX_LOG_SECS 1800
#if DNS_RRL_MAX_LOG_SECS >= (1<<DNS_RRL_LOG_BITS)
#error "DNS_RRL_MAX_LOG_SECS is too large"
#endif
#define DNS_RRL_STOP_LOG_SECS 60
#if DNS_RRL_STOP_LOG_SECS >= (1<<DNS_RRL_LOG_BITS)
#error "DNS_RRL_STOP_LOG_SECS is too large"
#endif
/*
* A hash table of rate-limit entries.
*/
struct dns_rrl_hash {
isc_stdtime_t check_time;
unsigned int gen :DNS_RRL_HASH_GEN_BITS;
int length;
dns_rrl_bin_t bins[1];
};
/*
* A block of rate-limit entries.
*/
typedef struct dns_rrl_block dns_rrl_block_t;
struct dns_rrl_block {
ISC_LINK(dns_rrl_block_t) link;
int size;
dns_rrl_entry_t entries[1];
};
/*
* A rate limited qname buffer.
*/
typedef struct dns_rrl_qname_buf dns_rrl_qname_buf_t;
struct dns_rrl_qname_buf {
ISC_LINK(dns_rrl_qname_buf_t) link;
const dns_rrl_entry_t *e;
unsigned int index;
dns_fixedname_t qname;
};
typedef struct dns_rrl_rate dns_rrl_rate_t;
struct dns_rrl_rate {
int r;
int scaled;
const char *str;
};
/*
* Per-view query rate limit parameters and a pointer to database.
*/
typedef struct dns_rrl dns_rrl_t;
struct dns_rrl {
isc_mutex_t lock;
isc_mem_t *mctx;
bool log_only;
dns_rrl_rate_t responses_per_second;
dns_rrl_rate_t referrals_per_second;
dns_rrl_rate_t nodata_per_second;
dns_rrl_rate_t nxdomains_per_second;
dns_rrl_rate_t errors_per_second;
dns_rrl_rate_t all_per_second;
dns_rrl_rate_t slip;
int window;
double qps_scale;
int max_entries;
dns_acl_t *exempt;
int num_entries;
int qps_responses;
isc_stdtime_t qps_time;
double qps;
unsigned int probes;
unsigned int searches;
ISC_LIST(dns_rrl_block_t) blocks;
ISC_LIST(dns_rrl_entry_t) lru;
dns_rrl_hash_t *hash;
dns_rrl_hash_t *old_hash;
unsigned int hash_gen;
unsigned int ts_gen;
# define DNS_RRL_TS_BASES (1<<DNS_RRL_TS_GEN_BITS)
isc_stdtime_t ts_bases[DNS_RRL_TS_BASES];
int ipv4_prefixlen;
uint32_t ipv4_mask;
int ipv6_prefixlen;
uint32_t ipv6_mask[4];
isc_stdtime_t log_stops_time;
dns_rrl_entry_t *last_logged;
int num_logged;
int num_qnames;
ISC_LIST(dns_rrl_qname_buf_t) qname_free;
# define DNS_RRL_QNAMES (1<<DNS_RRL_QNAMES_BITS)
dns_rrl_qname_buf_t *qnames[DNS_RRL_QNAMES];
};
typedef enum {
DNS_RRL_RESULT_OK,
DNS_RRL_RESULT_DROP,
DNS_RRL_RESULT_SLIP,
} dns_rrl_result_t;
dns_rrl_result_t
dns_rrl(dns_view_t *view,
const isc_sockaddr_t *client_addr, bool is_tcp,
dns_rdataclass_t rdclass, dns_rdatatype_t qtype,
dns_name_t *qname, isc_result_t resp_result, isc_stdtime_t now,
bool wouldlog, char *log_buf, unsigned int log_buf_len);
void
dns_rrl_view_destroy(dns_view_t *view);
isc_result_t
dns_rrl_init(dns_rrl_t **rrlp, dns_view_t *view, int min_entries);
ISC_LANG_ENDDECLS
#endif /* DNS_RRL_H */