/* * include/types/dns.h * This file provides structures and types for DNS. * * Copyright (C) 2014 Baptiste Assmann * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation, version 2.1 * exclusively. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #ifndef _TYPES_DNS_H #define _TYPES_DNS_H /*DNS maximum values */ /* * Maximum issued from RFC: * RFC 1035: https://www.ietf.org/rfc/rfc1035.txt chapter 2.3.4 * RFC 2671: http://tools.ietf.org/html/rfc2671 */ #define DNS_MAX_LABEL_SIZE 63 #define DNS_MAX_NAME_SIZE 255 #define DNS_MAX_UDP_MESSAGE 512 /* DNS minimun record size: 1 char + 1 NULL + type + class */ #define DNS_MIN_RECORD_SIZE ( 1 + 1 + 2 + 2 ) /* maximum number of query records in a DNS response * For now, we allow only one */ #define DNS_MAX_QUERY_RECORDS 1 /* maximum number of answer record in a DNS response */ #define DNS_MAX_ANSWER_RECORDS ((DNS_MAX_UDP_MESSAGE - DNS_HEADER_SIZE) / DNS_MIN_RECORD_SIZE) /* size of dns_buffer used to store responses from the buffer * dns_buffer is used to store data collected from records found in a response. * Before using it, caller will always check that there is at least DNS_MAX_NAME_SIZE bytes * available */ #define DNS_ANALYZE_BUFFER_SIZE DNS_MAX_UDP_MESSAGE + DNS_MAX_NAME_SIZE /* DNS error messages */ #define DNS_TOO_LONG_FQDN "hostname too long" #define DNS_LABEL_TOO_LONG "one label too long" #define DNS_INVALID_CHARACTER "found an invalid character" /* dns query class */ #define DNS_RCLASS_IN 1 /* internet class */ /* dns record types (non exhaustive list) */ #define DNS_RTYPE_A 1 /* IPv4 address */ #define DNS_RTYPE_CNAME 5 /* canonical name */ #define DNS_RTYPE_AAAA 28 /* IPv6 address */ #define DNS_RTYPE_ANY 255 /* all records */ /* dns rcode values */ #define DNS_RCODE_NO_ERROR 0 /* no error */ #define DNS_RCODE_NX_DOMAIN 3 /* non existent domain */ #define DNS_RCODE_REFUSED 5 /* query refused */ /* dns flags masks */ #define DNS_FLAG_TRUNCATED 0x0200 /* mask for truncated flag */ #define DNS_FLAG_REPLYCODE 0x000F /* mask for reply code */ /* max number of network preference entries are avalaible from the * configuration file. */ #define SRV_MAX_PREF_NET 5 /* DNS header size */ #define DNS_HEADER_SIZE sizeof(struct dns_header) /* DNS request or response header structure */ struct dns_header { uint16_t id; uint16_t flags; uint16_t qdcount; uint16_t ancount; uint16_t nscount; uint16_t arcount; } __attribute__ ((packed)); /* short structure to describe a DNS question */ /* NOTE: big endian structure */ struct dns_question { unsigned short qtype; /* question type */ unsigned short qclass; /* query class */ }; /* NOTE: big endian structure */ struct dns_query_item { struct list list; char name[DNS_MAX_NAME_SIZE]; /* query name */ unsigned short type; /* question type */ unsigned short class; /* query class */ }; /* NOTE: big endian structure */ struct dns_answer_item { struct list list; char *name; /* answer name * For SRV type, name also includes service * and protocol value */ int16_t type; /* question type */ int16_t class; /* query class */ int32_t ttl; /* response TTL */ int16_t priority; /* SRV type priority */ int16_t weight; /* SRV type weight */ int16_t port; /* SRV type port */ int16_t data_len; /* number of bytes in target below */ struct sockaddr address; /* IPv4 or IPv6, network format */ char *target; /* Response data: SRV or CNAME type target */ }; struct dns_response_packet { struct dns_header header; struct list query_list; struct list answer_list; /* authority and additional_information ignored for now */ }; /* * resolvers section and parameters. It is linked to the name servers * servers points to it. * current resolution are stored in a FIFO list. */ struct dns_resolvers { struct list list; /* resolvers list */ char *id; /* resolvers unique identifier */ struct { const char *file; /* file where the section appears */ int line; /* line where the section appears */ } conf; /* config information */ struct list nameserver_list; /* dns server list */ int count_nameservers; /* total number of nameservers in a resolvers section */ int resolve_retries; /* number of retries before giving up */ struct { /* time to: */ int retry; /* wait for a response before retrying */ } timeout; struct { /* time to hold current data when */ int valid; /* a response is valid */ int nx; /* a response doesn't exist */ int timeout; /* no answer was delivered */ int refused; /* dns server refused to answer */ int other; /* other dns response errors */ } hold; struct task *t; /* timeout management */ struct list curr_resolution; /* current running resolutions */ struct eb_root query_ids; /* tree to quickly lookup/retrieve query ids currently in use */ /* used by each nameserver, but stored in resolvers since there must */ /* be a unique relation between an eb_root and an eb_node (resolution) */ }; /* * structure describing a name server used during name resolution. * A name server belongs to a resolvers section. */ struct dns_nameserver { struct list list; /* nameserver chained list */ char *id; /* nameserver unique identifier */ struct { const char *file; /* file where the section appears */ int line; /* line where the section appears */ } conf; /* config information */ struct dns_resolvers *resolvers; struct dgram_conn *dgram; /* transport layer */ struct sockaddr_storage addr; /* IP address */ struct { /* numbers relted to this name server: */ long int sent; /* - queries sent */ long int valid; /* - valid response */ long int update; /* - valid response used to update server's IP */ long int cname; /* - CNAME response requiring new resolution */ long int cname_error; /* - error when resolving CNAMEs */ long int any_err; /* - void response (usually because ANY qtype) */ long int nx; /* - NX response */ long int timeout; /* - queries which reached timeout */ long int refused; /* - queries refused */ long int other; /* - other type of response */ long int invalid; /* - malformed DNS response */ long int too_big; /* - too big response */ long int outdated; /* - outdated response (server slower than the other ones) */ long int truncated; /* - truncated response */ } counters; }; struct dns_options { int family_prio; /* which IP family should the resolver use when both are returned */ struct { int family; union { struct in_addr in4; struct in6_addr in6; } addr; union { struct in_addr in4; struct in6_addr in6; } mask; } pref_net[SRV_MAX_PREF_NET]; int pref_net_nb; /* The number of registered prefered networks. */ }; /* * resolution structure associated to single server and used to manage name resolution for * this server. * The only link between the resolution and a nameserver is through the query_id. */ struct dns_resolution { struct list list; /* resolution list */ struct dns_resolvers *resolvers; /* resolvers section associated to this resolution */ void *requester; /* owner of this name resolution */ int (*requester_cb)(struct dns_resolution *, struct dns_nameserver *, struct dns_response_packet *); /* requester callback for valid response */ int (*requester_error_cb)(struct dns_resolution *, int); /* requester callback, for error management */ char *hostname_dn; /* server hostname in domain name label format */ int hostname_dn_len; /* server domain name label len */ struct dns_options *opts; /* IP selection options inherited from the configuration file. */ unsigned int last_resolution; /* time of the lastest valid resolution */ unsigned int last_sent_packet; /* time of the latest DNS packet sent */ unsigned int last_status_change; /* time of the latest DNS resolution status change */ int query_id; /* DNS query ID dedicated for this resolution */ struct eb32_node qid; /* ebtree query id */ int query_type; /* query type to send. By default DNS_RTYPE_A or DNS_RTYPE_AAAA depending on resolver_family_priority */ int status; /* status of the resolution being processed RSLV_STATUS_* */ int step; /* */ int try; /* current resolution try */ int try_cname; /* number of CNAME requests sent */ int nb_responses; /* count number of responses received */ }; /* last resolution status code */ enum { RSLV_STATUS_NONE = 0, /* no resolution occured yet */ RSLV_STATUS_VALID, /* no error */ RSLV_STATUS_INVALID, /* invalid responses */ RSLV_STATUS_ERROR, /* error */ RSLV_STATUS_NX, /* NXDOMAIN */ RSLV_STATUS_REFUSED, /* server refused our query */ RSLV_STATUS_TIMEOUT, /* no response from DNS servers */ RSLV_STATUS_OTHER, /* other errors */ }; /* current resolution step */ enum { RSLV_STEP_NONE = 0, /* nothing happening currently */ RSLV_STEP_RUNNING, /* resolution is running */ }; /* return codes after analyzing a DNS response */ enum { DNS_RESP_VALID = 0, /* valid response */ DNS_RESP_INVALID, /* invalid response (various type of errors can trigger it) */ DNS_RESP_ERROR, /* DNS error code */ DNS_RESP_NX_DOMAIN, /* resolution unsuccessful */ DNS_RESP_REFUSED, /* DNS server refused to answer */ DNS_RESP_ANCOUNT_ZERO, /* no answers in the response */ DNS_RESP_WRONG_NAME, /* response does not match query name */ DNS_RESP_CNAME_ERROR, /* error when resolving a CNAME in an atomic response */ DNS_RESP_TIMEOUT, /* DNS server has not answered in time */ DNS_RESP_TRUNCATED, /* DNS response is truncated */ DNS_RESP_NO_EXPECTED_RECORD, /* No expected records were found in the response */ DNS_RESP_QUERY_COUNT_ERROR, /* we did not get the expected number of queries in the response */ }; /* return codes after searching an IP in a DNS response buffer, using a family preference */ enum { DNS_UPD_NO = 1, /* provided IP was found and preference is matched * OR provided IP found and preference is not matched, but no IP * matching preference was found */ DNS_UPD_SRVIP_NOT_FOUND, /* provided IP not found * OR provided IP found and preference is not match and an IP * matching preference was found */ DNS_UPD_CNAME, /* CNAME without any IP provided in the response */ DNS_UPD_NAME_ERROR, /* name in the response did not match the query */ DNS_UPD_NO_IP_FOUND, /* no IP could be found in the response */ }; #endif /* _TYPES_DNS_H */