dns_client.h

DNS 的实现代码

/* ###########################################################################
# (c) Copyright Virata Limited 2001 
#
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/*
 * file:  dns_client.h
 *
 * description:  this file contains defines and structures used by the 
 *               dns_client code.  in particular this file contains the
 *               structures used for internal representation of the DNS
 *               messages and defines used for parsing.  the file also
 *               contains the structure to maintain the needed configuration
 *               data.
 *
 */
/*
 * List of New Routines:
 *     SOCKEQUAL()
 *     long2sock()
 *     data2sock()
 *     sock2long()
 *     reverse_sockaddr_int()
 *     reverse_sockaddr_arpa()
 *     
 */

#ifndef _DNS_CLIENT_H
#define _DNS_CLIENT_H 

#include <atypes.h>
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <timelib.h>
#include "dns_resolv.h"


#undef DEBUG

#define DNSC_MSG(x...)      printf("%C " x)

#ifdef DEBUG

#define DNS_DEBUG 
#define DNS_VERBOSE

#define DEBUG_LEVEL     (0x01 | 0x02)

#define DNSC_TRACE(x...) \
    do {                                            \
        if (DEBUG_LEVEL & 0x01)                     \
        {                                           \
            kprintf("<%C>: " x);                    \
        }                                           \
    } while (0)

#define DNSC_DEBUG(x...) \
    do {                                            \
        if (DEBUG_LEVEL & 0x02)                     \
        {                                           \
            kprintf("[%C]: " __FUNCTION__ ": " x);  \
        }                                           \
    } while (0)

#define ASSERT(x)           assert(x)

#else

#define DNSC_TRACE(x...)
#define DNSC_DEBUG(x...)
#define ASSERT(x)

#endif

#ifdef ATIC_SUPPORT_IPV6
#define DNS_HAVE_IP6STACK
#endif

#ifndef IN
#define IN
#endif
#ifndef OUT
#define OUT
#endif

#ifdef DNS_DEBUG
#define dprintf(args...)  kprintf(args)
#else
#define dprintf(args...)  ((void) 0)
#endif


#define LABELMAX             63    /* max label size, see RFC 1034 */ 
#define DNSMAX              512    /* max size of DNS message */
#define CMPMASK       (U8 )0xC0    /* compression test mask */ 
#define CMPSTRIP   (U16 )0x3FFF    /* zero the first two bits of the short */

#define CMPBITSET(byte)  (((byte) & CMPMASK) == CMPMASK)


#define MIN(x,y)  (x) < (y) ? (x) : (y)


/* 
 * typedef for the DNS message header.  a DNS message is defined for both queries 
 * and responses.  it has a fixed 12 byte header followed by 4 variable length
 * fields.  (RR are resource records)
 */

typedef struct {
    U16  id;         /* identification */
    U16  flags;      /* flags, see below */
    U16  nquest;     /* number questions */
    U16  nansrr;     /* number of answer RRs */
    U16  nauthrr;    /* number of authority RRs, also called NS RRs */
    U16  naddrr;     /* number of additional RRs */
} DnsHdr; 

/*
 * defines used for the flags field of the DNS message, see RFC 1035.
 *
 * flag format:
 *
 * --------------------------------------------------
 * | QR | opcode | AA | TC | RD | RA | zero | rcode |
 * --------------------------------------------------
 *   1      4       1    1    1    1     3      4
 *
 * QR     - 0 = query .
 *          1 = response.
 *
 * opcode - 0 = a standard query.
 *          1 = an inverse query.
 *          2 = server status request.
 *
 * AA     - 1 = is an authoritative answer.
 *
 * TC     - 1 = message truncated, the reply would exceed 512 bytes so only the
 *              first 512 bytes were returned.
 *
 * RD     - 1 = recursion desired (recursive query).
 *
 * RA     - 1 = recursion available.
 *
 * zero   - must be 0. (see RFC 1035 section 4.1.1 and RFC 2065 section 6 and 6.1)
 *
 * rcode  - 0 = no error.
 *          3 = name error, authoritative name server says the domain does not exist.
 *              other errors described in section 4.1.1 of RFC 1035.
 */

#define RSV_STDQUERY   0x0100   /* standard query with recursion desired, (requested) */
#define RSV_INVQUERY   0x0900   /* inverse query with recursion desired, (requested) */
 
#define DNS_QR         0x8000   /* query or response */
#define DNS_OPCODE     0x7800   /* dns header op code */
#define DNS_STDQUERY   0x0000   /* standard query, 0 */
#define DNS_INVQUERY   0x0800   /* inverse query, 1 */
#define DNS_STATUS     0x0100   /* server status request */
#define DNS_AUTHANS    0x0400   /* authoritive answer */
#define DNS_TRUNC      0x0200   /* truncated answer */
#define DNS_RECURDD    0x0100   /* recursion desired */
#define DNS_RECURAV    0x0080   /* recursion available */
#define DNS_RCODE      0x000F   /* rcode */
#define DNS_NOERROR    0x0000   /* rcode = 0 no error */
#define DNS_NAMEERR    0x0003   /* name server says domain does not exist */
#define DNS_FMTERR     0x0001   /* format error - name server unable to interpret query */
#define DNS_SVRFAILERR 0x0002   /* server failure - problem with the name server */
#define DNS_NOTIMPERR  0x0004   /* not implemented - server doesn't support query type */
#define DNS_REFUSEERR  0x0005   /* refused - name server refuses to perform query */



/*
 * structures and defines used to represent DNS messages.  a DNS message is
 * defined in RFC 1035.  the messages contain a 12 byte header, questions and
 * resource records. (resource records are abreviated in the comments and code
 * in several places as RR.)
 */

/* DNS question */

typedef struct question_t {
    struct question_t *q_next;           /* pointer to the next question if there is one */
    BOOL              q_used;            /* indicator as to whether this one's free */
    char              q_name[NAMEMAX+1]; /* query name, (domain name or IP address) */
    U16               q_type;            /* query type, (for us either A or PTR) */
    U16               q_class;           /* query class, will normally 1 for IP address */
} DnsQuestion;


/* query types */

#define QT_A       1      /* IP address */
#define QT_NS      2      /* name server */
#define QT_CNAME   5      /* canonical name */
#define QT_SOA     6      /* start of zone of authority */
#define QT_PTR    12      /* pointer record */
#define QT_HINFO  13      /* host info */
#define QT_MX     15      /* mail exchange record */
#define QT_AAAA   28      /* IP6 address, RFC 1886 */
#define QT_SRV    33      /* SRV RFC 2782 */
#define QT_NAPTR  35      /* NAPTR RFC 2915 */
#define QT_A6     38      /* A6, RFC 2874 */

/* query class */

#define QC_IN      1      /* the internet */


/* DNS resource record */

typedef struct RR_t {
    struct RR_t  *r_next;             /* pointer to the next RR if there is one */
    BOOL         r_used;              /* indicator as to whether this one's free */
    char         r_dname[NAMEMAX+1];  /* domain name */
    U16          r_type;              /* type */
    U16          r_class;             /* class */
    U32          r_ttl;               /* time to live */
    U16          r_datalen;           /* resource data length */
    U8           *r_data;             /* resource data */
} DnsRRec;


/* parsed or created DNS message */

typedef struct {
    DnsHdr       m_dnshdr;        /* the DNS message header */
    DnsQuestion  *m_questions;    /* list of DNS questions */
    DnsRRec      *m_answers;      /* list of answer RRs */
    DnsRRec      *m_authoritys;   /* list of authority RRs, (NS RRs) */
    DnsRRec      *m_additionals;  /* list of additional RRs */
} DnsMsg;


/* general use defines */

#define INADDR_ARPA   "in-addr.arpa."
#define IP6_ARPA      "ip6.arpa."
#define IP6_INT       "ip6.int."
#define DOT           '.'
#define SDOT          "."
#define COLON         ":"


/* SOA rdata structure, used with negative caching, see RFC 1035 section 3.3.13 and
 * RFC 2181 and RFC 2308.
 */

typedef struct {
    BOOL   s_used;              /* in use indicator */
    char   s_mname[NAMEMAX+1];  /* domain name of NS that was primary source for zone */
    char   s_rname[NAMEMAX+1];  /* domain specifies mailbox of responsible person */
    U32    s_serial;            /* version number of original copy of zone */
    U32    s_refresh;           /* time interval before zone should be refreshed */
    U32    s_retry;             /* time interval before failed refresh should be retried */
    U32    s_expire;            /* time interval before zone is no longer authoritative */
    U32    s_minimum;           /* TTL field to be exported with RR from this zone */
} SOArec;
 

/* the following structures are used internally only. */

typedef struct {
    char *dname;   /* the domain name */
    int  dparts;   /* number of parts to the name */
} Dcmp;


typedef enum {
    ptr_t,
    addr_t,
    aaaa_t
} query_t;


typedef struct {
    query_t            qtype;       /* query type, PTR, ADDRESS, etc */
    char               *hostname;   /* domain name for ADDRESS queries */
    U32                ipaddr;      /* IP address for PTR queries */
    BOOL               cache_flag;  /* cache use flag (IPv4 only) */
    int                qcnt;        /* query count */
    ATMOS_MESSAGE      *amsg;       /* the message to use */
    struct dns_hostent *hptr;       /* structure for results (IPv4 only) */
    struct hostent     *hent;       /* structure for results (IPv6) */
} Qinfo_t;