dns_client_util6.c

DNS 的实现代码

/*
 * DNS Resolver
 * IPv6 Resolver Utility Routines
 *
 * Author: Pavel A. Bolokhov   <[e-mail]>
 *
 * External API:
 *     dns_fmt_ip6_answer()
 *     dns_fmt_cname6_answer()
 *     dns_fmt_cache6_answer()
 *     dns_fmt_ptr6_answer()
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include "messages.h"
#include "dns_client.h"
#include "dns_client_query.h"

#include "dns_client_util6.h"
#include "dns_client_resource.h"


/* dns_fmt_ip6_answer --
 *     Puts the answer with address into message.
 *
 * PARAMETERS
 *     query  - query state structure
 *     dnsmsg - dns message with results
 *
 * RETURNS:
 *      0 - for success, or
 *     -1 - for an error condition.
 */
int
dns_fmt_ip6_answer(IN QueryState *query, IN DnsMsg *dnsmsg)
{
    struct hostent  *hent;
    DnsRRec         *RR;
    int              nanswers, i;

    MSG_D_DNS_GET_NODEBYNAME(dmsg, query->reply);

    DNSC_DEBUG("entry\n");

    if ((hent = dns_alloc_struct_hostent()) == NULL)
    {
        dmsg->error = ENOMEM;
        DNSC_DEBUG("exit - dns_alloc_struct_hostent failed\n");
        return -1;
    }
    
    if (strlen(query->cname) > 0)
    {
        if (dns_alloc_aliases(hent, 1) == NULL)
        {
            dmsg->error = ENOMEM;
            return -1;
        }
        if ((hent->h_aliases[0] = malloc(strlen(query->cname) + 1)) == NULL)
        {
            dns_freehostent(hent);
            dmsg->error = ENOMEM;
            return -1;
        }
        strcpy(hent->h_aliases[0], query->cname);
    }

    nanswers = find_num_match(query->domain, dnsmsg->m_answers, QT_AAAA) +
               find_num_match(query->domain, dnsmsg->m_answers, QT_A6);

    if (nanswers == 0)
    {
        DNSC_TRACE("unexpected format error no addresses for %s\n",
                   query->domain);
#ifdef DNS_DEBUG
        print_dns_message(dnsmsg);
#endif
        dns_freehostent(hent);
        dmsg->error = ETRYAGAIN;
        return -1;
    }

    if (dns_alloc_hostname(hent, query->domain) == NULL)
    {
        dmsg->error = ENOMEM;
        DNSC_DEBUG("exit - dns_alloc_hostname failed\n");
        return -1;
    }

    hent->h_addr_list = dns_alloc_addrlist(hent, nanswers, AF_INET6);
    if (hent->h_addr_list == NULL)
    {
        dmsg->error = ENOMEM;
        DNSC_DEBUG("exit - dns_alloc_addrlist failed\n");
        return -1;
    }
    
    hent->h_addrtype = AF_INET6;
    hent->h_length = sizeof(struct in6_addr);

    RR = find_match_rrecord(query->domain, dnsmsg->m_answers, QT_AAAA);
    for (i = 0; i < nanswers && RR != NULL; i++)
    {
        memcpy(hent->h_addr_list[i], RR->r_data, sizeof(struct in6_addr));
        RR = find_match_rrecord(query->domain, RR->r_next, QT_AAAA);
    }

    RR = find_match_rrecord(query->domain, dnsmsg->m_answers, QT_A6);
    for (; i < nanswers && RR != NULL; i++)
    {
        memcpy(hent->h_addr_list[i], RR->r_data, sizeof(struct in6_addr));
        RR = find_match_rrecord(query->domain, RR->r_next, QT_A6);
    }

    /*
     * If we've not filled all the addresses, release the reserved
     * by 'dns_alloc_addrlist()' space
     */
    if (i < nanswers)
    {
        int k;

        for (k = i; k < nanswers; k++)
        {
            free(hent->h_addr_list[k]);
            hent->h_addr_list[k] = NULL;
        }
    }
    
    dmsg->hent = hent;
    dmsg->error = ESUCCESS;

    DNSC_DEBUG("exit - success\n");

    return 0;

} /* dns_fmt_ip6_answer */


/* dns_fmt_cname6_answer --
 *     This one is a little more complicated than the IP and PTR formatters.
 *     Here it could be the case that the query already had known it was
 *     looking for a CNAME which is indicated by a query type of ac_type or
 *     the query received a DNS response and it told us then which is
 *     indicated by a query type of aaaa_type;  we handle both cases.
 *     Then we need to locate the AAAA records for the CNAME.  Note that it
 *     is unlikely that there would be AAAA records for the CNAME in both
 *     the answer records and additional records both we handle that situation.
 *     We get up to the limit indicated by the user.
 *
 * PARAMETERS:
 *     query  - query state structure
 *     dnsmsg - dns message with results
 *
 * RETURNS:
 *      0 - for success, and
 *     -1 - indicates an error condition.
 */
int
dns_fmt_cname6_answer(IN QueryState *query, IN DnsMsg *dnsmsg)
{
    struct hostent  *hent;
    DnsRRec         *RR;
    int              cnt;
    int              num_answ;

    MSG_D_DNS_GET_NODEBYNAME(dmsg, query->reply);


    DNSC_DEBUG("entry\n");

    if ((hent = dns_alloc_struct_hostent()) == NULL)
    {
        dmsg->error = ENOMEM;
        DNSC_DEBUG("exit - dns_alloc_struct_hostent failed\n");
        return -1;
    }

    hent->h_addrtype = AF_INET6;
    hent->h_length = sizeof(struct in6_addr);

    switch(query->qtype)
    {
        case a6_type:
        case aaaa_type:
            if ((RR = find_match_rrecord(query->domain, dnsmsg->m_answers,
                                         QT_CNAME)) == NULL)
            {
                DNSC_TRACE("unexpect format error, no CNAME record for %s\n",
                           query->domain);
    #ifdef DNS_DEBUG
                print_dns_message(dnsmsg);
    #endif
                dmsg->error = ETRYAGAIN;
                return -1;
            }
            if (dns_alloc_aliases(hent, 1) == NULL)
            {
                dmsg->error = ENOMEM;
                return -1;
            }
            if ((hent->h_aliases[0] = malloc(strlen(query->domain) + 1))
                == NULL)
            {
                dns_freehostent(hent);
                dmsg->error = ENOMEM;
                return -1;
            }
            strcpy(hent->h_aliases[0], query->domain);
            if (dns_alloc_hostname(hent, RR->r_data) == NULL)
            {
                dmsg->error = ENOMEM;
                return -1;
            }
            break;

        case ac_type:
            if (dns_alloc_hostname(hent, query->domain) == NULL)
            {
                dmsg->error = ENOMEM;
                return -1;
            }
            if (dns_alloc_aliases(hent, 1) == NULL)
            {
                dmsg->error = ENOMEM;
                return -1;
            }
            if ((hent->h_aliases[0] = malloc(strlen(query->cname) + 1))
                == NULL)
            {
                dns_freehostent(hent);
                dmsg->error = ENOMEM;
                return -1;
            }
            strcpy(hent->h_aliases[0], query->cname);
            break;

        default:
            DNSC_TRACE("unrecognized query type: %d\n", query->qtype);
            dmsg->error = ETRYAGAIN;
            return -1;
    }

    cnt = 0;
    num_answ =
        find_num_match(hent->h_name, dnsmsg->m_answers, QT_AAAA) +
        find_num_match(hent->h_name, dnsmsg->m_answers, QT_A6) +
        find_num_match(hent->h_name, dnsmsg->m_additionals, QT_AAAA) +
        find_num_match(hent->h_name, dnsmsg->m_additionals, QT_A6);
	
    /* Allocate memory for addresses */
    if (dns_alloc_addrlist(hent, num_answ, AF_INET6) == NULL)
    {
        dmsg->error = ENOMEM;
        return -1;
    }
    RR = find_match_rrecord(hent->h_name, dnsmsg->m_answers, QT_AAAA);
    while ( RR != NULL && cnt < num_answ ) {
        memcpy(hent->h_addr_list[cnt++], RR->r_data,
               sizeof(struct in6_addr));
        RR = find_match_rrecord(hent->h_name, RR->r_next, QT_AAAA);
    }
    RR = find_match_rrecord(hent->h_name, dnsmsg->m_answers, QT_A6);
    while ( RR != NULL && cnt < num_answ ) {
        memcpy(hent->h_addr_list[cnt++], RR->r_data,
               sizeof(struct in6_addr));
        RR = find_match_rrecord(hent->h_name, RR->r_next, QT_A6);
    }
    RR = find_match_rrecord(hent->h_name, dnsmsg->m_additionals, QT_AAAA);
    while ( RR != NULL && cnt < num_answ ) {
        memcpy(hent->h_addr_list[cnt++], RR->r_data,
               sizeof(struct in6_addr));
        RR = find_match_rrecord(hent->h_name, RR->r_next, QT_AAAA);
    }
    RR = find_match_rrecord(hent->h_name, dnsmsg->m_additionals, QT_A6);
    while ( RR != NULL && cnt < num_answ ) {
        memcpy(hent->h_addr_list[cnt++], RR->r_data,
               sizeof(struct in6_addr));
        RR = find_match_rrecord(hent->h_name, RR->r_next, QT_A6);
    }

    /*
     * If we've not filled all the addresses, release the reserved
     * by 'dns_alloc_addrlist()' space
     */
    if (cnt < num_answ)
    {
        int k;

        for (k = cnt; k < num_answ; k++)
        {
            free(hent->h_addr_list[k]);
            hent->h_addr_list[k] = NULL;
        }
    }

    dmsg->hent = hent;
    dmsg->error = ESUCCESS;

    DNSC_DEBUG("exit - success\n");

    return 0;

} /* dns_fmt_cname6_answer */


/* dns_fmt_cache6_answer --
 *     This routine is called when the cache returned a result and we don't
 *     know if it is just the addresses or a CNAME.  The results are expected
 *     to have the the AAAA records for the CNAME if that is there.
 *
 * PARAMETERS:
 *     query  - query state structure
 *     dnsmsg - dns message with results
 *
 * RETURNS:
 *      0 - for success, or
 *     -1 - to incidate an error condition.
 */
int
dns_fmt_cache6_answer(IN QueryState *query, IN DnsMsg *dnsmsg)
{
    DnsRRec *RR = dnsmsg->m_answers;
    char     tmpName[NAMEMAX+1];


    DNSC_DEBUG("entry\n");

    /*
     * Note that all the names coming out of the cache are in all lower
     * case.  So we have to convert the domain name in the query to lower
     * case so that the search for matching records in the formatting
     * routines will work.
     */

    strcpy(tmpName, query->domain);
    lowercase_copy(query->domain, tmpName);
    if (RR->r_type == QT_CNAME)
    {
        query->qtype = aaaa_type;
        return dns_fmt_cname6_answer(query, dnsmsg);
    }

    DNSC_DEBUG("exit - call dns_fmt_ip6_answer\n");

    return dns_fmt_ip6_answer(query, dnsmsg);

} /* dns_fmt_cache6_answer */


/* dns_fmt_ptr6_answer --
 *     This routine is called to format the response to a PTR query.
 *     It should only be called for PTR queries since it makes an
 *     assumption on the message type.
 *
 * PARAMETERS:
 *     query  - query state structure
 *     dnsmsg - dns message with results
 *
 * RETURNS:
 *      0 - for success, or
 *     -1 - to incidate an error condition.
 */
int
dns_fmt_ptr6_answer(IN QueryState *query, IN DnsMsg *dnsmsg)
{
    DnsRRec         *RR;
    struct hostent  *hent;
    struct sockaddr_storage tmp;

    MSG_D_DNS_GET_HOSTBYADDR6(dmsg, query->reply);


    DNSC_DEBUG("entry\n");

    if ((hent = dns_alloc_struct_hostent()) == NULL)
    {
        dmsg->error = ENOMEM;
        DNSC_DEBUG("exit - dns_alloc_struct_hostent failed\n");
        return -1;
    }

    hent->h_addrtype = AF_INET6;
    hent->h_length = sizeof(struct in6_addr);

    RR = find_match_rrecord(query->domain, dnsmsg->m_answers, QT_PTR);
    if (RR == NULL)
    {
#ifdef DNS_DEBUG
        print_dns_message(dnsmsg);
#endif
        dmsg->error = ETRYAGAIN;
        dns_freehostent(hent);
        DNSC_DEBUG("exit - unexpected formating error, no pointer "
                   "answer for %s\n", query->domain);
        return -1;
    }
    if (dns_alloc_hostname(hent, RR->r_data) == NULL)
    {
        dmsg->error = ENOMEM;
        DNSC_DEBUG("exit - dns_alloc_hostname failed\n");
        return -1;
    }
    if (dns_alloc_addrlist(hent, 1, AF_INET6) == NULL)
    {
        dmsg->error = ENOMEM;
        DNSC_DEBUG("exit - dns_alloc_addrlist failed\n");
        return -1;
    }

    /*
     * All our macros and functions assume we submit sockaddr_storage
     * structure, so we use this even though we know here we need
     * struct sockaddr_in6 only.
     */

    convert_addr_arpa(query->domain, &tmp);
    memcpy(hent->h_addr_list[0],
           &((struct sockaddr_in6 *)&tmp)->sin6_addr,
           sizeof(struct in6_addr));

    dmsg->hent = hent;
    dmsg->error = ESUCCESS;

    DNSC_DEBUG("exit - success\n");

    return 0;

} /* dns_fmt_ptr6_answer */