dns_strrecord.c

[詳解]

/*++
/* NAME
/*  dns_strrecord 3
/* SUMMARY
/*  name service resource record printable forms
/* SYNOPSIS
/*  #include <dns.h>
/*
/*  char    *dns_strrecord(buf, record)
/*  VSTRING *buf;
/*  DNS_RR  *record;
/* DESCRIPTION
/*  dns_strrecord() formats a DNS resource record as "name ttl
/*  class type preference value", where the class field is
/*  always "IN", the preference field exists only for MX records,
/*  and all names end in ".". The result value is the payload
/*  of the buffer argument.
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*
/*  Wietse Venema
/*  Google, Inc.
/*  111 8th Avenue
/*  New York, NY 10011, USA
/*--*/

/* System library. */

#include <sys_defs.h>
#include <string.h>         /* memcpy */

/* Utility library. */

#include <vstring.h>
#include <msg.h>

/* DNS library. */

#include <dns.h>

/* dns_strrecord - format resource record as generic string */

char   *dns_strrecord(VSTRING *buf, DNS_RR *rr)
{
    const char myname[] = "dns_strrecord";
    MAI_HOSTADDR_STR host;
    UINT32_TYPE soa_buf[5];

    vstring_sprintf(buf, "%s. %u IN %s ",
            rr->rname, rr->ttl, dns_strtype(rr->type));
    switch (rr->type) {
    case T_A:
#ifdef T_AAAA
    case T_AAAA:
#endif
    if (dns_rr_to_pa(rr, &host) == 0)
        msg_fatal("%s: conversion error for resource record type %s: %m",
              myname, dns_strtype(rr->type));
    vstring_sprintf_append(buf, "%s", host.buf);
    break;
    case T_CNAME:
    case T_DNAME:
    case T_MB:
    case T_MG:
    case T_MR:
    case T_NS:
    case T_PTR:
    vstring_sprintf_append(buf, "%s.", rr->data);
    break;
    case T_TXT:
    vstring_sprintf_append(buf, "%s", rr->data);
    break;
    case T_MX:
    vstring_sprintf_append(buf, "%u %s.", rr->pref, rr->data);
    break;
    case T_TLSA:
    if (rr->data_len >= 3) {
        uint8_t *ip = (uint8_t *) rr->data;
        uint8_t usage = *ip++;
        uint8_t selector = *ip++;
        uint8_t mtype = *ip++;
        unsigned i;

        /* /\.example\. \d+ IN TLSA \d+ \d+ \d+ [\da-f]*$/ IGNORE */
        vstring_sprintf_append(buf, "%d %d %d ", usage, selector, mtype);
        for (i = 3; i < rr->data_len; ++i)
        vstring_sprintf_append(buf, "%02x", *ip++);
    } else {
        vstring_sprintf_append(buf, "[truncated record]");
    }

    /*
     * We use the SOA record TTL to determine the negative reply TTL. We
     * save the time fields in the SOA record for debugging, but for now
     * we don't bother saving the source host and mailbox information, as
     * that would require changes to the DNS_RR structure. See also code
     * in dns_get_rr().
     */
    case T_SOA:
    memcpy(soa_buf, rr->data, sizeof(soa_buf));
    vstring_sprintf_append(buf, "- - %u %u %u %u %u",
                   soa_buf[0], soa_buf[1], soa_buf[2],
                   soa_buf[3], soa_buf[4]);
    break;
    default:
    msg_fatal("%s: don't know how to print type %s",
          myname, dns_strtype(rr->type));
    }
    return (vstring_str(buf));
}