DNS RFC1035 中的 QD 代表什么

Question

我只是对 DNS RFC 中某些变量部分的命名法感到好奇：https://www.ietf.org/rfc/rfc1035.txt

虽然我能够找到大多数其他缩写词：

ANCOUNT 中的 AN 似乎代表
• Answer NSCOUNT 中的
NS 代表
• Name Server ARCOUNT 中的 AR 代表
A
• additional Record
我想知道“

QD

”在“QDCOUNT”中代表什么？

Answer 1

注意这个字段现在没用了，因为 BIND 一直拒绝 QDCOUNT != 1。每笔交易无法询问多个问题，这不是疏忽，而是因为只有一个 AA 位来描述整个答案部分。

Answer 2

https://tools.ietf.org/html/rfc2929

我相信它可能代表查询数据，但我不相信除了询问设计DNS的人之外你会得到官方答案。

The unsigned fields query count (QDCOUNT), answer count (ANCOUNT),
   authority count (NSCOUNT), and additional information count (ARCOUNT)
   express the number of records in each section for all opcodes except
   Update.  These fields have the same structure and data type for
   Update but are instead the counts for the zone (ZOCOUNT),
   prerequisite (PRCOUNT), update (UPCOUNT), and additional information
   (ARCOUNT) sections. 

其他参考：

1

，2 我们也可以直接使用

DNSRR 迭代

，这意味着查询 DNS 计数。 :) 编辑（2024）：

由于这个问题仍然受到关注，而且我对套接字编程已经非常深入，所以我想我应该从

bind4.8 源代码

添加这段代码

*%
 * Structure for query header.  The order of the fields is machine- and
 * compiler-dependent, depending on the byte/bit order and the layout
 * of bit fields.  We use bit fields only in int variables, as this
 * is all ANSI requires.  This requires a somewhat confusing rearrangement.
 */

typedef struct {
    unsigned    id :16;     /*%< query identification number */
#if __BYTE_ORDER == __BIG_ENDIAN
            /* fields in third byte */
    unsigned    qr: 1;      /*%< response flag */
    unsigned    opcode: 4;  /*%< purpose of message */
    unsigned    aa: 1;      /*%< authoritative answer */
    unsigned    tc: 1;      /*%< truncated message */
    unsigned    rd: 1;      /*%< recursion desired */
            /* fields in fourth byte */
    unsigned    ra: 1;      /*%< recursion available */
    unsigned    unused :1;  /*%< unused bits (MBZ as of 4.9.3a3) */
    unsigned    ad: 1;      /*%< authentic data from named */
    unsigned    cd: 1;      /*%< checking disabled by resolver */
    unsigned    rcode :4;   /*%< response code */
#endif
#if __BYTE_ORDER == __LITTLE_ENDIAN || __BYTE_ORDER == __PDP_ENDIAN
            /* fields in third byte */
    unsigned    rd :1;      /*%< recursion desired */
    unsigned    tc :1;      /*%< truncated message */
    unsigned    aa :1;      /*%< authoritative answer */
    unsigned    opcode :4;  /*%< purpose of message */
    unsigned    qr :1;      /*%< response flag */
            /* fields in fourth byte */
    unsigned    rcode :4;   /*%< response code */
    unsigned    cd: 1;      /*%< checking disabled by resolver */
    unsigned    ad: 1;      /*%< authentic data from named */
    unsigned    unused :1;  /*%< unused bits (MBZ as of 4.9.3a3) */
    unsigned    ra :1;      /*%< recursion available */
#endif
            /* remaining bytes */
    unsigned    qdcount :16;    /*%< number of question entries */
    unsigned    ancount :16;    /*%< number of answer entries */
    unsigned    nscount :16;    /*%< number of authority entries */
    unsigned    arcount :16;    /*%< number of resource entries */
} HEADER;

这是我能找到的最旧的版本。看起来它可能代表“问题”，而不是“查询”，但我仍然不知道“D 代表什么。

Answer 3

Q

uestionDefinition或更好的QueryDefinition，因为每个包含的元素都被称为查询。