RD是1bit字段,表示“期望递归(recursiondesired)”; RA是1bit字段,表示“可用递归”; 随后3bit必须为0; rcode是4bit字段,通常值为0(没有差错)和3(名字差错)。 根据协议,DNS客户端可以使用TCP或者UDP协议与域名服务器通信。使用TCP协议进行通信的交互过程为: (1)DNS客户端向域名服务器发起TCP协议的三次握手:...
#include<stdio.h>#include<stdlib.h>#include<string.h>#include<arpa/inet.h>#include<unistd.h>#define DNS_PORT 53#define DNS_HEADER_SIZE 12// DNS header structurestructdns_header{unsignedshortid;// Identifierunsignedcharrd:1;// Recursion Desiredunsignedchartc:1;// TrunCationunsignedcharaa:1;/...
This is in contrast to an iterative DNS query, where the client communicates directly with each DNS server involved in the lookup. While this is a very technical definition, a closer look at the DNS system and the difference between recursion and iteration should help clear things up. What ...
a DNS server does the recursion and continues querying other DNS servers until it has an IP address to return to the client (often a user’s operating system). In an iterative DNS query, each DNS query responds directly to the client with an address for another DNS server to ask, and ...
RD(Recursion Desired): 这个字段是期望递归字段,该字段在查询中设置,并在响应中返回。该标志告诉名称服务器必须处理这个查询,这种方式被称为一个递归查询。如果该位为 0,且被请求的名称服务器没有一个授权回答,它将返回一个能解答该查询的其他名称服务器列表。这种方式被称为迭代查询。 RA(Recursion Available): ...
recursion no; fetch-glue no; allow-query {192.168.123.0/24;}; dump-file "/var/named/data/cache_dump.db"; statistics-file "/var/named/data/named_stats.txt"; /* * If there is a firewall between you and nameservers you want * to talk to, you might need to uncomment the query-sour...
This usually entails disabling open recursion, thereby reducing DNS attack loopholes. Open recursion causes the server to accept DNS requests from any IP address, and this opens up the infrastructure to attackers. Setting up Response Rate Limiting (RRL) will also prevent the rate of DRDoS incidenc...
3.3.3、禁止DNS域名递归查询操作方法要禁止DNS域名递归查询,在options〔或特定的zone区域〕节中增加: recursion no; fetch-glue no; 操作结果防止了DNS域名的递归查询。 3.3.4、增加出站查询请求的ID值的随机性操作方法在options节中增加: use-id-pool yes; 如此效劳器将跟踪其出站查询ID值以防止出现重复,并...
allow-query{}; address_match_list是允许进行域名查询的主机IP列表,如"1.2.3.4; 5.6.7/24;"。 操作结果 限制对DNS服务器进行域名查询的主机。 3. 操作方法 在options(或特定的zone区域)节中增加: allow-recursion{}; address_match_list是允许进行域名递归查询的主机IP列表,如"1.2.3.4; 5.6.7/24;"。
HTTP/2 with at least TLS v1.3 is recommended. OCSP stapling must be enabled, otherwise DNS recursion may happen. Configuration file The main configuration file isdoh-client.conf. Server selectors.If several upstream servers are set, one is selected according toupstream_selectorfor each request. ...