[英]Retrieve IPv6 DNS servers list programmatically on Linux
I'm trying to retrieve a list of IPv6 DNS servers programmatically. 我正在尝试以编程方式检索IPv6 DNS服务器列表。 Currently I'm using libresolv and next code: 目前我正在使用libresolv和下一个代码:
#include <stdio.h>
#include <netinet/in.h>
#include <resolv.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, char** argv)
{
res_state res = malloc(sizeof(struct __res_state));
res_ninit(res);
printf("%p\n", res->_u._ext.nsaddrs[0]); // (nil) here
}
According to resolv.h, res->_u._ext.nsaddrs field should contain an array of "struct sockaddr_in6 *" with needed addresses, but it contains an array of NULLs. 根据resolv.h,res - > _ u._ext.nsaddrs字段应该包含一个带有所需地址的“struct sockaddr_in6 *”数组,但它包含一个NULL数组。
IPv4 DNS servers list is accessible via res->nsaddr_list field, but IPv6 list is always empty. 可以通过res-> nsaddr_list字段访问IPv4 DNS服务器列表,但IPv6列表始终为空。 I've checked this with both Ubuntu and CentOS. 我用Ubuntu和CentOS检查过这个。 IPv6 is configured correctly. IPv6配置正确。
Your code seems to be correct. 你的代码似乎是正确的。 Most likely res_ninit()
doesn't put any IPv6 DNS servers into the struct res_state
because your system is not aware of any. 最有可能res_ninit()
不会将任何IPv6 DNS服务器放入struct res_state
因为您的系统不知道任何。
Try to put the following line into your /etc/resolv.conf : 尝试将以下行放入/etc/resolv.conf :
nameserver 2001:4860:4860::8844 nameserver 2001:4860:4860 :: 8844
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