转自：http://blog.csdn.net/fty8788/article/details/7480334
adns是一个开源的dns解析库
官方文档：http://www.chiark.greenend.org.uk/~ian/adns/
1. 初始化
adns_state adns;
adns_query query;
adns_answer *answer; 函数原型：
int adns_init(adns_state *newstate_r, adns_initflags flags, FILE *diagfile /*0=>stderr*/); 举例：
adns_init(&adns, adns_if_noenv, 0);
2. 提交待解析的域名
函数原型：
int adns_submit(adns_state ads,
const char *owner,
adns_rrtype type,
adns_queryflags flags,
void *context,
adns_query *query_r); 举例：
adns_submit(adns, argv[1], adns_r_a, (adns_queryflags) 0, NULL, &query);
3. 检测是否有域名已检测完成
函数原型：
int adns_check(adns_state ads,
adns_query *query_io,
adns_answer **answer_r,
void **context_r); 例：adns_check(adns, &query, &answer, NULL);
4.
函数原型：
int adns_wait(adns_state ads,
adns_query *query_io,
adns_answer **answer_r,
void **context_r); 例：adns_wait(adns, &query, &answer, NULL);
5. 检测是否已完成所有提交的域名的解析
函数原型：
void adns_finish(adns_state ads); 例：adns_finish(adns);
6. 范例代码（解析IPv4地址可使用adns v1.2或adns v1.4，解析IPv6地址请使用adns v1.6）
可从此处下载：https://github.com/sunada/adns_example/tree/71c9bf8555b67199c6b94c83027fb71eaa0c0241
#include "adns.h"
#include <sys/errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h> int test_dns(char *host)
{
adns_state ads;
adns_initflags flags;
flags = adns_if_nosigpipe | adns_if_noerrprint;
adns_init(&ads, flags, NULL); adns_query quer = NULL; adns_submit(ads, host, (adns_rrtype) adns_r_a, (adns_queryflags) 0, NULL, &quer); int tryCount = -1;
int adns_cname = 0; while(tryCount < 32) {
tryCount += 1; adns_answer *ans;
int res = adns_check(ads, &quer, &ans, NULL);
if(res == 0) {
if (ans->status == adns_s_prohibitedcname) {
char cname[128];
strncpy(cname, ans->cname, 127);
cname[strlen(ans->cname)] = '\0';
adns_query quer = NULL;
adns_submit(ads, cname, (adns_rrtype) adns_r_addr, (adns_queryflags) 0, NULL, &quer);
adns_cname = 1;
} else {
//resolve IPv4 address
/*
* if(adns_cname)
* printf("ip: %s\n", ans->status == adns_s_ok ? inet_ntoa(ans->rrs.addr->addr.inet.sin_addr) : "no");
* else
* printf("ip: %s\n", ans->status == adns_s_ok ? inet_ntoa(*(ans->rrs.inaddr)) : "no");
*/ //resolve IPv6 address
if(adns_cname){
if(ans->status == adns_s_ok){
char buf[INET6_ADDRSTRLEN];
inet_ntop(AF_INET6, &ans->rrs.addr->addr.inet6.sin6_addr, buf, sizeof(buf));
printf("ip: %s\n", buf);
}
else{
printf("no\n");
}
}
else{
if(ans->status == adns_s_ok){
char buf[INET6_ADDRSTRLEN];
inet_ntop(AF_INET6, ans->rrs.in6addr, buf, sizeof(buf));
printf("ip: %s\n", buf);
}
else{
printf("no\n");
}
}
adns_finish(ads);
break;
}
}
else if (res == ESRCH || res == EAGAIN) {
sleep(1);
} else {
printf("host(%s) is err!\n", host);
}
}
return 0;
} int main(int argc, char *argv[]) {
char host[128];
while(1) {
scanf("%s", host);
if(strlen(host) == 3 && strcmp(host, "eof")) break;
test_dns(host); }
return 0;
}
Makefile
CFLAGS= -g
TARGETS=libadns.a
LIBOBJS=types.o event.o query.o reply.o general.o setup.o transmit.om parse.o poll.o check.o all: testdns testdns: testdns.c libadns.a
libadns.a: $(LIBOBJS)
rm -f $@
$(AR) cq $@ $(LIBOBJS)
clean:
rm -f $(LIBOBJS) libadns.a *~ config.status distclean: clean
rm -f config.h .depend $(LIBOBJS): adns.h internal.h config.h