c - 当我为 localhost 执行 getaddrinfo 时，我没有收到 127.0.0.1

Question

我仍在学习套接字，并不清楚为什么这不会打印出 127.0.0.1。即使我用 127.0.0.1 替换了 localhost 这个词，我也会收到一些其他的 ip，我猜是我的路由器之类的。我一直认为这应该返回 127.0.0.1。这是我收到的输出:

hostname: 28.30.0.0
hostname: 28.30.0.0
hostname: 28.30.0.0
hostname: 28.30.0.0
hostname: 16.2.0.0
hostname: 16.2.0.0

下面是基本代码:

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>

int main()
{
    struct addrinfo* feed_server = NULL;

    getaddrinfo("localhost", NULL, NULL, &feed_server);
    struct addrinfo *res;
    for(res = feed_server; res != NULL; res = res->ai_next)
    {   
        printf("hostname: %s\n", inet_ntoa(*((struct in_addr*)(res->ai_addr))));
    } 

    return 0;
}

Answer 1

res->ai_addr类型为 struct sockaddr* ，不是 struct in_addr* .

你需要做这样的事情:

for(res = feed_server; res != NULL; res = res->ai_next)
{
    /* ideally look at the sa_family here to make sure it is AF_INET before casting */
    struct sockaddr_in* saddr = (struct sockaddr_in*)res->ai_addr;
    printf("hostname: %s\n", inet_ntoa(saddr->sin_addr));
}