如何在C中获取我的非环回网络ip地址? [英] How to get my non-loopback network ip address in C?

问题描述

要在两个主机之间进行通信，我需要将主机的IP地址发送到另一个站点.问题是，如果我请求我的IP地址，可能是我找回了本地环回IP地址(127.x.x.x)，而不是网络(以太网)IP地址.

For a communication between two hosts, I need to send the IP address of my host to the other site. The problem is that if I request my IP address, it might be that I get back my local loopback IP addres (127.x.x.x) , not the network (ethernet) IP address.

我使用以下代码:

char myhostname[32];


gethostname(myhostname, 32);
hp = gethostbyname(myhostname);
unsigned my_ip = *(unsigned*)(hp->h_addr);

if( (my_ip % 256) == 127) {
  /* Wrong IP adress as it's 127.x.x.x */
  printf("Error, local IP address!");
  return;
}

解决此问题的唯一方法是确保/etc/hosts中的主机名位于真实的网络地址后面，而不是本地环回(例如Ubuntu的默认值).

The only way to solve it is to make sure my hostname in /etc/hosts is behind the real network address, not the local loopback (the default for e.g. Ubuntu).

有没有一种方法可以不依赖于/etc/hosts的内容来解决此问题?

Is there a way to solve this without relying on the content of /etc/hosts?

我更改了上面的代码，以使其使用getaddrinfo，但我仍会取回回送设备的号码(127.0,0,1)，而不是真实的IP地址:

I changed the above code so it makes use of getaddrinfo, but I still get back the loopback device's number (127.0,0,1) instead of the real IP address:

struct addrinfo hint = {0};
struct addrinfo *aip = NULL;
unsigned ip = 0;
struct sockaddr_in *sinp = NULL;

hint.ai_family = AF_INET; /* IPv4 */
hint.ai_socktype = SOCK_STREAM;

if(getaddrinfo(hostname, NULL, &hint, &aip) != 0) {
    return 0;
}
sinp = (struct sockaddr_in *) aip->ai_addr;
ip   = *(unsigned *) &sinp->sin_addr;

(我曾经用3个SOCK_STREAM，SOCK_DGRAM和SOCK_RAW取回3个addrinfo的列表，但提示阻止了这一点)

(I used to get back a list of 3 addrinfo's with the three SOCK_STREAM,SOCK_DGRAM and SOCK_RAW, but the hint prevents that)

所以我的问题仍然存在...

So my question still stands...

推荐答案

有POSIX函数getaddrinfo()返回给定主机名的地址的链接列表，因此您只需要遍历该列表并找到非环回地址.

There is POSIX function getaddrinfo() that returns linked list of addresses for given hostname, so you just need to go through that list and find non-loopback address.

请参见man getaddrinfo.

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