Linux C 网络编程 - 获取本地 ip 地址，mac，通过域名获取对应的 ip

获取本地 ip 地址，mac，通过域名获取对应的 ip，

是网络编程可能遇到的比较常见的操作了，所以总结如下（封装了3个函数），

直接上代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>

#include <netdb.h>
#include <net/if.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>

#define MAC_SIZE	18
#define IP_SIZE		16

// function declare
int get_ip_by_domain(const char *domain, char *ip); // 根据域名获取ip
int get_local_mac(const char *eth_inf, char *mac); // 获取本机mac
int get_local_ip(const char *eth_inf, char *ip); // 获取本机ip


/****** main test **********/
int main(void)
{
	char ip[IP_SIZE];
	char mac[MAC_SIZE];
	const char *test_domain = "www.baidu.com";
	const char *test_eth = "eth0";

	get_ip_by_domain(test_domain, ip);
	printf("%s ip: %s\n", test_domain, ip);

	get_local_mac(test_eth, mac);
	printf("local %s mac: %s\n", test_eth, mac);

	get_local_ip(test_eth, ip);
	printf("local %s ip: %s\n", test_eth, ip);

	return 0;
}

// 根据域名获取ip
int get_ip_by_domain(const char *domain, char *ip)
{
	char **pptr;
	struct hostent *hptr;

	hptr = gethostbyname(domain);
	if(NULL == hptr)
	{
		printf("gethostbyname error for host:%s/n", domain);
		return -1;
	}

	for(pptr = hptr->h_addr_list ; *pptr != NULL; pptr++)
	{
		if (NULL != inet_ntop(hptr->h_addrtype, *pptr, ip, IP_SIZE) )
		{
			return 0; // 只获取第一个 ip
		}
	}

	return -1;
}

// 获取本机mac
int get_local_mac(const char *eth_inf, char *mac)
{
	struct ifreq ifr;
	int sd;
	
	bzero(&ifr, sizeof(struct ifreq));
	if( (sd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
	{
		printf("get %s mac address socket creat error\n", eth_inf);
		return -1;
	}
	
	strncpy(ifr.ifr_name, eth_inf, sizeof(ifr.ifr_name) - 1);

	if(ioctl(sd, SIOCGIFHWADDR, &ifr) < 0)
	{
		printf("get %s mac address error\n", eth_inf);
		return -1;
	}

	snprintf(mac, MAC_SIZE, "%02x:%02x:%02x:%02x:%02x:%02x",
		(unsigned char)ifr.ifr_hwaddr.sa_data[0], 
		(unsigned char)ifr.ifr_hwaddr.sa_data[1],
		(unsigned char)ifr.ifr_hwaddr.sa_data[2], 
		(unsigned char)ifr.ifr_hwaddr.sa_data[3],
		(unsigned char)ifr.ifr_hwaddr.sa_data[4],
		(unsigned char)ifr.ifr_hwaddr.sa_data[5]);

	close(sd);
	
	return 0;
}


// 获取本机ip
int get_local_ip(const char *eth_inf, char *ip)
{
	int sd;
	struct sockaddr_in sin;
	struct ifreq ifr;

	sd = socket(AF_INET, SOCK_DGRAM, 0);
	if (-1 == sd)
	{
		printf("socket error: %s\n", strerror(errno));
		return -1;		
	}

	strncpy(ifr.ifr_name, eth_inf, IFNAMSIZ);
	ifr.ifr_name[IFNAMSIZ - 1] = 0;
	
	// if error: No such device
	if (ioctl(sd, SIOCGIFADDR, &ifr) < 0)
	{
		printf("ioctl error: %s\n", strerror(errno));
		close(sd);
		return -1;
	}

	memcpy(&sin, &ifr.ifr_addr, sizeof(sin));
	snprintf(ip, IP_SIZE, "%s", inet_ntoa(sin.sin_addr));

	close(sd);
	return 0;
}