Linux下使用NetLink 监听网络变化

本文来源http://blog.csdn.net/gt945/article/details/45315911

其实网上已经有类似代码,但是还是自己重新写了一遍,实践出真知

/*
 * NetMonitor.c
 *
 *  Created on: 2015年4月25日
 *      Author: tao
 */
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define BUFLEN 20480

#define t_assert(x) { \
	if(!(x))  {err = -__LINE__;goto error;} \
}

/*Ctrl + C 退出*/
static volatile int keepRunning = 1;

void intHandler(int dummy)
{
	keepRunning = 0;
}

/**
 * 解析RTA,并存入tb
 */
void parse_rtattr(struct rtattr **tb, int max, struct rtattr *attr, int len)
{
	for (; RTA_OK(attr, len); attr = RTA_NEXT(attr, len)) {
		if (attr->rta_type <= max) {
			tb[attr->rta_type] = attr;
		}
	}
}

/**
 * 显示连接信息
 * 当网卡变动的时候触发这个信息,例如插/拔网线,增/减网卡设备,启用/禁用接口等.
 */
void print_ifinfomsg(struct nlmsghdr *nh)
{
	int len;
	struct rtattr *tb[IFLA_MAX + 1];
	struct ifinfomsg *ifinfo;
	bzero(tb, sizeof(tb));
	ifinfo = NLMSG_DATA(nh);
	len = nh->nlmsg_len - NLMSG_SPACE(sizeof(*ifinfo));
	parse_rtattr(tb, IFLA_MAX, IFLA_RTA (ifinfo), len);
	printf("%s: %s ", (nh->nlmsg_type==RTM_NEWLINK)?"NEWLINK":"DELLINK", (ifinfo->ifi_flags & IFF_UP) ? "up" : "down");
	if(tb[IFLA_IFNAME]) {
		printf("%s", RTA_DATA(tb[IFLA_IFNAME]));
	}
	printf("\n");
}

/**
 * 显示地址信息
 * 当地址变动的时候触发这个信息,例如通过DHCP获取到地址后
 */
void print_ifaddrmsg(struct nlmsghdr *nh)
{
	int len;
	struct rtattr *tb[IFA_MAX + 1];
	struct ifaddrmsg *ifaddr;
	char tmp[256];
	bzero(tb, sizeof(tb));
	ifaddr = NLMSG_DATA(nh);
	len = nh->nlmsg_len - NLMSG_SPACE(sizeof(*ifaddr));
	parse_rtattr(tb, IFA_MAX, IFA_RTA (ifaddr), len);

	printf("%s ", (nh->nlmsg_type==RTM_NEWADDR)?"NEWADDR":"DELADDR");
	if (tb[IFA_LABEL] != NULL) {
		printf("%s ", RTA_DATA(tb[IFA_LABEL]));
	}
	if (tb[IFA_ADDRESS] != NULL) {
		inet_ntop(ifaddr->ifa_family, RTA_DATA(tb[IFA_ADDRESS]), tmp, sizeof(tmp));
		printf("%s ", tmp);
	}
	printf("\n");
}

/**
 * 显示路由信息
 * 当路由变动的时候触发这个信息
 */
void print_rtmsg(struct nlmsghdr *nh)
{
	int len;
	struct rtattr *tb[RTA_MAX + 1];
	struct rtmsg *rt;
	char tmp[256];
	bzero(tb, sizeof(tb));
	rt = NLMSG_DATA(nh);
	len = nh->nlmsg_len - NLMSG_SPACE(sizeof(*rt));
	parse_rtattr(tb, RTA_MAX, RTM_RTA(rt), len);
	printf("%s: ", (nh->nlmsg_type==RTM_NEWROUTE)?"NEWROUT":"DELROUT");
	if (tb[RTA_DST] != NULL) {
		inet_ntop(rt->rtm_family, RTA_DATA(tb[RTA_DST]), tmp, sizeof(tmp));
		printf("RTA_DST %s ", tmp);
	}
	if (tb[RTA_SRC] != NULL) {
		inet_ntop(rt->rtm_family, RTA_DATA(tb[RTA_SRC]), tmp, sizeof(tmp));
		printf("RTA_SRC %s ", tmp);
	}
	if (tb[RTA_GATEWAY] != NULL) {
		inet_ntop(rt->rtm_family, RTA_DATA(tb[RTA_GATEWAY]), tmp, sizeof(tmp));
		printf("RTA_GATEWAY %s ", tmp);
	}

	printf("\n");
}
int main(int argc, char *argv[])
{
	int socket_fd;
	int err = 0;
	fd_set rd_set;
	struct timeval timeout;
	int select_r;
	int read_r;
	struct sockaddr_nl sa;
	struct nlmsghdr *nh;


	int len = BUFLEN;
	char buff[2048];
	signal(SIGINT, intHandler);

	/*打开NetLink Socket*/
	socket_fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
	t_assert(socket_fd > 0);
	t_assert(!setsockopt(socket_fd, SOL_SOCKET, SO_RCVBUF, &len, sizeof(len)));

	/*设定接收类型并绑定Socket*/
	bzero(&sa, sizeof(sa));
	sa.nl_family = AF_NETLINK;
	sa.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR | RTMGRP_IPV4_ROUTE | RTMGRP_IPV6_IFADDR | RTMGRP_IPV6_ROUTE;
	t_assert(!bind(socket_fd, (struct sockaddr *) &sa, sizeof(sa)));

	while (keepRunning) {
		FD_ZERO(&rd_set);
		FD_SET(socket_fd, &rd_set);
		timeout.tv_sec = 5;
		timeout.tv_usec = 0;
		select_r = select(socket_fd + 1, &rd_set, NULL, NULL, &timeout);
		if (select_r < 0) {
			perror("select");
		} else if (select_r > 0) {
			if (FD_ISSET(socket_fd, &rd_set)) {
				read_r = read(socket_fd, buff, sizeof(buff));
				for (nh = (struct nlmsghdr *) buff; NLMSG_OK(nh, read_r); nh = NLMSG_NEXT(nh, read_r)) {
					switch (nh->nlmsg_type) {
					default:
						/*收到些奇怪的信息*/
						printf("nh->nlmsg_type = %d\n", nh->nlmsg_type);
						break;
					case NLMSG_DONE:
					case NLMSG_ERROR:
						break;
					case RTM_NEWLINK:
					case RTM_DELLINK:
						print_ifinfomsg(nh);
						break;
					case RTM_NEWADDR:
					case RTM_DELADDR:
						print_ifaddrmsg(nh);
						break;
					case RTM_NEWROUTE:
					case RTM_DELROUTE:
						print_rtmsg(nh);
						break;
					}

				}
			}
		}
	}

	close(socket_fd);

error:
	if (err < 0) {
		printf("Error at line %d\nErrno=%d\n", -err, errno);
	}
	return err;
}