1、前言

  针对4G，WIFI和有线网络，需要根据参数切换网络路由状态，本文介绍一种通过/proc/net/route 获取路由方法。

2、route命令

  静态路由表

~ # cat /proc/net/route 
Iface   Destination     Gateway         Flags   RefCnt  Use     Metric  Mask            MTU     Window  IRTT                                                       
eth0    00000000        FE00A8C0        0003    0       0       0       00000000        0       0       0                                                                               
eth0    0000A8C0        00000000        0001    0       0       0       00FFFFFF        0       0       0 


~ # route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.0.254   0.0.0.0         UG    0      0        0 eth0
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0

3、实例

static unsigned int  GetDefaultGateway()
{

#define PROC_NET_ROUTE	 "/proc/net/route"
	unsigned int dest = 0;
	unsigned int gateway = 0;
	char buf[256] = {};	
	FILE *fp = NULL;
	char *p = NULL;

	fp = fopen(PROC_NET_ROUTE, "r");
	if(NULL == fp)
	{
		printf("GetDefaultGateway open file: %s failure\n", PROC_NET_ROUTE);
		return 0;
	}

	while(fgets(buf, 255, fp))
	{
		p = strchr(buf, '\t');
		if(NULL == p)
		{
			continue;
		}
		p++;

		sscanf(p, "%X %X", &dest, &gateway);

		if((dest != 0) || (0 == gateway))
		{
			continue;
		}

		fclose(fp);

		return gateway;
	}

	fclose(fp);

	return 0;
}