嵌入式 获取指定网卡在路由表中的网关以及源地址和目的地址

承诺没有内存泄漏以及sockfd未关闭等bug，如发现bug请及时通知我，谢谢！

代码如下：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <asm/types.h>
#include <netinet/ether.h>
#include <netinet/in.h>
#include <net/if.h>
#include <stdio.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <sys/types.h>


#define BUFSIZE 8192

typedef struct route_info{
u_int dstAddr;
u_int srcAddr;
u_int gateWay;
char ifName[IF_NAMESIZE];
}JOSEPH_ROUTE_INFO;


#ifdef JOSEPH_CAT_ENUM
/* Routing message attributes */
enum rtattr_type_t {
RTA_UNSPEC,
RTA_DST,
RTA_SRC,
RTA_IIF,
RTA_OIF,
RTA_GATEWAY,
RTA_PRIORITY,
RTA_PREFSRC,
RTA_METRICS,
RTA_MULTIPATH,
RTA_PROTOINFO, /* no longer used */
RTA_FLOW,
RTA_CACHEINFO,
RTA_SESSION, /* no longer used */
RTA_MP_ALGO, /* no longer used */
RTA_TABLE,
RTA_MARK,
__RTA_MAX
};
#endif


int Joseph_ReadNlSock(int sockFd, char *bufPtr, int seqNum, int pId)
{
struct nlmsghdr *nlHdr;
int readLen = 0, msgLen = 0;


do
{
/* Recieve response from the kernel */
if((readLen = recv(sockFd, bufPtr, BUFSIZE - msgLen, 0)) < 0){
printf("SOCK READ Error !\n");
return -1;
}


nlHdr = (struct nlmsghdr *)bufPtr;


/* Check if the header is valid */
if((NLMSG_OK(nlHdr, readLen) == 0) || (nlHdr->nlmsg_type == NLMSG_ERROR))
{
printf("Error in recieved packet !\n");
return -1;
}


/* Check if the its the last message */
if(nlHdr->nlmsg_type == NLMSG_DONE) 
{
break;
}
else
{
/* Else move the pointer to buffer appropriately */
bufPtr += readLen;
msgLen += readLen;
}


/* Check if its a multi part message */
if((nlHdr->nlmsg_flags & NLM_F_MULTI) == 0) 
{
/* return if its not */
break;
}
} while((nlHdr->nlmsg_seq != seqNum) || (nlHdr->nlmsg_pid != pId));

return msgLen;
}




/* For printing the routes. */
void Joseph_PrintRoute(struct route_info *rtInfo,char *if_name_in)
{


char tempBuf[512];


if(strcmp(rtInfo->ifName,if_name_in) == 0)
{
/* Print Destination address */
if(rtInfo->dstAddr != 0)
strcpy(tempBuf, (char *)inet_ntoa(rtInfo->dstAddr));
else
sprintf(tempBuf,"0.0.0.0\t");
fprintf(stdout,"%s\t", tempBuf);


/* Print Gateway address */
if(rtInfo->gateWay != 0)
strcpy(tempBuf, (char *)inet_ntoa(rtInfo->gateWay));
else
sprintf(tempBuf,"0.0.0.0\t");
fprintf(stdout,"%s\t", tempBuf);


/* Print Interface Name*/
fprintf(stdout,"%s\t", rtInfo->ifName);


/* Print Source address */
if(rtInfo->srcAddr != 0)
strcpy(tempBuf, (char *)inet_ntoa(rtInfo->srcAddr));
else
sprintf(tempBuf,"0.0.0.0\t");
fprintf(stdout,"%s\n", tempBuf);
}


}


/* For parsing the route info returned */
int Joseph_ParseRoutes(struct nlmsghdr *nlHdr, struct route_info *rtInfo,char *gateway,char *if_name_in)
{
struct rtmsg *rtMsg;
struct rtattr *rtAttr;
int rtLen;
char *tempBuf = NULL;


tempBuf = (char *)malloc(100);
rtMsg = (struct rtmsg *)NLMSG_DATA(nlHdr);


/* If the route is not for AF_INET or does not belong to main routing table then return. */
if((rtMsg->rtm_family != AF_INET) || (rtMsg->rtm_table != RT_TABLE_MAIN))
{
free(tempBuf);
tempBuf = NULL;
return -1;
}




/* get the rtattr field */
rtAttr = (struct rtattr *)RTM_RTA(rtMsg);
rtLen = RTM_PAYLOAD(nlHdr);

for(;RTA_OK(rtAttr,rtLen);rtAttr = RTA_NEXT(rtAttr,rtLen))
{
switch(rtAttr->rta_type) 
{
case RTA_OIF:
if_indextoname(*(int *)RTA_DATA(rtAttr), rtInfo->ifName);
break;
case RTA_GATEWAY:
rtInfo->gateWay = *(u_int *)RTA_DATA(rtAttr);
break;
case RTA_PREFSRC:
rtInfo->srcAddr = *(u_int *)RTA_DATA(rtAttr);
break;
case RTA_DST:
rtInfo->dstAddr = *(u_int *)RTA_DATA(rtAttr);
break;
}
}

//printf("%s\n", (char *)inet_ntoa(rtInfo->dstAddr));
//ADDED BY BOB - ALSO COMMENTED Joseph_PrintRoute


if (strstr((char *)inet_ntoa(rtInfo->dstAddr), "0.0.0.0"))
{
sprintf(gateway,"%s",(char *)inet_ntoa(rtInfo->gateWay));
}


Joseph_PrintRoute(rtInfo,if_name_in);


free(tempBuf);
tempBuf = NULL;


return 0;
}


int Joseph_Get_Gateway(char *gateway,char *if_name)
{
struct nlmsghdr *nlMsg;
struct rtmsg *rtMsg;
struct route_info *rtInfo;
char msgBuf[BUFSIZE];


int sock, len, msgSeq = 0;
char buff[1024];


if(strlen(if_name) == 0 || gateway == NULL)
{
return -1;
}

/* Create Socket */
if((sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)) < 0)
{
printf("Socket Creation Error !\n");
return -1;
}

/* Initialize the buffer */
memset(msgBuf, 0, BUFSIZE);


/* point the header and the msg structure pointers into the buffer */
nlMsg = (struct nlmsghdr *)msgBuf;
rtMsg = (struct rtmsg *)NLMSG_DATA(nlMsg);


/* Fill in the nlmsg header*/
nlMsg->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg)); // Length of message.
nlMsg->nlmsg_type = RTM_GETROUTE; // Get the routes from kernel routing table .
nlMsg->nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST; // The message is a request for dump.
nlMsg->nlmsg_seq = msgSeq++; // Sequence of the message packet.
nlMsg->nlmsg_pid = getpid(); // PID of process sending the request.




/* Send the request */
if(send(sock, nlMsg, nlMsg->nlmsg_len, 0) < 0)
{
printf("Write To Socket Failed...\n");
close(sock);
return -1;
}


/* Read the response */
if((len = Joseph_ReadNlSock(sock, msgBuf, msgSeq, getpid())) < 0) 
{
printf("Read From Socket Failed...\n");
close(sock);
return -1;
}

/* Parse and print the response */
rtInfo = (struct route_info *)malloc(sizeof(struct route_info));

/* THIS IS THE NETTSTAT -RL code I commented out the printing here and in parse routes */
//fprintf(stdout, "Destination\tGateway\tInterface\tSource\n");


for( ; NLMSG_OK(nlMsg,len); nlMsg = NLMSG_NEXT(nlMsg,len))
{
memset(rtInfo, 0, sizeof(struct route_info));
Joseph_ParseRoutes(nlMsg,rtInfo,gateway,if_name);
}

free(rtInfo);
rtInfo = NULL;
close(sock);


return 0;
}




int main(int argc,char *argv[])
{
int itertion = 0;
char gateway[16]={0};
int Qy_Ret = 0;

if(argc != 2)
{
return -1;
}

while(itertion < 30)
{

Qy_Ret = Joseph_Get_Gateway(gateway,argv[1]);
if(Qy_Ret <0)
{
return -1;
}
itertion++;
printf("Gateway:%s\n", gateway);
sleep(1);
}

return 0;
}