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#include "FiveLinux.ch"

function Main()

   MsgInfo( GateWay() )
   
return nil

#pragma BEGINDUMP   

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

#include <sys/socket.h>
#include <net/if.h>
#include <linux/rtnetlink.h>

#include <unistd.h>
#include <arpa/inet.h>

#define BUFSIZE 8192

struct route_info
{
struct in_addr dstAddr;
struct in_addr srcAddr;
struct in_addr gateWay;
char ifName[IF_NAMESIZE];
};


static int 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)
{
perror("SOCK READ: ");
return -1;
}

nlHdr = (struct nlmsghdr *)bufPtr;

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

/* parse the route info returned */
static void parseRoutes(struct nlmsghdr *nlHdr, struct route_info *rtInfo)
{
struct rtmsg *rtMsg;
struct rtattr *rtAttr;
int rtLen;

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))
return;

/* 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:
memcpy(&rtInfo->gateWay, RTA_DATA(rtAttr), sizeof(rtInfo->gateWay));
break;

case RTA_PREFSRC:
memcpy(&rtInfo->srcAddr, RTA_DATA(rtAttr), sizeof(rtInfo->srcAddr));
break;

case RTA_DST:
memcpy(&rtInfo->dstAddr, RTA_DATA(rtAttr), sizeof(rtInfo->dstAddr));
break;
}
}

return;
}

// meat
static int get_gatewayip(char *gatewayip, socklen_t size)
{
int found_gatewayip = 0;

struct nlmsghdr *nlMsg;
struct rtmsg *rtMsg;
struct route_info *rtInfo;
char msgBuf[BUFSIZE]; // pretty large buffer

int sock, len, msgSeq = 0;

/* Create Socket */
if((sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)) < 0)
{
perror("Socket Creation: ");
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)
{
fprintf(stderr, "Write To Socket Failed...\n");
return -1;
}

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

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

for(;NLMSG_OK(nlMsg,len);nlMsg = NLMSG_NEXT(nlMsg,len))
{
memset(rtInfo, 0, sizeof(struct route_info));
parseRoutes(nlMsg, rtInfo);

// Check if default gateway
if (strstr((char *)inet_ntoa(rtInfo->dstAddr), "0.0.0.0"))
{
// copy it over
inet_ntop(AF_INET, &rtInfo->gateWay, gatewayip, size);
found_gatewayip = 1;
break;
}
}

free(rtInfo);
close(sock);

return found_gatewayip;
}

HB_FUNC( GATEWAY )
{
   char gateway[ 200 ];
    
   get_gatewayip( gateway, 200 ); 
   hb_retc( gateway );
}     

#pragma ENDDUMP