test tproxy

tproxy.c

#include <stdio.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <errno.h>
#include <string.h>
#include <arpa/inet.h>
int main(){

	int fd = socket(AF_INET, SOCK_DGRAM, 0);
	int value = 1;
	int ret;
	ret = setsockopt(fd, SOL_IP, IP_TRANSPARENT, &value, sizeof(value));
	if (ret != 0)
        {
                fprintf (stderr, "error setting transparency for listening socket. err (#%d %s)\n",
			 errno, strerror(errno));
                close (fd);
                return -4;
        }
	ret = setsockopt(fd, SOL_IP, IP_RECVORIGDSTADDR, &value, sizeof(value));
	if (ret != 0)
        {
                fprintf (stderr, "error setting transparency for listening socket. err (#%d %s)\n",
			 errno, strerror(errno));
                close (fd);
                return -4;
        }

	struct sockaddr_in name;
	name.sin_family = AF_INET;
	name.sin_port = htons(3333);
	name.sin_addr.s_addr = htonl(INADDR_ANY);
	if(bind(fd, (const struct sockaddr*)&name, sizeof(name))<0)
	{
                fprintf (stderr, "error calling bind()\n");
                return -6;
        }

	while(1){

	 char cntrlbuf[64];

	char buffer[548];
	struct sockaddr_storage src_addr;

	struct iovec iov[1];
	iov[0].iov_base=buffer;
	iov[0].iov_len=sizeof(buffer);

	struct msghdr message;
	message.msg_name=&src_addr;
	message.msg_namelen=sizeof(src_addr);
	message.msg_iov=iov;
	message.msg_iovlen=1;
	message.msg_control=cntrlbuf;
	message.msg_controllen=sizeof(cntrlbuf);

	ssize_t count=recvmsg(fd,&message,0);

	if (count==-1) {
	    printf("%s\n",strerror(errno));
	} else if (message.msg_flags & MSG_TRUNC) {
	    printf("datagram too large for buffer: truncated");
	} else {
		buffer[count] = 0;
		printf("src_addr %s data(%d) %s", inet_ntoa(((struct sockaddr_in*)&src_addr)->sin_addr), 
			(int)count, (const char*)buffer);


		struct sockaddr_in      *clntaddr;
        	struct sockaddr_in      dstaddr={0,};
	        struct cmsghdr          *cmsg;
        	int                     ret;
	        int                     found=0;

		struct msghdr*	msg = &message;

	        /* get original destination address */
	        for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg))
		{
        	        if (cmsg->cmsg_level == SOL_IP && cmsg->cmsg_type == IP_RECVORIGDSTADDR)
                	{
                        	memcpy (&dstaddr, CMSG_DATA(cmsg), sizeof (struct sockaddr_in));
	                        dstaddr.sin_family = AF_INET;
        	                printf ("original dst address %s:%d\n",
					 inet_ntoa(dstaddr.sin_addr),
					 ntohs(dstaddr.sin_port));
        	        }
	        }
	}//if


	}//while
}

reference:
http://sen-wiki.blogspot.jp/2011/05/tproxy-transparent-proxy-udp-program.html
http://sen-wiki.blogspot.jp/2011/05/tproxy-transparent-proxy-tcp-program.html