// sysctl net.ipv4.ip_nonlocal_bind=1

int	fd	= socket (PF_INET, SOCK_STREAM, 0);
int	setopt	= 1;

int	result	= setsockopt (fd, IPPROTO_IP, IP_TRANSPARENT, &setopt, sizeof(setopt));

struct	sockaddr_in	nonlocal;
struct	sockaddr_in	remote;

memset (&nonlocal, 0, sizeof(nonlocal));
memset (&remote, 0, sizeof(remote));

char	NONLOCAL_ADDR[]	= "8.8.8.8";
enum	{ NONLOCAL_PORT = 53 };
char	REMOTE_ADDR[]	= "192.168.96.1";
enum	{ REMOTE_PORT	= 53 };

// eg only 0- use getaddrinfo(3)
	nonlocal.sin_family	= AF_INET;
	remote.sin_family	= AF_INET;
	nonlocal.sin_port	= htons(NONLOCAL_PORT);
	remote.sin_port		= htons(REMOTE_PORT);
	nonlocal.sin_addr.s_addr	= inet_addr(NONLOCAL_ADDR);
	remote.sin_addr.s_addr	= inet_addr(REMOTE_ADDR);
	
int	result	= bind (fd, &nonlocal, sizeof(nonlocal));
int	result	= connect (fd, &remote, sizeof(remote));

// In reality you will be fetching the original source address
// from the "input" socket to spoof it on the "output" socket
// to complete the "illusion" :)