memcpy

int main()
{
....
void* recv_buf;
recv_buf = init_buf();
int recvbytes;
recvbytes = recv(sockfd, recv_buf, MAX_SIZE, 0);

struct ofp10_packet_in* of10_msg;
struct ofp_packet_in* of_pi;

of10_msg = obtain_recv_msg(of10_msg, recv_buf, &of_pi);

void* data = (void*)malloc(12);
memcpy(data, (void*)of10_msg+8, 12);
struct ofp_packet_in* of_pi_1;
of_pi_1 = (struct ofp_packet_in*)data;
.....
}


void*
init_buf(void)
{
    void* buf;
    buf = (void*)malloc(MAX_SIZE);
    if( buf == NULL )
         return 1;
    memset(buf, 0, MAX_SIZE);
    return buf;
}

struct ofp10_packet_in*
obtain_recv_msg(void* msg, void* buf, struct ofp_packet_in* ofp_pi)
{
   msg = buf;
   struct ofp10_packet_in* tmp;
   tmp = (struct ofp10_packet_in*)msg;
   size_t len = tmp->total;
   memcpy(tmp, buf, len);
   return tmp;
}