int gtnets_create_flow(int src, int dst, long datasize, void *metadata);
double gtnets_get_time_to_next_flow_completion();
double gtnets_run_until_next_flow_completion(void ***metadata,
int gtnets_create_flow(int src, int dst, long datasize, void *metadata);
double gtnets_get_time_to_next_flow_completion();
double gtnets_run_until_next_flow_completion(void ***metadata,