caretta notes

tcp.c

int handle_tcp_data_queue(struct pt_regs *ctx) {
  // first argument to tcp_data_queue is a struct sock*
  struct sock *sock = (struct sock *)PT_REGS_PARM1_CORE(ctx);

  struct connection_identifier conn_id = {};
  struct connection_throughput_stats throughput = {};

  if (parse_sock_data(sock, &conn_id.tuple, &throughput) == BPF_ERROR) {
    debug_print("error parsing sock");
    return BPF_ERROR;
  }
  
  //..
  // fill the conn_id extra details from sock_info map entry, or create one
  struct sock_info *sock_info = bpf_map_lookup_elem(&sock_infos, &sock);
  if (sock_info == NULL) {
    // first time we encounter this sock
    // check if server or client and insert to the maps

    enum connection_role role = get_sock_role(sock);

    struct sock_info info = {
        .pid = 0, // can't associate to pid anyway
        .role = role,
        .is_active = true,
        .id = get_unique_id(),
    };
    bpf_map_update_elem(&sock_infos, &sock, &info, BPF_ANY);

    conn_id.pid = info.pid;
    conn_id.id = info.id;
    conn_id.role = info.role;
    throughput.is_active = true;

    bpf_map_update_elem(&connections, &conn_id, &throughput, BPF_ANY);

    return BPF_SUCCESS;

  } 

  // filling the existing sock item
  conn_id.pid = sock_info->pid;
  conn_id.id = sock_info->id;
  conn_id.role = sock_info->role;
  if (!sock_info->is_active) {
    debug_print("inactive sock in tcp_data_queue");
    return -1;
  }
  throughput.is_active = sock_info->is_active; 
  
  bpf_map_update_elem(&connections, &conn_id, &throughput, BPF_ANY);

  return BPF_SUCCESS;
}