int parse_hdr_opt()

in katran/lib/bpf/pckt_parsing.h [144:197]

• 43 lines of code
• 11 McCabe index (conditional complexity)

int parse_hdr_opt(const struct xdp_md *xdp, struct hdr_opt_state *state)
{
  const void* data = (void*)(long)xdp->data;
  const void* data_end = (void*)(long)xdp->data_end;
  __u8 *tcp_opt, kind, hdr_len;

  // Need this check to satisify the verifier
  if (!state) {
    return -1;
  }

  tcp_opt = (__u8*)(data + state->byte_offset);
  if (tcp_opt + 1 > data_end) {
    return -1;
  }

  kind = tcp_opt[0];
  if (kind == TCP_OPT_EOL) {
    return -1;
  }

  if (kind == TCP_OPT_NOP) {
    state->hdr_bytes_remaining--;
    state->byte_offset++;
    return 0;
  }

  if (state->hdr_bytes_remaining < 2 ||
      tcp_opt + sizeof(__u8) + sizeof(__u8) > data_end) {
    return -1;
  }

  hdr_len = tcp_opt[1];
  if (hdr_len > state->hdr_bytes_remaining) {
    return -1;
  }

  if (kind == TCP_HDR_OPT_KIND_TPR) {
    if (hdr_len != TCP_HDR_OPT_LEN_TPR) {
      return -1;
    }

    if (tcp_opt + TCP_HDR_OPT_LEN_TPR > data_end) {
      return -1;
    }

    state->server_id = *(__u32*)&tcp_opt[2];
    return 1;
  }

  state->hdr_bytes_remaining -= hdr_len;
  state->byte_offset += hdr_len;
  return 0;
}