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Commit 017c88c4 authored by Hansong Zhang's avatar Hansong Zhang
Browse files

ERTM: Fix sequence number comparison 

We need to account for sequence number overflow when we compare sequence
numbers. The allowed overflow is the tx window size.

Test: cert/run --host
Tag: #gd-refactor
Bug: 157613312
Change-Id: I8cee8b0d58209c17d1c0493c9f071dcdefbd12c2
parent e6fefdbb

system/gd/l2cap/internal/enhanced_retransmission_mode_channel_data_controller.cc

+24 −8
Original line number Diff line number Diff line
@@ -490,16 +490,30 @@ struct ErtmController::impl { 
    return retry_count_ < controller_->local_max_transmit_;

  }



  // Compares two sequence numbers (tx_seq or rx_seq)

  bool sequence_less_than(uint8_t x, uint8_t y) {

    // Assuming the maximum overflow of sequence number is the same as local_tx_window_ (10 by default).

    return x < y || kMaxTxWin - (x - y) < controller_->local_tx_window_;

  }



  // Compares two sequence numbers (tx_seq or rx_seq)

  bool sequence_less_than_or_equal(uint8_t x, uint8_t y) {

    // Assuming the maximum overflow of sequence number is the same as local_tx_window_ (10 by default).

    return x <= y || kMaxTxWin - (x - y) <= controller_->local_tx_window_;

  }



  bool with_expected_tx_seq(uint8_t tx_seq) {

    return tx_seq == expected_tx_seq_;

  }



  bool with_valid_req_seq(uint8_t req_seq) {

    return expected_ack_seq_ <= req_seq && req_seq <= next_tx_seq_;

    return sequence_less_than_or_equal(expected_ack_seq_, req_seq) &&

           sequence_less_than_or_equal(req_seq, next_tx_seq_);

  }



  bool with_valid_req_seq_retrans(uint8_t req_seq) {

    return expected_ack_seq_ <= req_seq && req_seq <= next_tx_seq_;

    return sequence_less_than_or_equal(expected_ack_seq_, req_seq) &&

           sequence_less_than_or_equal(req_seq, next_tx_seq_);

  }



  bool with_valid_f_bit(Final f) {
@@ -507,24 +521,26 @@ struct ErtmController::impl { 
  }



  bool with_unexpected_tx_seq(uint8_t tx_seq) {

    return tx_seq > expected_tx_seq_ && tx_seq <= expected_tx_seq_ + controller_->local_tx_window_;

    return sequence_less_than(expected_tx_seq_, tx_seq) &&

           sequence_less_than_or_equal(tx_seq, expected_tx_seq_ + controller_->local_tx_window_);

  }



  bool with_duplicate_tx_seq(uint8_t tx_seq) {

    return tx_seq < expected_tx_seq_ && tx_seq >= expected_tx_seq_ - controller_->local_tx_window_;

    return sequence_less_than(tx_seq, expected_tx_seq_) &&

           sequence_less_than_or_equal(expected_tx_seq_ - controller_->local_tx_window_, tx_seq);

  }



  bool with_invalid_tx_seq(uint8_t tx_seq) {

    return tx_seq < expected_tx_seq_ - controller_->local_tx_window_ ||

           tx_seq > expected_tx_seq_ + controller_->local_tx_window_;

    return sequence_less_than(tx_seq, expected_tx_seq_ - controller_->local_tx_window_) ||

           sequence_less_than(expected_tx_seq_ + controller_->local_tx_window_, tx_seq);

  }



  bool with_invalid_req_seq(uint8_t req_seq) {

    return req_seq < expected_ack_seq_ || req_seq > next_tx_seq_;

    return sequence_less_than(req_seq, expected_ack_seq_) || sequence_less_than(next_tx_seq_, req_seq);

  }



  bool with_invalid_req_seq_retrans(uint8_t req_seq) {

    return req_seq < expected_ack_seq_ || req_seq > next_tx_seq_;

    return sequence_less_than(req_seq, expected_ack_seq_) || sequence_less_than(next_tx_seq_, req_seq);

  }



  bool not_with_expected_tx_seq(uint8_t tx_seq) {