Workaround for H4 HCI stream corruption during LE scans (bed7dde6) · Commits · e / os / android_packages_modules_Bluetooth

system/hci/src/hci_hal_h4.c

+43 −0

Original line number	Diff line number	Diff line
		@@ -31,6 +31,7 @@
		#include "vendor.h"

		#define HCI_HAL_SERIAL_BUFFER_SIZE 1026
		#define HCI_BLE_EVENT 0x3e

		// Increased HCI thread priority to keep up with the audio sub-system
		// when streaming time sensitive data (A2DP).
		@@ -47,6 +48,8 @@ static int uart_fd;
		static eager_reader_t *uart_stream;
		static serial_data_type_t current_data_type;
		static bool stream_has_interpretation;
		static bool stream_corruption_detected;
		static uint8_t stream_corruption_bytes_to_ignore;

		static void event_uart_has_bytes(eager_reader_t reader, void context);

		@@ -86,6 +89,8 @@ static bool hal_open() {
		}

		stream_has_interpretation = false;
		stream_corruption_detected = false;
		stream_corruption_bytes_to_ignore = 0;
		eager_reader_register(uart_stream, thread_get_reactor(thread), event_uart_has_bytes, NULL);

		// Raise thread priorities to keep up with audio
		@@ -177,6 +182,40 @@ done:;

		// Internal functions

		// WORKAROUND:
		// As exhibited by b/23934838, during result-heavy LE scans, the UART byte
		// stream can get corrupted, leading to assertions caused by mis-interpreting
		// the bytes following the corruption.
		// This workaround looks for tell-tale signs of a BLE event and attempts to
		// skip the correct amount of bytes in the stream to re-synchronize onto
		// a packet boundary.
		// Function returns true if \|byte_read\| has been processed by the workaround.
		static bool stream_corrupted_during_le_scan_workaround(const uint8_t byte_read)
		{
		if (!stream_corruption_detected && byte_read == HCI_BLE_EVENT) {
		LOG_ERROR("%s HCI stream corrupted (message type 0x3E)!", __func__);
		stream_corruption_detected = true;
		return true;
		}

		if (stream_corruption_detected) {
		if (stream_corruption_bytes_to_ignore == 0) {
		stream_corruption_bytes_to_ignore = byte_read;
		LOG_ERROR("%s About to skip %d bytes...", __func__, stream_corruption_bytes_to_ignore);
		} else {
		--stream_corruption_bytes_to_ignore;
		}

		if (stream_corruption_bytes_to_ignore == 0) {
		LOG_ERROR("%s Back to our regularly scheduled program...", __func__);
		stream_corruption_detected = false;
		}
		return true;
		}

		return false;
		}

		// See what data is waiting, and notify the upper layer
		static void event_uart_has_bytes(eager_reader_t reader, UNUSED_ATTR void context) {
		if (stream_has_interpretation) {
		@@ -187,6 +226,10 @@ static void event_uart_has_bytes(eager_reader_t reader, UNUSED_ATTR void conte
		LOG_ERROR("%s could not read HCI message type", __func__);
		return;
		}

		if (stream_corrupted_during_le_scan_workaround(type_byte))
		return;

		if (type_byte < DATA_TYPE_ACL \|\| type_byte > DATA_TYPE_EVENT) {
		LOG_ERROR("%s Unknown HCI message type. Dropping this byte 0x%x, min %x, max %x", __func__, type_byte, DATA_TYPE_ACL, DATA_TYPE_EVENT);
		return;

system/hci/test/hci_hal_h4_test.cpp

+7 −0

Original line number	Diff line number	Diff line
		@@ -43,6 +43,9 @@ DECLARE_TEST_MODES(
		type_byte_only
		);

		// Use as packet type to test stream_corrupted_during_le_scan_workaround()
		static const uint8_t HCI_BLE_EVENT = 0x3e;

		static char sample_data1[100] = "A point is that which has no part.";
		static char sample_data2[100] = "A line is breadthless length.";
		static char sample_data3[100] = "The ends of a line are points.";
		@@ -50,6 +53,9 @@ static char acl_data[100] = "A straight line is a line which lies evenly wit
		static char sco_data[100] = "A surface is that which has length and breadth only.";
		static char event_data[100] = "The edges of a surface are lines.";

		// Test data for stream_corrupted_during_le_scan_workaround()
		static char corrupted_data[] = { 0x5 /* length of remaining data */, 'H', 'e', 'l', 'l', 'o' };

		static const hci_hal_t *hal;
		static int dummy_serial_fd;
		static int reentry_i = 0;
		@@ -221,6 +227,7 @@ TEST_F(HciHalH4Test, test_read_synchronous) {
		reset_for(read_synchronous);

		write_packet(sockfd[1], DATA_TYPE_ACL, acl_data);
		write_packet(sockfd[1], HCI_BLE_EVENT, corrupted_data);
		write_packet(sockfd[1], DATA_TYPE_SCO, sco_data);
		write_packet(sockfd[1], DATA_TYPE_EVENT, event_data);