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1#!/usr/bin/env python
2"""
3This script extracts btsnooz content from bugreports and generates
4a valid btsnoop log file which can be viewed using standard tools
5like Wireshark.
6
7btsnooz is a custom format designed to be included in bugreports.
8It can be described as:
9
10base64 {
11  file_header
12  deflate {
13    repeated {
14      record_header
15      record_data
16    }
17  }
18}
19
20where the file_header and record_header are modified versions of
21the btsnoop headers.
22"""
23
24
25import base64
26import fileinput
27import struct
28import sys
29import zlib
30
31
32# Enumeration of the values the 'type' field can take in a btsnooz
33# header. These values come from the Bluetooth stack's internal
34# representation of packet types.
35TYPE_IN_EVT = 0x10
36TYPE_IN_ACL = 0x11
37TYPE_IN_SCO = 0x12
38TYPE_OUT_CMD = 0x20
39TYPE_OUT_ACL = 0x21
40TYPE_OUT_SCO = 0x22
41
42
43def type_to_direction(type):
44  """
45  Returns the inbound/outbound direction of a packet given its type.
46  0 = sent packet
47  1 = received packet
48  """
49  if type in [TYPE_IN_EVT, TYPE_IN_ACL, TYPE_IN_SCO]:
50    return 1
51  return 0
52
53
54def type_to_hci(type):
55  """
56  Returns the HCI type of a packet given its btsnooz type.
57  """
58  if type == TYPE_OUT_CMD:
59    return '\x01'
60  if type == TYPE_IN_ACL or type == TYPE_OUT_ACL:
61    return '\x02'
62  if type == TYPE_IN_SCO or type == TYPE_OUT_SCO:
63    return '\x03'
64  if type == TYPE_IN_EVT:
65    return '\x04'
66
67
68def decode_snooz(snooz):
69  """
70  Decodes all known versions of a btsnooz file into a btsnoop file.
71  """
72  version, last_timestamp_ms = struct.unpack_from('=bQ', snooz)
73
74  if version != 1 and version != 2:
75    sys.stderr.write('Unsupported btsnooz version: %s\n' % version)
76    exit(1)
77
78  # Oddly, the file header (9 bytes) is not compressed, but the rest is.
79  decompressed = zlib.decompress(snooz[9:])
80
81  sys.stdout.write('btsnoop\x00\x00\x00\x00\x01\x00\x00\x03\xea')
82
83  if version == 1:
84    decode_snooz_v1(decompressed, last_timestamp_ms)
85  elif version == 2:
86    decode_snooz_v2(decompressed, last_timestamp_ms)
87
88
89def decode_snooz_v1(decompressed, last_timestamp_ms):
90  """
91  Decodes btsnooz v1 files into a btsnoop file.
92  """
93  # An unfortunate consequence of the file format design: we have to do a
94  # pass of the entire file to determine the timestamp of the first packet.
95  first_timestamp_ms = last_timestamp_ms + 0x00dcddb30f2f8000
96  offset = 0
97  while offset < len(decompressed):
98    length, delta_time_ms, type = struct.unpack_from('=HIb', decompressed, offset)
99    offset += 7 + length - 1
100    first_timestamp_ms -= delta_time_ms
101
102  # Second pass does the actual writing out to stdout.
103  offset = 0
104  while offset < len(decompressed):
105    length, delta_time_ms, type = struct.unpack_from('=HIb', decompressed, offset)
106    first_timestamp_ms += delta_time_ms
107    offset += 7
108    sys.stdout.write(struct.pack('>II', length, length))
109    sys.stdout.write(struct.pack('>II', type_to_direction(type), 0))
110    sys.stdout.write(struct.pack('>II', (first_timestamp_ms >> 32), (first_timestamp_ms & 0xFFFFFFFF)))
111    sys.stdout.write(type_to_hci(type))
112    sys.stdout.write(decompressed[offset : offset + length - 1])
113    offset += length - 1
114
115
116def decode_snooz_v2(decompressed, last_timestamp_ms):
117  """
118  Decodes btsnooz v2 files into a btsnoop file.
119  """
120  # An unfortunate consequence of the file format design: we have to do a
121  # pass of the entire file to determine the timestamp of the first packet.
122  first_timestamp_ms = last_timestamp_ms + 0x00dcddb30f2f8000
123  offset = 0
124  while offset < len(decompressed):
125    length, packet_length, delta_time_ms, snooz_type = struct.unpack_from('=HHIb', decompressed, offset)
126    offset += 9 + length - 1
127    first_timestamp_ms -= delta_time_ms
128
129  # Second pass does the actual writing out to stdout.
130  offset = 0
131  while offset < len(decompressed):
132    length, packet_length, delta_time_ms, snooz_type = struct.unpack_from('=HHIb', decompressed, offset)
133    first_timestamp_ms += delta_time_ms
134    offset += 9
135    sys.stdout.write(struct.pack('>II', packet_length, length))
136    sys.stdout.write(struct.pack('>II', type_to_direction(snooz_type), 0))
137    sys.stdout.write(struct.pack('>II', (first_timestamp_ms >> 32), (first_timestamp_ms & 0xFFFFFFFF)))
138    sys.stdout.write(type_to_hci(snooz_type))
139    sys.stdout.write(decompressed[offset : offset + length - 1])
140    offset += length - 1
141
142
143def main():
144  if len(sys.argv) > 2:
145    sys.stderr.write('Usage: %s [bugreport]\n' % sys.argv[0])
146    exit(1)
147
148  iterator = fileinput.input()
149  found = False
150  base64_string = ""
151  for line in iterator:
152    if found:
153      if line.find('--- END:BTSNOOP_LOG_SUMMARY') != -1:
154        decode_snooz(base64.standard_b64decode(base64_string))
155        sys.exit(0)
156      base64_string += line.strip()
157
158    if line.find('--- BEGIN:BTSNOOP_LOG_SUMMARY') != -1:
159      found = True
160
161  if not found:
162    sys.stderr.write('No btsnooz section found in bugreport.\n')
163    sys.exit(1)
164
165
166if __name__ == '__main__':
167  main()
168