Fix PHY rate parsing for vht (802.11ac).
This also changes 802.11n-style MCS values 8..15 (2 spatial streams) and
16..23 (3 spatial streams) into MCS 0..7 with an opt.spatialstreams of 2 or
3 respectively.
diff --git a/app.py b/app.py
index f841cd4..f1d51bb 100644
--- a/app.py
+++ b/app.py
@@ -23,7 +23,7 @@
BROADCAST = 'ff:ff:ff:ff:ff:ff'
DEFAULT_FIELDS = ['seq', 'rate']
-AVAIL_FIELDS = ['seq', 'mcs', 'rate', 'retry',
+AVAIL_FIELDS = ['seq', 'mcs', 'spatialstreams', 'bw', 'rate', 'retry',
'type', 'typestr', 'dbm_antsignal', 'dbm_antnoise',
'bad']
diff --git a/wifipacket.py b/wifipacket.py
index 54c0763..9cd7deb 100755
--- a/wifipacket.py
+++ b/wifipacket.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
"""Functions for decoding wifi pcap files."""
from __future__ import print_function
@@ -43,6 +43,7 @@
TCPDUMP_MAGIC = 0xa1b2c3d4
TCPDUMP_VERSION = (2, 4)
LINKTYPE_IEEE802_11_RADIOTAP = 127
+SHORT_GI_MULT = 10 / 9.
class Flags(object):
@@ -165,64 +166,41 @@
return out
+# (modulation_name, coding_rate, data_rate(20M, 40M, 80M, 160M))
+# To get the data rate with short guard interval, multiply by SHORT_GI_MULT.
MCS_TABLE = [
- (1, 'BPSK', '1/2', (6.50, 7.20, 13.50, 15.00)),
- (1, 'QPSK', '1/2', (13.00, 14.40, 27.00, 30.00)),
- (1, 'QPSK', '3/4', (19.50, 21.70, 40.50, 45.00)),
- (1, '16-QAM', '1/2', (26.00, 28.90, 54.00, 60.00)),
- (1, '16-QAM', '3/4', (39.00, 43.30, 81.00, 90.00)),
- (1, '64-QAM', '2/3', (52.00, 57.80, 108.00, 120.00)),
- (1, '64-QAM', '3/4', (58.50, 65.00, 121.50, 135.00)),
- (1, '64-QAM', '5/6', (65.00, 72.20, 135.00, 150.00)),
- (2, 'BPSK', '1/2', (13.00, 14.40, 27.00, 30.00)),
- (2, 'QPSK', '1/2', (26.00, 28.90, 54.00, 60.00)),
- (2, 'QPSK', '3/4', (39.00, 43.30, 81.00, 90.00)),
- (2, '16-QAM', '1/2', (52.00, 57.80, 108.00, 120.00)),
- (2, '16-QAM', '3/4', (78.00, 86.70, 162.00, 180.00)),
- (2, '64-QAM', '2/3', (104.00, 115.60, 216.00, 240.00)),
- (2, '64-QAM', '3/4', (117.00, 130.00, 243.00, 270.00)),
- (2, '64-QAM', '5/6', (130.00, 144.40, 270.00, 300.00)),
- (3, 'BPSK', '1/2', (19.50, 21.70, 40.50, 45.00)),
- (3, 'QPSK', '1/2', (39.00, 43.30, 81.00, 90.00)),
- (3, 'QPSK', '3/4', (58.50, 65.00, 121.50, 135.00)),
- (3, '16-QAM', '1/2', (78.00, 86.70, 162.00, 180.00)),
- (3, '16-QAM', '3/4', (117.00, 130.00, 243.00, 270.00)),
- (3, '64-QAM', '2/3', (156.00, 173.30, 324.00, 360.00)),
- (3, '64-QAM', '3/4', (175.50, 195.00, 364.50, 405.00)),
- (3, '64-QAM', '5/6', (195.00, 216.70, 405.00, 450.00)),
- (4, 'BPSK', '1/2', (26.00, 28.80, 54.00, 60.00)),
- (4, 'QPSK', '1/2', (52.00, 57.60, 108.00, 120.00)),
- (4, 'QPSK', '3/4', (78.00, 86.80, 162.00, 180.00)),
- (4, '16-QAM', '1/2', (104.00, 115.60, 216.00, 240.00)),
- (4, '16-QAM', '3/4', (156.00, 173.20, 324.00, 360.00)),
- (4, '64-QAM', '2/3', (208.00, 231.20, 432.00, 480.00)),
- (4, '64-QAM', '3/4', (234.00, 260.00, 486.00, 540.00)),
- (4, '64-QAM', '5/6', (260.00, 288.80, 540.00, 600.00)),
- (1, 'BPSK', '1/2', (0, 0, 6.50, 7.20)),
+ ('BPSK', '1/2', (6.5, 13.5, 29.3, 58.5)),
+ ('QPSK', '1/2', (13, 27, 58.5, 117)),
+ ('QPSK', '3/4', (19.5, 40.5, 87.8, 175.5)),
+ ('16-QAM', '1/2', (26, 54, 117, 234)),
+ ('16-QAM', '3/4', (39, 81, 175.5, 351)),
+ ('64-QAM', '2/3', (52, 108, 234, 468)),
+ ('64-QAM', '3/4', (58.5, 121.5, 263.3, 526.5)),
+ ('64-QAM', '5/6', (65, 135, 292.5, 585)),
+ # 802.11ac only:
+ ('256-QAM', '3/4', (78, 162, 351, 702)),
+ ('256-QAM', '5/6', (86.7, 180, 390, 780)),
]
def McsToRate(known, flags, index):
"""Given MCS information for a packet, return the corresponding bitrate."""
- if known & (1 << 0):
- bw = (20, 40, 20, 20)[flags & 0x3]
+ if known & 0x01:
+ bw_index = (0, 1, 0, 0)[flags & 0x3]
else:
- bw = 20
- if known & (1 << 2):
- gi = ((flags & 0x4) >> 2)
+ bw_index = 0 # 20 MHz
+ if known & 0x04:
+ gi = ((flags & 0x04) >> 2)
else:
gi = 0
- if known & (1 << 1):
- mcs = index
+ gi_mult = (SHORT_GI_MULT if gi else 1)
+ if known & 0x02:
+ mcs = index & 0x07
+ nss = ((index & 0x18) >> 3) + 1
else:
mcs = 0
- if bw == 20:
- si = 0
- else:
- si = 2
- if gi:
- si += 1
- return MCS_TABLE[mcs][3][si]
+ nss = 1
+ return bw_index, MCS_TABLE[mcs][2][bw_index] * nss * gi_mult
def Packetize(stream):
@@ -298,12 +276,34 @@
elif name == 'channel':
opt.freq = v[0]
opt.channel_flags = v[1]
+ elif name == 'rate':
+ opt.rate = v[0] / 2. # convert multiples of 500 kb/sec -> Mb/sec
elif name == 'ht':
ht_known, ht_flags, ht_index = v
opt.ht = v
- opt.mcs = ht_index
- opt.rate = McsToRate(ht_known, ht_flags, ht_index)
- opt.spatialstreams = MCS_TABLE[ht_index][0]
+ opt.mcs = ht_index & 0x07
+ opt.spatialstreams = 1 + ((ht_index & 0x18) >> 3)
+ width, opt.rate = McsToRate(ht_known, ht_flags, ht_index)
+ opt.bw = 20 << width
+ elif name == 'vht':
+ (vht_known, vht_flags, vht_bw, vht_mcs_nss,
+ vhd_coding, vht_group_id, vht_partial_aid) = v
+ vmn = ord(vht_mcs_nss[0])
+ opt.mcs = (vmn & 0xf0) >> 4
+ opt.spatialstreams = vmn & 0x0f
+ if vht_bw == 0:
+ width = 0
+ elif vht_bw < 4:
+ width = 1
+ elif vht_bw < 11:
+ width = 2
+ else:
+ width = 3
+ opt.bw = 20 << width
+ gi = (vht_flags & 0x04)
+ gi_mult = (SHORT_GI_MULT if gi else 1)
+ opt.rate = (MCS_TABLE[opt.mcs][2][width]
+ * opt.spatialstreams * gi_mult)
else:
opt[name] = v if len(v) > 1 else v[0]
ofs += sz
@@ -422,18 +422,13 @@
seq = opt.seq
else:
seq = 'noseq'
- print(i+1, opt.get('flags'), opt.get('bad'))
if 'flags' in opt:
if opt.flags & Flags.BAD_FCS:
continue
- if 'mcs' in opt:
- print(i + 1,
- src, opt.dsmode, opt.typestr, ts, opt.rate, mac_usecs,
- opt.orig_len, seq, opt.flags)
- else:
- print(i + 1,
- src, opt.dsmode, opt.typestr, ts, opt.get('rate'), mac_usecs,
- opt.orig_len, seq, opt.get('flags'))
+ print(i + 1,
+ src, opt.dsmode, opt.typestr, ts,
+ opt.rate, opt.get('mcs'), opt.get('spatialstreams'),
+ mac_usecs, opt.orig_len, seq, opt.get('flags'))
def ZOpen(fn):
