tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
docs: networking: Add documentation for MAPv5
Adding documentation explaining the new MAPv4/v5 packet formats
and the corresponding checksum offload headers.
Signed-off-by: Sharath Chandra Vurukala <sharathv@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
authored by
Sharath Chandra Vurukala
and committed by
David S. Miller
710b797c
e0ae757c
+114
-12
+114
-12
Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst
+114
-12
Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst
···
27
27
2. Packet format
28
28
================
29
29
30
-
a. MAP packet (data / control)
30
+
a. MAP packet v1 (data / control)
31
31
32
-
MAP header has the same endianness of the IP packet.
32
+
MAP header fields are in big endian format.
33
33
34
34
Packet format::
35
35
36
-
Bit 0 1 2-7 8 - 15 16 - 31
36
+
Bit 0 1 2-7 8-15 16-31
37
37
Function Command / Data Reserved Pad Multiplexer ID Payload length
38
-
Bit 32 - x
39
-
Function Raw Bytes
38
+
39
+
Bit 32-x
40
+
Function Raw bytes
40
41
41
42
Command (1)/ Data (0) bit value is to indicate if the packet is a MAP command
42
-
or data packet. Control packet is used for transport level flow control. Data
43
+
or data packet. Command packet is used for transport level flow control. Data
43
44
packets are standard IP packets.
44
45
45
-
Reserved bits are usually zeroed out and to be ignored by receiver.
46
+
Reserved bits must be zero when sent and ignored when received.
46
47
47
-
Padding is number of bytes to be added for 4 byte alignment if required by
48
-
hardware.
48
+
Padding is the number of bytes to be appended to the payload to
49
+
ensure 4 byte alignment.
49
50
50
51
Multiplexer ID is to indicate the PDN on which data has to be sent.
51
52
52
53
Payload length includes the padding length but does not include MAP header
53
54
length.
54
55
55
-
b. MAP packet (command specific)::
56
+
b. Map packet v4 (data / control)
56
57
57
-
Bit 0 1 2-7 8 - 15 16 - 31
58
+
MAP header fields are in big endian format.
59
+
60
+
Packet format::
61
+
62
+
Bit 0 1 2-7 8-15 16-31
63
+
Function Command / Data Reserved Pad Multiplexer ID Payload length
64
+
65
+
Bit 32-(x-33) (x-32)-x
66
+
Function Raw bytes Checksum offload header
67
+
68
+
Command (1)/ Data (0) bit value is to indicate if the packet is a MAP command
69
+
or data packet. Command packet is used for transport level flow control. Data
70
+
packets are standard IP packets.
71
+
72
+
Reserved bits must be zero when sent and ignored when received.
73
+
74
+
Padding is the number of bytes to be appended to the payload to
75
+
ensure 4 byte alignment.
76
+
77
+
Multiplexer ID is to indicate the PDN on which data has to be sent.
78
+
79
+
Payload length includes the padding length but does not include MAP header
80
+
length.
81
+
82
+
Checksum offload header, has the information about the checksum processing done
83
+
by the hardware.Checksum offload header fields are in big endian format.
84
+
85
+
Packet format::
86
+
87
+
Bit 0-14 15 16-31
88
+
Function Reserved Valid Checksum start offset
89
+
90
+
Bit 31-47 48-64
91
+
Function Checksum length Checksum value
92
+
93
+
Reserved bits must be zero when sent and ignored when received.
94
+
95
+
Valid bit indicates whether the partial checksum is calculated and is valid.
96
+
Set to 1, if its is valid. Set to 0 otherwise.
97
+
98
+
Padding is the number of bytes to be appended to the payload to
99
+
ensure 4 byte alignment.
100
+
101
+
Checksum start offset, Indicates the offset in bytes from the beginning of the
102
+
IP header, from which modem computed checksum.
103
+
104
+
Checksum length is the Length in bytes starting from CKSUM_START_OFFSET,
105
+
over which checksum is computed.
106
+
107
+
Checksum value, indicates the checksum computed.
108
+
109
+
c. MAP packet v5 (data / control)
110
+
111
+
MAP header fields are in big endian format.
112
+
113
+
Packet format::
114
+
115
+
Bit 0 1 2-7 8-15 16-31
116
+
Function Command / Data Next header Pad Multiplexer ID Payload length
117
+
118
+
Bit 32-x
119
+
Function Raw bytes
120
+
121
+
Command (1)/ Data (0) bit value is to indicate if the packet is a MAP command
122
+
or data packet. Command packet is used for transport level flow control. Data
123
+
packets are standard IP packets.
124
+
125
+
Next header is used to indicate the presence of another header, currently is
126
+
limited to checksum header.
127
+
128
+
Padding is the number of bytes to be appended to the payload to
129
+
ensure 4 byte alignment.
130
+
131
+
Multiplexer ID is to indicate the PDN on which data has to be sent.
132
+
133
+
Payload length includes the padding length but does not include MAP header
134
+
length.
135
+
136
+
d. Checksum offload header v5
137
+
138
+
Checksum offload header fields are in big endian format.
139
+
140
+
Bit 0 - 6 7 8-15 16-31
141
+
Function Header Type Next Header Checksum Valid Reserved
142
+
143
+
Header Type is to indicate the type of header, this usually is set to CHECKSUM
144
+
145
+
Header types
146
+
= ==========================================
147
+
0 Reserved
148
+
1 Reserved
149
+
2 checksum header
150
+
151
+
Checksum Valid is to indicate whether the header checksum is valid. Value of 1
152
+
implies that checksum is calculated on this packet and is valid, value of 0
153
+
indicates that the calculated packet checksum is invalid.
154
+
155
+
Reserved bits must be zero when sent and ignored when received.
156
+
157
+
e. MAP packet v1/v5 (command specific)::
158
+
159
+
Bit 0 1 2-7 8 - 15 16 - 31
58
160
Function Command Reserved Pad Multiplexer ID Payload length
59
161
Bit 32 - 39 40 - 45 46 - 47 48 - 63
60
162
Function Command name Reserved Command Type Reserved
···
176
74
3 is for error during processing of commands
177
75
= ==========================================
178
76
179
-
c. Aggregation
77
+
f. Aggregation
180
78
181
79
Aggregation is multiple MAP packets (can be data or command) delivered to
182
80
rmnet in a single linear skb. rmnet will process the individual