Re: [PATCH net-next v4 1/3] docs: networking: Add documentation for MAPv5
From: Alex Elder
Date: Fri Apr 23 2021 - 08:32:10 EST
On 4/22/21 3:02 PM, Sharath Chandra Vurukala wrote:
Adding documentation explaining the new MAPv4/v5 packet formats
and the corresponding checksum offload headers.
Signed-off-by: Sharath Chandra Vurukala <sharathv@xxxxxxxxxxxxxx>
Thank you for updating this document, and in particular
for adding documentation for QMAPv4.
While I might suggest minor changes here or there to
wording, I think the document does a good enough job
of describing RMNet data structures.
My main interest right now is enabling inline checksum
offload functionality, so for now I'm content to just
acknowledge this patch.
Acked-by: Alex Elder <elder@xxxxxxxxxx>
---
.../device_drivers/cellular/qualcomm/rmnet.rst | 126 +++++++++++++++++++--
1 file changed, 114 insertions(+), 12 deletions(-)
diff --git a/Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst b/Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst
index 70643b5..4118384 100644
--- a/Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst
+++ b/Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst
@@ -27,34 +27,136 @@ these MAP frames and send them to appropriate PDN's.
2. Packet format
================
-a. MAP packet (data / control)
+a. MAP packet v1 (data / control)
-MAP header has the same endianness of the IP packet.
+MAP header fields are in big endian format.
Packet format::
- Bit 0 1 2-7 8 - 15 16 - 31
+ Bit 0 1 2-7 8-15 16-31
Function Command / Data Reserved Pad Multiplexer ID Payload length
- Bit 32 - x
- Function Raw Bytes
+
+ Bit 32-x
+ Function Raw bytes
Command (1)/ Data (0) bit value is to indicate if the packet is a MAP command
-or data packet. Control packet is used for transport level flow control. Data
+or data packet. Command packet is used for transport level flow control. Data
packets are standard IP packets.
-Reserved bits are usually zeroed out and to be ignored by receiver.
+Reserved bits must be zero when sent and ignored when received.
-Padding is number of bytes to be added for 4 byte alignment if required by
-hardware.
+Padding is the number of bytes to be appended to the payload to
+ensure 4 byte alignment.
Multiplexer ID is to indicate the PDN on which data has to be sent.
Payload length includes the padding length but does not include MAP header
length.
-b. MAP packet (command specific)::
+b. Map packet v4 (data / control)
+
+MAP header fields are in big endian format.
+
+Packet format::
+
+ Bit 0 1 2-7 8-15 16-31
+ Function Command / Data Reserved Pad Multiplexer ID Payload length
+
+ Bit 32-(x-33) (x-32)-x
+ Function Raw bytes Checksum offload header
+
+Command (1)/ Data (0) bit value is to indicate if the packet is a MAP command
+or data packet. Command packet is used for transport level flow control. Data
+packets are standard IP packets.
+
+Reserved bits must be zero when sent and ignored when received.
+
+Padding is the number of bytes to be appended to the payload to
+ensure 4 byte alignment.
+
+Multiplexer ID is to indicate the PDN on which data has to be sent.
+
+Payload length includes the padding length but does not include MAP header
+length.
+
+Checksum offload header, has the information about the checksum processing done
+by the hardware.Checksum offload header fields are in big endian format.
+
+Packet format::
+
+ Bit 0-14 15 16-31
+ Function Reserved Valid Checksum start offset
+
+ Bit 31-47 48-64
+ Function Checksum length Checksum value
+
+Reserved bits must be zero when sent and ignored when received.
+
+Valid bit indicates whether the partial checksum is calculated and is valid.
+Set to 1, if its is valid. Set to 0 otherwise.
+
+Padding is the number of bytes to be appended to the payload to
+ensure 4 byte alignment.
+
+Checksum start offset, Indicates the offset in bytes from the beginning of the
+IP header, from which modem computed checksum.
+
+Checksum length is the Length in bytes starting from CKSUM_START_OFFSET,
+over which checksum is computed.
+
+Checksum value, indicates the checksum computed.
+
+c. MAP packet v5 (data / control)
+
+MAP header fields are in big endian format.
+
+Packet format::
+
+ Bit 0 1 2-7 8-15 16-31
+ Function Command / Data Next header Pad Multiplexer ID Payload length
+
+ Bit 32-x
+ Function Raw bytes
+
+Command (1)/ Data (0) bit value is to indicate if the packet is a MAP command
+or data packet. Command packet is used for transport level flow control. Data
+packets are standard IP packets.
+
+Next header is used to indicate the presence of another header, currently is
+limited to checksum header.
+
+Padding is the number of bytes to be appended to the payload to
+ensure 4 byte alignment.
+
+Multiplexer ID is to indicate the PDN on which data has to be sent.
+
+Payload length includes the padding length but does not include MAP header
+length.
+
+d. Checksum offload header v5
+
+Checksum offload header fields are in big endian format.
+
+ Bit 0 - 6 7 8-15 16-31
+ Function Header Type Next Header Checksum Valid Reserved
+
+Header Type is to indicate the type of header, this usually is set to CHECKSUM
+
+Header types
+= ==========================================
+0 Reserved
+1 Reserved
+2 checksum header
+
+Checksum Valid is to indicate whether the header checksum is valid. Value of 1
+implies that checksum is calculated on this packet and is valid, value of 0
+indicates that the calculated packet checksum is invalid.
+
+Reserved bits must be zero when sent and ignored when received.
+
+e. MAP packet v1/v5 (command specific)::
- Bit 0 1 2-7 8 - 15 16 - 31
+ Bit 0 1 2-7 8 - 15 16 - 31
Function Command Reserved Pad Multiplexer ID Payload length
Bit 32 - 39 40 - 45 46 - 47 48 - 63
Function Command name Reserved Command Type Reserved
@@ -74,7 +176,7 @@ Command types
3 is for error during processing of commands
= ==========================================
-c. Aggregation
+f. Aggregation
Aggregation is multiple MAP packets (can be data or command) delivered to
rmnet in a single linear skb. rmnet will process the individual