Hello netdev experts,
On 5/6/20 12:30 PM, Murali Karicheri wrote:
This RFC series add support for Parallel Redundancy Protocol (PRP)
as defined in IEC-62439-3 in the kernel networking subsystem. PRP
Uses a Redundancy Control Trailer (RCT) the format of which is
similar to HSR Tag. This is used for implementing redundancy.
RCT consists of 6 bytes similar to HSR tag and contain following
fields:-
- 16-bit sequence number (SeqNr);
- 4-bit LAN identifier (LanId);
- 12 bit frame size (LSDUsize);
- 16-bit suffix (PRPsuffix).
The PRPsuffix identifies PRP frames and distinguishes PRP frames
from other protocols that also append a trailer to their useful
data. The LSDUsize field allows the receiver to distinguish PRP
frames from random, nonredundant frames as an additional check.
LSDUsize is the size of the Ethernet payload inclusive of the
RCT. Sequence number along with LanId is used for duplicate
detection and discard.
PRP node is also known as Dual Attached Node (DAN-P) since it
is typically attached to two different LAN for redundancy.
DAN-P duplicates each of L2 frames and send it over the two
Ethernet links. Each outgoing frame is appended with RCT.
Unlike HSR, these are added to the end of L2 frame and may be
treated as padding by bridges and therefore would be work with
traditional bridges or switches, where as HSR wouldn't as Tag
is prefixed to the Ethenet frame. At the remote end, these are
received and the duplicate frame is discarded before the stripped
frame is send up the networking stack. Like HSR, PRP also sends
periodic Supervision frames to the network. These frames are
received and MAC address from the SV frames are populated in a
database called Node Table. The above functions are grouped into
a block called Link Redundancy Entity (LRE) in the IEC spec.
As there are many similarities between HSR and PRP protocols,
this patch re-use the code from HSR driver to implement PRP
driver. As many part of the code can be re-used, this patch
introduces a new common API definitions for both protocols and
propose to obsolete the existing HSR defines in
include/uapi/linux/if_link.h. New definitions are prefixed
with a HSR_PRP prefix. Similarly include/uapi/linux/hsr_netlink.h
is proposed to be replaced with include/uapi/linux/hsr_prp_netlink.h
which also uses the HSR_PRP prefix. The netlink socket interface
code is migrated (as well as the iproute2 being sent as a follow up
patch) to use the new API definitions. To re-use the code,
following are done as a preparatory patch before adding the PRP
functionality:-
- prefix all common code with hsr_prp
- net/hsr -> renamed to net/hsr-prp
- All common struct types, constants, functions renamed with
hsr{HSR}_prp{PRP} prefix.
Please review this and provide me feedback so that I can work to
incorporate them and send a formal patch series for this. As this
series impacts user space, I am not sure if this is the right
approach to introduce a new definitions and obsolete the old
API definitions for HSR. The current approach is choosen
to avoid redundant code in iproute2 and in the netlink driver
code (hsr_netlink.c). Other approach we discussed internally was
to Keep the HSR prefix in the user space and kernel code, but
live with the redundant code in the iproute2 and hsr netlink
code. Would like to hear from you what is the best way to add
this feature to networking core. If there is any other
alternative approach possible, I would like to hear about the
same.
The patch was tested using two TI AM57x IDK boards which are
connected back to back over two CPSW ports.
Script used for creating the hsr/prp interface is given below
and uses the ip link command. Also provided logs from the tests
I have executed for your reference.
iproute2 related patches will follow soon....
Could someone please review this and provide some feedback to take
this forward?
Thanks and regards,
Murali Karicheri
Texas Instruments
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