Re: Requesting DLT_* values for Ethernet switches proprietary tagging protocol

[Florian Fainelli <f.fainelli () gmail com>]

On 1/17/2019 6:56 PM, Guy Harris wrote:
> On Jan 17, 2019, at 2:39 PM, Florian Fainelli <f.fainelli () gmail com> wrote:
>
> > DSA currently supports the following tagging protocols (details can be
> > found under net/dsa/tag_*.c in Linux source for exactly length and offset
> > within the Ethernet frame):
>
> Unfortunately, tag_brcm.c, for example, doesn't give *enough* details - it has a bunch of uncommented #defines (some 
> of which suggest overlap between fields in the same byte of the tag) and some code that doesn't handle all the fields 
> in both ingress and egress tags.
>
> Can you construct "ASCII-art" diagrams and explanatory text, of the sort seen in, for example:
>
>       http://www.tcpdump.org/linktypes/LINKTYPE_LINUX_SLL.html
>
> for the tags?

Most certainly, I can only answer for the Broadcom tags, since I am not
very familiar with the other protocols, and I am hoping someone else
could fill in for Intel/Qualcomm/Mediatek etc.

We have two different formats, presented below. Let me know if you need
more details on each field and I can expand.

Egress (switch to management port) format:

+----------------------------------------------------------+
| Ethernet Destination address (6 octets)                  |
+----------------------------------------------------------+
+----------------------------------------------------------+
| Ethernet Source address (6 octets)                       |
+----------------------------------------------------------+
+----------------------------------------------------------+
| OPcode[7:5] | Traffic class[4:2] | Tag enforcement [1:0] |
+----------------------------------------------------------+
| Time stamp [7] | Unused                                  |
+----------------------------------------------------------+
+----------------------------------------------------------+
| Reserved [7:1]                        | Desination map[1]|
+----------------------------------------------------------+
+----------------------------------------------------------+
| Destination map [7:0]                                    |
+----------------------------------------------------------+
+----------------------------------------------------------+
| Ethernet Type/Length (2 bytes)                           |
+----------------------------------------------------------+
+----------------------------------------------------------+
| Ethernet payload                                         |
.                                                          .
.                                                          .
.                                                          .

Ingress (management port to switch) format

+----------------------------------------------------------+
| Ethernet Destination address (6 octets)                  |
+----------------------------------------------------------+
+----------------------------------------------------------+
| Ethernet Source address (6 octets)                       |
+----------------------------------------------------------+
+----------------------------------------------------------+
| OPcode[7:5] | Reserved[4:0]                              |
+----------------------------------------------------------+
| Classification ID [7:0]                                  |
+----------------------------------------------------------+
+----------------------------------------------------------+
| Reason code [7:0]                                        |
+----------------------------------------------------------+
+----------------------------------------------------------+
| Traffic class [7:5] | Source port number [4:0]           |
+----------------------------------------------------------+
+----------------------------------------------------------+
| Ethernet Type/Length (2 bytes)                           |
+----------------------------------------------------------+
+----------------------------------------------------------+
| Ethernet payload                                         |
.                                                          .
.                                                          .
.                                                          .
-- 
Florian
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