netdev - Re: [PATCH net-next 5/5 v2] net: dsa: rtl8366rb: Support fast aging

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Date:   Fri, 10 Sep 2021 15:59:18 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        Alvin Šipraga <alsi@...g-olufsen.dk>,
        Mauri Sandberg <sandberg@...lfence.com>,
        DENG Qingfang <dqfext@...il.com>
Subject: Re: [PATCH net-next 5/5 v2] net: dsa: rtl8366rb: Support fast aging

On Wed, Sep 8, 2021 at 10:10 PM Vladimir Oltean <olteanv@...il.com> wrote:

> Your interpretation seems correct (I can't think of anything else being meant),
> but I don't know why you say "duh" about the update of STP state
> resulting in the port losing its dynamic L2 entries. Sure, it makes
> sense, but many other vendors do not do that automatically, and DSA
> calls .port_fast_age whenever the STP state transitions from a value
> capable of learning (LEARNING, FORWARDING) to one incapable of learning
> (DISABLED, BLOCKING, LISTENING).
>
> To prove/disprove, it would be interesting to implement port STP states,
> without implementing .port_fast_age, force a port down and then back up,
> and then run "bridge fdb" and see whether it is true that STP state
> changes also lead to FDB flushing but at a hardware level (whether there
> is any 'self' entry being reported).

I have been looking into this.

What makes RTL8366RB so confusing is a compulsive use of FIDs.

For example Linux DSA has:

ds->ops->port_stp_state_set(ds, port, state);

This is pretty straight forward. The vendor RTL8366RB API however has this:

int32 rtl8368s_setAsicSpanningTreeStatus(enum PORTID port, enum
FIDVALUE fid, enum SPTSTATE state)

So this is set per FID instead of per VID.

I also looked into proper FDB support and there is the same problem.
For example I want to implement:

static int rtl8366rb_port_fdb_add(struct dsa_switch *ds, int port,
                  const unsigned char *addr, u16 vid)

But the FDB static (also autolearn) entries has this format:

struct l2tb_macstatic_st{
    ether_addr_t     mac;
    uint16     fid:3;
    uint16     reserved1:13;
    uint16     mbr:8;
    uint16     reserved2:4;
    uint16    block:1;
    uint16     auth:1;
    uint16     swst:1;
    uint16     ipmulti:1;
    uint16     reserved3;
};

(swst indicates a static entry ipmulti a multicast entry, mbr is apparently
for S-VLAN, which I'm not familiar with.)

So again using a FID rather than port or VID in the database.

I am starting to wonder whether I should just associate 1-1 the FID:s
with the 6 ports (0..5) to simplify things. Or one FID per defined VID
until they run out, as atleast OpenWRT connects VLAN1 to all ports on
a bridge.

Yours,
Linus Walleij