This drops the code setting bit 9 on egress frames on the
Realtek "type A" (RTL8366RB) frames.
This bit was set on ingress frames for unknown reason,
and was set on egress frames as the format of ingress
and egress frames was believed to be the same. As that
assumption turned out to be false, and since this bit
seems to have zero effect on the behaviour of the switch
let's drop this bit entirely.
Signed-off-by: Linus Walleij <redacted>
---
net/dsa/tag_rtl4_a.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
@@ -54,7 +54,7 @@ static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb,p=(__be16*)tag;*p=htons(RTL4_A_ETHERTYPE);-out=(RTL4_A_PROTOCOL_RTL8366RB<<RTL4_A_PROTOCOL_SHIFT)|(2<<8);+out=(RTL4_A_PROTOCOL_RTL8366RB<<RTL4_A_PROTOCOL_SHIFT);/* The lower bits indicate the port number */out|=BIT(dp->index);
From: Andrew Lunn <andrew@lunn.ch> Date: 2021-09-13 16:05:50
On Mon, Sep 13, 2021 at 04:31:56PM +0200, Linus Walleij wrote:
This drops the code setting bit 9 on egress frames on the
Realtek "type A" (RTL8366RB) frames.
This bit was set on ingress frames for unknown reason,
and was set on egress frames as the format of ingress
and egress frames was believed to be the same. As that
assumption turned out to be false, and since this bit
seems to have zero effect on the behaviour of the switch
let's drop this bit entirely.
Signed-off-by: Linus Walleij <redacted>
This drops the code setting bit 9 on egress frames on the
Realtek "type A" (RTL8366RB) frames.
This bit was set on ingress frames for unknown reason,
and was set on egress frames as the format of ingress
and egress frames was believed to be the same. As that
assumption turned out to be false, and since this bit
seems to have zero effect on the behaviour of the switch
let's drop this bit entirely.
Signed-off-by: Linus Walleij <redacted>
Hello:
This patch was applied to netdev/net-next.git (refs/heads/master):
On Mon, 13 Sep 2021 16:31:56 +0200 you wrote:
This drops the code setting bit 9 on egress frames on the
Realtek "type A" (RTL8366RB) frames.
This bit was set on ingress frames for unknown reason,
and was set on egress frames as the format of ingress
and egress frames was believed to be the same. As that
assumption turned out to be false, and since this bit
seems to have zero effect on the behaviour of the switch
let's drop this bit entirely.
[...]
From: DENG Qingfang <dqfext@gmail.com> Date: 2021-09-15 07:20:28
On Mon, Sep 13, 2021 at 04:31:56PM +0200, Linus Walleij wrote:
This drops the code setting bit 9 on egress frames on the
Realtek "type A" (RTL8366RB) frames.
FYI, on RTL8366S, bit 9 on egress frames is disable learning.
This bit was set on ingress frames for unknown reason,
I think it could be the reason why the frame is forwarded to the CPU.
and was set on egress frames as the format of ingress
and egress frames was believed to be the same. As that
assumption turned out to be false, and since this bit
seems to have zero effect on the behaviour of the switch
let's drop this bit entirely.
Signed-off-by: Linus Walleij <redacted>
On Fri, Sep 24, 2021 at 12:12 AM Vladimir Oltean [off-list ref] wrote:
quoted
Hm I suspect it disable learning on RTL8366RB as well.
Suspicion based on what?
I have a not yet finished patch that dumps the FDB :)
The contents change around a bit under the patch
sets I have floating, but can certainly be determined
when I have time to test things properly.
quoted
Do we have some use for that feature in DSA taggers?
Yes.
OK I'll add it to my TODO, right now trying to fix up the base
of the RTL8366RB patch set to handle VLANs the right way.
Yours,
Linus Walleij
From: Vladimir Oltean <olteanv@gmail.com> Date: 2021-09-23 22:25:55
On Fri, Sep 24, 2021 at 12:21:39AM +0200, Linus Walleij wrote:
On Fri, Sep 24, 2021 at 12:12 AM Vladimir Oltean [off-list ref] wrote:
quoted
quoted
Hm I suspect it disable learning on RTL8366RB as well.
Suspicion based on what?
I have a not yet finished patch that dumps the FDB :)
The contents change around a bit under the patch
sets I have floating, but can certainly be determined
when I have time to test things properly.
To be clear, if bit 9 is a "disable learning" bit, address learning is a
process that takes place on the ingress of a packet, and in this case
the ingress port is the CPU port. But the ndo_fdb_dump works with net
devices, of which CPU ports have none. So it seems unlikely that you
would see any difference in the output of "bridge fdb" that could be
attributed to that bit.
quoted
quoted
Do we have some use for that feature in DSA taggers?
Yes.
OK I'll add it to my TODO, right now trying to fix up the base
of the RTL8366RB patch set to handle VLANs the right way.
From: Vladimir Oltean <olteanv@gmail.com> Date: 2021-09-23 23:11:50
On Fri, Sep 24, 2021 at 12:58:00AM +0200, Linus Walleij wrote:
On Fri, Sep 24, 2021 at 12:25 AM Vladimir Oltean [off-list ref] wrote:
quoted
On Fri, Sep 24, 2021 at 12:21:39AM +0200, Linus Walleij wrote:
quoted
quoted
quoted
Do we have some use for that feature in DSA taggers?
Yes.
OK I'll add it to my TODO, right now trying to fix up the base
of the RTL8366RB patch set to handle VLANs the right way.
But you didn't ask what that use is...
Allright spill the beans :D I might not be the most clever at times...
So the essence of the answer is in the discussion we've already had on
your v1 attempt to disable this "unknown" bit:
https://patchwork.kernel.org/project/netdevbpf/patch/20210828235619.249757-1-linus.walleij@linaro.org/
The idea is that bridges should learn only from data plane packets, and
the only chance a DSA tagger has to distinguish between a data and a
control packet sent by the network stack is to look at
skb->offload_fwd_mark, which will be set on xmit by the bridge driver,
if you implement the .port_bridge_tx_fwd_offload and .port_bridge_tx_fwd_unoffload
methods, and declare a non-zero ds->max_num_bridges value (note: the API
for bridge TX forwarding offload in DSA is subject to change/get
simplified during this development cycle). And to offload the replication
for data packets correctly, you should really re-read the discussion we
had about what happens when the egress port mask set by the tagger is all-zeroes.
Not to blow my own horn or anything, but I've repeated this stuff for so many
times now that I wrote it down for future reference, you can find the basic
concepts detailed in chapter "The data plane and the control plane" from the
paper attached here (there are also pictures, not sure how much they help):
https://linuxplumbersconf.org/event/11/contributions/949/