On Thu, Jun 4, 2020 at 1:23 PM Vladimir Oltean <olte...@gmail.com> wrote:
> In the code you pointed to, there is a potentially relevant comment: > > 1532//CPU tag: Realtek Ethertype==0x8899(2 bytes)+protocol==0x9(4 > MSB)+priority(2 bits)+reserved(4 bits)+portmask(6 LSB) > > https://svn.dd-wrt.com/browser/src/linux/universal/linux-3.2/drivers/net/ethernet/raeth/rb/rtl_multicast_snooping.c#L1527 > https://svn.dd-wrt.com/browser/src/linux/universal/linux-3.2/drivers/net/ethernet/raeth/rb/rtl_multicast_snooping.c#L5224 > > This strongly indicates to me that the insertion tag is the same as > the extraction tag. This code is a problem because it is Realtek-development style. This style seems to be that the hardware people write the drivers using copy/paste from the previous ASIC and ship is as soon as possible. Keep this in mind. The above tag is using protocol 9 and is actually even documented in a PDF I have for RTL8306. The problem is that the RTL8366RB (I suspect also RTL8366S) uses protocol "a" (as in hex 10). Which is of course necessarily different. I have *really* tried to figure out how the bits in protocol a works when transmissing from the CPU port to any switch port. When nothing else worked, I just tried all bit combinations with 0xannp where a is protocol and p is port. I looped through all values several times trying to get a response from ping. So this is really how far I can get right now, even with brute force. > It is completely opaque to me why in patch "[net-next PATCH 2/5] net: > dsa: rtl8366rb: Support the CPU DSA tag" you are _disabling_ the > injection of these tags via RTL8368RB_CPU_INSTAG. I think it's natural > that the switch drops these packets when CPU tag insertion is > disabled. This is another Realtek-ism where they managed to invert the meaning of a bit. Bit 15 in register 0x0061 (RTL8368RB_CPU_CTRL_REG) can be set to 1 and then the special (custom) CPU tag 0x8899 protocol a will be DISABLED. This value Realtek calls "RTL8368RB_CPU_INSTAG" which makes you think that the tag will be inserted, it is named "instag" right? But that is not how it works. That bit needs to be set to 0 to insert the tag and 1 to disable insertion of the tag. For this reason the patch also renames this bit to RTL8368RB_CPU_NO_TAG which is more to the point. Yours, Linus Walleij
