Messages in this thread | | | Date | Tue, 11 Aug 2020 12:42:55 -0400 | From | Sasha Levin <> | Subject | Re: [PATCH AUTOSEL 5.7 03/60] net: mscc: ocelot: fix encoding destination ports into multicast IPv4 address |
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On Tue, Aug 11, 2020 at 12:01:08AM +0300, Vladimir Oltean wrote: >Hi Sasha, > >On Mon, Aug 10, 2020 at 03:09:31PM -0400, Sasha Levin wrote: >> From: Vladimir Oltean <vladimir.oltean@nxp.com> >> >> [ Upstream commit 0897ecf7532577bda3dbcb043ce046a96948889d ] >> >> The ocelot hardware designers have made some hacks to support multicast >> IPv4 and IPv6 addresses. Normally, the MAC table matches on MAC >> addresses and the destination ports are selected through the DEST_IDX >> field of the respective MAC table entry. The DEST_IDX points to a Port >> Group ID (PGID) which contains the bit mask of ports that frames should >> be forwarded to. But there aren't a lot of PGIDs (only 80 or so) and >> there are clearly many more IP multicast addresses than that, so it >> doesn't scale to use this PGID mechanism, so something else was done. >> Since the first portion of the MAC address is known, the hack they did >> was to use a single PGID for _flooding_ unknown IPv4 multicast >> (PGID_MCIPV4 == 62), but for known IP multicast, embed the destination >> ports into the first 3 bytes of the MAC address recorded in the MAC >> table. >> >> The VSC7514 datasheet explains it like this: >> >> 3.9.1.5 IPv4 Multicast Entries >> >> MAC table entries with the ENTRY_TYPE = 2 settings are interpreted >> as IPv4 multicast entries. >> IPv4 multicasts entries match IPv4 frames, which are classified to >> the specified VID, and which have DMAC = 0x01005Exxxxxx, where >> xxxxxx is the lower 24 bits of the MAC address in the entry. >> Instead of a lookup in the destination mask table (PGID), the >> destination set is programmed as part of the entry MAC address. This >> is shown in the following table. >> >> Table 78: IPv4 Multicast Destination Mask >> >> Destination Ports Record Bit Field >> --------------------------------------------- >> Ports 10-0 MAC[34-24] >> >> Example: All IPv4 multicast frames in VLAN 12 with MAC 01005E112233 are >> to be forwarded to ports 3, 8, and 9. This is done by inserting the >> following entry in the MAC table entry: >> VALID = 1 >> VID = 12 >> MAC = 0x000308112233 >> ENTRY_TYPE = 2 >> DEST_IDX = 0 >> >> But this procedure is not at all what's going on in the driver. In fact, >> the code that embeds the ports into the MAC address looks like it hasn't >> actually been tested. This patch applies the procedure described in the >> datasheet. >> >> Since there are many other fixes to be made around multicast forwarding >> until it works properly, there is no real reason for this patch to be >> backported to stable trees, or considered a real fix of something that >> should have worked. >> >> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> >> Signed-off-by: David S. Miller <davem@davemloft.net> >> Signed-off-by: Sasha Levin <sashal@kernel.org> >> --- > >Could you please drop this patch from the 'stable' queues for 5.7 and >5.8? I haven't tested it on older kernels and without the other patches >sent in that series. I would like to avoid unexpected regressions if >possible.
Will do, thanks!
-- Thanks, Sasha
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