<feed xmlns='http://www.w3.org/2005/Atom'>
<title>user/sven/linux.git/include/linux/dsa, branch v5.15.3</title>
<subtitle>Linux Kernel
</subtitle>
<id>https://git.stealer.net/cgit.cgi/user/sven/linux.git/atom?h=v5.15.3</id>
<link rel='self' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/atom?h=v5.15.3'/>
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<updated>2021-11-18T18:17:06Z</updated>
<entry>
<title>net: dsa: felix: fix broken VLAN-tagged PTP under VLAN-aware bridge</title>
<updated>2021-11-18T18:17:06Z</updated>
<author>
<name>Vladimir Oltean</name>
<email>vladimir.oltean@nxp.com</email>
</author>
<published>2021-11-02T19:31:22Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=932224ba805d16dd42258e792224c6050b9f92ce'/>
<id>urn:sha1:932224ba805d16dd42258e792224c6050b9f92ce</id>
<content type='text'>
[ Upstream commit 92f62485b3715882cd397b0cbd80a96d179b86d6 ]

Normally it is expected that the dsa_device_ops :: rcv() method finishes
parsing the DSA tag and consumes it, then never looks at it again.

But commit c0bcf537667c ("net: dsa: ocelot: add hardware timestamping
support for Felix") added support for RX timestamping in a very
unconventional way. On this switch, a partial timestamp is available in
the DSA header, but the driver got away with not parsing that timestamp
right away, but instead delayed that parsing for a little longer:

dsa_switch_rcv():
	nskb = cpu_dp-&gt;rcv(skb, dev); &lt;------------- not here
	-&gt; ocelot_rcv()
	...

	skb = nskb;
	skb_push(skb, ETH_HLEN);
	skb-&gt;pkt_type = PACKET_HOST;
	skb-&gt;protocol = eth_type_trans(skb, skb-&gt;dev);

	...

	if (dsa_skb_defer_rx_timestamp(p, skb)) &lt;--- but here
	-&gt; felix_rxtstamp()
		return 0;

When in felix_rxtstamp(), this driver accounted for the fact that
eth_type_trans() happened in the meanwhile, so it got a hold of the
extraction header again by subtracting (ETH_HLEN + OCELOT_TAG_LEN) bytes
from the current skb-&gt;data.

This worked for quite some time but was quite fragile from the very
beginning. Not to mention that having DSA tag parsing split in two
different files, under different folders (net/dsa/tag_ocelot.c vs
drivers/net/dsa/ocelot/felix.c) made it quite non-obvious for patches to
come that they might break this.

Finally, the blamed commit does the following: at the end of
ocelot_rcv(), it checks whether the skb payload contains a VLAN header.
If it does, and this port is under a VLAN-aware bridge, that VLAN ID
might not be correct in the sense that the packet might have suffered
VLAN rewriting due to TCAM rules (VCAP IS1). So we consume the VLAN ID
from the skb payload using __skb_vlan_pop(), and take the classified
VLAN ID from the DSA tag, and construct a hwaccel VLAN tag with the
classified VLAN, and the skb payload is VLAN-untagged.

The big problem is that __skb_vlan_pop() does:

	memmove(skb-&gt;data + VLAN_HLEN, skb-&gt;data, 2 * ETH_ALEN);
	__skb_pull(skb, VLAN_HLEN);

aka it moves the Ethernet header 4 bytes to the right, and pulls 4 bytes
from the skb headroom (effectively also moving skb-&gt;data, by definition).
So for felix_rxtstamp()'s fragile logic, all bets are off now.
Instead of having the "extraction" pointer point to the DSA header,
it actually points to 4 bytes _inside_ the extraction header.
Corollary, the last 4 bytes of the "extraction" header are in fact 4
stale bytes of the destination MAC address from the Ethernet header,
from prior to the __skb_vlan_pop() movement.

So of course, RX timestamps are completely bogus when the system is
configured in this way.

The fix is actually very simple: just don't structure the code like that.
For better or worse, the DSA PTP timestamping API does not offer a
straightforward way for drivers to present their RX timestamps, but
other drivers (sja1105) have established a simple mechanism to carry
their RX timestamp from dsa_device_ops :: rcv() all the way to
dsa_switch_ops :: port_rxtstamp() and even later. That mechanism is to
simply save the partial timestamp to the skb-&gt;cb, and complete it later.

Question: why don't we simply populate the skb's struct
skb_shared_hwtstamps from ocelot_rcv(), and bother with this
complication of propagating the timestamp to felix_rxtstamp()?

Answer: dsa_switch_ops :: port_rxtstamp() answers the question whether
PTP packets need sleepable context to retrieve the full RX timestamp.
Currently felix_rxtstamp() answers "no, thanks" to that question, and
calls ocelot_ptp_gettime64() from softirq atomic context. This is
understandable, since Felix VSC9959 is a PCIe memory-mapped switch, so
hardware access does not require sleeping. But the felix driver is
preparing for the introduction of other switches where hardware access
is over a slow bus like SPI or MDIO:
https://lore.kernel.org/lkml/20210814025003.2449143-1-colin.foster@in-advantage.com/

So I would like to keep this code structure, so the rework needed when
that driver will need PTP support will be minimal (answer "yes, I need
deferred context for this skb's RX timestamp", then the partial
timestamp will still be found in the skb-&gt;cb.

Fixes: ea440cd2d9b2 ("net: dsa: tag_ocelot: use VLAN information from tagging header when available")
Reported-by: Po Liu &lt;po.liu@nxp.com&gt;
Cc: Yangbo Lu &lt;yangbo.lu@nxp.com&gt;
Signed-off-by: Vladimir Oltean &lt;vladimir.oltean@nxp.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
</entry>
<entry>
<title>net: dsa: tag_ocelot_8021q: break circular dependency with ocelot switch lib</title>
<updated>2021-10-13T00:35:18Z</updated>
<author>
<name>Vladimir Oltean</name>
<email>vladimir.oltean@nxp.com</email>
</author>
<published>2021-10-12T11:40:41Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=49f885b2d97093451410e7279aa29d81e094e108'/>
<id>urn:sha1:49f885b2d97093451410e7279aa29d81e094e108</id>
<content type='text'>
Michael reported that when using the "ocelot-8021q" tagging protocol,
the switch driver module must be manually loaded before the tagging
protocol can be loaded/is available.

This appears to be the same problem described here:
https://lore.kernel.org/netdev/20210908220834.d7gmtnwrorhharna@skbuf/
where due to the fact that DSA tagging protocols make use of symbols
exported by the switch drivers, circular dependencies appear and this
breaks module autoloading.

The ocelot_8021q driver needs the ocelot_can_inject() and
ocelot_port_inject_frame() functions from the switch library. Previously
the wrong approach was taken to solve that dependency: shims were
provided for the case where the ocelot switch library was compiled out,
but that turns out to be insufficient, because the dependency when the
switch lib _is_ compiled is problematic too.

We cannot declare ocelot_can_inject() and ocelot_port_inject_frame() as
static inline functions, because these access I/O functions like
__ocelot_write_ix() which is called by ocelot_write_rix(). Making those
static inline basically means exposing the whole guts of the ocelot
switch library, not ideal...

We already have one tagging protocol driver which calls into the switch
driver during xmit but not using any exported symbol: sja1105_defer_xmit.
We can do the same thing here: create a kthread worker and one work item
per skb, and let the switch driver itself do the register accesses to
send the skb, and then consume it.

Fixes: 0a6f17c6ae21 ("net: dsa: tag_ocelot_8021q: add support for PTP timestamping")
Reported-by: Michael Walle &lt;michael@walle.cc&gt;
Signed-off-by: Vladimir Oltean &lt;vladimir.oltean@nxp.com&gt;
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
</content>
</entry>
<entry>
<title>net: dsa: tag_ocelot: break circular dependency with ocelot switch lib driver</title>
<updated>2021-10-13T00:35:18Z</updated>
<author>
<name>Vladimir Oltean</name>
<email>vladimir.oltean@nxp.com</email>
</author>
<published>2021-10-12T11:40:40Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=deab6b1cd9789bb9bd466d5e76aecb8b336259b4'/>
<id>urn:sha1:deab6b1cd9789bb9bd466d5e76aecb8b336259b4</id>
<content type='text'>
As explained here:
https://lore.kernel.org/netdev/20210908220834.d7gmtnwrorhharna@skbuf/
DSA tagging protocol drivers cannot depend on symbols exported by switch
drivers, because this creates a circular dependency that breaks module
autoloading.

The tag_ocelot.c file depends on the ocelot_ptp_rew_op() function
exported by the common ocelot switch lib. This function looks at
OCELOT_SKB_CB(skb) and computes how to populate the REW_OP field of the
DSA tag, for PTP timestamping (the command: one-step/two-step, and the
TX timestamp identifier).

None of that requires deep insight into the driver, it is quite
stateless, as it only depends upon the skb-&gt;cb. So let's make it a
static inline function and put it in include/linux/dsa/ocelot.h, a
file that despite its name is used by the ocelot switch driver for
populating the injection header too - since commit 40d3f295b5fe ("net:
mscc: ocelot: use common tag parsing code with DSA").

With that function declared as static inline, its body is expanded
inside each call site, so the dependency is broken and the DSA tagger
can be built without the switch library, upon which the felix driver
depends.

Fixes: 39e5308b3250 ("net: mscc: ocelot: support PTP Sync one-step timestamping")
Signed-off-by: Vladimir Oltean &lt;vladimir.oltean@nxp.com&gt;
Reviewed-by: Florian Fainelli &lt;f.fainelli@gmail.com&gt;
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
</content>
</entry>
<entry>
<title>net: dsa: sja1105: break dependency between dsa_port_is_sja1105 and switch driver</title>
<updated>2021-10-13T00:33:36Z</updated>
<author>
<name>Vladimir Oltean</name>
<email>vladimir.oltean@nxp.com</email>
</author>
<published>2021-09-22T14:37:26Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=4ac0567e40b334b54988e3c28a2425ff9c8bdd35'/>
<id>urn:sha1:4ac0567e40b334b54988e3c28a2425ff9c8bdd35</id>
<content type='text'>
It's nice to be able to test a tagging protocol with dsa_loop, but not
at the cost of losing the ability of building the tagging protocol and
switch driver as modules, because as things stand, there is a circular
dependency between the two. Tagging protocol drivers cannot depend on
switch drivers, that is a hard fact.

The reasoning behind the blamed patch was that accessing dp-&gt;priv should
first make sure that the structure behind that pointer is what we really
think it is.

Currently the "sja1105" and "sja1110" tagging protocols only operate
with the sja1105 switch driver, just like any other tagging protocol and
switch combination. The only way to mix and match them is by modifying
the code, and this applies to dsa_loop as well (by default that uses
DSA_TAG_PROTO_NONE). So while in principle there is an issue, in
practice there isn't one.

Until we extend dsa_loop to allow user space configuration, treat the
problem as a non-issue and just say that DSA ports found by tag_sja1105
are always sja1105 ports, which is in fact true. But keep the
dsa_port_is_sja1105 function so that it's easy to patch it during
testing, and rely on dead code elimination.

Fixes: 994d2cbb08ca ("net: dsa: tag_sja1105: be dsa_loop-safe")
Link: https://lore.kernel.org/netdev/20210908220834.d7gmtnwrorhharna@skbuf/
Signed-off-by: Vladimir Oltean &lt;vladimir.oltean@nxp.com&gt;
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
</content>
</entry>
<entry>
<title>net: dsa: move sja1110_process_meta_tstamp inside the tagging protocol driver</title>
<updated>2021-10-13T00:33:36Z</updated>
<author>
<name>Vladimir Oltean</name>
<email>vladimir.oltean@nxp.com</email>
</author>
<published>2021-09-22T14:37:25Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=28da0555c3b542d605e4ca26eea6a740cf2c9174'/>
<id>urn:sha1:28da0555c3b542d605e4ca26eea6a740cf2c9174</id>
<content type='text'>
The problem is that DSA tagging protocols really must not depend on the
switch driver, because this creates a circular dependency at insmod
time, and the switch driver will effectively not load when the tagging
protocol driver is missing.

The code was structured in the way it was for a reason, though. The DSA
driver-facing API for PTP timestamping relies on the assumption that
two-step TX timestamps are provided by the hardware in an out-of-band
manner, typically by raising an interrupt and making that timestamp
available inside some sort of FIFO which is to be accessed over
SPI/MDIO/etc.

So the API puts .port_txtstamp into dsa_switch_ops, because it is
expected that the switch driver needs to save some state (like put the
skb into a queue until its TX timestamp arrives).

On SJA1110, TX timestamps are provided by the switch as Ethernet
packets, so this makes them be received and processed by the tagging
protocol driver. This in itself is great, because the timestamps are
full 64-bit and do not require reconstruction, and since Ethernet is the
fastest I/O method available to/from the switch, PTP timestamps arrive
very quickly, no matter how bottlenecked the SPI connection is, because
SPI interaction is not needed at all.

DSA's code structure and strict isolation between the tagging protocol
driver and the switch driver break the natural code organization.

When the tagging protocol driver receives a packet which is classified
as a metadata packet containing timestamps, it passes those timestamps
one by one to the switch driver, which then proceeds to compare them
based on the recorded timestamp ID that was generated in .port_txtstamp.

The communication between the tagging protocol and the switch driver is
done through a method exported by the switch driver, sja1110_process_meta_tstamp.
To satisfy build requirements, we force a dependency to build the
tagging protocol driver as a module when the switch driver is a module.
However, as explained in the first paragraph, that causes the circular
dependency.

To solve this, move the skb queue from struct sja1105_private :: struct
sja1105_ptp_data to struct sja1105_private :: struct sja1105_tagger_data.
The latter is a data structure for which hacks have already been put
into place to be able to create persistent storage per switch that is
accessible from the tagging protocol driver (see sja1105_setup_ports).

With the skb queue directly accessible from the tagging protocol driver,
we can now move sja1110_process_meta_tstamp into the tagging driver
itself, and avoid exporting a symbol.

Fixes: 566b18c8b752 ("net: dsa: sja1105: implement TX timestamping for SJA1110")
Link: https://lore.kernel.org/netdev/20210908220834.d7gmtnwrorhharna@skbuf/
Signed-off-by: Vladimir Oltean &lt;vladimir.oltean@nxp.com&gt;
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
</content>
</entry>
<entry>
<title>net: dsa: mv88e6xxx: isolate the ATU databases of standalone and bridged ports</title>
<updated>2021-10-08T22:47:46Z</updated>
<author>
<name>Vladimir Oltean</name>
<email>vladimir.oltean@nxp.com</email>
</author>
<published>2021-10-07T16:47:11Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=5bded8259ee3815a91791462dfb3312480779c3d'/>
<id>urn:sha1:5bded8259ee3815a91791462dfb3312480779c3d</id>
<content type='text'>
Similar to commit 6087175b7991 ("net: dsa: mt7530: use independent VLAN
learning on VLAN-unaware bridges"), software forwarding between an
unoffloaded LAG port (a bonding interface with an unsupported policy)
and a mv88e6xxx user port directly under a bridge is broken.

We adopt the same strategy, which is to make the standalone ports not
find any ATU entry learned on a bridge port.

Theory: the mv88e6xxx ATU is looked up by FID and MAC address. There are
as many FIDs as VIDs (4096). The FID is derived from the VID when
possible (the VTU maps a VID to a FID), with a fallback to the port
based default FID value when not (802.1Q Mode is disabled on the port,
or the classified VID isn't present in the VTU).

The mv88e6xxx driver makes the following use of FIDs and VIDs:

- the port's DefaultVID (to which untagged &amp; pvid-tagged packets get
  classified) is 0 and is absent from the VTU, so this kind of packets is
  processed in FID 0, the default FID assigned by mv88e6xxx_setup_port.

- every time a bridge VLAN is created, mv88e6xxx_port_vlan_join() -&gt;
  mv88e6xxx_atu_new() associates a FID with that VID which increases
  linearly starting from 1. Like this:

  bridge vlan add dev lan0 vid 100 # FID 1
  bridge vlan add dev lan1 vid 100 # still FID 1
  bridge vlan add dev lan2 vid 1024 # FID 2

The FID allocation made by the driver is sub-optimal for the following
reasons:

(a) A standalone port has a DefaultPVID of 0 and a default FID of 0 too.
    A VLAN-unaware bridged port has a DefaultPVID of 0 and a default FID
    of 0 too. The difference is that the bridged ports may learn ATU
    entries, while the standalone port has the requirement that it must
    not, and must not find them either. Standalone ports must not use
    the same FID as ports belonging to a bridge. All standalone ports
    can use the same FID, since the ATU will never have an entry in
    that FID.

(b) Multiple VLAN-unaware bridges will all use a DefaultPVID of 0 and a
    default FID of 0 on all their ports. The FDBs will not be isolated
    between these bridges. Every VLAN-unaware bridge must use the same
    FID on all its ports, different from the FID of other bridge ports.

(c) Each bridge VLAN uses a unique FID which is useful for Independent
    VLAN Learning, but the same VLAN ID on multiple VLAN-aware bridges
    will result in the same FID being used by mv88e6xxx_atu_new().
    The correct behavior is for VLAN 1 in br0 to have a different FID
    compared to VLAN 1 in br1.

This patch cannot fix all the above. Traditionally the DSA framework did
not care about this, and the reality is that DSA core involvement is
needed for the aforementioned issues to be solved. The only thing we can
solve here is an issue which does not require API changes, and that is
issue (a), aka use a different FID for standalone ports vs ports under
VLAN-unaware bridges.

The first step is deciding what VID and FID to use for standalone ports,
and what VID and FID for bridged ports. The 0/0 pair for standalone
ports is what they used up till now, let's keep using that. For bridged
ports, there are 2 cases:

- VLAN-aware ports will never end up using the port default FID, because
  packets will always be classified to a VID in the VTU or dropped
  otherwise. The FID is the one associated with the VID in the VTU.

- On VLAN-unaware ports, we _could_ leave their DefaultVID (pvid) at
  zero (just as in the case of standalone ports), and just change the
  port's default FID from 0 to a different number (say 1).

However, Tobias points out that there is one more requirement to cater to:
cross-chip bridging. The Marvell DSA header does not carry the FID in
it, only the VID. So once a packet crosses a DSA link, if it has a VID
of zero it will get classified to the default FID of that cascade port.
Relying on a port default FID for upstream cascade ports results in
contradictions: a default FID of 0 breaks ATU isolation of bridged ports
on the downstream switch, a default FID of 1 breaks standalone ports on
the downstream switch.

So not only must standalone ports have different FIDs compared to
bridged ports, they must also have different DefaultVID values.
IEEE 802.1Q defines two reserved VID values: 0 and 4095. So we simply
choose 4095 as the DefaultVID of ports belonging to VLAN-unaware
bridges, and VID 4095 maps to FID 1.

For the xmit operation to look up the same ATU database, we need to put
VID 4095 in DSA tags sent to ports belonging to VLAN-unaware bridges
too. All shared ports are configured to map this VID to the bridging
FID, because they are members of that VLAN in the VTU. Shared ports
don't need to have 802.1QMode enabled in any way, they always parse the
VID from the DSA header, they don't need to look at the 802.1Q header.

We install VID 4095 to the VTU in mv88e6xxx_setup_port(), with the
mention that mv88e6xxx_vtu_setup() which was located right below that
call was flushing the VTU so those entries wouldn't be preserved.
So we need to relocate the VTU flushing prior to the port initialization
during -&gt;setup(). Also note that this is why it is safe to assume that
VID 4095 will get associated with FID 1: the user ports haven't been
created, so there is no avenue for the user to create a bridge VLAN
which could otherwise race with the creation of another FID which would
otherwise use up the non-reserved FID value of 1.

[ Currently mv88e6xxx_port_vlan_join() doesn't have the option of
  specifying a preferred FID, it always calls mv88e6xxx_atu_new(). ]

mv88e6xxx_port_db_load_purge() is the function to access the ATU for
FDB/MDB entries, and it used to determine the FID to use for
VLAN-unaware FDB entries (VID=0) using mv88e6xxx_port_get_fid().
But the driver only called mv88e6xxx_port_set_fid() once, during probe,
so no surprises, the port FID was always 0, the call to get_fid() was
redundant. As much as I would have wanted to not touch that code, the
logic is broken when we add a new FID which is not the port-based
default. Now the port-based default FID only corresponds to standalone
ports, and FDB/MDB entries belong to the bridging service. So while in
the future, when the DSA API will support FDB isolation, we will have to
figure out the FID based on the bridge number, for now there's a single
bridging FID, so hardcode that.

Lastly, the tagger needs to check, when it is transmitting a VLAN
untagged skb, whether it is sending it towards a bridged or a standalone
port. When we see it is bridged we assume the bridge is VLAN-unaware.
Not because it cannot be VLAN-aware but:

- if we are transmitting from a VLAN-aware bridge we are likely doing so
  using TX forwarding offload. That code path guarantees that skbs have
  a vlan hwaccel tag in them, so we would not enter the "else" branch
  of the "if (skb-&gt;protocol == htons(ETH_P_8021Q))" condition.

- if we are transmitting on behalf of a VLAN-aware bridge but with no TX
  forwarding offload (no PVT support, out of space in the PVT, whatever),
  we would indeed be transmitting with VLAN 4095 instead of the bridge
  device's pvid. However we would be injecting a "From CPU" frame, and
  the switch won't learn from that - it only learns from "Forward" frames.
  So it is inconsequential for address learning. And VLAN 4095 is
  absolutely enough for the frame to exit the switch, since we never
  remove that VLAN from any port.

Fixes: 57e661aae6a8 ("net: dsa: mv88e6xxx: Link aggregation support")
Reported-by: Tobias Waldekranz &lt;tobias@waldekranz.com&gt;
Signed-off-by: Vladimir Oltean &lt;vladimir.oltean@nxp.com&gt;
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
</content>
</entry>
<entry>
<title>net: update NXP copyright text</title>
<updated>2021-09-17T12:52:17Z</updated>
<author>
<name>Vladimir Oltean</name>
<email>vladimir.oltean@nxp.com</email>
</author>
<published>2021-09-17T11:17:35Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=3c9cfb5269f76d447dbadb67835368f3111a91d7'/>
<id>urn:sha1:3c9cfb5269f76d447dbadb67835368f3111a91d7</id>
<content type='text'>
NXP Legal insists that the following are not fine:

- Saying "NXP Semiconductors" instead of "NXP", since the company's
  registered name is "NXP"

- Putting a "(c)" sign in the copyright string

- Putting a comma in the copyright string

The only accepted copyright string format is "Copyright &lt;year-range&gt; NXP".

This patch changes the copyright headers in the networking files that
were sent by me, or derived from code sent by me.

Signed-off-by: Vladimir Oltean &lt;vladimir.oltean@nxp.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
</entry>
<entry>
<title>net: dsa: tag_sja1105: stop asking the sja1105 driver in sja1105_xmit_tpid</title>
<updated>2021-08-25T10:14:34Z</updated>
<author>
<name>Vladimir Oltean</name>
<email>vladimir.oltean@nxp.com</email>
</author>
<published>2021-08-24T17:15:02Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=8ded9160928e545c2e694b77a87263fa078ff4c6'/>
<id>urn:sha1:8ded9160928e545c2e694b77a87263fa078ff4c6</id>
<content type='text'>
Introduced in commit 38b5beeae7a4 ("net: dsa: sja1105: prepare tagger
for handling DSA tags and VLAN simultaneously"), the sja1105_xmit_tpid
function solved quite a different problem than our needs are now.

Then, we used best-effort VLAN filtering and we were using the xmit_tpid
to tunnel packets coming from an 8021q upper through the TX VLAN allocated
by tag_8021q to that egress port. The need for a different VLAN protocol
depending on switch revision came from the fact that this in itself was
more of a hack to trick the hardware into accepting tunneled VLANs in
the first place.

Right now, we deny 8021q uppers (see sja1105_prechangeupper). Even if we
supported them again, we would not do that using the same method of
{tunneling the VLAN on egress, retagging the VLAN on ingress} that we
had in the best-effort VLAN filtering mode. It seems rather simpler that
we just allocate a VLAN in the VLAN table that is simply not used by the
bridge at all, or by any other port.

Anyway, I have 2 gripes with the current sja1105_xmit_tpid:

1. When sending packets on behalf of a VLAN-aware bridge (with the new
   TX forwarding offload framework) plus untagged (with the tag_8021q
   VLAN added by the tagger) packets, we can see that on SJA1105P/Q/R/S
   and later (which have a qinq_tpid of ETH_P_8021AD), some packets sent
   through the DSA master have a VLAN protocol of 0x8100 and others of
   0x88a8. This is strange and there is no reason for it now. If we have
   a bridge and are therefore forced to send using that bridge's TPID,
   we can as well blend with that bridge's VLAN protocol for all packets.

2. The sja1105_xmit_tpid introduces a dependency on the sja1105 driver,
   because it looks inside dp-&gt;priv. It is desirable to keep as much
   separation between taggers and switch drivers as possible. Now it
   doesn't do that anymore.

Signed-off-by: Vladimir Oltean &lt;vladimir.oltean@nxp.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
</entry>
<entry>
<title>net: dsa: sja1105: drop untagged packets on the CPU and DSA ports</title>
<updated>2021-08-25T10:14:33Z</updated>
<author>
<name>Vladimir Oltean</name>
<email>vladimir.oltean@nxp.com</email>
</author>
<published>2021-08-24T17:15:01Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=b0b8c67eaa5c65f8426017e78fcce12dc7d85110'/>
<id>urn:sha1:b0b8c67eaa5c65f8426017e78fcce12dc7d85110</id>
<content type='text'>
The sja1105 driver is a bit special in its use of VLAN headers as DSA
tags. This is because in VLAN-aware mode, the VLAN headers use an actual
TPID of 0x8100, which is understood even by the DSA master as an actual
VLAN header.

Furthermore, control packets such as PTP and STP are transmitted with no
VLAN header as a DSA tag, because, depending on switch generation, there
are ways to steer these control packets towards a precise egress port
other than VLAN tags. Transmitting control packets as untagged means
leaving a door open for traffic in general to be transmitted as untagged
from the DSA master, and for it to traverse the switch and exit a random
switch port according to the FDB lookup.

This behavior is a bit out of line with other DSA drivers which have
native support for DSA tagging. There, it is to be expected that the
switch only accepts DSA-tagged packets on its CPU port, dropping
everything that does not match this pattern.

We perhaps rely a bit too much on the switches' hardware dropping on the
CPU port, and place no other restrictions in the kernel data path to
avoid that. For example, sja1105 is also a bit special in that STP/PTP
packets are transmitted using "management routes"
(sja1105_port_deferred_xmit): when sending a link-local packet from the
CPU, we must first write a SPI message to the switch to tell it to
expect a packet towards multicast MAC DA 01-80-c2-00-00-0e, and to route
it towards port 3 when it gets it. This entry expires as soon as it
matches a packet received by the switch, and it needs to be reinstalled
for the next packet etc. All in all quite a ghetto mechanism, but it is
all that the sja1105 switches offer for injecting a control packet.
The driver takes a mutex for serializing control packets and making the
pairs of SPI writes of a management route and its associated skb atomic,
but to be honest, a mutex is only relevant as long as all parties agree
to take it. With the DSA design, it is possible to open an AF_PACKET
socket on the DSA master net device, and blast packets towards
01-80-c2-00-00-0e, and whatever locking the DSA switch driver might use,
it all goes kaput because management routes installed by the driver will
match skbs sent by the DSA master, and not skbs generated by the driver
itself. So they will end up being routed on the wrong port.

So through the lens of that, maybe it would make sense to avoid that
from happening by doing something in the network stack, like: introduce
a new bit in struct sk_buff, like xmit_from_dsa. Then, somewhere around
dev_hard_start_xmit(), introduce the following check:

	if (netdev_uses_dsa(dev) &amp;&amp; !skb-&gt;xmit_from_dsa)
		kfree_skb(skb);

Ok, maybe that is a bit drastic, but that would at least prevent a bunch
of problems. For example, right now, even though the majority of DSA
switches drop packets without DSA tags sent by the DSA master (and
therefore the majority of garbage that user space daemons like avahi and
udhcpcd and friends create), it is still conceivable that an aggressive
user space program can open an AF_PACKET socket and inject a spoofed DSA
tag directly on the DSA master. We have no protection against that; the
packet will be understood by the switch and be routed wherever user
space says. Furthermore: there are some DSA switches where we even have
register access over Ethernet, using DSA tags. So even user space
drivers are possible in this way. This is a huge hole.

However, the biggest thing that bothers me is that udhcpcd attempts to
ask for an IP address on all interfaces by default, and with sja1105, it
will attempt to get a valid IP address on both the DSA master as well as
on sja1105 switch ports themselves. So with IP addresses in the same
subnet on multiple interfaces, the routing table will be messed up and
the system will be unusable for traffic until it is configured manually
to not ask for an IP address on the DSA master itself.

It turns out that it is possible to avoid that in the sja1105 driver, at
least very superficially, by requesting the switch to drop VLAN-untagged
packets on the CPU port. With the exception of control packets, all
traffic originated from tag_sja1105.c is already VLAN-tagged, so only
STP and PTP packets need to be converted. For that, we need to uphold
the equivalence between an untagged and a pvid-tagged packet, and to
remember that the CPU port of sja1105 uses a pvid of 4095.

Now that we drop untagged traffic on the CPU port, non-aggressive user
space applications like udhcpcd stop bothering us, and sja1105 effectively
becomes just as vulnerable to the aggressive kind of user space programs
as other DSA switches are (ok, users can also create 8021q uppers on top
of the DSA master in the case of sja1105, but in future patches we can
easily deny that, but it still doesn't change the fact that VLAN-tagged
packets can still be injected over raw sockets).

Signed-off-by: Vladimir Oltean &lt;vladimir.oltean@nxp.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
</entry>
<entry>
<title>net: dsa: tag_sja1105: be dsa_loop-safe</title>
<updated>2021-08-18T09:33:15Z</updated>
<author>
<name>Vladimir Oltean</name>
<email>vladimir.oltean@nxp.com</email>
</author>
<published>2021-08-17T14:58:47Z</published>
<link rel='alternate' type='text/html' href='https://git.stealer.net/cgit.cgi/user/sven/linux.git/commit/?id=994d2cbb08ca05e3c1af954ec63a3ae32a862ac5'/>
<id>urn:sha1:994d2cbb08ca05e3c1af954ec63a3ae32a862ac5</id>
<content type='text'>
Add support for tag_sja1105 running on non-sja1105 DSA ports, by making
sure that every time we dereference dp-&gt;priv, we check the switch's
dsa_switch_ops (otherwise we access a struct sja1105_port structure that
is in fact something else).

This adds an unconditional build-time dependency between sja1105 being
built as module =&gt; tag_sja1105 must also be built as module. This was
there only for PTP before.

Some sane defaults must also take place when not running on sja1105
hardware. These are:

- sja1105_xmit_tpid: the sja1105 driver uses different VLAN protocols
  depending on VLAN awareness and switch revision (when an encapsulated
  VLAN must be sent). Default to 0x8100.

- sja1105_rcv_meta_state_machine: this aggregates PTP frames with their
  metadata timestamp frames. When running on non-sja1105 hardware, don't
  do that and accept all frames unmodified.

- sja1105_defer_xmit: calls sja1105_port_deferred_xmit in sja1105_main.c
  which writes a management route over SPI. When not running on sja1105
  hardware, bypass the SPI write and send the frame as-is.

Signed-off-by: Vladimir Oltean &lt;vladimir.oltean@nxp.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
</entry>
</feed>
