linux.git/net/dsa, branch v6.4-rc2

net: dsa: tag_ocelot: call only the relevant portion of __skb_vlan_pop() on TX

2023-04-23T13:16:45+00:00

ocelot_xmit_get_vlan_info() calls __skb_vlan_pop() as the most
appropriate helper I could find which strips away a VLAN header.
That's all I need it to do, but __skb_vlan_pop() has more logic, which
will become incompatible with the future revert of commit 6d1ccff62780
("net: reset mac header in dev_start_xmit()").

Namely, it performs a sanity check on skb_mac_header(), which will stop
being set after the above revert, so it will return an error instead of
removing the VLAN tag.

ocelot_xmit_get_vlan_info() gets called in 2 circumstances:

(1) the port is under a VLAN-aware bridge and the bridge sends
    VLAN-tagged packets

(2) the port is under a VLAN-aware bridge and somebody else (an 8021q
    upper) sends VLAN-tagged packets (using a VID that isn't in the
    bridge vlan tables)

In case (1), there is actually no bug to defend against, because
br_dev_xmit() calls skb_reset_mac_header() and things continue to work.

However, in case (2), illustrated using the commands below, it can be
seen that our intervention is needed, since __skb_vlan_pop() complains:

$ ip link add br0 type bridge vlan_filtering 1 && ip link set br0 up
$ ip link set $eth master br0 && ip link set $eth up
$ ip link add link $eth name $eth.100 type vlan id 100 && ip link set $eth.100 up
$ ip addr add 192.168.100.1/24 dev $eth.100

I could fend off the checks in __skb_vlan_pop() with some
skb_mac_header_was_set() calls, but seeing how few callers of
__skb_vlan_pop() there are from TX paths, that seems rather
unproductive.

As an alternative solution, extract the bare minimum logic to strip a
VLAN header, and move it to a new helper named vlan_remove_tag(), close
to the definition of vlan_insert_tag(). Document it appropriately and
make ocelot_xmit_get_vlan_info() call this smaller helper instead.

Seeing that it doesn't appear illegal to test skb->protocol in the TX
path, I guess it would be a good for vlan_remove_tag() to also absorb
the vlan_set_encap_proto() function call.

Signed-off-by: Vladimir Oltean 
Reviewed-by: Simon Horman 
Reviewed-by: Florian Fainelli 
Reviewed-by: Eric Dumazet 
Signed-off-by: David S. Miller

net: dsa: update TX path comments to not mention skb_mac_header()

2023-04-23T13:16:45+00:00

Once commit 6d1ccff62780 ("net: reset mac header in dev_start_xmit()")
will be reverted, it will no longer be true that skb->data points at
skb_mac_header(skb) - since the skb->mac_header will not be set - so
stop saying that, and just say that it points to the MAC header.

I've reviewed vlan_insert_tag() and it does not *actually* depend on
skb_mac_header(), so reword that to avoid the confusion.

Signed-off-by: Vladimir Oltean 
Reviewed-by: Eric Dumazet 
Reviewed-by: Simon Horman 
Reviewed-by: Florian Fainelli 
Signed-off-by: David S. Miller

net: dsa: tag_sja1105: replace skb_mac_header() with vlan_eth_hdr()

2023-04-23T13:16:44+00:00

This is a cosmetic patch which consolidates the code to use the helper
function offered by if_vlan.h.

Signed-off-by: Vladimir Oltean 
Reviewed-by: Eric Dumazet 
Reviewed-by: Simon Horman 
Reviewed-by: Florian Fainelli 
Signed-off-by: David S. Miller

net: dsa: tag_sja1105: don't rely on skb_mac_header() in TX paths

2023-04-23T13:16:44+00:00

skb_mac_header() will no longer be available in the TX path when
reverting commit 6d1ccff62780 ("net: reset mac header in
dev_start_xmit()"). As preparation for that, let's use
skb_vlan_eth_hdr() to get to the VLAN header instead, which assumes it's
located at skb->data (assumption which holds true here).

Signed-off-by: Vladimir Oltean 
Reviewed-by: Eric Dumazet 
Reviewed-by: Simon Horman 
Reviewed-by: Florian Fainelli 
Signed-off-by: David S. Miller

net: dsa: tag_ksz: do not rely on skb_mac_header() in TX paths

2023-04-23T13:16:44+00:00

skb_mac_header() will no longer be available in the TX path when
reverting commit 6d1ccff62780 ("net: reset mac header in
dev_start_xmit()"). As preparation for that, let's use skb_eth_hdr() to
get to the Ethernet header's MAC DA instead, helper which assumes this
header is located at skb->data (assumption which holds true here).

Signed-off-by: Vladimir Oltean 
Reviewed-by: Eric Dumazet 
Reviewed-by: Simon Horman 
Reviewed-by: Florian Fainelli 
Signed-off-by: David S. Miller

net: dsa: tag_ocelot: do not rely on skb_mac_header() for VLAN xmit

2023-04-23T13:16:44+00:00

skb_mac_header() will no longer be available in the TX path when
reverting commit 6d1ccff62780 ("net: reset mac header in
dev_start_xmit()"). As preparation for that, let's use
skb_vlan_eth_hdr() to get to the VLAN header instead, which assumes it's
located at skb->data (assumption which holds true here).

Signed-off-by: Vladimir Oltean 
Reviewed-by: Eric Dumazet 
Reviewed-by: Simon Horman 
Reviewed-by: Florian Fainelli 
Signed-off-by: David S. Miller

net: dsa: add trace points for VLAN operations

2023-04-12T07:36:07+00:00

These are not as critical as the FDB/MDB trace points (I'm not aware of
outstanding VLAN related bugs), but maybe they are useful to somebody,
either debugging something or simply trying to learn more.

Signed-off-by: Vladimir Oltean 
Signed-off-by: David S. Miller

net: dsa: add trace points for FDB/MDB operations

2023-04-12T07:36:07+00:00

DSA performs non-trivial housekeeping of unicast and multicast addresses
on shared (CPU and DSA) ports, and puts a bit of pressure on higher
layers, requiring them to behave correctly (remove these addresses
exactly as many times as they were added). Otherwise, either addresses
linger around forever, or DSA returns -ENOENT complaining that entries
that were already deleted must be deleted again.

To aid debugging, introduce some trace points specifically for FDB and
MDB - that's where some of the bugs still are right now.

Some bugs I have seen were also due to race conditions, see:
- 630fd4822af2 ("net: dsa: flush switchdev workqueue on bridge join error path")
- a2614140dc0f ("net: dsa: mv88e6xxx: flush switchdev FDB workqueue before removing VLAN")

so it would be good to not disturb the timing too much, hence the choice
to use trace points vs regular dev_dbg().

I've had these for some time on my computer in a less polished form, and
they've proven useful. What I found most useful was to enable
CONFIG_BOOTTIME_TRACING, add "trace_event=dsa" to the kernel cmdline,
and run "cat /sys/kernel/debug/tracing/trace". This is to debug more
complex environments with network managers started by the init system,
things like that.

Signed-off-by: Vladimir Oltean 
Signed-off-by: David S. Miller

net: dsa: replace NETDEV_PRE_CHANGE_HWTSTAMP notifier with a stub

2023-04-09T14:35:49+00:00

There was a sort of rush surrounding commit 88c0a6b503b7 ("net: create a
netdev notifier for DSA to reject PTP on DSA master"), due to a desire
to convert DSA's attempt to deny TX timestamping on a DSA master to
something that doesn't block the kernel-wide API conversion from
ndo_eth_ioctl() to ndo_hwtstamp_set().

What was required was a mechanism that did not depend on ndo_eth_ioctl(),
and what was provided was a mechanism that did not depend on
ndo_eth_ioctl(), while at the same time introducing something that
wasn't absolutely necessary - a new netdev notifier.

There have been objections from Jakub Kicinski that using notifiers in
general when they are not absolutely necessary creates complications to
the control flow and difficulties to maintainers who look at the code.
So there is a desire to not use notifiers.

In addition to that, the notifier chain gets called even if there is no
DSA in the system and no one is interested in applying any restriction.

Take the model of udp_tunnel_nic_ops and introduce a stub mechanism,
through which net/core/dev_ioctl.c can call into DSA even when
CONFIG_NET_DSA=m.

Compared to the code that existed prior to the notifier conversion, aka
what was added in commits:
- 4cfab3566710 ("net: dsa: Add wrappers for overloaded ndo_ops")
- 3369afba1e46 ("net: Call into DSA netdevice_ops wrappers")

this is different because we are not overloading any struct
net_device_ops of the DSA master anymore, but rather, we are exposing a
rather specific functionality which is orthogonal to which API is used
to enable it - ndo_eth_ioctl() or ndo_hwtstamp_set().

Also, what is similar is that both approaches use function pointers to
get from built-in code to DSA.

There is no point in replicating the function pointers towards
__dsa_master_hwtstamp_validate() once for every CPU port (dev->dsa_ptr).
Instead, it is sufficient to introduce a singleton struct dsa_stubs,
built into the kernel, which contains a single function pointer to
__dsa_master_hwtstamp_validate().

I find this approach preferable to what we had originally, because
dev->dsa_ptr->netdev_ops->ndo_do_ioctl() used to require going through
struct dsa_port (dev->dsa_ptr), and so, this was incompatible with any
attempts to add any data encapsulation and hide DSA data structures from
the outside world.

Link: https://lore.kernel.org/netdev/20230403083019.120b72fd@kernel.org/
Signed-off-by: Vladimir Oltean 
Reviewed-by: Florian Fainelli 
Signed-off-by: David S. Miller

net: create a netdev notifier for DSA to reject PTP on DSA master

2023-04-03T09:04:27+00:00

The fact that PTP 2-step TX timestamping is broken on DSA switches if
the master also timestamps the same packets is documented by commit
f685e609a301 ("net: dsa: Deny PTP on master if switch supports it").
We attempt to help the users avoid shooting themselves in the foot by
making DSA reject the timestamping ioctls on an interface that is a DSA
master, and the switch tree beneath it contains switches which are aware
of PTP.

The only problem is that there isn't an established way of intercepting
ndo_eth_ioctl calls, so DSA creates avoidable burden upon the network
stack by creating a struct dsa_netdevice_ops with overlaid function
pointers that are manually checked from the relevant call sites. There
used to be 2 such dsa_netdevice_ops, but now, ndo_eth_ioctl is the only
one left.

There is an ongoing effort to migrate driver-visible hardware timestamping
control from the ndo_eth_ioctl() based API to a new ndo_hwtstamp_set()
model, but DSA actively prevents that migration, since dsa_master_ioctl()
is currently coded to manually call the master's legacy ndo_eth_ioctl(),
and so, whenever a network device driver would be converted to the new
API, DSA's restrictions would be circumvented, because any device could
be used as a DSA master.

The established way for unrelated modules to react on a net device event
is via netdevice notifiers. So we create a new notifier which gets
called whenever there is an attempt to change hardware timestamping
settings on a device.

Finally, there is another reason why a netdev notifier will be a good
idea, besides strictly DSA, and this has to do with PHY timestamping.

With ndo_eth_ioctl(), all MAC drivers must manually call
phy_has_hwtstamp() before deciding whether to act upon SIOCSHWTSTAMP,
otherwise they must pass this ioctl to the PHY driver via
phy_mii_ioctl().

With the new ndo_hwtstamp_set() API, it will be desirable to simply not
make any calls into the MAC device driver when timestamping should be
performed at the PHY level.

But there exist drivers, such as the lan966x switch, which need to
install packet traps for PTP regardless of whether they are the layer
that provides the hardware timestamps, or the PHY is. That would be
impossible to support with the new API.

The proposal there, too, is to introduce a netdev notifier which acts as
a better cue for switching drivers to add or remove PTP packet traps,
than ndo_hwtstamp_set(). The one introduced here "almost" works there as
well, except for the fact that packet traps should only be installed if
the PHY driver succeeded to enable hardware timestamping, whereas here,
we need to deny hardware timestamping on the DSA master before it
actually gets enabled. This is why this notifier is called "PRE_", and
the notifier that would get used for PHY timestamping and packet traps
would be called NETDEV_CHANGE_HWTSTAMP. This isn't a new concept, for
example NETDEV_CHANGEUPPER and NETDEV_PRECHANGEUPPER do the same thing.

In expectation of future netlink UAPI, we also pass a non-NULL extack
pointer to the netdev notifier, and we make DSA populate it with an
informative reason for the rejection. To avoid making it go to waste, we
make the ioctl-based dev_set_hwtstamp() create a fake extack and print
the message to the kernel log.

Link: https://lore.kernel.org/netdev/20230401191215.tvveoi3lkawgg6g4@skbuf/
Link: https://lore.kernel.org/netdev/20230310164451.ls7bbs6pdzs4m6pw@skbuf/
Signed-off-by: Vladimir Oltean 
Reviewed-by: Florian Fainelli 
Signed-off-by: David S. Miller