Re: [RFC PATCH net-next 0/5] net: allow hw addresses for virtual devices

[Florian Fainelli <f.fainelli@gmail.com>]

On 12/3/18 10:40 AM, Ivan Khoronzhuk wrote:
> One of the reasons of this proposition is safety and performance -
> host should not receive traffic which is not designated for it.
> 
> Some network devices can hold separate address tables for vlans and
> real device, but for some reason there is no possibility to apply it
> with generic net addressing scheme easily. At this moment the fastest
> solution is to add mcast/ucast entries for every created vlan
> including real device. But it also adds holes in the filtering and
> thus wastes cpus cycles.
> 
> This patchseries tries to correct core to assign mcast and ucast
> addresses only for vlans that really require it and as result an end
> driver can exclusively and simply set its rx filters. As an example
> it's implemented on cpsw TI driver, but generic changes provided by
> this series can be reused by other ethernet drivers having similar
> rx filter address possibilities.
> 
> An address+vid is considered as separate address. The reserved device
> address length is 32 Bytes, for ethernet devices it's additional
> opportunity to pass auxiliary address info, like virtual ID
> identifying a device the address belongs to. This series makes it
> possible at least for ETH_P_8021Q, but can be easily extended for ab.
> Thus end real device can setup separate tables for virtual devices
> just retrieving VID from the address. A device address space can
> maintain addresses and references on them separately for each virtual
> device if it needs so, or only addresses for real device (and all its
> vlans) it holds usually.
> 
> A vlan device can be in any place of device chain upper real device,
> say smth like rdevice/bonding/vlan or even rdevice/macvlan/vlan.
> Similar approach can be used for passing additional information for
> virtual devices as allmulti flag or/and promisc flag and do this per
> vlan, but this is separate story and could be added as a continuation.
> 
> I was biased by try to add exclusive mcast and ucast support for vlans
> and now have same with small generic correction and mostly locally in
> the cpsw driver:
> https://git.linaro.org/people/ivan.khoronzhuk/tsn_kernel.git/log/?h=ucast_vlan_fix
> https://git.linaro.org/people/ivan.khoronzhuk/tsn_kernel.git/log/?h=mcast_vlan
> and can say it looks better with generic changes provided by this patchset,
> that's why this RFC. Above links can be used as fallback.
> 
> This series is verified on TI am572x EVM that can hold separate tables
> for vlans. Potentially it can be easily extended to netcp driver for
> keystone 2 boards (including k2g) and also new am6 chipsets. As a
> simple test case, different combinations of vlan+macvlan, macvlan+vlan
> were used and tested as with unicast as multicast addresses.

I think I get what you want to do, which is make sure that on per VID
basis, only the necessary UC and MC addresses are programmed into the
respective filters, when each of your network ports operate in what cpsw
calls "dual emac"? Which is really something that should be called "NIC"
mode, and/or is analogous to how we bring up ports in DSA: each of them
acts as a separate network device. Speaking of the later, we have some
known issues in unmanaged mode with MC addresses which I am working on
addressing.

It seems to me, as replied in patch 2, that what you are missing is the
source of the address programming request, and therefore either you pass
an additional "source net_device" to functions like dev_{uc,mc}_sync(),
or you pass a well defined structured that can encode the address as
well as the interface type, but the approach you have right now, where
the address storage is extended to include the VID is both extremely
specific to VLAN devices, as well as not scaling particularly well. With
your patches we have VLAN devices covered, but what about MACVLAN, bond,
team or anything that needs to look at specific MAC addresses to be
filtered to make management decisions?

Also imagine being able to store up to 4K MAC addresses for a total of
4K VLANs, this would have occupied 4K * sizeof(some structure) and now
it's 2 bytes bigger...

> 
> Based on net-next/master
> 
> Ivan Khoronzhuk (5):
>   net: core: dev_addr_lists: add VID to device address space
>   net: 8021q: vlan_dev: add vid tag for uc and mc address lists
>   net: 8021q: vlan_dev: add vid tag for vlan device mac address
>   net: ethernet: add default vid len for all ehternet kind devices
>   net: ethernet: ti: cpsw: update mc vlan and add uc vlan support based
>     on addr vids
> 
>  drivers/net/ethernet/ti/cpsw.c |  86 +++++++++++++++++++----
>  include/linux/if_vlan.h        |   1 +
>  include/linux/netdevice.h      |   7 ++
>  net/8021q/vlan.c               |   3 +
>  net/8021q/vlan_core.c          |  10 +++
>  net/8021q/vlan_dev.c           | 103 ++++++++++++++++++++++-----
>  net/core/dev_addr_lists.c      | 124 +++++++++++++++++++++++++++------
>  net/ethernet/eth.c             |  15 +++-
>  8 files changed, 290 insertions(+), 59 deletions(-)
> 


-- 
Florian