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  1. 23 Jul, 2018 4 commits
    • David S. Miller's avatar
      Merge branch 'net-bridge-add-support-for-backup-port' · f8b2990f
      David S. Miller authored 
      Nikolay Aleksandrov says:

====================
net: bridge: add support for backup port

This set introduces a new bridge port option that allows any port to have
any other port (in the same bridge of course) as its backup and traffic
will be forwarded to the backup port when the primary goes down. This is
mainly used in MLAG and EVPN setups where we have peerlink path which is
a backup of many (or even all) ports and is a participating bridge port
itself. There's more detailed information in patch 02. Patch 01 just
prepares the port sysfs code for options that take raw value. The main
issues that this set solves are scalability and fallback latency.

We have used similar code for over 6 months now to bring the fallback
latency of the backup peerlink down and avoid fdb notification storms.
Also due to the nature of master devices such setup is currently not
possible, and last but not least having tens of thousands of fdbs require
thousands of calls to switch.

I've also CCed our MLAG experts that have been using similar option.

Roopa also adds:

"Two switches acting in a MLAG pair are connected by the peerlink
interface which is a bridge port.

the config on one of the switches looks like the below. The other
switch also has a similar config.
eth0 is connected to one port on the server. And the server is
connected to both switches.

br0 -- team0---eth0
      |
      -- switch-peerlink

switch-peerlink becomes the failover/backport port when say team0 to
the server goes down.
Today, when team0 goes down, control plane has to withdraw all the fdb
entries pointing to team0
and re-install the fdb entries pointing to switch-peerlink...and
restore the fdb entries when team0 comes back up again.
and  this is the problem we are trying to solve.

This also becomes necessary when multihoming is implemented by a
standard like E-VPN https://tools.ietf.org/html/rfc8365#section-8
where the 'switch-peerlink' is an overlay vxlan port (like nikolay
mentions in his patch commit). In these implementations, the fdb scale
can be much larger.

On why bond failover cannot be used here ?: the point that nikolay was
alluding to is, switch-peerlink in the above example is a bridge port
and is a failover/backport port for more than one or all ports in the
bridge br0. And you cannot enslave switch-peerlink into a second level
team
with other bridge ports. Hence a multi layered team device is not an
option (FWIW, switch-peerlink is also a teamed interface to the peer
switch)."

v3: Added Roopa's explanation and diagram
v2: In patch 01 use kstrdup/kfree to avoid casting the const buf. In order
to avoid using GFP_ATOMIC or always allocating I kept the spinlock inside
each branch.
====================
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      f8b2990f
    • Nikolay Aleksandrov's avatar
      net: bridge: add support for backup port · 2756f68c
      Nikolay Aleksandrov authored 
      This patch adds a new port attribute - IFLA_BRPORT_BACKUP_PORT, which
allows to set a backup port to be used for known unicast traffic if the
port has gone carrier down. The backup pointer is rcu protected and set
only under RTNL, a counter is maintained so when deleting a port we know
how many other ports reference it as a backup and we remove it from all.
Also the pointer is in the first cache line which is hot at the time of
the check and thus in the common case we only add one more test.
The backup port will be used only for the non-flooding case since
it's a part of the bridge and the flooded packets will be forwarded to it
anyway. To remove the forwarding just send a 0/non-existing backup port.
This is used to avoid numerous scalability problems when using MLAG most
notably if we have thousands of fdbs one would need to change all of them
on port carrier going down which takes too long and causes a storm of fdb
notifications (and again when the port comes back up). In a Multi-chassis
Link Aggregation setup usually hosts are connected to two different
switches which act as a single logical switch. Those switches usually have
a control and backup link between them called peerlink which might be used
for communication in case a host loses connectivity to one of them.
We need a fast way to failover in case a host port goes down and currently
none of the solutions (like bond) cannot fulfill the requirements because
the participating ports are actually the "master" devices and must have the
same peerlink as their backup interface and at the same time all of them
must participate in the bridge device. As Roopa noted it's normal practice
in routing called fast re-route where a precalculated backup path is used
when the main one is down.
Another use case of this is with EVPN, having a single vxlan device which
is backup of every port. Due to the nature of master devices it's not
currently possible to use one device as a backup for many and still have
all of them participate in the bridge (which is master itself).
More detailed information about MLAG is available at the link below.
https://docs.cumulusnetworks.com/display/DOCS/Multi-Chassis+Link+Aggregation+-+MLAG

Further explanation and a diagram by Roopa:
Two switches acting in a MLAG pair are connected by the peerlink
interface which is a bridge port.

the config on one of the switches looks like the below. The other
switch also has a similar config.
eth0 is connected to one port on the server. And the server is
connected to both switches.

br0 -- team0---eth0
      |
      -- switch-peerlink
Signed-off-by: default avatarNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      2756f68c
    • Nikolay Aleksandrov's avatar
      net: bridge: add support for raw sysfs port options · a5f3ea54
      Nikolay Aleksandrov authored 
      This patch adds a new alternative store callback for port sysfs options
which takes a raw value (buf) and can use it directly. It is needed for the
backup port sysfs support since we have to pass the device by its name.
Signed-off-by: default avatarNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      a5f3ea54
    • YueHaibing's avatar
      net: mediatek: use dma_zalloc_coherent instead of allocator/memset · 0a78c380
      YueHaibing authored 
      Use dma_zalloc_coherent instead of dma_alloc_coherent
followed by memset 0.
Signed-off-by: default avatarYueHaibing <yuehaibing@huawei.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      0a78c380
  3. 22 Jul, 2018 18 commits
  5. 21 Jul, 2018 18 commits
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