From: sfeldma@gmail.com
To: netdev@vger.kernel.org
Cc: jiri@resnulli.us, simon.horman@netronome.com,
roopa@cumulusnetworks.com, ronen.arad@intel.com,
john.r.fastabend@intel.com, andrew@lunn.ch, f.fainelli@gmail.com,
linux@roeck-us.net, davidch@broadcom.com,
stephen@networkplumber.org
Subject: [RFC PATCH net-next v2 0/5] switchdev: avoid duplicate packet forwarding
Date: Wed, 17 Jun 2015 14:53:09 -0700 [thread overview]
Message-ID: <1434577994-22409-1-git-send-email-sfeldma@gmail.com> (raw)
From: Scott Feldman <sfeldma@gmail.com>
(RFC because we're at rc7+ now)
v2:
- s/fwd_mark/offload_fwd_mark
- use consume_skb rather than kfree_skb when dropping pkt on egress.
- Use Jiri's suggestion to use ifindex of one of the ports in a group
as the mark for all the ports in the group. This can be done with
no additional storage (no hashtable from v1). To pull it off, we
need some simple recursive routines to walk the netdev tree ensuring
all leaves in the tree (ports) in the same group (e.g. bridge)
belonging to the same switch device will have the same offload fwd mark.
Maybe someone sees a better design for the recusive routines? They're
not too bad, and should cover the stacked driver cases.
v1:
With switchdev support for offloading L2/L3 forwarding data path to a
switch device, we have a general problem where both the device and the
kernel may forward the packet, resulting in duplicate packets on the wire.
Anytime a packet is forwarded by the device and a copy is sent to the CPU,
there is potential for duplicate forwarding, as the kernel may also do a
forwarding lookup and send the packet on the wire.
The specific problem this patch series is interested in solving is avoiding
duplicate packets on bridged ports. There was a previous RFC from Roopa
(http://marc.info/?l=linux-netdev&m=142687073314252&w=2) to address this
problem, but didn't solve the problem of mixed ports in the bridge from
different devices; there was no way to exclude some ports from forwarding
and include others. This RFC solves that problem by tagging the ingressing
packet with a unique mark, and then comparing the packet mark with the
egress port mark, and skip forwarding when there is a match. For the mixed
ports bridge case, only those ports with matching marks are skipped.
The switchdev port driver must do two things:
1) Generate a fwd_mark for each switch port, using some unique key of the
switch device (and optionally port). This is done when the port netdev
is registered or if the port's group membership changes (joins/leaves
a bridge, for example).
2) On packet ingress from port, mark the skb with the ingress port's
fwd_mark. If the device supports it, it's useful to only mark skbs
which were already forwarded by the device. If the device does not
support such indication, all skbs can be marked, even if they're
local dst.
Two new 32-bit fields are added to struct sk_buff and struct netdevice to
hold the fwd_mark. I've wrapped these with CONFIG_NET_SWITCHDEV for now. I
tried using skb->mark for this purpose, but ebtables can overwrite the
skb->mark before the bridge gets it, so that will not work.
In general, this fwd_mark can be used for any case where a packet is
forwarded by the device and a copy is sent to the CPU, to avoid the kernel
re-forwarding the packet. sFlow is another use-case that comes to mind,
but I haven't explored the details.
Scott Feldman (5):
net: don't reforward packets already forwarded by offload device
net: add phys ID compare helper to test if two IDs are the same
switchdev: add offload_fwd_mark generator helper
rocker: add offload_fwd_mark support
switchdev: update documentation for offload_fwd_mark
Documentation/networking/switchdev.txt | 14 +++-
drivers/net/ethernet/rocker/rocker.c | 14 +++-
drivers/net/ethernet/rocker/rocker.h | 1 +
include/linux/netdevice.h | 13 ++++
include/linux/skbuff.h | 4 ++
include/net/switchdev.h | 9 +++
net/core/dev.c | 10 +++
net/switchdev/switchdev.c | 111 ++++++++++++++++++++++++++++++--
8 files changed, 167 insertions(+), 9 deletions(-)
--
1.7.10.4
next reply other threads:[~2015-06-17 21:51 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-17 21:53 sfeldma [this message]
2015-06-17 21:53 ` [RFC PATCH net-next v2 1/5] net: don't reforward packets already forwarded by offload device sfeldma
2015-06-17 21:53 ` [RFC PATCH net-next v2 2/5] net: add phys ID compare helper to test if two IDs are the same sfeldma
2015-06-18 14:11 ` Sergei Shtylyov
2015-06-17 21:53 ` [RFC PATCH net-next v2 3/5] switchdev: add offload_fwd_mark generator helper sfeldma
2015-06-17 21:53 ` [RFC PATCH net-next v2 4/5] rocker: add offload_fwd_mark support sfeldma
2015-06-17 21:53 ` [RFC PATCH net-next v2 5/5] switchdev: update documentation for offload_fwd_mark sfeldma
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