Hi Scott, On 18/07/15 18:24, sfel...@gmail.com wrote: > From: Scott Feldman <sfel...@gmail.com> > > v3: > > - Per Nicolas Dichtel review: remove errant empty union. > > v2: > > - Per davem review: in sk_buff, union fwd_mark with secmark to save space > since features appear to be mutually exclusive. > - Per Simon Horman review: > - fix grammar in switchdev.txt wrt fwd_mark > - remove some unrelated changes that snuck in > > v1: > > This patchset was previously submitted as RFC. No changes from the last > version (v2) sent under RFC. Including RFC version history here for > reference.
This looks good to me, and it looks like this is also relevant for DSA-driven switches, however I am not exactly clear on how we could potentially use this on such switches. For Broadcom tags, there is a reason code forwarded along with the tag making it to the CPU, and the "mirror" bit sounds like something that should dictate whether we should be setting the fwd_mark or not. What does it look like on Marvell switches? > > RFC 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. > > RFC 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 | 11 ++++ > drivers/net/ethernet/rocker/rocker.h | 1 + > include/linux/netdevice.h | 13 ++++ > include/linux/skbuff.h | 9 ++- > include/net/switchdev.h | 9 +++ > net/core/dev.c | 10 +++ > net/switchdev/switchdev.c | 111 > ++++++++++++++++++++++++++++++-- > 8 files changed, 169 insertions(+), 9 deletions(-) > -- Florian -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
