[RFC PATCH net-next 1/4] net: don't reforward packets already forwarded by offload device

sfeldma
2015-06-13T18:02:37Z

From: Scott Feldman <sfeldma@gmail.com>

Just before queuing skb for xmit on port, check if skb has been marked by
switchdev port driver as already fordwarded by device. If so, drop skb. A
non-zero skb->fwd_mark field is set by the switchdev port driver/device on
ingress to indicate the skb has already been forwarded by the device to
egress ports with matching dev->skb_mark. The switchdev port driver would
assign a non-zero dev->skb_mark for each device port netdev during
registration, for example.

Signed-off-by: Scott Feldman <sfeldma@gmail.com>
---
include/linux/netdevice.h | 6 ++++++
include/linux/skbuff.h | 4 ++++
net/core/dev.c | 9 +++++++++
3 files changed, 19 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 6f5f71f..181b08f 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1444,6 +1444,8 @@ enum netdev_priv_flags {
*
* @xps_maps: XXX: need comments on this one
*
+ * @fwd_mark: Offload device fwding mark
+ *
* @trans_start: Time (in jiffies) of last Tx
* @watchdog_timeo: Represents the timeout that is used by
* the watchdog ( see dev_watchdog() )
@@ -1681,6 +1683,10 @@ struct net_device {
struct xps_dev_maps __rcu *xps_maps;
#endif

+#ifdef CONFIG_NET_SWITCHDEV
+ u32 fwd_mark;
+#endif
+
/* These may be needed for future network-power-down code. */

/*
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index cc612fc..ba98c05 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -501,6 +501,7 @@ static inline u32 skb_mstamp_us_delta(const struct skb_mstamp *t1,
* @no_fcs: Request NIC to treat last 4 bytes as Ethernet FCS
* @napi_id: id of the NAPI struct this skb came from
* @secmark: security marking
+ * @fwd_mark: fwding offload mark
* @mark: Generic packet mark
* @vlan_proto: vlan encapsulation protocol
* @vlan_tci: vlan tag control information
@@ -648,6 +649,9 @@ struct sk_buff {
#ifdef CONFIG_NETWORK_SECMARK
__u32 secmark;
#endif
+#ifdef CONFIG_NET_SWITCHDEV
+ __u32 fwd_mark;
+#endif
union {
__u32 mark;
__u32 reserved_tailroom;
diff --git a/net/core/dev.c b/net/core/dev.c
index 6778a99..558bf33 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3065,6 +3065,15 @@ static int __dev_queue_xmit(struct sk_buff *skb, void *accel_priv)
else
skb_dst_force(skb);

+#ifdef CONFIG_NET_SWITCHDEV
+ /* Don't forward if offload device already forwarded */
+ if (skb->fwd_mark && skb->fwd_mark == dev->fwd_mark) {
+ kfree_skb(skb);
+ rc = NET_XMIT_SUCCESS;
+ goto out;
+ }
+#endif
+
txq = netdev_pick_tx(dev, skb, accel_priv);
q = rcu_dereference_bh(txq->qdisc);

--
1.7.10.4