[PATCH net v3 1/4] net: hsr: fix packet drops caused by GRO superpackets

[Xin Xie]

HSR/PRP append a 6-byte tag/RCT to every forwarded frame and process
each frame individually (sequence numbering, duplicate discard). When
a lower device aggregates received frames into a GRO super-packet --
in software, or in hardware on GRO_HW-capable NICs -- the HSR
receive/forward path sees a single skb instead of the individual
frames. Depending on the lower device, that super-skb is then either
rejected outright (for example when it exceeds the lower MTU at
egress), or forwarded without valid per-wire-frame HSR/PRP
processing: its single trailing tag/RCT cannot represent the
per-frame trailers and sequence numbers of the aggregated frames. On
memory-constrained devices, processing super-skbs in softirq context
can also pressure atomic memory allocation.

The HSR/PRP stack already disables LRO on enslaved devices for the
same reason. Extend that treatment to GRO: add netif_disable_gro()
and dev_disable_gro() mirroring netif_disable_lro()/dev_disable_lro(),
and call dev_disable_gro() from hsr_portdev_setup() so enslavement to
an HSR/PRP master automatically strips NETIF_F_GRO and NETIF_F_GRO_HW
on the lower device (recursively on its own lowers, as with LRO).

This is a setup-time default, not an immutable feature policy: a
later privileged feature override, or a lower newly attached below a
stacked slave, can re-enable GRO without re-walking the HSR
enslavement path. Patch 3 is the fail-safe for that case: a GSO skb
that nevertheless reaches the forward entry is segmented on the
plain master/interlink paths or rejected on the LAN/tagged paths, so
invalid aggregates are never forwarded as-is -- though a later
override can still cost traffic on a LAN ingress.

Fixes: f421436a591d ("net/hsr: Add support for the High-availability Seamless Redundancy protocol (HSRv0)")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Xin Xie <xiexinet@xxxxxxxxx>
---
 include/linux/netdevice.h |  2 ++
 net/core/dev.c            | 18 ++++++++++++++++++
 net/core/dev_api.c        | 16 ++++++++++++++++
 net/hsr/hsr_slave.c       |  1 +
 4 files changed, 37 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 9981d637f8b5..eba2c26a49ba 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3434,6 +3434,8 @@ void dev_close(struct net_device *dev);
 void netif_close_many(struct list_head *head, bool unlink);
 void netif_disable_lro(struct net_device *dev);
 void dev_disable_lro(struct net_device *dev);
+void netif_disable_gro(struct net_device *dev);
+void dev_disable_gro(struct net_device *dev);
 int dev_loopback_xmit(struct net *net, struct sock *sk, struct sk_buff *newskb);
 u16 dev_pick_tx_zero(struct net_device *dev, struct sk_buff *skb,
 		     struct net_device *sb_dev);
diff --git a/net/core/dev.c b/net/core/dev.c
index 5933c5dab09e..a6cf2adc8625 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1840,6 +1840,24 @@ void netif_disable_lro(struct net_device *dev)
 	}
 }
 
+void netif_disable_gro(struct net_device *dev)
+{
+	struct net_device *lower_dev;
+	struct list_head *iter;
+
+	dev->wanted_features &= ~(NETIF_F_GRO | NETIF_F_GRO_HW);
+	netdev_update_features(dev);
+
+	if (unlikely(dev->features & (NETIF_F_GRO | NETIF_F_GRO_HW)))
+		netdev_WARN(dev, "failed to disable GRO!\n");
+
+	netdev_for_each_lower_dev(dev, lower_dev, iter) {
+		netdev_lock_ops(lower_dev);
+		netif_disable_gro(lower_dev);
+		netdev_unlock_ops(lower_dev);
+	}
+}
+
 /**
  *	dev_disable_gro_hw - disable HW Generic Receive Offload on a device
  *	@dev: device
diff --git a/net/core/dev_api.c b/net/core/dev_api.c
index 437947dd08ed..02fb21629512 100644
--- a/net/core/dev_api.c
+++ b/net/core/dev_api.c
@@ -269,6 +269,22 @@ void dev_disable_lro(struct net_device *dev)
 }
 EXPORT_SYMBOL(dev_disable_lro);
 
+/**
+ * dev_disable_gro() - disable Generic Receive Offload on a device
+ * @dev: device
+ *
+ * Disable Generic Receive Offload (GRO) on a net device.  Must be
+ * called under RTNL.  This is needed if received packets may be
+ * forwarded to another interface.
+ */
+void dev_disable_gro(struct net_device *dev)
+{
+	netdev_lock_ops(dev);
+	netif_disable_gro(dev);
+	netdev_unlock_ops(dev);
+}
+EXPORT_SYMBOL(dev_disable_gro);
+
 /**
  * dev_set_promiscuity() - update promiscuity count on a device
  * @dev: device
diff --git a/net/hsr/hsr_slave.c b/net/hsr/hsr_slave.c
index 01c73b4b50dd..da06b21cdf51 100644
--- a/net/hsr/hsr_slave.c
+++ b/net/hsr/hsr_slave.c
@@ -170,6 +170,7 @@ static int hsr_portdev_setup(struct hsr_priv *hsr, struct net_device *dev,
 	if (res)
 		goto fail_rx_handler;
 	dev_disable_lro(dev);
+	dev_disable_gro(dev);
 
 	return 0;
 
-- 
2.43.0