[PATCH net v5 1/4] net: hsr: fix packet drops caused by GRO superpackets

[Xin Xie <xiexinet@gmail.com>]

HSR/PRP process each wire frame separately for tagging and duplicate
discard. GRO on a lower device hides multiple frames in one skb, which
cannot be forwarded with valid per-frame metadata.

Disable GRO and GRO_HW when a lower device is enslaved, matching the
existing LRO handling.

This is best effort because GRO may be re-enabled and some devices cannot
disable GRO_HW. The forward-entry segmentation fix handles plain,
trailer-free GSO skbs that still arrive; device-specific fixed-on GRO_HW
output is outside this guarantee.

Fixes: f421436a591d ("net/hsr: Add support for the High-availability Seamless Redundancy protocol (HSRv0)")
Cc: stable@vger.kernel.org
Signed-off-by: Xin Xie <xiexinet@gmail.com>
---
 include/linux/netdevice.h |  2 ++
 net/core/dev.c            | 15 +++++++++++++++
 net/core/dev_api.c        | 21 +++++++++++++++++++++
 net/hsr/hsr_slave.c       |  5 +++++
 4 files changed, 43 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..f20d5ab0cf72 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1840,6 +1840,21 @@ 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);
+
+	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..3ca2515ad048 100644
--- a/net/core/dev_api.c
+++ b/net/core/dev_api.c
@@ -269,6 +269,27 @@ 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
+ *
+ * Best-effort disable of 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.
+ *
+ * The disable is best-effort: a device with a fixed-on feature (for
+ * example GRO_HW on a virtio-net device negotiated without
+ * VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) keeps it enabled.  Callers that
+ * need a hard guarantee must inspect the resulting feature state.
+ */
+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..3cae70754bc4 100644
--- a/net/hsr/hsr_slave.c
+++ b/net/hsr/hsr_slave.c
@@ -171,6 +171,11 @@ static int hsr_portdev_setup(struct hsr_priv *hsr, struct net_device *dev,
 		goto fail_rx_handler;
 	dev_disable_lro(dev);
 
+	/* GRO disabling is best-effort: devices with fixed-on
+	 * GRO/GRO_HW cannot be forced off.
+	 */
+	dev_disable_gro(dev);
+
 	return 0;
 
 fail_rx_handler:
-- 
2.43.0