[PATCH RFC 1/2] br: add notifier for when bridge changes it GSO maximums

[Stephen Hemminger <stephen@networkplumber.org>]

Add a callback notifier for when the minimum GSO values calculated
across all the bridge ports changes. This allows for veth to adjust
based on the devices in the bridge.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
---
 include/linux/netdevice.h | 1 +
 net/bridge/br_if.c        | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ef789e1d679e..0da966ffec70 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2326,6 +2326,7 @@ struct netdev_lag_lower_state_info {
 #define NETDEV_UDP_TUNNEL_PUSH_INFO	0x001C
 #define NETDEV_UDP_TUNNEL_DROP_INFO	0x001D
 #define NETDEV_CHANGE_TX_QUEUE_LEN	0x001E
+#define NETDEV_CHANGE_GSO_MAX	0x001F
 
 int register_netdevice_notifier(struct notifier_block *nb);
 int unregister_netdevice_notifier(struct notifier_block *nb);
diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index 9ba4ed65c52b..ca4ccadd78d0 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -453,8 +453,15 @@ static void br_set_gso_limits(struct net_bridge *br)
 		gso_max_size = min(gso_max_size, p->dev->gso_max_size);
 		gso_max_segs = min(gso_max_segs, p->dev->gso_max_segs);
 	}
+
+	if (br->dev->gso_max_size == gso_max_size &&
+	    br->dev->gso_max_segs == gso_max_segs)
+		return;
+
 	br->dev->gso_max_size = gso_max_size;
 	br->dev->gso_max_segs = gso_max_segs;
+
+	call_netdevice_notifiers(NETDEV_CHANGE_GSO_MAX, br->dev);
 }
 
 /*
-- 
2.11.0