[PATCH net 2/2] bridge: update max_gso_segs and max_gso_size

[Eric Dumazet <edumazet@google.com>]

It can be useful to lower max_gso_segs on NIC with very low
number of TX descriptors like bcmgenet.

However, this is defeated by bridge since it does not propagate
the lower value of max_gso_segs and max_gso_size.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Petri Gynther <pgynther@google.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
---
 net/bridge/br_if.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index a73df3315df9..8217aecf025b 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -437,6 +437,20 @@ int br_min_mtu(const struct net_bridge *br)
 	return mtu;
 }
 
+static void br_set_gso_limits(struct net_bridge *br)
+{
+	unsigned int gso_max_size = GSO_MAX_SIZE;
+	u16 gso_max_segs = GSO_MAX_SEGS;
+	const struct net_bridge_port *p;
+
+	list_for_each_entry(p, &br->port_list, list) {
+		gso_max_size = min(gso_max_size, p->dev->gso_max_size);
+		gso_max_segs = min(gso_max_segs, p->dev->gso_max_segs);
+	}
+	br->dev->gso_max_size = gso_max_size;
+	br->dev->gso_max_segs = gso_max_segs;
+}
+
 /*
  * Recomputes features using slave's features
  */
@@ -564,6 +578,7 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
 		call_netdevice_notifiers(NETDEV_CHANGEADDR, br->dev);
 
 	dev_set_mtu(br->dev, br_min_mtu(br));
+	br_set_gso_limits(br);
 
 	kobject_uevent(&p->kobj, KOBJ_ADD);
 
@@ -610,6 +625,7 @@ int br_del_if(struct net_bridge *br, struct net_device *dev)
 	del_nbp(p);
 
 	dev_set_mtu(br->dev, br_min_mtu(br));
+	br_set_gso_limits(br);
 
 	spin_lock_bh(&br->lock);
 	changed_addr = br_stp_recalculate_bridge_id(br);
-- 
2.8.0.rc3.226.g39d4020