On 30.3.2026 20:15, Mohsin Bashir wrote:

quoted

+static int bcmgenet_xdp_setup(struct net_device *dev,
+			      struct netdev_bpf *xdp)
+{
+	struct bcmgenet_priv *priv = netdev_priv(dev);
+	struct bpf_prog *old_prog;
+	struct bpf_prog *prog = xdp->prog;
+
+	if (prog && dev->mtu > PAGE_SIZE - GENET_RX_HEADROOM -
+	    SKB_DATA_ALIGN(sizeof(struct skb_shared_info))) {
+		NL_SET_ERR_MSG_MOD(xdp->extack,
+				   "MTU too large for single-page XDP buffer");
+		return -EOPNOTSUPP;
+	}

The MTU check here is great. But I do not see support for 
.ndo_change_mtu. This would allow users to change MTU size AFTER the 
program is attached.

Good point. I had planned to add ndo_change_mtu in a follow-up series, 
but this leaves a gap where MTU can be changed while XDP is attached.

Options:
1. Add a minimal ndo_change_mtu to this series that only rejects MTU 
changes incompatible with XDP, default behavior otherwise
2. Reject any MTU change while XDP is attached
3. Defer to the ndo_change_mtu follow-up series

Thoughts?

Thanks
Nicolai