netdev - Re: [PATCH v3 net-next 5/8] net: mvneta: add basic XDP support

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Date:   Tue, 15 Oct 2019 16:20:47 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     netdev@...r.kernel.org, lorenzo.bianconi@...hat.com,
        davem@...emloft.net, thomas.petazzoni@...tlin.com,
        brouer@...hat.com, ilias.apalodimas@...aro.org,
        matteo.croce@...hat.com, mw@...ihalf.com
Subject: Re: [PATCH v3 net-next 5/8] net: mvneta: add basic XDP support

On Mon, 14 Oct 2019 12:49:52 +0200, Lorenzo Bianconi wrote:
> @@ -3983,6 +4071,46 @@ static int mvneta_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
>  	return phylink_mii_ioctl(pp->phylink, ifr, cmd);
>  }
>  
> +static int mvneta_xdp_setup(struct net_device *dev, struct bpf_prog *prog,
> +			    struct netlink_ext_ack *extack)
> +{
> +	struct mvneta_port *pp = netdev_priv(dev);
> +	struct bpf_prog *old_prog;
> +
> +	if (prog && dev->mtu > MVNETA_MAX_RX_BUF_SIZE) {
> +		NL_SET_ERR_MSG_MOD(extack, "Jumbo frames not supported on XDP");
> +		return -EOPNOTSUPP;
> +	}
> +
> +	if (netif_running(dev))
> +		mvneta_stop(dev);
> +
> +	old_prog = xchg(&pp->xdp_prog, prog);
> +	if (old_prog)
> +		bpf_prog_put(old_prog);
> +
> +	if (netif_running(dev))
> +		mvneta_open(dev);

Ah, the stopping and starting of the interface is sad. If start fails
the interface is left in a funky state until someone does a stop/start
cycle. Not that you introduced that.

> +	return 0;
> +}
> +
> +static int mvneta_xdp(struct net_device *dev, struct netdev_bpf *xdp)
> +{
> +	struct mvneta_port *pp = netdev_priv(dev);
> +
> +	switch (xdp->command) {
> +	case XDP_SETUP_PROG:
> +		return mvneta_xdp_setup(dev, xdp->prog, xdp->extack);
> +	case XDP_QUERY_PROG:
> +		xdp->prog_id = pp->xdp_prog ? pp->xdp_prog->aux->id : 0;
> +		return 0;
> +	default:
> +		NL_SET_ERR_MSG_MOD(xdp->extack, "unknown XDP command");

Please drop this message here, there are commands you legitimately
don't care about, just return -EINVAL, no need to risk leaking a
meaningless warning to the user space.

> +		return -EINVAL;
> +	}
> +}