Re: [PATCH v4 net-next 4/7] net: mvneta: add basic XDP support

[Jakub Kicinski]

On Wed, 16 Oct 2019 23:03:09 +0200, Lorenzo Bianconi wrote:
> Add basic XDP support to mvneta driver for devices that rely on software
> buffer management. Currently supported verdicts are:
> - XDP_DROP
> - XDP_PASS
> - XDP_REDIRECT
> - XDP_ABORTED
> 
> - iptables drop:
> $iptables -t raw -I PREROUTING -p udp --dport 9 -j DROP
> $nstat -n && sleep 1 && nstat
> IpInReceives          151169          0.0
> IpExtInOctets         6953544         0.0
> IpExtInNoECTPkts      151165          0.0
> 
> - XDP_DROP via xdp1
> $./samples/bpf/xdp1 3
> proto 0:      421419 pkt/s
> proto 0:      421444 pkt/s
> proto 0:      421393 pkt/s
> proto 0:      421440 pkt/s
> proto 0:      421184 pkt/s
> 
> Tested-by: Matteo Croce <mcr...@redhat.com>
> Signed-off-by: Lorenzo Bianconi <lore...@kernel.org>

> +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);

Actually if pp->prog && prog you don't have to stop/start, right?
You just gotta restart if !!pp->prog != !!prog?

> +     old_prog = xchg(&pp->xdp_prog, prog);
> +     if (old_prog)
> +             bpf_prog_put(old_prog);
> +
> +     if (netif_running(dev))
> +             return mvneta_open(dev);
> +
> +     return 0;
> +}