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Date: Wed, 25 Oct 2023 22:21:01 +0300
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Jiri Pirko <jiri@...nulli.us>, Daniel Borkmann <daniel@...earbox.net>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, martin.lau@...ux.dev,
ast@...nel.org, andrii@...nel.org, john.fastabend@...il.com, sdf@...gle.com,
toke@...nel.org, kuba@...nel.org, andrew@...n.ch,
Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCH bpf-next v4 1/7] netkit, bpf: Add bpf programmable net
device
On 10/25/23 18:47, Jiri Pirko wrote:
> Tue, Oct 24, 2023 at 11:48:58PM CEST, daniel@...earbox.net wrote:
>> This work adds a new, minimal BPF-programmable device called "netkit"
[snip]
>
> Couple of nitpicks below:
>
> [..]
>
>
Hi,
Thanks for the review. I know about the nits below but decided against
changing them, more below each...
>> +static int netkit_check_policy(int policy, struct nlattr *tb,
>> + struct netlink_ext_ack *extack)
>> +{
>> + switch (policy) {
>> + case NETKIT_PASS:
>> + case NETKIT_DROP:
>> + return 0;
>> + default:
>
> Isn't this job for netlink policy?
>
>
This cannot be handled by policies AFAIK, because only 2 sparse values
from more are allowed. We could potentially do it through validate() but
it's the same minus the explicit policy type info. IMO this approach is
good.
>> + NL_SET_ERR_MSG_ATTR(extack, tb,
>> + "Provided default xmit policy not supported");
>> + return -EINVAL;
>> + }
>> +}
>> +
>> +static int netkit_check_mode(int mode, struct nlattr *tb,
>> + struct netlink_ext_ack *extack)
>> +{
>> + switch (mode) {
>> + case NETKIT_L2:
>> + case NETKIT_L3:
>> + return 0;
>> + default:
>
> Isn't this job for netlink policy?
>
>
This one can be handled by policy indeed, but then we lose the nice user
error. Again can be done through validate(), but it's the same and we
lose explicit policy type information.
>> + NL_SET_ERR_MSG_ATTR(extack, tb,
>> + "Provided device mode can only be L2 or L3");
>> + return -EINVAL;
>> + }
>> +}
>> +
>> +static int netkit_validate(struct nlattr *tb[], struct nlattr *data[],
>> + struct netlink_ext_ack *extack)
>> +{
>> + struct nlattr *attr = tb[IFLA_ADDRESS];
>> +
>> + if (!attr)
>> + return 0;
>> + NL_SET_ERR_MSG_ATTR(extack, attr,
>> + "Setting Ethernet address is not supported");
>> + return -EOPNOTSUPP;
>> +}
>> +
>> +static struct rtnl_link_ops netkit_link_ops;
>> +
>> +static int netkit_new_link(struct net *src_net, struct net_device *dev,
>> + struct nlattr *tb[], struct nlattr *data[],
>> + struct netlink_ext_ack *extack)
>> +{
>> + struct nlattr *peer_tb[IFLA_MAX + 1], **tbp = tb, *attr;
>> + enum netkit_action default_prim = NETKIT_PASS;
>> + enum netkit_action default_peer = NETKIT_PASS;
>> + enum netkit_mode mode = NETKIT_L3;
>> + unsigned char ifname_assign_type;
>> + struct ifinfomsg *ifmp = NULL;
>> + struct net_device *peer;
>> + char ifname[IFNAMSIZ];
>> + struct netkit *nk;
>> + struct net *net;
>> + int err;
>> +
>> + if (data) {
>> + if (data[IFLA_NETKIT_MODE]) {
>> + attr = data[IFLA_NETKIT_MODE];
>> + mode = nla_get_u32(attr);
>> + err = netkit_check_mode(mode, attr, extack);
>> + if (err < 0)
>> + return err;
>> + }
>> + if (data[IFLA_NETKIT_PEER_INFO]) {
>> + attr = data[IFLA_NETKIT_PEER_INFO];
>> + ifmp = nla_data(attr);
>> + err = rtnl_nla_parse_ifinfomsg(peer_tb, attr, extack);
>> + if (err < 0)
>> + return err;
>> + err = netkit_validate(peer_tb, NULL, extack);
>> + if (err < 0)
>> + return err;
>> + tbp = peer_tb;
>> + }
>> + if (data[IFLA_NETKIT_POLICY]) {
>> + attr = data[IFLA_NETKIT_POLICY];
>> + default_prim = nla_get_u32(attr);
>> + err = netkit_check_policy(default_prim, attr, extack);
>> + if (err < 0)
>> + return err;
>> + }
>> + if (data[IFLA_NETKIT_PEER_POLICY]) {
>> + attr = data[IFLA_NETKIT_PEER_POLICY];
>> + default_peer = nla_get_u32(attr);
>> + err = netkit_check_policy(default_peer, attr, extack);
>> + if (err < 0)
>> + return err;
>> + }
>> + }
>> +
>> + if (ifmp && tbp[IFLA_IFNAME]) {
>> + nla_strscpy(ifname, tbp[IFLA_IFNAME], IFNAMSIZ);
>> + ifname_assign_type = NET_NAME_USER;
>> + } else {
>> + strscpy(ifname, "nk%d", IFNAMSIZ);
>> + ifname_assign_type = NET_NAME_ENUM;
>> + }
>> +
>> + net = rtnl_link_get_net(src_net, tbp);
>> + if (IS_ERR(net))
>> + return PTR_ERR(net);
>> +
>> + peer = rtnl_create_link(net, ifname, ifname_assign_type,
>> + &netkit_link_ops, tbp, extack);
>> + if (IS_ERR(peer)) {
>> + put_net(net);
>> + return PTR_ERR(peer);
>> + }
>> +
>> + netif_inherit_tso_max(peer, dev);
>> +
>> + if (mode == NETKIT_L2)
>> + eth_hw_addr_random(peer);
>> + if (ifmp && dev->ifindex)
>> + peer->ifindex = ifmp->ifi_index;
>> +
>> + nk = netkit_priv(peer);
>> + nk->primary = false;
>> + nk->policy = default_peer;
>> + nk->mode = mode;
>> + bpf_mprog_bundle_init(&nk->bundle);
>> + RCU_INIT_POINTER(nk->active, NULL);
>> + RCU_INIT_POINTER(nk->peer, NULL);
>
> Aren't these already 0?
>
>
Yep, they are. Here decided in favor of explicit show of values,
although it's minor and I'm fine either way.
>> +
>> + err = register_netdevice(peer);
>> + put_net(net);
>> + if (err < 0)
>> + goto err_register_peer;
>> + netif_carrier_off(peer);
>> + if (mode == NETKIT_L2)
>> + dev_change_flags(peer, peer->flags & ~IFF_NOARP, NULL);
>> +
>> + err = rtnl_configure_link(peer, NULL, 0, NULL);
>> + if (err < 0)
>> + goto err_configure_peer;
>> +
>> + if (mode == NETKIT_L2)
>> + eth_hw_addr_random(dev);
>> + if (tb[IFLA_IFNAME])
>> + nla_strscpy(dev->name, tb[IFLA_IFNAME], IFNAMSIZ);
>> + else
>> + strscpy(dev->name, "nk%d", IFNAMSIZ);
>> +
>> + nk = netkit_priv(dev);
>> + nk->primary = true;
>> + nk->policy = default_prim;
>> + nk->mode = mode;
>> + bpf_mprog_bundle_init(&nk->bundle);
>> + RCU_INIT_POINTER(nk->active, NULL);
>> + RCU_INIT_POINTER(nk->peer, NULL);
>> +
>> + err = register_netdevice(dev);
>> + if (err < 0)
>> + goto err_configure_peer;
>> + netif_carrier_off(dev);
>> + if (mode == NETKIT_L2)
>> + dev_change_flags(dev, dev->flags & ~IFF_NOARP, NULL);
>> +
>> + rcu_assign_pointer(netkit_priv(dev)->peer, peer);
>> + rcu_assign_pointer(netkit_priv(peer)->peer, dev);
>> + return 0;
>> +err_configure_peer:
>> + unregister_netdevice(peer);
>> + return err;
>> +err_register_peer:
>> + free_netdev(peer);
>> + return err;
>> +}
>> +
>
> [..]
Cheers,
Nik
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