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Message-ID: <f57df221-0790-3a93-c7e2-d85136fb07c8@iogearbox.net> Date: Sat, 21 Oct 2023 00:38:30 +0200 From: Daniel Borkmann <daniel@...earbox.net> To: Andrew Lunn <andrew@...n.ch> Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, martin.lau@...ux.dev, razor@...ckwall.org, ast@...nel.org, andrii@...nel.org, john.fastabend@...il.com, sdf@...gle.com, toke@...nel.org Subject: Re: [PATCH bpf-next v2 1/7] netkit, bpf: Add bpf programmable net device On 10/21/23 12:18 AM, Andrew Lunn wrote: >> +static void netkit_get_drvinfo(struct net_device *dev, >> + struct ethtool_drvinfo *info) >> +{ >> + strscpy(info->driver, DRV_NAME, sizeof(info->driver)); >> + strscpy(info->version, "n/a", sizeof(info->version)); > > If you don't put anything in version, the core will put in the git > hash of the kernel. Its more useful than "n/a". Thanks, I wasn't aware of this! Agree that this is better! >> + ether_setup(dev); >> + dev->min_mtu = ETH_MIN_MTU; > > ether_setup() sets min_mtu to ETH_MIN_MTU. Will fix. >> +static int netkit_new_link(struct net *src_net, struct net_device *dev, >> + struct nlattr *tb[], struct nlattr *data[], >> + struct netlink_ext_ack *extack) >> +{ > > ... > >> + err = register_netdevice(peer); >> + put_net(net); >> + if (err < 0) >> + goto err_register_peer; >> + >> + netif_carrier_off(peer); >> + >> + err = rtnl_configure_link(peer, ifmp, 0, NULL); >> + if (err < 0) >> + goto err_configure_peer; > > Seeing code after calling register_netdevice() often means bugs. The > interface is live, and in use before the function even returns. The > kernel can try to get an IP address, mount an NFS root etc. This might > be safe, because you have two linked interfaces here, and the other > one is not yet registered. Maybe some comment about this would be > good, or can the rtnl_configure_link() be done earlier? I'll check if it's possible to reorder resp. add a comment if not. >> + >> + if (mode == NETKIT_L2) >> + eth_hw_addr_random(dev); >> + if (tb[IFLA_IFNAME]) >> + nla_strscpy(dev->name, tb[IFLA_IFNAME], IFNAMSIZ); >> + else >> + snprintf(dev->name, IFNAMSIZ, "m%%d"); >> + >> + err = register_netdevice(dev); >> + if (err < 0) >> + goto err_configure_peer; > > We have the same here, but now we have both peers registers, the > kernel could of configured both up in order to find its NFS root etc. > Is it safe to have packets flowing at this point? Before the remaining > configuration happens? They would be dropped in xmit if the peer is linked yet. >> + netif_carrier_off(dev); >> + >> + nk = netdev_priv(dev); >> + nk->primary = true; >> + nk->policy = default_prim; >> + nk->mode = mode; >> + if (nk->mode == NETKIT_L2) >> + dev_change_flags(dev, dev->flags & ~IFF_NOARP, NULL); >> + bpf_mprog_bundle_init(&nk->bundle); >> + RCU_INIT_POINTER(nk->active, NULL); >> + rcu_assign_pointer(nk->peer, peer); >> + >> + nk = netdev_priv(peer); >> + nk->primary = false; >> + nk->policy = default_peer; >> + nk->mode = mode; >> + if (nk->mode == NETKIT_L2) >> + dev_change_flags(peer, peer->flags & ~IFF_NOARP, NULL); >> + bpf_mprog_bundle_init(&nk->bundle); >> + RCU_INIT_POINTER(nk->active, NULL); >> + rcu_assign_pointer(nk->peer, dev); >> + return 0; >> +err_configure_peer: >> + unregister_netdevice(peer); >> + return err; >> +err_register_peer: >> + free_netdev(peer); >> + return err; >> +} Thanks, Daniel
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