netdev - Re: [PATCH net-next 1/4] net: rtnetlink: support for fdb get

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Date:   Fri, 14 Dec 2018 10:55:26 -0700
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Roopa Prabhu <roopa@...ulusnetworks.com>, davem@...emloft.net
Cc:     netdev@...r.kernel.org, nikolay@...ulusnetworks.com,
        stephen@...workplumber.org
Subject: Re: [PATCH net-next 1/4] net: rtnetlink: support for fdb get

On 12/14/18 10:43 AM, Roopa Prabhu wrote:
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index f8bdb8ad..fcea76b 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -4021,6 +4021,111 @@ static int rtnl_fdb_dump(struct sk_buff *skb, struct netlink_callback *cb)
>  	return skb->len;
>  }
>  
> +static int rtnl_fdb_get(struct sk_buff *in_skb, struct nlmsghdr *nlh,
> +			struct netlink_ext_ack *extack)
> +{
> +	const struct net_device_ops *ops = NULL;
> +	struct net *net = sock_net(in_skb->sk);
> +	struct net_device *dev = NULL, *br_dev = NULL;
> +	struct nlattr *tb[NDA_MAX + 1];
> +	struct sk_buff *skb;
> +	struct ndmsg *ndm;
> +	int br_idx = 0;
> +	u8 *addr;
> +	u16 vid;
> +	int err;
> +
> +	err = nlmsg_parse(nlh, sizeof(*ndm), tb, NDA_MAX, NULL, extack);

New stuff should go in with strict checking, so nlmsg_parse_strict and a
check for any unsupported attributes (NDA) or ndm entries in the request.

Also, please add an nla_policy for easier NDA attributes ...

> +	if (err < 0)
> +		return err;
> +
> +	ndm = nlmsg_data(nlh);
> +	if (ndm->ndm_ifindex) {
> +		dev = __dev_get_by_index(net, ndm->ndm_ifindex);
> +		if (!dev) {
> +			NL_SET_ERR_MSG(extack, "unknown dev ifindex");

General comment on all of the extack messages: No abbreviations in the
message, and it is nice to always start with a capital letter. "Unknown
device index"

> +			return -ENODEV;
> +		}
> +	}
> +
> +	if (!tb[NDA_LLADDR] || nla_len(tb[NDA_LLADDR]) != ETH_ALEN) {
> +		NL_SET_ERR_MSG(extack, "invalid address");
> +		return -EINVAL;
> +	}
> +
> +	addr = nla_data(tb[NDA_LLADDR]);
> +
> +	err = fdb_vid_parse(tb[NDA_VLAN], &vid, extack);
> +	if (err)
> +		return err;
> +
> +	if (tb[NDA_MASTER]) {
> +		if (dev) {
> +			NL_SET_ERR_MSG(extack, "master and dev are mutually exclusive");
> +			return -EINVAL;
> +		}
> +
> +		br_idx = nla_get_u32(tb[NDA_MASTER]);

... so you know that NDA_MASTER is a u32.

> +		br_dev = __dev_get_by_index(net, br_idx);
> +		if (!br_dev) {
> +			NL_SET_ERR_MSG(extack, "invalid master ifindex");
> +			return -EINVAL;
> +		}
> +		ops = br_dev->netdev_ops;
> +	}
> +