netdev - Re: [PATCH net-next v5] rtnetlink: Support fine-grained netdevice bulk deletion

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Date:   Mon, 6 Dec 2021 08:20:10 -0700
From:   David Ahern <dsahern@...il.com>
To:     nicolas.dichtel@...nd.com,
        Lahav Schlesinger <lschlesinger@...venets.com>,
        netdev@...r.kernel.org
Cc:     kuba@...nel.org, nikolay@...dia.com
Subject: Re: [PATCH net-next v5] rtnetlink: Support fine-grained netdevice
 bulk deletion

On 12/6/21 1:25 AM, Nicolas Dichtel wrote:
>> @@ -3050,6 +3052,78 @@ static int rtnl_group_dellink(const struct net *net, int group)
>>  	return 0;
>>  }
>>  
>> +static int dev_ifindex_cmp(const void *a, const void *b)
>> +{
>> +	struct net_device * const *dev1 = a, * const *dev2 = b;
>> +
>> +	return (*dev1)->ifindex - (*dev2)->ifindex;
>> +}
>> +
>> +static int rtnl_ifindex_dellink(struct net *net, struct nlattr *head, int len,
>> +				struct netlink_ext_ack *extack)
>> +{
>> +	int i = 0, num_devices = 0, rem;
>> +	struct net_device **dev_list;
>> +	const struct nlattr *nla;
>> +	LIST_HEAD(list_kill);
>> +	int ret;
>> +
>> +	nla_for_each_attr(nla, head, len, rem) {
>> +		if (nla_type(nla) == IFLA_IFINDEX)
>> +			num_devices++;
>> +	}
>> +
>> +	dev_list = kmalloc_array(num_devices, sizeof(*dev_list), GFP_KERNEL);
>> +	if (!dev_list)
>> +		return -ENOMEM;
>> +
>> +	nla_for_each_attr(nla, head, len, rem) {
>> +		const struct rtnl_link_ops *ops;
>> +		struct net_device *dev;
>> +		int ifindex;
>> +
>> +		if (nla_type(nla) != IFLA_IFINDEX)
>> +			continue;
>> +
>> +		ifindex = nla_get_s32(nla);
>> +		ret = -ENODEV;
>> +		dev = __dev_get_by_index(net, ifindex);
>> +		if (!dev) {
>> +			NL_SET_ERR_MSG_ATTR(extack, nla, "Unknown ifindex");
> It would be nice to have the ifindex in the error message. This message does not
> give more information than "ENODEV".

extack infra does not allow dynamic messages. It does point to the
location of the bad index, so userspace could figure it out.

> 
>> +			goto out_free;
>> +		}
>> +
>> +		ret = -EOPNOTSUPP;
>> +		ops = dev->rtnl_link_ops;
>> +		if (!ops || !ops->dellink) {
>> +			NL_SET_ERR_MSG_ATTR(extack, nla, "Device cannot be deleted");
> Same here.
> 
> 
> Thank you,
> Nicolas
>