netdev - Re: [PATCH v1 1/2] bpf: add a longest prefix match trie map implementation

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Date:   Thu, 5 Jan 2017 21:14:42 +0100
From:   Daniel Mack <daniel@...que.org>
To:     Daniel Borkmann <daniel@...earbox.net>, ast@...com
Cc:     dh.herrmann@...il.com, netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH v1 1/2] bpf: add a longest prefix match trie map
 implementation

Hi,

On 01/05/2017 09:01 PM, Daniel Borkmann wrote:
> On 01/05/2017 05:25 PM, Daniel Borkmann wrote:
>> On 12/29/2016 06:28 PM, Daniel Mack wrote:

> [...]
>>> +static struct bpf_map *trie_alloc(union bpf_attr *attr)
>>> +{
>>> +    struct lpm_trie *trie;
>>> +
>>> +    /* check sanity of attributes */
>>> +    if (attr->max_entries == 0 || attr->map_flags ||
>>> +        attr->key_size < sizeof(struct bpf_lpm_trie_key) + 1   ||
>>> +        attr->key_size > sizeof(struct bpf_lpm_trie_key) + 256 ||
>>> +        attr->value_size != sizeof(u64))
>>> +        return ERR_PTR(-EINVAL);
> 
> One more question on this regarding value size as u64 (perhaps I
> missed it along the way): reason this was chosen was because for
> keeping stats? Why not making user choose a size as in other maps,
> so also custom structs could be stored there?

In my use case, the actual value of a node is in fact ignored, all that
matters is whether a node exists in a trie or not. The test code uses
u64 for its tests.

I can change it around so that the value size can be defined by
userspace, but ideally it would also support 0-byte lengths then. The
bpf map syscall handler should handle the latter just fine if I read the
code correctly?


Thanks,
Daniel