netdev - Re: [PATCH net-next 2/3] mpls: consistently use u8 to store number of labels

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Date:	Wed, 12 Aug 2015 20:25:02 -0700
From:	roopa <roopa@...ulusnetworks.com>
To:	Robert Shearman <rshearma@...cade.com>
CC:	davem@...emloft.net, ebiederm@...ssion.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/3] mpls: consistently use u8 to store number
 of labels

On 8/12/15, 12:17 PM, Robert Shearman wrote:
> On 11/08/15 22:45, Roopa Prabhu wrote:
>> From: Roopa Prabhu <roopa@...ulusnetworks.com>
>>
>> change all types representing number of labels to u8
>> to be consistent.
>>
>> This also changes labels to u8 in the light weight
>> mpls_tunnel_encap structure. This is because the
>> light weight mpls iptunnel code shares some of the label
>> encoding functions like nla_get/put_labels with the af_mpls
>> code.
>>
>> Signed-off-by: Roopa Prabhu <roopa@...ulusnetworks.com>
>> ---
> ...
>> @@ -243,11 +243,11 @@ static const struct nla_policy 
>> rtm_mpls_policy[RTA_MAX+1] = {
>>   struct mpls_route_config {
>>       u32            rc_protocol;
>>       u32            rc_ifindex;
>> -    u16            rc_via_table;
>> -    u16            rc_via_alen;
>> +    u8            rc_via_table;
>> +    u8            rc_via_alen;
>
> IMHO, it would be better to make rc_via_alen an int to avoid overflow 
> which could cause false negatives in this check on the RTA_VIA attribute:
>
>             if (cfg->rc_via_alen > MAX_VIA_ALEN)
>                 goto errout;
>

ok,
> ...
>>       u8            rc_via[MAX_VIA_ALEN];
>> +    u8            rc_output_labels;
>>       u32            rc_label;
>> -    u32            rc_output_labels;
>>       u32            rc_output_label[MAX_NEW_LABELS];
>>       u32            rc_nlflags;
>>       enum mpls_payload_type    rc_payload_type;
>> @@ -751,7 +751,7 @@ int nla_put_labels(struct sk_buff *skb, int 
>> attrtype,
>>   EXPORT_SYMBOL_GPL(nla_put_labels);
>>
>>   int nla_get_labels(const struct nlattr *nla,
>> -           u32 max_labels, u32 *labels, u32 label[])
>> +           u32 max_labels, u8 *labels, u32 label[])
>
> How about making max_labels a u8? That would make it even more 
> consistent and avoids any problem of overflow in the number of labels.
>
yes, I did want to change max_labels to u8. will do in v2.

thanks,
Roopa

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