Re: [Xen-devel] [PATCH 2/6] xen-netfront: reduce gso_max_size to account for ethernet header

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.03.13 at 15:23, David Vrabel <david.vrabel@xxxxxxxxxx> wrote:
> On 25/03/13 11:08, Wei Liu wrote:
>> The maximum packet including ethernet header that can be handled by netfront 
> /
>> netback wire format is 65535. Reduce gso_max_size accordingly.
>> 
>> Drop skb and print warning when skb->len > 65535. This can 1) save the effort
>> to send malformed packet to netback, 2) help spotting misconfiguration of
>> netfront in the future.
> [...]
>> --- a/drivers/net/xen-netfront.c
>> +++ b/drivers/net/xen-netfront.c
>> @@ -547,6 +547,18 @@ static int xennet_start_xmit(struct sk_buff *skb, 
>> struct 
> net_device *dev)
>>      unsigned int len = skb_headlen(skb);
>>      unsigned long flags;
>>  
>> +    /* Wire format of xen_netif_tx_request only supports skb->len
>> +     * < 64K, because size field in xen_netif_tx_request is
>> +     * uint16_t. If skb->len is too big, drop it and alert user about
>> +     * misconfiguration.
>> +     */
>> +    if (unlikely(skb->len >= (uint16_t)(~0))) {
> 
> Suggest a #define for this maximum added to include/xen/interface/io/netif.h

I don't see a point in doing so. If you want the connection to be
explicit, just use typeof() here instead of uint16_t.

Jan


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