[ovs-dev] [recirculation 2/3] datapath: add hash action

[Jesse Gross]

On Wed, Apr 16, 2014 at 7:39 PM, Pravin Shelar <pshelar at nicira.com> wrote:
> On Wed, Apr 16, 2014 at 2:09 AM, Andy Zhou <azhou at nicira.com> wrote:
>> Thanks for the review. I will send V2.
>>
>> On Tue, Apr 15, 2014 at 7:14 AM, Pravin Shelar <pshelar at nicira.com> wrote:
>>> On Sat, Apr 12, 2014 at 3:30 AM, Andy Zhou <azhou at nicira.com> wrote:
>>>> Implements Linux kernel datapath hash action. Hash action computes
>>>> hash and stores it into current packet key.
>>>>
>>>> Signed-off-by: Andy Zhou <azhou at nicira.com>
>>>>
>>>>         [OVS_KEY_ATTR_ARP] = sizeof(struct ovs_key_arp),
>>>>         [OVS_KEY_ATTR_ND] = sizeof(struct ovs_key_nd),
>>>> +       [OVS_KEY_ATTR_DP_HASH] = sizeof(u32),
>>>>         [OVS_KEY_ATTR_TUNNEL] = -1,
>>>>  };
>>>>
>>>> @@ -455,6 +461,19 @@ static int ipv4_tun_to_nlattr(struct sk_buff *skb,
>>>>  static int metadata_from_nlattrs(struct sw_flow_match *match,  u64 *attrs,
>>>>                                  const struct nlattr **a, bool is_mask)
>>>>  {
>>>> +
>>>> +       if (*attrs & (1ULL << OVS_KEY_ATTR_DP_HASH)) {
>>>> +               u32 hash_val = nla_get_u32(a[OVS_KEY_ATTR_DP_HASH]);
>>>> +
>>>> +               if (!is_mask && !hash_val) {
>>>> +                       OVS_NLERR("Hash value can not be zero\n");
>>>> +                       return -EINVAL;
>>>> +               }
>>>> +
>>>> +               SW_FLOW_KEY_PUT(match, dp_hash, hash_val, is_mask);
>>>> +               *attrs &= ~(1ULL << OVS_KEY_ATTR_DP_HASH);
>>>> +       }
>>> Is hash allowed to be partially masked?
>> Yes.
>
> How can arbitrary hash value which is outside control of vswitchd can
> be partially masked. I think we can either exact match it or
> completely wildcard. Am I missing something?

If you are trying to split between bond slaves then you probably want
to mask off some number of bits based on the number of interfaces to
randomly divide the traffic.