netdev - Re: [PATCH net-next v2 9/9] geneve: Implement rtnl changelink

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Message-ID: <CALnjE+qRTFXono-qTknRkREWRJnVp1qJQMnDCy7ODqGu-9xRhQ@mail.gmail.com>
Date:	Wed, 19 Aug 2015 13:12:40 -0700
From:	Pravin Shelar <pshelar@...ira.com>
To:	Jesse Gross <jesse@...ira.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2 9/9] geneve: Implement rtnl changelink

On Wed, Aug 19, 2015 at 12:40 PM, Jesse Gross <jesse@...ira.com> wrote:
> On Mon, Aug 17, 2015 at 2:11 PM, Pravin B Shelar <pshelar@...ira.com> wrote:
>> diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
>> index e47cdd9..0d7fbef 100644
>> --- a/drivers/net/geneve.c
>> +++ b/drivers/net/geneve.c
>> -static int geneve_configure(struct net *net, struct net_device *dev,
>> -                           __be32 rem_addr, __u32 vni, __u8 ttl, __u8 tos,
>> -                           __u16 dst_port, bool metadata)
>> +static int __geneve_configure(struct net *net, struct net_device *dev,
>> +                             __be32 rem_addr, __u32 vni, __u8 ttl, __u8 tos,
>> +                             __u16 dst_port, bool metadata)
>>  {
> [...]
>>         geneve->net = net;
>>         geneve->dev = dev;
>
> I guess this stuff should really be in geneve_configure() - it seems a
> bit odd to change it for a running device (even if it shouldn't
> change).
>
ok.

>>         geneve->remote.sin_addr.s_addr = rem_addr;
>>         if (IN_MULTICAST(ntohl(geneve->remote.sin_addr.s_addr)))
>>                 return -EINVAL;
>>
>> +       u32_to_vni(vni, geneve->vni);
>>         list_for_each_entry(t, &gn->geneve_list, next) {
>>                 if (!memcmp(geneve->vni, t->vni, sizeof(t->vni)) &&
>>                     rem_addr == t->remote.sin_addr.s_addr &&
>
> I'm not sure that these types of operations are safe if the device is
> already running. We first overwrite the remote value and then we do
> error checking but that means that if there is an error, then the
> device will be left in a broken state. Don't we also need to update
> the hash table if some of these parameters change?
>
ok, I will stop device before making changes. that way we can add it
to hash table.

>> +static int geneve_changelink(struct net_device *dev,
>> +                            struct nlattr *tb[], struct nlattr *data[])
>> +{
> [...]
>> -       if (data[IFLA_GENEVE_PORT])
>> -               dst_port = nla_get_u16(data[IFLA_GENEVE_PORT]);
>> +       if (geneve->sock && (dst_port != ntohs(geneve->dst_port) ||
>> +                            metadata != geneve->collect_md)) {
>
> It seems like in an ideal world, we wouldn't need to recreate the
> socket if metadata collection changed (assuming that there are no new
> conflicts).

To keep changelink simple I am thinking of disallowing metadata changes.
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