Re: [Xen-devel] [RFC v2 2/4] net: enables interface option to skip IP

[Dan Williams <dcbw@xxxxxxxxxx>]

On Fri, 2014-02-14 at 18:59 -0800, Luis R. Rodriguez wrote:
> From: "Luis R. Rodriguez" <mcgrof@xxxxxxxx>
> 
> Some interfaces do not need to have any IPv4 or IPv6
> addresses, so enable an option to specify this. One
> example where this is observed are virtualization
> backend interfaces which just use the net_device
> constructs to help with their respective frontends.
> 
> This should optimize boot time and complexity on
> virtualization environments for each backend interface
> while also avoiding triggering SLAAC and DAD, which is
> simply pointless for these type of interfaces.

Would it not be better/cleaner to use disable_ipv6 and then add a
disable_ipv4 sysctl, then use those with that interface?  The
IFF_SKIP_IP seems to duplicate at least part of what disable_ipv6 is
already doing.

Dan

> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> cC: Alexey Kuznetsov <kuznet@xxxxxxxxxxxxx>
> Cc: James Morris <jmorris@xxxxxxxxx>
> Cc: Hideaki YOSHIFUJI <yoshfuji@xxxxxxxxxxxxxx>
> Cc: Patrick McHardy <kaber@xxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Luis R. Rodriguez <mcgrof@xxxxxxxx>
> ---
>  include/uapi/linux/if.h | 1 +
>  net/ipv4/devinet.c      | 3 +++
>  net/ipv6/addrconf.c     | 6 ++++++
>  3 files changed, 10 insertions(+)
> 
> diff --git a/include/uapi/linux/if.h b/include/uapi/linux/if.h
> index 8d10382..566d856 100644
> --- a/include/uapi/linux/if.h
> +++ b/include/uapi/linux/if.h
> @@ -85,6 +85,7 @@
>                                        * change when it's running */
>  #define IFF_MACVLAN 0x200000         /* Macvlan device */
>  #define IFF_BRIDGE_NON_ROOT 0x400000    /* Don't consider for root bridge */
> +#define IFF_SKIP_IP  0x800000        /* Skip IPv4, IPv6 */
>  
> 
>  #define IF_GET_IFACE 0x0001          /* for querying only */
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index a1b5bcb..8e9ef07 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -1342,6 +1342,9 @@ static int inetdev_event(struct notifier_block *this, 
> unsigned long event,
>  
>       ASSERT_RTNL();
>  
> +     if (dev->priv_flags & IFF_SKIP_IP)
> +             goto out;
> +
>       if (!in_dev) {
>               if (event == NETDEV_REGISTER) {
>                       in_dev = inetdev_init(dev);
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index 4b6b720..57f58e3 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -314,6 +314,9 @@ static struct inet6_dev *ipv6_add_dev(struct net_device 
> *dev)
>  
>       ASSERT_RTNL();
>  
> +     if (dev->priv_flags & IFF_SKIP_IP)
> +             return NULL;
> +
>       if (dev->mtu < IPV6_MIN_MTU)
>               return NULL;
>  
> @@ -2749,6 +2752,9 @@ static int addrconf_notify(struct notifier_block *this, 
> unsigned long event,
>       int run_pending = 0;
>       int err;
>  
> +     if (dev->priv_flags & IFF_SKIP_IP)
> +             return NOTIFY_OK;
> +
>       switch (event) {
>       case NETDEV_REGISTER:
>               if (!idev && dev->mtu >= IPV6_MIN_MTU) {



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