[ovs-dev] [PATCH v5] netdev-dpdk: fix ifindex assignment for DPDK ports

Lal, PrzemyslawX przemyslawx.lal at intel.com
Tue Apr 4 10:09:00 UTC 2017


On 04/04/2017 06:14, Darrell Ball wrote:

>
> On 4/3/17, 5:27 AM, "ovs-dev-bounces at openvswitch.org on behalf of Przemyslaw Lal" <ovs-dev-bounces at openvswitch.org on behalf of przemyslawx.lal at intel.com> wrote:
>
>      In current implementation port_id is used as an ifindex for all netdev-dpdk
>      interfaces.
>      
>      For physical DPDK interfaces using port_id as ifindex causes that '0' is set as
>      ifindex for 'dpdk0' interface, '1' for 'dpdk1' and so on. For the DPDK vHost
>      interfaces ifindexes are not even assigned (0 is used by default) due to the
>      fact that vHost ports don't use port_id field from the DPDK library.
>      
>      This causes multiple negative side-effects. First of all 0 is an invalid
>      ifindex value. The other issue is possible overlapping of 'dpdkX' interfaces
>      ifindex values with the ifindexes of kernel space interfaces which may cause
>      problems in any external tools that use those values. Neither 'dpdk0', nor any
>      DPDK vHost interfaces are visible in sFlow collector tools, as all interfaces
>      with ifindexes smaller than 1 are ignored.
>      
>      Proposed solution to these issues is to calculate a hash of interface's name
>      and use calculated value as an ifindex. This way interfaces keep their
>      ifindexes during OVS-DPDK restarts, ports re-initialization events, etc., show
>      up in sFlow collectors and meet RFC 2863 specification regarding re-using
>      ifindex values by the same virtual interfaces and maximum ifindex value.
>      
>      Signed-off-by: Przemyslaw Lal <przemyslawx.lal at intel.com>
>      ---
>       lib/netdev-dpdk.c | 6 +++++-
>       1 file changed, 5 insertions(+), 1 deletion(-)
>      
>      diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
>      index ddc651b..687b0a5 100644
>      --- a/lib/netdev-dpdk.c
>      +++ b/lib/netdev-dpdk.c
>      @@ -2215,7 +2215,11 @@ netdev_dpdk_get_ifindex(const struct netdev *netdev)
>           int ifindex;
>       
>           ovs_mutex_lock(&dev->mutex);
>      -    ifindex = dev->port_id;
>      +    /* Calculate hash from the netdev name. Ensure that ifindex is a 24-bit
>      +     * postive integer to meet RFC 2863 recommendations.
>      +     */
>      +    uint32_t h = hash_string(netdev->name, 0);
>      +    ifindex = (int)(h % 0xfffffe + 1);
>
>
> If user configuration was supported, enforcing uniqueness would be the
> responsibility of the user.

This was already discussed on this mailing list and outcome was that while hash is not perfect, it is the best solution for now.
Also please keep in mind that names of the physical DPDK devices and dpdkvhostuser interfaces are configurable, so user can still enforce uniqueness.

>
> One minor question:
> I know other ifindex implementations do not limit to 24 bits, so I checked RFC 2863.
> What section is the 24 bit limit recommendation mentioned in RFC 2863; I missed it.

Recommendation of RFC 2863 is to use "small integers". Main purpose of this patch is to enable dpdkvhostuser interfaces in sFlow metrics collecting tools.
After posting previous version I've received feedback from the community that not all interfaces are visible in sFlow collectors and maximum supported ifindex is 2^24.
Here's the sFlow v5 specification: http://sflow.org/sflow_version_5.txt

>
>
>
>           ovs_mutex_unlock(&dev->mutex);
>       
>           return ifindex;
>      --
>      1.9.1
>      
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