[ovs-dev] [PATCH V2] netdev-dpdk: fix ifindex assignment for DPDK ports

Przemyslaw Lal przemyslawx.lal at intel.com
Thu Dec 8 12:16:22 UTC 2016

In current implementation port_id is used as an ifindex for all netdev-dpdk

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 infindexes 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 RFC2863 specification regarding re-using
ifindex values by the same virtual interfaces.

Signed-off-by: Przemyslaw Lal <przemyslawx.lal at intel.com>
 lib/netdev-dpdk.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
index de78ddd..ef99eb3 100644
--- a/lib/netdev-dpdk.c
+++ b/lib/netdev-dpdk.c
@@ -2075,7 +2075,13 @@ netdev_dpdk_get_ifindex(const struct netdev *netdev)
     int ifindex;
-    ifindex = dev->port_id;
+    /* Calculate hash from the netdev name using hash_bytes() function.
+     * Because ifindex is declared as signed int in the kernel sources and
+     * OVS follows this implementation right shift is needed to set sign bit
+     * to 0 and then XOR to slightly improve collision rate.
+     */
+    uint32_t h = hash_bytes(netdev->name, strlen(netdev->name), 0);
+    ifindex = (int)((h >> 1) ^ (h & 0x0FFFFFFF));
     return ifindex;

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