Embedded Connectivity
Intel network controllers, Firmware, and drivers support systems
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KPDK problem with KNI: ifconfig timeout due to IPv6 autoconfig


On the:


OS: RHEL 2.6.32

the command "ifconfig vEth0 up" to start the KNI interface fails a few times with

SIOCSIFFLAGS: Timer expired

After some time (around 1 minute) the command "ifconfig vEth0 up" works OK.

It looks that it is linked to the IPv6 auto configuration as the kernel syslog shows the message kernel: vEth0: no IPv6 routers present.

I am using the DPDK application on IPv4 and there is no IPv6 router in the LAN.

Question how do I deactivate the IPv6 auto configuration for the KNI interface ?

I tried to create a entry in /etc/sysconfig/ifcfg_vETh0 with IPV6INIT="no" and IPV6_AUTOCONF="no" without success.

I guess that the kernel does not apply this setting as at boot time the the DPDK application does not run.

Interestingly, it seems that the tap/tun interface does not have this problem.

I am wondering how Linux avoid doing the IPv6 auto configuration on a tap/tun interface ?

2 Replies

I solve my problem.

The issue is the KNI function


* It is called in the same lcore of receiving packets, and polls the request

* mbufs sent from kernel space. Then analyzes it and calls the specific

* actions for the specific requests. Finally constructs the response mbuf and

* puts it back to the resp_q.


static int kni_request_handler(struct rte_kni *kni)

This function is only called by

unsigned rte_kni_tx_burst(struct rte_kni *kni, struct rte_mbuf **mbufs, unsigned num)

So if there is no incoming PDU from the NIC to be sent to the Linux kernel, the function rte_kni_tx_burst is not called.

The KNI layer does not read the request PDU so does not get the if_up message so does not answer to the kernel module so the KNI kernel module replies to IP with a time out.

Work around:

Call regularly rte_kni_tx_burst(kni, NULL, 0).

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Nice job on finding the work around!

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