Re: [PATCH] kni: fix device address set

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 6 Apr 2022 16:22:13 +0800
"Min Hu (Connor)" <humin29@huawei.com> wrote:

> Currently, run KNI APP When Kernel version is 5.17. When quit the APP,
> dmesg buffer get calltrace, info like:
> [ 5965.847401] rte_kni: Creating kni...
> [ 6225.627205] vEth0 (unregistered): Current addr:  70 fd 45 d0 72 a7 00..
> [ 6225.640113] vEth0 (unregistered): Expected addr: 00 00 00 00 00 00 00..
> [ 6225.653010] ------------[ cut here ]------------
> [ 6225.657609] netdevice: vEth0 (unregistered): Incorrect netdev->dev_addr
> [ 6225.832647] Call trace:
> [ 6225.835083]  dev_addr_check+0xa0/0x144
> [ 6225.838816]  dev_addr_flush+0x30/0x9c
> [ 6225.842462]  free_netdev+0x8c/0x1e0
> [ 6225.845939]  kni_release+0xc0/0x1d0 [rte_kni]
> [ 6225.850281]  __fput+0x78/0x220
> [ 6225.853327]  ____fput+0x1c/0x30
> [ 6225.856455]  task_work_run+0x88/0xc0
> [ 6225.860017]  do_exit+0x2fc/0x940
> [ 6225.863232]  do_group_exit+0x40/0xac
> [ 6225.866791]  get_signal+0x190/0x960
> [ 6225.870265]  do_notify_resume+0x26c/0x1360
> [ 6225.874346]  el0_interrupt+0x60/0xe0
> [ 6225.877910]  __el0_irq_handler_common+0x18/0x24
> [ 6225.882420]  el0t_64_irq_handler+0x14/0x20
> [ 6225.886499]  el0t_64_irq+0x1a0/0x1a4
> [ 6225.890059] ---[ end trace 0000000000000000 ]---
> [ 6245.598157] rte_kni: Creating kni...
> 
> The reason is that 5.17 kernel introduce 'dev_addr_shadow' in function
> 'dev_addr_set' to ensure that netdev->dev_addr should only be modified
> via helpers('dev_addr_set'). 'dev_addr_check' will check if
> netdev->dev_addr is modified by other ways, like 'memcpy'.
> 
> More info could get by referring to kernel patch:
> https://patchwork.kernel.org/project/netdevbpf/patch/
> 20211118041501.3102861-8-kuba@kernel.org/
> https://www.spinics.net/lists/netdev/msg764992.html
> 
> Fixes: ea6b39b5b847 ("kni: remove ethtool support")
> 
> Signed-off-by: Min Hu (Connor) <humin29@huawei.com>
> ---
>  kernel/linux/kni/kni_misc.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/linux/kni/kni_misc.c b/kernel/linux/kni/kni_misc.c
> index 780187d8bf..046de0311f 100644
> --- a/kernel/linux/kni/kni_misc.c
> +++ b/kernel/linux/kni/kni_misc.c
> @@ -299,6 +299,7 @@ kni_ioctl_create(struct net *net, uint32_t ioctl_num,
>  	struct kni_net *knet = net_generic(net, kni_net_id);
>  	int ret;
>  	struct rte_kni_device_info dev_info;
> +	unsigned char mac_addr[ETH_ALEN];
>  	struct net_device *net_dev = NULL;
>  	struct kni_dev *kni, *dev, *n;
>  
> @@ -403,10 +404,15 @@ kni_ioctl_create(struct net *net, uint32_t ioctl_num,
>  
>  	/* if user has provided a valid mac address */
>  	if (is_valid_ether_addr(dev_info.mac_addr))
> -		memcpy(net_dev->dev_addr, dev_info.mac_addr, ETH_ALEN);
> +		memcpy(mac_addr, dev_info.mac_addr, ETH_ALEN);
>  	else
>  		/* Generate random MAC address. */
> -		eth_random_addr(net_dev->dev_addr);
> +		eth_random_addr(mac_addr);
> +#if KERNEL_VERSION(5, 17, 0) > LINUX_VERSION_CODE
> +	memcpy(net_dev->dev_addr, mac_addr, ETH_ALEN);
> +#else
> +	dev_addr_set(net_dev, mac_addr);
> +#endif

This is still not the best way to handle this.
If you use eth_hw_addr_random() it will set the address assign type.
Right now KNI is not doing this correctly.

Also, the code is more readable if all the kernel compatibility
stuff is handled in compat.h. There should be no kernel version
checks in the functions.