when test snull driver, ping remote1 sometimes return 100% packet loss

[lzq420241]

This issue occurs in ubuntu 18.04 and 20.04

[lzq420241]

It turns out that it may not be driver issue.

I used journalctl -f to monitor the snull_load process.
After add printk in snull_rx_ints and snull_hw_tx, I found that
right after sn1 send pkt to remote1, snull_napi_interrupt set sn0's rx_int_enabled to 0, but before the sn0's snull_poll begin to excute, the below log appeared.

NetworkManager[574]: [1632110381.7007] device (sn0): state change: unmanaged -> unavailable (reason 'managed', sys-iface-state: 'external')

NetworkManager[574]: [1632110381.7197] device (sn0): state change: config -> ip-config (reason 'none', sys-iface-state: 'managed')

NetworkManager seems drop napi_schedule from the execution flow.

Thus sn0's rx_int_enabled has no chance to get update to 1, and sn0's rx is disabled totally.

[lzq420241]

To verify the above issue, I made sn0, sn1 unmanaged by networkmanager:

append to /etc/NetworkManager/NetworkManager.conf with

[keyfile]
unmanaged-devices=interface-name:sn0,interface-name:sn1

and use service network-manager restart to reload the change.
check with nmcli dev status.

[lzq420241]

Can someone help check below changes:
before:

if (statusword & SNULL_RX_INTR) {
    snull_rx_ints(dev, 0);  /* Disable further interrupts */
    napi_schedule(&priv->napi);
}

after:

if (statusword & SNULL_RX_INTR && napi_schedule_prep(&priv->napi)) {
    snull_rx_ints(dev, 0);  /* Disable further interrupts */
    __napi_schedule(&priv->napi); 
}

seems works with Netmanager enabled.

before you start ping remote1, do ifconfig sn0 local0; ifconfig sn1 local1 again, as netmanager will remove them.

[dwalkes]

Thanks @lzq420241 sorry for the delay. Do you want to submit a pull request for this change?