Expired IPv6 router causes an infinite loop

[ghost]

An expired IPv6 router causes an infinite loop where iface_router_run_timer() repeatedly scheduled a work item with negative delay.

Environment: Zephyr v2.0.0 on native_posix, SDK 0.10.3. This bug also manifests itself on newer versions (current master 3765e46) and on ARM Cortex-M hardware.

Steps to reproduce on v2.0.0:

• Use samples/net/eth_native_posix
• Remove CONFIG_NET_CONFIG_* from prj.conf to get SLAAC
• Run net-setup.sh from net-tools
• Start radvd with a config like this:

interface zeth
{
    AdvSendAdvert on;
    MinRtrAdvInterval 3;
    MaxRtrAdvInterval 4;
    AdvDefaultLifetime 7;

    prefix 2001:db8::/64
    {
        AdvValidLifetime infinity;
        AdvPreferredLifetime infinity;
    };
};

• Start eth_native_posix sample and wait until it gets a prefix
• Stop radvd from working with ctrl-z (not ctrl-c)
• Wait for the router to time out (7 seconds)
• Observe iface_router_expired and iface_router_run_timer getting called repeatedly (you might have added a printk there)

On master this problem still exists, but the infinite loop doesn't happen until the router re-appears. I'm not exactly sure why.