Linux console shows something like "x.x.x.x sent an invalid ICMP type 11, code 0 error to a broadcast ..."
What's the problem?
Let's see kernel source net/ipv4/icmp.c
if (!sysctl_icmp_ignore_bogus_error_responses)
{
if (inet_addr_type(iph->daddr) == RTN_BROADCAST)
{
if (net_ratelimit())
printk(KERN_WARNING "%u.%u.%u.%u sent an invalid ICMP type %u, code %u error to a broadcast: %u.%u.%u.%u on %s\n
NIPQUAD(skb->nh.iph->saddr),
icmph->type, icmph->code,
NIPQUAD(iph->daddr),
skb->dev->name);
goto out;
}
}
It is because recieve ICMP bogus response,
to ignore this, add net.ipv4.icmp_ignore_bogus_error_responses=1 to /etc/sysctl.conf