Hi Team,

Had a doubt regarding Optimistic DAD implementation in linux kernel.

The RFC of Optimistic DAD states:

“Section 3.3

        A router SHOULD NOT configure an Optimistic Address.”

To check the same there is a condition in kernel code wherein we check if ipv6.devconf_all is set.

Now, my query is that we are checking if forwarding is enabled on all interfaces, then we consider the system to be a router.

But even if forwarding is enabled from few interfaces(not all) isn’t the system behaving like a router?

void addrconf_add_linklocal(struct inet6_dev *idev,
 const struct in6_addr *addr, u32 flags)
{
  .
  .
  .
  .
 
#ifdef CONFIG_IPV6_OPTIMISTIC_DAD
 if ((dev_net(idev->dev)->ipv6.devconf_all->optimistic_dad ||
 idev->cnf.optimistic_dad) &&
 !dev_net(idev->dev)->ipv6.devconf_all->forwarding)
 cfg.ifa_flags |= IFA_F_OPTIMISTIC;
#endif
 
  .
  .
  .
  .
}

Thanks

Chinmay