解释一种情况

#define EADDRNOTAVAIL 99 /* Cannot assign requested address */

有一种情况是：当IP6的地址处于tentative的时候，就会返回这个错误。下面的是bind的调用的时候会check地址的flag。如果是tentative就返回：err = -EADDRNOTAVAIL;

tentative 的解释

就是一个临时的地址，还没有分配到网卡之上，正处于验证是否有duplicate的情况。
[RFC2462/4429]) - an address whose uniqueness on a link is being verified, prior to its assignment to an interface. A Tentative address is not considered assigned to an interface in the usual sense. An interface discards received packets addressed to a Tentative address, but accepts Neighbor Discovery packets related to Duplicate Address Detection for the Tentative address.