A question on inet_select_addr()

From: ahtraps (ahtraps@runbox.com)
Date: Fri Aug 08 2003 - 18:58:48 EST


Hello,

I don't quite understand the comment, and the logic following it, in inet_select_addr() function.

Specifically:

1. How is it guranteed that a loopback address is not chosen? (there is no check for 127.X.X.X
addresses!)

2. Why is it important that the loopback interface be the first in the list. What would go wrong
if the search starts from the second device in the list (i.e., skipping the loopback device).

3. And what does this test mean:
(ifa->ifa_scope != RT_SCOPE_LINK && ifa->ifa_scope <= scope)?

u32 inet_select_addr(const struct net_device *dev, u32 dst, int scope)
{

... SNIP ...

/* Not loopback addresses on loopback should be preferred
in this case. It is importnat that lo is the first interface
in dev_base list.
*/
read_lock(&dev_base_lock);
read_lock(&inetdev_lock);
for (dev=dev_base; dev; dev=dev->next) {
if ((in_dev=__in_dev_get(dev)) == NULL)
continue;

read_lock(&in_dev->lock);
for_primary_ifa(in_dev) {
if (ifa->ifa_scope != RT_SCOPE_LINK &&
ifa->ifa_scope <= scope) {
read_unlock(&in_dev->lock);
read_unlock(&inetdev_lock);
read_unlock(&dev_base_lock);
return ifa->ifa_local;
}
} endfor_ifa(in_dev);
read_unlock(&in_dev->lock);
}
read_unlock(&inetdev_lock);
read_unlock(&dev_base_lock);

return 0;
}


tx
Andy




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