Hello,
On Wed, 1 Feb 2017, Steffen Klassert wrote:
> On Tue, Jan 31, 2017 at 11:57:05PM +0200, Julian Anastasov wrote:
> >
> > +static void xfrm_confirm_neigh(const struct dst_entry *dst, const void
> > *daddr)
> > +{
> > + const struct dst_entry *path = dst->path;
> > +
> > + if (path == dst) {
>
> I think path can not be equal to dst here, otherwise we would
> have an infinite recursion.
Yep, I know that, this place remained unfinished.
> > + dst->ops->confirm_neigh(dst, daddr);
> > + } else {
> > + /* daddr can be from different family and we need the
> > + * tunnel address. How to get it?
> > + */
>
> This is only called on a xfrm_dst, so you should have dst->xfrm set.
> You can get the daddr of this transform with:
>
> xfrm_address_t *daddr = &xfrm->id.daddr;
I hope so but see below...
> > + path->ops->confirm_neigh(path, NULL);
>
> I think here it is better to go through the whole chain
> of transformations with
>
> child->ops->confirm_neigh(path, daddr);
It may sounds good. But only dst->path->ops->confirm_neigh
points to real IPv4/IPv6 function. And also, I guess, the
family can change while walking the chain, so we should be
careful while providing the original daddr (which comes from
sendmsg). I had the idea to walk all xforms to get the latest
tunnel address but this can be slow. Something like this?:
static void xfrm_confirm_neigh(const struct dst_entry *dst, const void
*daddr)
{
const struct dst_entry *path = dst->path;
/* By default, daddr is from sendmsg() if we have no tunnels */
for (;dst != path; dst = dst->child) {
const struct xfrm_state *xfrm = dst->xfrm;
/* Use address from last tunnel */
if (xfrm->props.mode != XFRM_MODE_TRANSPORT)
daddr = &xfrm->id.daddr;
}
path->ops->confirm_neigh(path, daddr);
}
This should work as long as path and last tunnel are
from same family. Also, after checking xfrm_dst_lookup() I'm not
sure using just &xfrm->id.daddr is enough. Should we consider
more places for daddr value?
> > int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo)
> > {
> > int err = 0;
> > @@ -2882,6 +2896,8 @@ int xfrm_policy_register_afinfo(struct
> > xfrm_policy_afinfo *afinfo)
> > dst_ops->link_failure = xfrm_link_failure;
> > if (likely(dst_ops->neigh_lookup == NULL))
> > dst_ops->neigh_lookup = xfrm_neigh_lookup;
> > + if (likely(!dst_ops->confirm_neigh))
> > + dst_ops->confirm_neigh = xfrm_confirm_neigh;
>
> We also have address family depended dst_ops, look for
> xfrm4_dst_ops_template/xfrm6_dst_ops_template.
For now I installed common handler, just like
xfrm_neigh_lookup. BTW this function has problem from
commit f894cbf847c9, it looks like dst is wrongly provided,
first arg should be dst->path.
But as dst_ops contains the family, I think, we can know
what kind of daddr is provided initially (dst->ops->family).
So far, the above logic does not need to compare the families.
But as I don't know the code well, I'm not sure, my assumptions are:
- transports do not change the family
- tunnels may change the family
- last tunnel gets dst0->path route from its family
Regards
--
Julian Anastasov <j...@ssi.bg>
