On Thu, Feb 02, 2017 at 01:04:34AM +0200, Julian Anastasov wrote:
>
> Hello,
>
> On Wed, 1 Feb 2017, Steffen Klassert wrote:
>
> >
> > 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.
Is this a per packet call or is the information cached somewhere?
> 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);
> }
I thought about this (completely untested) one:
static void xfrm_confirm_neigh(const struct dst_entry *dst, const void
*daddr)
{
const struct dst_entry *dst = dst->child;
const struct xfrm_state *xfrm = dst->xfrm;
if (xfrm)
daddr = &xfrm->id.daddr;
dst->ops->confirm_neigh(dst, daddr);
}
Only the last dst_entry in this call chain (path) sould
not have dst->xfrm set. So it finally calls path->ops->confirm_neigh
with the daddr of the last transformation. But your version
should do the same.
>
> This should work as long as path and last tunnel are
> from same family.
Yes, the outer mode of the last transformation has the same
family as path.
> 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?
Yes, indeed. We should do it like xfrm_dst_lookup() does it.
>
> > > 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.
Yes, this should use dst->path of course. I really wonder why
nobody noticed this for the last five years.
>
> 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
This is correct.
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