inet_peer is indexed by the dst address alone. However, the fib6 tree
could have multiple routing entries (rt6_info) for the same dst. For
example,
1. A /128 dst via multiple gateways.
2. A RTF_CACHE route cloned from a /128 route.
In the above cases, all of them will share the same metrics and
step on each other.
This patch will steer away from inet_peer's metrics and use
dst_cow_metrics_generic() for everything.
Change Highlights:
1. Remove rt6_cow_metrics() which currently acquires metrics from
inet_peer for DST_HOST route (i.e. /128 route).
2. Add rt6i_pmtu to take care of the pmtu update to avoid creating a
full size metrics just to override the RTAX_MTU.
3. After (2), the RTF_CACHE route can also share the metrics with its
dst.from route, by:
dst_init_metrics(&cache_rt->dst, dst_metrics_ptr(cache_rt->dst.from), true);
4. Stop creating RTF_CACHE route by cloning another RTF_CACHE route. Instead,
directly clone from rt->dst.
[ Currently, cloning from another RTF_CACHE is only possible during
rt6_do_redirect(). Also, the old clone is removed from the tree
immediately after the new clone is added. ]
In case of cloning from an older redirect RTF_CACHE, it should work as
before.
In case of cloning from an older pmtu RTF_CACHE, this patch will forget
the pmtu and re-learn it (if there is any) from the redirected route.
The _rt6i_peer and DST_METRICS_FORCE_OVERWRITE will be removed
in the next cleanup patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Reviewed-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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