[ofa-general] removing PR caching from IPoIB

[Roland Dreier]

 > I'm looking at removing the PR caching in IPoIB.
 > 
 > Is there any reason why structs ipoib_path and ipoib_neigh cannot be
 > merged?  (And ipoib_path removed?)
 > 
 > Is there any issue with the PR/AH scope aligning with that of ipoib_neigh?

There are some packets that are sent with no neighbour structure;
unicast ARPs are the case that I know of, although I'm not positive
there aren't other such cases.  See unicast_arp_send() in the IPoIB
source for details.

So you may not be able to merge ipoib_path and ipoib_neigh.  However
it should be possible to only keep the AH once a path record lookup is
done.  OTOH I'm not sure it will end up simplifying anything, since
you would have to deal with allocating/freeing somewhere to hold the
struct ib_sa_path_rec between starting the path record lookup and when
it finishes.

 - R.