linux-toradex.git/net/ipv4/route.c, branch v2.6.31.2

ipv4 routing: Ensure that route cache entries are usable and reclaimable with caching is off

2009-06-23T23:36:26+00:00

When route caching is disabled (rt_caching returns false), We still use route
cache entries that are created and passed into rt_intern_hash once.  These
routes need to be made usable for the one call path that holds a reference to
them, and they need to be reclaimed when they're finished with their use.  To be
made usable, they need to be associated with a neighbor table entry (which they
currently are not), otherwise iproute_finish2 just discards the packet, since we
don't know which L2 peer to send the packet to.  To do this binding, we need to
follow the path a bit higher up in rt_intern_hash, which calls
arp_bind_neighbour, but not assign the route entry to the hash table.
Currently, if caching is off, we simply assign the route to the rp pointer and
are reutrn success.  This patch associates us with a neighbor entry first.

Secondly, we need to make sure that any single use routes like this are known to
the garbage collector when caching is off.  If caching is off, and we try to
hash in a route, it will leak when its refcount reaches zero.  To avoid this,
this patch calls rt_free on the route cache entry passed into rt_intern_hash.
This places us on the gc list for the route cache garbage collector, so that
when its refcount reaches zero, it will be reclaimed (Thanks to Alexey for this
suggestion).

I've tested this on a local system here, and with these patches in place, I'm
able to maintain routed connectivity to remote systems, even if I set
/proc/sys/net/ipv4/rt_cache_rebuild_count to -1, which forces rt_caching to
return false.

Signed-off-by: Neil Horman 
Reported-by: Jarek Poplawski 
Reported-by: Maxime Bizon 
Signed-off-by: David S. Miller

ipv4: fix NULL pointer + success return in route lookup path

2009-06-20T08:15:16+00:00

Don't drop route if we're not caching	

	I recently got a report of an oops on a route lookup.  Maxime was
testing what would happen if route caching was turned off (doing so by setting
making rt_caching always return 0), and found that it triggered an oops.  I
looked at it and found that the problem stemmed from the fact that the route
lookup routines were returning success from their lookup paths (which is good),
but never set the **rp pointer to anything (which is bad).  This happens because
in rt_intern_hash, if rt_caching returns false, we call rt_drop and return 0.
This almost emulates slient success.  What we should be doing is assigning *rp =
rt and _not_ dropping the route.  This way, during slow path lookups, when we
create a new route cache entry, we don't immediately discard it, rather we just
don't add it into the cache hash table, but we let this one lookup use it for
the purpose of this route request.  Maxime has tested and reports it prevents
the oops.  There is still a subsequent routing issue that I'm looking into
further, but I'm confident that, even if its related to this same path, this
patch makes sense to take.

Signed-off-by: Neil Horman 
Signed-off-by: David S. Miller

net: use a deferred timer in rt_check_expire

2009-06-14T06:36:31+00:00

For the sake of power saver lovers, use a deferrable timer to fire
rt_check_expire()

As some big routers cache equilibrium depends on garbage collection
done in time, we take into account elapsed time between two
rt_check_expire() invocations to adjust the amount of slots we have to
check.

Based on an initial idea and patch from Tero Kristo

Signed-off-by: Eric Dumazet 
Signed-off-by: Tero Kristo 
Signed-off-by: David S. Miller

net: skb->dst accessors

2009-06-03T09:51:04+00:00

Define three accessors to get/set dst attached to a skb

struct dst_entry *skb_dst(const struct sk_buff *skb)

void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst)

void skb_dst_drop(struct sk_buff *skb)
This one should replace occurrences of :
dst_release(skb->dst)
skb->dst = NULL;

Delete skb->dst field

Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

net: skb->rtable accessor

2009-06-03T09:51:02+00:00

Define skb_rtable(const struct sk_buff *skb) accessor to get rtable from skb

Delete skb->rtable field

Setting rtable is not allowed, just set dst instead as rtable is an alias.

Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

net: fix rtable leak in net/ipv4/route.c

2009-05-21T00:18:02+00:00

Alexander V. Lukyanov found a regression in 2.6.29 and made a complete
analysis found in http://bugzilla.kernel.org/show_bug.cgi?id=13339
Quoted here because its a perfect one :

begin_of_quotation
 2.6.29 patch has introduced flexible route cache rebuilding. Unfortunately the
 patch has at least one critical flaw, and another problem.

 rt_intern_hash calculates rthi pointer, which is later used for new entry
 insertion. The same loop calculates cand pointer which is used to clean the
 list. If the pointers are the same, rtable leak occurs, as first the cand is
 removed then the new entry is appended to it.

 This leak leads to unregister_netdevice problem (usage count > 0).

 Another problem of the patch is that it tries to insert the entries in certain
 order, to facilitate counting of entries distinct by all but QoS parameters.
 Unfortunately, referencing an existing rtable entry moves it to list beginning,
 to speed up further lookups, so the carefully built order is destroyed.

 For the first problem the simplest patch it to set rthi=0 when rthi==cand, but
 it will also destroy the ordering.
end_of_quotation

Problematic commit is 1080d709fb9d8cd4392f93476ee46a9d6ea05a5b
(net: implement emergency route cache rebulds when gc_elasticity is exceeded)

Trying to keep dst_entries ordered is too complex and breaks the fact that
order should depend on the frequency of use for garbage collection.

A possible fix is to make rt_intern_hash() simpler, and only makes
rt_check_expire() a litle bit smarter, being able to cope with an arbitrary
entries order. The added loop is running on cache hot data, while cpu
is prefetching next object, so should be unnoticied.

Reported-and-analyzed-by: Alexander V. Lukyanov 
Signed-off-by: Eric Dumazet 
Acked-by: Neil Horman 
Signed-off-by: David S. Miller

net: fix length computation in rt_check_expire()

2009-05-21T00:18:01+00:00

rt_check_expire() computes average and standard deviation of chain lengths,
but not correclty reset length to 0 at beginning of each chain.
This probably gives overflows for sum2 (and sum) on loaded machines instead
of meaningful results.

Signed-off-by: Eric Dumazet 
Acked-by: Neil Horman 
Signed-off-by: David S. Miller

ipv4: Limit size of route cache hash table

2009-04-27T12:42:24+00:00

Right now we have no upper limit on the size of the route cache hash table.
On a 128GB POWER6 box it ends up as 32MB:

    IP route cache hash table entries: 4194304 (order: 9, 33554432 bytes)

It would be nice to cap this for memory consumption reasons, but a massive
hashtable also causes a significant spike when measuring OS jitter.

With a 32MB hashtable and 4 million entries, rt_worker_func is taking
5 ms to complete. On another system with more memory it's taking 14 ms.
Even though rt_worker_func does call cond_sched() to limit its impact,
in an HPC environment we want to keep all sources of OS jitter to a minimum.

With the patch applied we limit the number of entries to 512k which
can still be overriden by using the rt_entries boot option:

    IP route cache hash table entries: 524288 (order: 6, 4194304 bytes)

With this patch rt_worker_func now takes 0.460 ms on the same system.

Signed-off-by: Anton Blanchard 
Acked-by: Eric Dumazet 
Signed-off-by: David S. Miller

Merge branch 'core/percpu' into percpu-cpumask-x86-for-linus-2

2009-03-27T16:28:43+00:00

Conflicts:
	arch/parisc/kernel/irq.c
	arch/x86/include/asm/fixmap_64.h
	arch/x86/include/asm/setup.h
	kernel/irq/handle.c

Semantic merge:
        arch/x86/include/asm/fixmap.h

Signed-off-by: Ingo Molnar

alloc_percpu: add align argument to __alloc_percpu, fix

2009-02-25T13:09:41+00:00

Impact: build fix

API was changed, but not all usage sites were converted:

 net/ipv4/route.c: In function ‘ip_rt_init’:
 net/ipv4/route.c:3379: error: too few arguments to function ‘__alloc_percpu’

Cc: Rusty Russell 
Cc: Tejun Heo 
Signed-off-by: Ingo Molnar