The tcp_ehash hash table gets too big on systems with really big memory.
It is worse on systems with pages larger than 4KB.  It wastes memory that
could be better used.  It also makes the netstat command slow because reading
/proc/net/tcp and /proc/net/tcp6 needs to go through the full hash table.

  The default value should not be larger for larger page sizes.  It seems
that the effect of page size is an unintended error dating back a long
time.  I also wonder if the default value really should be a larger
fraction of memory for systems with more memory.  While systems with
really big ram can afford more space for hash tables, it is not clear to
me that they benefit from increasing the allocation ratio for this table.

  The amount of memory allocated is determined by net/ipv4/tcp.c:tcp_init and
mm/page_alloc.c:alloc_large_system_hash.

tcp_init calls alloc_large_system_hash passing parameters-
    bucketsize=sizeof(struct tcp_ehash_bucket)
    numentries=thash_entries
    scale=(num_physpages >= 128 * 1024) ? (25-PAGE_SHIFT) : (27-PAGE_SHIFT)
    limit=0

On i386, PAGE_SHIFT is 12 for a page size of 4K
On ia64, PAGE_SHIFT defaults to 14 for a page size of 16K

The num_physpages test above makes the allocation take a larger fraction
of the total memory on systems with larger memory.  The threshold size
for a i386 system is 512MB.  For an ia64 system with 16KB pages the
threshold is 2GB.

For smaller memory systems-
On i386, scale = (27 - 12) = 15
On ia64, scale = (27 - 14) = 13
For larger memory systems-
On i386, scale = (25 - 12) = 13
On ia64, scale = (25 - 14) = 11

  For the rest of this discussion, I'll just track the larger memory case.

  The default behavior has numentries=thash_entries=0, so the allocated
size is determined by either scale or by the default limit of 1/16 of
total memory.

In alloc_large_system_hash-
|	numentries = (flags & HASH_HIGHMEM) ? nr_all_pages : nr_kernel_pages;
|	numentries += (1UL << (20 - PAGE_SHIFT)) - 1;
|	numentries >>= 20 - PAGE_SHIFT;
|	numentries <<= 20 - PAGE_SHIFT;

  At this point, numentries is pages for all of memory, rounded up to the
nearest megabyte boundary.

|	/* limit to 1 bucket per 2^scale bytes of low memory */
|	if (scale > PAGE_SHIFT)
|		numentries >>= (scale - PAGE_SHIFT);
|	else
|		numentries <<= (PAGE_SHIFT - scale);

On i386, numentries >>= (13 - 12), so numentries is 1/8196 of
bytes of total memory.
On ia64, numentries <<= (14 - 11), so numentries is 1/2048 of
bytes of total memory.

|        log2qty = long_log2(numentries);
|
|        do {
|                size = bucketsize << log2qty;

bucketsize is 16, so size is 16 times numentries, rounded
down to a power of two.

On i386, size is 1/512 of bytes of total memory.
On ia64, size is 1/128 of bytes of total memory.

For smaller systems the results are
On i386, size is 1/2048 of bytes of total memory.
On ia64, size is 1/512 of bytes of total memory.

  The large page effect can be removed by just replacing
the use of PAGE_SHIFT with a constant of 12 in the calls to
alloc_large_system_hash.  That makes them more like the other uses of
that function from fs/inode.c and fs/dcache.c
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The following patch renames __in_dev_get() to __in_dev_get_rtnl() and
introduces __in_dev_get_rcu() to cover the second case.

1) RCU with refcnt should use in_dev_get().
2) RCU without refcnt should use __in_dev_get_rcu().
3) All others must hold RTNL and use __in_dev_get_rtnl().

There is one exception in net/ipv4/route.c which is in fact a pre-existing
race condition.  I've marked it as such so that we remember to fix it.

This patch is based on suggestions and prior work by Suzanne Wood and
Paul McKenney.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

	One such place that can damage the dst refcnts is route.c with
CONFIG_IP_ROUTE_MULTIPATH_CACHED enabled, i don't see the user's
.config. In this new code i see that rt_intern_hash is called before
dst->refcnt is set to 1, dst is the 2nd arg to rt_intern_hash.

Arg 2 of rt_intern_hash must come with refcnt 1 as it is added to
table or dropped depending on error/add/update. One such example is
ip_mkroute_input where __mkroute_input return rth with refcnt 0 which
is provided to rt_intern_hash. ip_mkroute_output looks like a 2nd such
place. Appending untested patch for comments and review.  The idea is
to put previous reference as we are going to return next result/error.
Signed-off-by: NJulian Anastasov <ja@ssi.bg>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NArnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch contains the following possible cleanups:
- make needlessly global code static
- #if 0 the following unused global function:
  - xfrm4_state.c: xfrm4_state_fini
- remove the following unneeded EXPORT_SYMBOL's:
  - ip_output.c: ip_finish_output
  - ip_output.c: sysctl_ip_default_ttl
  - fib_frontend.c: ip_dev_find
  - inetpeer.c: inet_peer_idlock
  - ip_options.c: ip_options_compile
  - ip_options.c: ip_options_undo
  - net/core/request_sock.c: sysctl_max_syn_backlog
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In some cases, we may be generating packets with a source address that
qualifies as martian. This can happen when we're in the middle of setting
up the network, and netfilter decides to reject a packet with an RST.
The IPv4 routing code would try to print a warning and oops, because
locally generated packets do not have a valid skb->mac.raw pointer
at this point.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

- rt_check_expire() fixes (an overflow occured if size of the hash
  was >= 65536)

reminder of the bugfix:

The rt_check_expire() has a serious problem on machines with large
route caches, and a standard HZ value of 1000.

With default values, ie ip_rt_gc_interval = 60*HZ = 60000 ;

the loop count :

     for (t = ip_rt_gc_interval << rt_hash_log; t >= 0;


overflows (t is a 31 bit value) as soon rt_hash_log is >= 16  (65536
slots in route cache hash table).

In this case, rt_check_expire() does nothing at all
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

- rt hash table allocated using alloc_large_system_hash() function.
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

- Locking abstraction
- Spinlocks moved out of rt hash table : Less memory (50%) used by rt 
  hash table. it's a win even on UP.
- Sizing of spinlocks table depends on NR_CPUS
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

I followed Thomas' proposal to see every martian destination as a case
where the ipInAddrErrors counter has to be incremented. There are
two advantages by doing so: (1) The relation between the ipInReceive
counter and all the other ipInXXX counters is more accurate in the
case the RTN_UNICAST code check fails and (2) it makes the code in
ip_route_input_slow easier.
Signed-off-by: NDietmar Eggemann <dietmar.eggemann@gmx.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off by: Chuck Short <zulcss@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch rectifies some rtnetlink message builders that derive the
flags from the pid. It is now explicit like the other cases
which get it right. Also fixes half a dozen dumpers which did not
set NLM_F_MULTI at all.
Signed-off-by: NJamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Ross moved.  Remove the bad email address so people will find the correct
one in ./CREDITS.
Signed-off-by: NJesper Juhl <juhl-lkml@dif.dk>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Signed-off-by: NOlaf Rempel <razzor@kopf-tisch.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This has been brought up before.. http://lkml.org/lkml/2000/1/21/116
but didnt seem to get resolved.  This morning I got someone
file a bugzilla about it breaking sysctl(8).
Signed-off-by: NDave Jones <davej@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Here is a revised alternative that uses BUG_ON/WARN_ON
(as suggested by Herbert Xu) to eliminate NET_CALLER.
Signed-off-by: NStephen Hemminger <shemminger@osdl.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!