[NETFILTER] NAT sequence adjustment: Save eight bytes per conntrack

[NETFILTER] NAT sequence adjustment: Save eight bytes per conntrack

[Harald Welte]

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Hi Dave!

Please apply this humble little step towards ip_conntrack shrinking,
thanks!

[NETFILTER] NAT sequence adjustment: Save eight bytes per conntrack

This patch reduces the size of 'struct ip_conntrack' on systems with NAT
by eight bytes.  The sequence number delta values can be int16_t, since
we only support one sequence number modification per window anyway, and
one such modification is not going to exceed 32kB ;)

Signed-off-by: Harald Welte <laforge@netfilter.org>

---
commit 94d3d40c84672b74e59ea5252f61602610e1513e
tree 63e5ae5174af9f982be6d8d1bbe11e750e4ace32
parent e3c7a1f99300fbd6de35a40fcd9c4dc1b0fbfee2
author Harald Welte <laforge@netfilter.org> Fri, 27 Jan 2006 16:03:45 +0100
committer Harald Welte <laforge@netfilter.org> Fri, 27 Jan 2006 16:03:45 +0100

 include/linux/netfilter_ipv4/ip_nat.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/netfilter_ipv4/ip_nat.h b/include/linux/netfilter_ipv4/ip_nat.h
index 41a107d..e9f5ed1 100644
--- a/include/linux/netfilter_ipv4/ip_nat.h
+++ b/include/linux/netfilter_ipv4/ip_nat.h
@@ -23,7 +23,7 @@ struct ip_nat_seq {
 	 * modification (if any) */
 	u_int32_t correction_pos;
 	/* sequence number offset before and after last modification */
-	int32_t offset_before, offset_after;
+	int16_t offset_before, offset_after;
 };
 
 /* Single range specification. */
-- 
- Harald Welte <laforge@netfilter.org>                 http://netfilter.org/
============================================================================
  "Fragmentation is like classful addressing -- an interesting early
   architectural error that shows how much experimentation was going
   on while IP was being designed."                    -- Paul Vixie

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Re: [NETFILTER] NAT sequence adjustment: Save eight bytes per conntrack

[David S. Miller]

From: Harald Welte <laforge@netfilter.org>
Date: Tue, 31 Jan 2006 00:22:09 +0100

> [NETFILTER] NAT sequence adjustment: Save eight bytes per conntrack
> 
> This patch reduces the size of 'struct ip_conntrack' on systems with NAT
> by eight bytes.  The sequence number delta values can be int16_t, since
> we only support one sequence number modification per window anyway, and
> one such modification is not going to exceed 32kB ;)
> 
> Signed-off-by: Harald Welte <laforge@netfilter.org>

Applied to net-2.6.17, thanks Harald.

Re: [NETFILTER] NAT sequence adjustment: Save eight bytes per conntrack

[Balazs Scheidler]

On Tue, 2006-01-31 at 00:22 +0100, Harald Welte wrote:

> ---
> commit 94d3d40c84672b74e59ea5252f61602610e1513e
> tree 63e5ae5174af9f982be6d8d1bbe11e750e4ace32
> parent e3c7a1f99300fbd6de35a40fcd9c4dc1b0fbfee2
> author Harald Welte <laforge@netfilter.org> Fri, 27 Jan 2006 16:03:45 +0100
> committer Harald Welte <laforge@netfilter.org> Fri, 27 Jan 2006 16:03:45 +0100
> 
>  include/linux/netfilter_ipv4/ip_nat.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/netfilter_ipv4/ip_nat.h b/include/linux/netfilter_ipv4/ip_nat.h
> index 41a107d..e9f5ed1 100644
> --- a/include/linux/netfilter_ipv4/ip_nat.h
> +++ b/include/linux/netfilter_ipv4/ip_nat.h
> @@ -23,7 +23,7 @@ struct ip_nat_seq {
>  	 * modification (if any) */
>  	u_int32_t correction_pos;
>  	/* sequence number offset before and after last modification */
> -	int32_t offset_before, offset_after;
> +	int16_t offset_before, offset_after;
>  };

Am I missing something or is it only 4 bytes?

-- 
Bazsi

Re: [NETFILTER] NAT sequence adjustment: Save eight bytes per conntrack

[Harald Welte]

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On Tue, Jan 31, 2006 at 09:50:52AM +0100, Balazs Scheidler wrote:

> > -	int32_t offset_before, offset_after;
> > +	int16_t offset_before, offset_after;
> 
> Am I missing something or is it only 4 bytes?

I knew someone would ask that question ;)

we have that structure as part of an IP_CT_DIR_MAX array, therefore it's
twice in every conntrack, and thus we save 8 bytes ;)

-- 
- Harald Welte <laforge@netfilter.org>                 http://netfilter.org/
============================================================================
  "Fragmentation is like classful addressing -- an interesting early
   architectural error that shows how much experimentation was going
   on while IP was being designed."                    -- Paul Vixie

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