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[NETFILTER]: reduce netfilter sk_buff enlargement

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As discussed at netconf'05, we're trying to save every bit in sk_buff.
The patch below makes sk_buff 8 bytes smaller.  I did some basic
testing on my notebook and it seems to work.

The only real in-tree user of nfcache was IPVS, who only needs a
single bit.  Unfortunately I couldn't find some other free bit in
sk_buff to stuff that bit into, so I introduced a separate field for
them.  Maybe the IPVS guys can resolve that to further save space.

Initially I wanted to shrink pkt_type to three bits (PACKET_HOST and
alike are only 6 values defined), but unfortunately the bluetooth code
overloads pkt_type :(

The conntrack-event-api (out-of-tree) uses nfcache, but Rusty just
came up with a way how to do it without any skb fields, so it's safe
to remove it.

- remove all never-implemented 'nfcache' code
- don't have ipvs code abuse 'nfcache' field. currently get's their own
  compile-conditional skb->ipvs_property field.  IPVS maintainers can
  decide to move this bit elswhere, but nfcache needs to die.
- remove skb->nfcache field to save 4 bytes
- move skb->nfctinfo into three unused bits to save further 4 bytes

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Harald Welte 2005-08-09 19:24:19 -07:00 • committed by David S. Miller
parent bf3a46aa9b
commit 6869c4d8e0
27 changed files with 36 additions and 64 deletions
Download patch file Download diff file Expand all files Collapse all files

3
include/linux/netfilter.h
View file

@ -21,10 +21,13 @@
#define NF_STOP 5
#define NF_MAX_VERDICT NF_STOP
/* only for userspace compatibility */
#ifndef __KERNEL__
/* Generic cache responses from hook functions.
<= 0x2000 is used for protocol-flags. */
#define NFC_UNKNOWN 0x4000
#define NFC_ALTERED 0x8000
#endif
#ifdef __KERNEL__
#include <linux/config.h>

3
include/linux/netfilter_decnet.h
View file

@ -9,6 +9,8 @@
#include <linux/netfilter.h>
/* only for userspace compatibility */
#ifndef __KERNEL__
/* IP Cache bits. */
/* Src IP address. */
#define NFC_DN_SRC 0x0001
@ -18,6 +20,7 @@
#define NFC_DN_IF_IN 0x0004
/* Output device. */
#define NFC_DN_IF_OUT 0x0008
#endif /* ! __KERNEL__ */
/* DECnet Hooks */
/* After promisc drops, checksum checks. */

3
include/linux/netfilter_ipv4.h
View file

@ -8,6 +8,8 @@
#include <linux/config.h>
#include <linux/netfilter.h>
/* only for userspace compatibility */
#ifndef __KERNEL__
/* IP Cache bits. */
/* Src IP address. */
#define NFC_IP_SRC 0x0001
@ -35,6 +37,7 @@
#define NFC_IP_DST_PT 0x0400
/* Something else about the proto */
#define NFC_IP_PROTO_UNKNOWN 0x2000
#endif /* ! __KERNEL__ */
/* IP Hooks */
/* After promisc drops, checksum checks. */

3
include/linux/netfilter_ipv6.h
View file

@ -10,6 +10,8 @@
#include <linux/netfilter.h>
/* only for userspace compatibility */
#ifndef __KERNEL__
/* IP Cache bits. */
/* Src IP address. */
#define NFC_IP6_SRC 0x0001
@ -38,6 +40,7 @@
#define NFC_IP6_DST_PT 0x0400
/* Something else about the proto */
#define NFC_IP6_PROTO_UNKNOWN 0x2000
#endif /* ! __KERNEL__ */
/* IP6 Hooks */

10
include/linux/skbuff.h
View file

@ -190,7 +190,6 @@ struct skb_shared_info {
* @end: End pointer
* @destructor: Destruct function
* @nfmark: Can be used for communication between hooks
* @nfcache: Cache info
* @nfct: Associated connection, if any
* @nfctinfo: Relationship of this skb to the connection
* @nf_bridge: Saved data about a bridged frame - see br_netfilter.c
@ -252,17 +251,18 @@ struct sk_buff {
__u8 local_df:1,
cloned:1,
ip_summed:2,
nohdr:1;
/* 3 bits spare */
nohdr:1,
nfctinfo:3;
__u8 pkt_type;
__be16 protocol;
void (*destructor)(struct sk_buff *skb);
#ifdef CONFIG_NETFILTER
__u32 nfmark;
__u32 nfcache;
__u32 nfctinfo;
struct nf_conntrack *nfct;
#if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
__u8 ipvs_property:1;
#endif
#ifdef CONFIG_BRIDGE_NETFILTER
struct nf_bridge_info *nf_bridge;
#endif