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netfilter: reduce NF_VERDICT_MASK to 0xff

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NF_VERDICT_MASK is currently 0xffff. This is because the upper
16 bits are used to store errno (for NF_DROP) or the queue number
(NF_QUEUE verdict).

As there are up to 0xffff different queues available, there is no more
room to store additional flags.

At the moment there are only 6 different verdicts, i.e. we can reduce
NF_VERDICT_MASK to 0xff to allow storing additional flags in the 0xff00 space.

NF_VERDICT_BITS would then be reduced to 8, but because the value is
exported to userspace, this might cause breakage; e.g.:

e.g. 'queuenr = (1 << NF_VERDICT_BITS) | NF_QUEUE'  would now break.

Thus, remove NF_VERDICT_BITS usage in the kernel and move the old value
to the 'userspace compat' section.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
This commit is contained in:
Florian Westphal 2011-01-18 15:52:14 +01:00 committed by Patrick McHardy
parent 06cdb6349c
commit f615df76ed
3 changed files with 18 additions and 8 deletions
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20
include/linux/netfilter.h
View File

@ -24,16 +24,19 @@
#define NF_MAX_VERDICT NF_STOP
/* we overload the higher bits for encoding auxiliary data such as the queue
* number. Not nice, but better than additional function arguments. */
#define NF_VERDICT_MASK 0x0000ffff
#define NF_VERDICT_BITS 16
* number or errno values. Not nice, but better than additional function
* arguments. */
#define NF_VERDICT_MASK 0x000000ff
/* extra verdict flags have mask 0x0000ff00 */
/* queue number (NF_QUEUE) or errno (NF_DROP) */
#define NF_VERDICT_QMASK 0xffff0000
#define NF_VERDICT_QBITS 16
#define NF_QUEUE_NR(x) ((((x) << NF_VERDICT_BITS) & NF_VERDICT_QMASK) | NF_QUEUE)
#define NF_QUEUE_NR(x) ((((x) << 16) & NF_VERDICT_QMASK) | NF_QUEUE)
#define NF_DROP_ERR(x) (((-x) << NF_VERDICT_BITS) | NF_DROP)
#define NF_DROP_ERR(x) (((-x) << 16) | NF_DROP)
/* only for userspace compatibility */
#ifndef __KERNEL__
@ -41,6 +44,9 @@
<= 0x2000 is used for protocol-flags. */
#define NFC_UNKNOWN 0x4000
#define NFC_ALTERED 0x8000
/* NF_VERDICT_BITS should be 8 now, but userspace might break if this changes */
#define NF_VERDICT_BITS 16
#endif
enum nf_inet_hooks {
@ -72,6 +78,10 @@ union nf_inet_addr {
#ifdef __KERNEL__
#ifdef CONFIG_NETFILTER
static inline int NF_DROP_GETERR(int verdict)
{
return -(verdict >> NF_VERDICT_QBITS);
}
static inline int nf_inet_addr_cmp(const union nf_inet_addr *a1,
const union nf_inet_addr *a2)

4
net/netfilter/core.c
View File

@ -175,12 +175,12 @@ int nf_hook_slow(u_int8_t pf, unsigned int hook, struct sk_buff *skb,
ret = 1;
} else if ((verdict & NF_VERDICT_MASK) == NF_DROP) {
kfree_skb(skb);
ret = -(verdict >> NF_VERDICT_BITS);
ret = NF_DROP_GETERR(verdict);
if (ret == 0)
ret = -EPERM;
} else if ((verdict & NF_VERDICT_MASK) == NF_QUEUE) {
ret = nf_queue(skb, elem, pf, hook, indev, outdev, okfn,
verdict >> NF_VERDICT_BITS);
verdict >> NF_VERDICT_QBITS);
if (ret < 0) {
if (ret == -ECANCELED)
goto next_hook;

2
net/netfilter/nf_queue.c
View File

@ -299,7 +299,7 @@ void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
case NF_QUEUE:
err = __nf_queue(skb, elem, entry->pf, entry->hook,
entry->indev, entry->outdev, entry->okfn,
verdict >> NF_VERDICT_BITS);
verdict >> NF_VERDICT_QBITS);
if (err < 0) {
if (err == -ECANCELED)
goto next_hook;