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|
/*
* Linux Socket Filter - Kernel level socket filtering
*
* Author:
* Jay Schulist <jschlst@samba.org>
*
* Based on the design of:
* - The Berkeley Packet Filter
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Andi Kleen - Fix a few bad bugs and races.
* Kris Katterjohn - Added many additional checks in sk_chk_filter()
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/fcntl.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_packet.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/unaligned.h>
#include <linux/filter.h>
/* No hurry in this branch */
static void *__load_pointer(struct sk_buff *skb, int k)
{
u8 *ptr = NULL;
if (k >= SKF_NET_OFF)
ptr = skb_network_header(skb) + k - SKF_NET_OFF;
else if (k >= SKF_LL_OFF)
ptr = skb_mac_header(skb) + k - SKF_LL_OFF;
if (ptr >= skb->head && ptr < skb_tail_pointer(skb))
return ptr;
return NULL;
}
static inline void *load_pointer(struct sk_buff *skb, int k,
unsigned int size, void *buffer)
{
if (k >= 0)
return skb_header_pointer(skb, k, size, buffer);
else {
if (k >= SKF_AD_OFF)
return NULL;
return __load_pointer(skb, k);
}
}
/**
* sk_run_filter - run a filter on a socket
* @skb: buffer to run the filter on
* @filter: filter to apply
* @flen: length of filter
*
* Decode and apply filter instructions to the skb->data.
* Return length to keep, 0 for none. skb is the data we are
* filtering, filter is the array of filter instructions, and
* len is the number of filter blocks in the array.
*/
unsigned int sk_run_filter(struct sk_buff *skb, struct sock_filter *filter, int flen)
{
struct sock_filter *fentry; /* We walk down these */
void *ptr;
u32 A = 0; /* Accumulator */
u32 X = 0; /* Index Register */
u32 mem[BPF_MEMWORDS]; /* Scratch Memory Store */
u32 tmp;
int k;
int pc;
/*
* Process array of filter instructions.
*/
for (pc = 0; pc < flen; pc++) {
fentry = &filter[pc];
switch (fentry->code) {
case BPF_ALU|BPF_ADD|BPF_X:
A += X;
continue;
case BPF_ALU|BPF_ADD|BPF_K:
A += fentry->k;
continue;
case BPF_ALU|BPF_SUB|BPF_X:
A -= X;
continue;
case BPF_ALU|BPF_SUB|BPF_K:
A -= fentry->k;
continue;
case BPF_ALU|BPF_MUL|BPF_X:
A *= X;
continue;
case BPF_ALU|BPF_MUL|BPF_K:
A *= fentry->k;
continue;
case BPF_ALU|BPF_DIV|BPF_X:
if (X == 0)
return 0;
A /= X;
continue;
case BPF_ALU|BPF_DIV|BPF_K:
A /= fentry->k;
continue;
case BPF_ALU|BPF_AND|BPF_X:
A &= X;
continue;
case BPF_ALU|BPF_AND|BPF_K:
A &= fentry->k;
continue;
case BPF_ALU|BPF_OR|BPF_X:
A |= X;
continue;
case BPF_ALU|BPF_OR|BPF_K:
A |= fentry->k;
continue;
case BPF_ALU|BPF_LSH|BPF_X:
A <<= X;
continue;
case BPF_ALU|BPF_LSH|BPF_K:
A <<= fentry->k;
continue;
case BPF_ALU|BPF_RSH|BPF_X:
A >>= X;
continue;
case BPF_ALU|BPF_RSH|BPF_K:
A >>= fentry->k;
continue;
case BPF_ALU|BPF_NEG:
A = -A;
continue;
case BPF_JMP|BPF_JA:
pc += fentry->k;
continue;
case BPF_JMP|BPF_JGT|BPF_K:
pc += (A > fentry->k) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JGE|BPF_K:
pc += (A >= fentry->k) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JEQ|BPF_K:
pc += (A == fentry->k) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JSET|BPF_K:
pc += (A & fentry->k) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JGT|BPF_X:
pc += (A > X) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JGE|BPF_X:
pc += (A >= X) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JEQ|BPF_X:
pc += (A == X) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JSET|BPF_X:
pc += (A & X) ? fentry->jt : fentry->jf;
continue;
case BPF_LD|BPF_W|BPF_ABS:
k = fentry->k;
load_w:
ptr = load_pointer(skb, k, 4, &tmp);
if (ptr != NULL) {
A = ntohl(get_unaligned((__be32 *)ptr));
continue;
}
break;
case BPF_LD|BPF_H|BPF_ABS:
k = fentry->k;
load_h:
ptr = load_pointer(skb, k, 2, &tmp);
if (ptr != NULL) {
A = ntohs(get_unaligned((__be16 *)ptr));
continue;
}
break;
case BPF_LD|BPF_B|BPF_ABS:
k = fentry->k;
load_b:
ptr = load_pointer(skb, k, 1, &tmp);
if (ptr != NULL) {
A = *(u8 *)ptr;
continue;
}
break;
case BPF_LD|BPF_W|BPF_LEN:
A = skb->len;
continue;
case BPF_LDX|BPF_W|BPF_LEN:
X = skb->len;
continue;
case BPF_LD|BPF_W|BPF_IND:
k = X + fentry->k;
goto load_w;
case BPF_LD|BPF_H|BPF_IND:
k = X + fentry->k;
goto load_h;
case BPF_LD|BPF_B|BPF_IND:
k = X + fentry->k;
goto load_b;
case BPF_LDX|BPF_B|BPF_MSH:
ptr = load_pointer(skb, fentry->k, 1, &tmp);
if (ptr != NULL) {
X = (*(u8 *)ptr & 0xf) << 2;
|