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01f2f3f6ef
Gcc is currenlty not in the ability to optimize the switch statement in sk_run_filter() because of dense case labels. This patch replace the OR'd labels with ordered sequenced case labels. The sk_chk_filter() function is modified to patch/replace the original OPCODES in a ordered but equivalent form. gcc is now in the ability to transform the switch statement in sk_run_filter into a jump table of complexity O(1). Until this patch gcc generates a sequence of conditional branches (O(n) of 567 byte .text segment size (arch x86_64): 7ff: 8b 06 mov (%rsi),%eax 801: 66 83 f8 35 cmp $0x35,%ax 805: 0f 84 d0 02 00 00 je adb <sk_run_filter+0x31d> 80b: 0f 87 07 01 00 00 ja 918 <sk_run_filter+0x15a> 811: 66 83 f8 15 cmp $0x15,%ax 815: 0f 84 c5 02 00 00 je ae0 <sk_run_filter+0x322> 81b: 77 73 ja 890 <sk_run_filter+0xd2> 81d: 66 83 f8 04 cmp $0x4,%ax 821: 0f 84 17 02 00 00 je a3e <sk_run_filter+0x280> 827: 77 29 ja 852 <sk_run_filter+0x94> 829: 66 83 f8 01 cmp $0x1,%ax [...] With the modification the compiler translate the switch statement into the following jump table fragment: 7ff: 66 83 3e 2c cmpw $0x2c,(%rsi) 803: 0f 87 1f 02 00 00 ja a28 <sk_run_filter+0x26a> 809: 0f b7 06 movzwl (%rsi),%eax 80c: ff 24 c5 00 00 00 00 jmpq *0x0(,%rax,8) 813: 44 89 e3 mov %r12d,%ebx 816: e9 43 03 00 00 jmpq b5e <sk_run_filter+0x3a0> 81b: 41 89 dc mov %ebx,%r12d 81e: e9 3b 03 00 00 jmpq b5e <sk_run_filter+0x3a0> Furthermore, I reordered the instructions to reduce cache line misses by order the most common instruction to the start. Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net> Signed-off-by: David S. Miller <davem@davemloft.net>
205 lines
4.9 KiB
C
205 lines
4.9 KiB
C
/*
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* Linux Socket Filter Data Structures
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*/
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#ifndef __LINUX_FILTER_H__
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#define __LINUX_FILTER_H__
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#include <linux/compiler.h>
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#include <linux/types.h>
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#ifdef __KERNEL__
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#include <asm/atomic.h>
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#endif
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/*
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* Current version of the filter code architecture.
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*/
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#define BPF_MAJOR_VERSION 1
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#define BPF_MINOR_VERSION 1
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/*
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* Try and keep these values and structures similar to BSD, especially
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* the BPF code definitions which need to match so you can share filters
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*/
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struct sock_filter { /* Filter block */
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__u16 code; /* Actual filter code */
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__u8 jt; /* Jump true */
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__u8 jf; /* Jump false */
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__u32 k; /* Generic multiuse field */
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};
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struct sock_fprog { /* Required for SO_ATTACH_FILTER. */
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unsigned short len; /* Number of filter blocks */
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struct sock_filter __user *filter;
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};
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/*
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* Instruction classes
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*/
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#define BPF_CLASS(code) ((code) & 0x07)
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#define BPF_LD 0x00
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#define BPF_LDX 0x01
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#define BPF_ST 0x02
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#define BPF_STX 0x03
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#define BPF_ALU 0x04
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#define BPF_JMP 0x05
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#define BPF_RET 0x06
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#define BPF_MISC 0x07
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/* ld/ldx fields */
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#define BPF_SIZE(code) ((code) & 0x18)
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#define BPF_W 0x00
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#define BPF_H 0x08
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#define BPF_B 0x10
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#define BPF_MODE(code) ((code) & 0xe0)
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#define BPF_IMM 0x00
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#define BPF_ABS 0x20
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#define BPF_IND 0x40
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#define BPF_MEM 0x60
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#define BPF_LEN 0x80
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#define BPF_MSH 0xa0
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/* alu/jmp fields */
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#define BPF_OP(code) ((code) & 0xf0)
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#define BPF_ADD 0x00
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#define BPF_SUB 0x10
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#define BPF_MUL 0x20
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#define BPF_DIV 0x30
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#define BPF_OR 0x40
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#define BPF_AND 0x50
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#define BPF_LSH 0x60
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#define BPF_RSH 0x70
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#define BPF_NEG 0x80
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#define BPF_JA 0x00
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#define BPF_JEQ 0x10
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#define BPF_JGT 0x20
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#define BPF_JGE 0x30
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#define BPF_JSET 0x40
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#define BPF_SRC(code) ((code) & 0x08)
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#define BPF_K 0x00
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#define BPF_X 0x08
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/* ret - BPF_K and BPF_X also apply */
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#define BPF_RVAL(code) ((code) & 0x18)
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#define BPF_A 0x10
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/* misc */
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#define BPF_MISCOP(code) ((code) & 0xf8)
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#define BPF_TAX 0x00
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#define BPF_TXA 0x80
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enum {
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BPF_S_RET_K = 0,
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BPF_S_RET_A,
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BPF_S_ALU_ADD_K,
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BPF_S_ALU_ADD_X,
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BPF_S_ALU_SUB_K,
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BPF_S_ALU_SUB_X,
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BPF_S_ALU_MUL_K,
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BPF_S_ALU_MUL_X,
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BPF_S_ALU_DIV_X,
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BPF_S_ALU_AND_K,
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BPF_S_ALU_AND_X,
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BPF_S_ALU_OR_K,
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BPF_S_ALU_OR_X,
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BPF_S_ALU_LSH_K,
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BPF_S_ALU_LSH_X,
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BPF_S_ALU_RSH_K,
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BPF_S_ALU_RSH_X,
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BPF_S_ALU_NEG,
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BPF_S_LD_W_ABS,
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BPF_S_LD_H_ABS,
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BPF_S_LD_B_ABS,
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BPF_S_LD_W_LEN,
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BPF_S_LD_W_IND,
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BPF_S_LD_H_IND,
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BPF_S_LD_B_IND,
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BPF_S_LD_IMM,
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BPF_S_LDX_W_LEN,
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BPF_S_LDX_B_MSH,
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BPF_S_LDX_IMM,
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BPF_S_MISC_TAX,
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BPF_S_MISC_TXA,
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BPF_S_ALU_DIV_K,
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BPF_S_LD_MEM,
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BPF_S_LDX_MEM,
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BPF_S_ST,
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BPF_S_STX,
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BPF_S_JMP_JA,
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BPF_S_JMP_JEQ_K,
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BPF_S_JMP_JEQ_X,
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BPF_S_JMP_JGE_K,
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BPF_S_JMP_JGE_X,
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BPF_S_JMP_JGT_K,
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BPF_S_JMP_JGT_X,
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BPF_S_JMP_JSET_K,
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BPF_S_JMP_JSET_X,
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};
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#ifndef BPF_MAXINSNS
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#define BPF_MAXINSNS 4096
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#endif
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/*
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* Macros for filter block array initializers.
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*/
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#ifndef BPF_STMT
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#define BPF_STMT(code, k) { (unsigned short)(code), 0, 0, k }
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#endif
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#ifndef BPF_JUMP
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#define BPF_JUMP(code, k, jt, jf) { (unsigned short)(code), jt, jf, k }
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#endif
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/*
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* Number of scratch memory words for: BPF_ST and BPF_STX
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*/
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#define BPF_MEMWORDS 16
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/* RATIONALE. Negative offsets are invalid in BPF.
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We use them to reference ancillary data.
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Unlike introduction new instructions, it does not break
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existing compilers/optimizers.
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*/
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#define SKF_AD_OFF (-0x1000)
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#define SKF_AD_PROTOCOL 0
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#define SKF_AD_PKTTYPE 4
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#define SKF_AD_IFINDEX 8
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#define SKF_AD_NLATTR 12
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#define SKF_AD_NLATTR_NEST 16
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#define SKF_AD_MARK 20
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#define SKF_AD_QUEUE 24
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#define SKF_AD_HATYPE 28
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#define SKF_AD_MAX 32
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#define SKF_NET_OFF (-0x100000)
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#define SKF_LL_OFF (-0x200000)
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#ifdef __KERNEL__
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struct sk_filter
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{
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atomic_t refcnt;
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unsigned int len; /* Number of filter blocks */
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struct rcu_head rcu;
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struct sock_filter insns[0];
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};
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static inline unsigned int sk_filter_len(const struct sk_filter *fp)
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{
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return fp->len * sizeof(struct sock_filter) + sizeof(*fp);
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}
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struct sk_buff;
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struct sock;
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extern int sk_filter(struct sock *sk, struct sk_buff *skb);
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extern unsigned int sk_run_filter(struct sk_buff *skb,
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struct sock_filter *filter, int flen);
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extern int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk);
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extern int sk_detach_filter(struct sock *sk);
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extern int sk_chk_filter(struct sock_filter *filter, int flen);
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#endif /* __KERNEL__ */
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#endif /* __LINUX_FILTER_H__ */
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