/* jhash.h: Jenkins hash support.
 *
 * Copyright (C) 2006. Bob Jenkins (bob_jenkins@burtleburtle.net)
 *
 * http://burtleburtle.net/bob/hash/
 *
 * These are the credits from Bob's sources:
 *
 * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
 *
 * These are functions for producing 32-bit hashes for hash table lookup.
 * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
 * are externally useful functions.  Routines to test the hash are included
 * if SELF_TEST is defined.  You can use this free for any purpose.  It's in
 * the public domain.  It has no warranty.
 *
 * Copyright (C) 2009-2010 Jozsef Kadlecsik (kadlec@blackhole.kfki.hu)
 *
 * I've modified Bob's hash to be useful in the Linux kernel, and
 * any bugs present are my fault.
 * Jozsef
 */

#include "flowood.h"

/* An arbitrary initial parameter */
#define JHASH_INITVAL		(0x20180601)  /* flowood项目代码启动开发的日期 */


#ifndef u32
typedef unsigned int u32;
#endif

#ifndef __u32
typedef unsigned int __u32;
#endif

/* Best hash sizes are of power of two */
#define jhash_size(n)   ((u32)1<<(n))
/* Mask the hash value, i.e (value & jhash_mask(n)) instead of (value % n) */
#define jhash_mask(n)   (jhash_size(n)-1)


/**
 * rol32 - rotate a 32-bit value left
 * @word: value to rotate
 * @shift: bits to roll
 */
static inline __u32 rol32(__u32 word, unsigned int shift)
{
	return (word << shift) | (word >> (32 - shift));
}

/* __jhash_mix -- mix 3 32-bit values reversibly. */
#define __jhash_mix(a, b, c)			\
{						\
	a -= c;  a ^= rol32(c, 4);  c += b;	\
	b -= a;  b ^= rol32(a, 6);  a += c;	\
	c -= b;  c ^= rol32(b, 8);  b += a;	\
	a -= c;  a ^= rol32(c, 16); c += b;	\
	b -= a;  b ^= rol32(a, 19); a += c;	\
	c -= b;  c ^= rol32(b, 4);  b += a;	\
}

/* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
#define __jhash_final(a, b, c)			\
{						\
	c ^= b; c -= rol32(b, 14);		\
	a ^= c; a -= rol32(c, 11);		\
	b ^= a; b -= rol32(a, 25);		\
	c ^= b; c -= rol32(b, 16);		\
	a ^= c; a -= rol32(c, 4);		\
	b ^= a; b -= rol32(a, 14);		\
	c ^= b; c -= rol32(b, 24);		\
}

#if 0
/* jhash - hash an arbitrary key
 * @k: sequence of bytes as key
 * @length: the length of the key
 * @initval: the previous hash, or an arbitray value
 *
 * The generic version, hashes an arbitrary sequence of bytes.
 * No alignment or length assumptions are made about the input key.
 *
 * Returns the hash value of the key. The result depends on endianness.
 */
static inline u32 jhash(const void *key, u32 length, u32 initval)
{
	u32 a, b, c;
	const u8 *k = key;

	/* Set up the internal state */
	a = b = c = JHASH_INITVAL + length + initval;

	/* All but the last block: affect some 32 bits of (a,b,c) */
	while (length > 12) {
		a += __get_unaligned_cpu32(k);
		b += __get_unaligned_cpu32(k + 4);
		c += __get_unaligned_cpu32(k + 8);
		__jhash_mix(a, b, c);
		length -= 12;
		k += 12;
	}
	/* Last block: affect all 32 bits of (c) */
	/* All the case statements fall through */
	switch (length) {
	case 12: c += (u32)k[11]<<24;
	case 11: c += (u32)k[10]<<16;
	case 10: c += (u32)k[9]<<8;
	case 9:  c += k[8];
	case 8:  b += (u32)k[7]<<24;
	case 7:  b += (u32)k[6]<<16;
	case 6:  b += (u32)k[5]<<8;
	case 5:  b += k[4];
	case 4:  a += (u32)k[3]<<24;
	case 3:  a += (u32)k[2]<<16;
	case 2:  a += (u32)k[1]<<8;
	case 1:  a += k[0];
		 __jhash_final(a, b, c);
	case 0: /* Nothing left to add */
		break;
	}

	return c;
}
#endif

/* jhash2 - hash an array of u32's
 * @k: the key which must be an array of u32's
 * @length: the number of u32's in the key
 * @initval: the previous hash, or an arbitray value
 *
 * Returns the hash value of the key.
 */
static inline u32 jhash2(const u32 *k, u32 length, u32 initval)
{
	u32 a, b, c;

	/* Set up the internal state */
	a = b = c = JHASH_INITVAL + (length<<2) + initval;

	/* Handle most of the key */
	while (length > 3) {
		a += k[0];
		b += k[1];
		c += k[2];
		__jhash_mix(a, b, c);
		length -= 3;
		k += 3;
	}

	/* Handle the last 3 u32's: all the case statements fall through */
	switch (length) {
	case 3: c += k[2];
	case 2: b += k[1];
	case 1: a += k[0];
		__jhash_final(a, b, c);
	case 0:	/* Nothing left to add */
		break;
	}

	return c;
}


/* jhash_3words - hash exactly 3, 2 or 1 word(s) */
static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
{
	a += JHASH_INITVAL;
	b += JHASH_INITVAL;
	c += initval;

	__jhash_final(a, b, c);

	return c;
}

/*
	NAT转换表和计算数据包指纹复用一个函数, 靠参数sport_with_no_id_hash区分:
	sport_with_no_id_hash=0: 用于计算四元组HASH,
	sport_with_no_id_hash=1: 用于计算数据包指纹;

	NOTE:
		做四元组hash计算时, 不需要看dir_reverse, 
		因为C2S方向和S2C方向生成的key的四元组实际二进制是一样的,
		都遵循大地址做为源的规则, 只是dir_reverse不同,
		C2S和S2C的来包方向不一样, dir_reverse肯定是相反的.	
*/
unsigned int flwd_tuple5_hash(const flwd_tuple5_t *tuple5, int sport_with_no_id_hash)
{
	unsigned int sip;
	unsigned int dip;
	unsigned int hash_val = 0;
	unsigned short sport; /* 计算四元组HASH时, 用全部的bit; 计算指纹信息时, 只用sport的最低8bit端口值, 即不含网关id, hash */
	unsigned short dport;

	if(flwd_likely(FLWD_IP_ADDR_TYPE_V4 == tuple5->addr_type)){
		sip = tuple5->ippair_v4.sip_net_order;
		dip = tuple5->ippair_v4.dip_net_order;	
	}else{
		sip = tuple5->ippair_v6->sip_net_order.s6_addr32[0]; /* 使用最低4字节 */
		dip = tuple5->ippair_v6->dip_net_order.s6_addr32[0]; /* 使用最低4字节 */
	}

	if(sport_with_no_id_hash){
		sport = ntohs(tuple5->sport_net_order) & FLWD_UDP_SPORT_ACTUAL_PORT_MASK; /* 只用真正的端口值, 不用id和hash字段 */
	}else{
		sport = tuple5->sport_net_order;
	}
	dport = tuple5->dport_net_order;
	
	hash_val = (unsigned int)sport;
	hash_val |= ((unsigned int)dport << 16);
	hash_val += JHASH_INITVAL;	
	
	__jhash_final(sip, dip, hash_val);

	return hash_val;
}



unsigned int __flwd_tuple5_hash(const flwd_tuple5_t *tuple5)
{
	unsigned int sip;
	unsigned int dip;
	unsigned int port_union;
	unsigned short sport_no_id_hash; /* 计算四元组HASH时, 只用sport的最低8bit端口值, 不含网关id, hash */
	unsigned short dport;

	if(flwd_likely(FLWD_IP_ADDR_TYPE_V4 == tuple5->addr_type)){
		if(0 == tuple5->dir_reverse){
			sip = tuple5->ippair_v4.sip_net_order;
			dip = tuple5->ippair_v4.dip_net_order;		
			sport_no_id_hash = ntohs(tuple5->sport_net_order) & FLWD_UDP_SPORT_ACTUAL_PORT_MASK; /* 只用真正的端口值, 不用id和hash字段 */
			dport = tuple5->dport_net_order;
		}else{
			sip = tuple5->ippair_v4.dip_net_order;
			dip = tuple5->ippair_v4.sip_net_order;			
			sport_no_id_hash = ntohs(tuple5->dport_net_order) & FLWD_UDP_SPORT_ACTUAL_PORT_MASK;  /* 只用真正的端口值, 不用id和hash字段 */
			dport = tuple5->sport_net_order;
		}
	}else{
		if(0 == tuple5->dir_reverse){
			sip = tuple5->ippair_v6->sip_net_order.s6_addr32[0]; /* 使用最低4字节 */
			dip = tuple5->ippair_v6->dip_net_order.s6_addr32[0]; /* 使用最低4字节 */
			sport_no_id_hash = ntohs(tuple5->sport_net_order) & FLWD_UDP_SPORT_ACTUAL_PORT_MASK;
			dport = tuple5->dport_net_order;
		}else{
			sip = tuple5->ippair_v6->dip_net_order.s6_addr32[0]; /* 使用最低4字节 */
			dip = tuple5->ippair_v6->sip_net_order.s6_addr32[0]; /* 使用最低4字节 */
			sport_no_id_hash = ntohs(tuple5->dport_net_order) & FLWD_UDP_SPORT_ACTUAL_PORT_MASK;
			dport = tuple5->sport_net_order;			
		}
	}

	port_union = (unsigned int)sport_no_id_hash;
	port_union |= ((unsigned int)dport << 16);
	port_union += JHASH_INITVAL;	
	
	__jhash_final(sip, dip, port_union);

	return port_union;
}