net/netfilter/ipvs/ip_vs_offh.c：
/*
* IPVS: Layer7 payload Hashing scheduling module
*
* Authors: ZHAOYA
* 基于ip_vs_sh/dh修改而来，详细注释请参见：
* net/netfilter/ipvs/ip_vs_sh.c
* net/netfilter/ipvs/ip_vs_dh.c
*/
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/ctype.h>
#include <net/ip.h>
#include <net/ip_vs.h>
struct ip_vs_offh_bucket {
struct ip_vs_dest *dest;
};
struct ip_vs_offh_data {
struct ip_vs_offh_bucket *tbl;
u32 offset;
u32 offlen;
};
#define IP_VS_OFFH_TAB_BITS 8
#define IP_VS_OFFH_TAB_SIZE (1 << IP_VS_OFFH_TAB_BITS)
#define IP_VS_OFFH_TAB_MASK (IP_VS_OFFH_TAB_SIZE - 1)
/*
* 全局变量
* offset：Layer7计算hash值的payload偏移量(相对于Layer7头)
* offlen：Layer7计算hash值的payload长度
*/
static u32 offset, offlen;
static int skip_atoi(char **s)
{
int i=0;
while (isdigit(**s))
i = i*10 + *((*s)++) - ‘0‘;
return i;
}
static inline struct ip_vs_dest *
ip_vs_offh_get(struct ip_vs_offh_bucket *tbl, const char *payload, u32 length)
{
__be32 v_fold = 0;
/* 算法有待优化 */
v_fold = (payload[0]^payload[length>>2]^payload[length])*2654435761UL;
return (tbl[v_fold & IP_VS_OFFH_TAB_MASK]).dest;
}
static int
ip_vs_offh_assign(struct ip_vs_offh_bucket *tbl, struct ip_vs_service *svc)
{
int i;
struct ip_vs_offh_bucket *b;
struct list_head *p;
struct ip_vs_dest *dest;
b = tbl;
p = &svc->destinations;
for (i=0; i<IP_VS_OFFH_TAB_SIZE; i++) {
if (list_empty(p)) {
b->dest = NULL;
} else {
if (p == &svc->destinations)
p = p->next;
dest = list_entry(p, struct ip_vs_dest, n_list);
atomic_inc(&dest->refcnt);
b->dest = dest;
p = p->next;
}
b++;
}
return 0;
}
static void ip_vs_offh_flush(struct ip_vs_offh_bucket *tbl)
{
int i;
struct ip_vs_offh_bucket *b;
b = tbl;
for (i=0; i<IP_VS_OFFH_TAB_SIZE; i++) {
if (b->dest) {
atomic_dec(&b->dest->refcnt);
b->dest = NULL;
}
b++;
}
}
static int ip_vs_offh_init_svc(struct ip_vs_service *svc)
{
struct ip_vs_offh_data *pdata;
struct ip_vs_offh_bucket *tbl;
pdata = kmalloc(sizeof(struct ip_vs_offh_data), GFP_ATOMIC);
if (pdata == NULL) {
pr_err("%s(): no memory\n", __func__);
return -ENOMEM;
}
tbl = kmalloc(sizeof(struct ip_vs_offh_bucket)*IP_VS_OFFH_TAB_SIZE,
GFP_ATOMIC);
if (tbl == NULL) {
kfree(pdata);
pr_err("%s(): no memory\n", __func__);
return -ENOMEM;
}
pdata->tbl = tbl;
pdata->offset = 0;
pdata->offlen = 0;
svc->sched_data = pdata;
ip_vs_offh_assign(tbl, svc);
return 0;
}
static int ip_vs_offh_done_svc(struct ip_vs_service *svc)
{
struct ip_vs_offh_data *pdata = svc->sched_data;
struct ip_vs_offh_bucket *tbl = pdata->tbl;
ip_vs_offh_flush(tbl);
kfree(tbl);
kfree(pdata);
return 0;
}
static int ip_vs_offh_update_svc(struct ip_vs_service *svc)
{
struct ip_vs_offh_bucket *tbl = svc->sched_data;
ip_vs_offh_flush(tbl);
ip_vs_offh_assign(tbl, svc);
return 0;
}
static inline int is_overloaded(struct ip_vs_dest *dest)
{
return dest->flags & IP_VS_DEST_F_OVERLOAD;
}
static struct ip_vs_dest *
ip_vs_offh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
{
struct ip_vs_dest *dest;
struct ip_vs_offh_data *pdata;
struct ip_vs_offh_bucket *tbl;
struct iphdr *iph;
void *transport_hdr;
char *payload;
u32 hdrlen = 0;
u32 _offset = 0;
u32 _offlen = 0;
iph = ip_hdr(skb);
hdrlen = iph->ihl*4;
if (hdrlen > skb->len) {
return NULL;
}
transport_hdr = (void *)iph + hdrlen;
switch (iph->protocol) {
case IPPROTO_TCP:
hdrlen += (((struct tcphdr*)transport_hdr)->doff)*4;
break;
case IPPROTO_UDP:
hdrlen += sizeof(struct udphdr);
break;
default:
return NULL;
}
#if 0
{
int i = 0;
_offset = offset;
_offlen = offlen;
payload = (char *)iph + hdrlen + _offset;
printk("begin:iplen:%d \n", hdrlen);
for (i = 0; i < _offlen; i++) {
printk("%02X ", payload[i]);
}
printk("\nend\n");
return NULL;
}
#endif
pdata = (struct ip_vs_offh_datai *)svc->sched_data;
tbl = pdata->tbl;
_offset = offset;//pdata->offset;
_offlen = offlen;//pdata->offlen;
if (_offlen + _offset > skb->len - hdrlen) {
IP_VS_ERR_RL("OFFH: exceed\n");
return NULL;
}
payload = (char *)iph + hdrlen + _offset;
dest = ip_vs_offh_get(tbl, payload, _offlen);
if (!dest
|| !(dest->flags & IP_VS_DEST_F_AVAILABLE)
|| atomic_read(&dest->weight) <= 0
|| is_overloaded(dest)) {
IP_VS_ERR_RL("OFFH: no destination available\n");
return NULL;
}
return dest;
}
static struct ip_vs_scheduler ip_vs_offh_scheduler =
{
.name = "offh",
.refcnt = ATOMIC_INIT(0),
.module = THIS_MODULE,
.n_list = LIST_HEAD_INIT(ip_vs_offh_scheduler.n_list),
.init_service = ip_vs_offh_init_svc,
.done_service = ip_vs_offh_done_svc,
.update_service = ip_vs_offh_update_svc,
.schedule = ip_vs_offh_schedule,
};
static ssize_t ipvs_sch_offset_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
int ret = 0;
ret = sprintf(buf, "offset:%u;offlen:%u\n", offset, offlen);
return ret;
}
/*
* 设置offset/offset length
* echo offset:$value1 offlen:$value2 >/proc/net/ipvs_sch_offset
*/
static int ipvs_sch_offset_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
int ret = count;
char *p = buf, *pstart;
if ((p = strstr(p, "offset:")) == NULL) {
ret = -EINVAL;
goto out;
}
p += strlen("offset:");
pstart = p;
if ((p = strstr(p, " ")) == NULL) {
ret = -EINVAL;
goto out;
}
p[0] = 0;
offset = skip_atoi(&pstart);
if (offset == 0 && strcmp(pstart, "0")) {
ret = -EINVAL;
goto out;
}
p += strlen(";");
if ((p = strstr(p, "offlen:")) == NULL) {
ret = -EINVAL;
goto out;
}
p += strlen("offlen:");
pstart = p;
offlen = skip_atoi(&pstart);
if (offlen == 0 && strcmp(pstart, "0")) {
ret = -EINVAL;
goto out;
}
out:
return ret;
}
/*
* 由于不想修改用户态的配置接口，还是觉得procfs这种方式比较靠普
**/
static const struct file_operations ipvs_sch_offset_file_ops = {
.owner = THIS_MODULE,
.read = ipvs_sch_offset_read,
.write = ipvs_sch_offset_write,
};
struct net *net = &init_net;
static int __init ip_vs_offh_init(void)
{
int ret = -1;
if (!proc_create("ipvs_sch_offset", 0644, net->proc_net, &ipvs_sch_offset_file_ops)) {
printk("OFFH: create proc entry failed\n");
goto out;
}
return register_ip_vs_scheduler(&ip_vs_offh_scheduler);
out:
return ret;
}
static void __exit ip_vs_offh_cleanup(void)
{
remove_proc_entry("ipvs_sch_offset", net->proc_net);
unregister_ip_vs_scheduler(&ip_vs_offh_scheduler);
}
module_init(ip_vs_offh_init);
module_exit(ip_vs_offh_cleanup);
MODULE_LICENSE("GPL");原文：http://blog.csdn.net/dog250/article/details/43638573