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xt_MARK源码请教

时间：2010-08-06

来源：互联网

内核版本2.6.22.19，iptables1.3.8

/* This is a module which is used for setting the NFMARK field of an skb. */
/* (C) 1999-2001 Marc Boucher <[email protected]>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <net/checksum.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_MARK.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Marc Boucher <[email protected]>");
MODULE_DESCRIPTION("ip[6]tables MARK modification module");
MODULE_ALIAS("ipt_MARK");
MODULE_ALIAS("ip6t_MARK");
static unsigned int
target_v0(struct sk_buff **pskb,
const struct net_device *in,
const struct net_device *out,
unsigned int hooknum,
const struct xt_target *target,
const void *targinfo)
{
const struct xt_mark_target_info *markinfo = targinfo;
(*pskb)->mark = markinfo->mark;
return XT_CONTINUE;
}
static unsigned int
target_v1(struct sk_buff **pskb,
const struct net_device *in,
const struct net_device *out,
unsigned int hooknum,
const struct xt_target *target,
const void *targinfo)
{
const struct xt_mark_target_info_v1 *markinfo = targinfo;
int mark = 0;
switch (markinfo->mode) {
case XT_MARK_SET:
mark = markinfo->mark;
break;
case XT_MARK_AND:
mark = (*pskb)->mark & markinfo->mark;
break;
case XT_MARK_OR:
mark = (*pskb)->mark | markinfo->mark;
break;
}
(*pskb)->mark = mark;
return XT_CONTINUE;
}
static int
checkentry_v0(const char *tablename,
const void *entry,
const struct xt_target *target,
void *targinfo,
unsigned int hook_mask)
{
struct xt_mark_target_info *markinfo = targinfo;
if (markinfo->mark > 0xffffffff) {
printk(KERN_WARNING "MARK: Only supports 32bit wide mark\n");
return 0;
}
return 1;
}
static int
checkentry_v1(const char *tablename,
const void *entry,
const struct xt_target *target,
void *targinfo,
unsigned int hook_mask)
{
struct xt_mark_target_info_v1 *markinfo = targinfo;
if (markinfo->mode != XT_MARK_SET
&& markinfo->mode != XT_MARK_AND
&& markinfo->mode != XT_MARK_OR) {
printk(KERN_WARNING "MARK: unknown mode %u\n",
markinfo->mode);
return 0;
}
if (markinfo->mark > 0xffffffff) {
printk(KERN_WARNING "MARK: Only supports 32bit wide mark\n");
return 0;
}
return 1;
}
#ifdef CONFIG_COMPAT
struct compat_xt_mark_target_info_v1 {
compat_ulong_t mark;
u_int8_t mode;
u_int8_t __pad1;
u_int16_t __pad2;
};
static void compat_from_user_v1(void *dst, void *src)
{
struct compat_xt_mark_target_info_v1 *cm = src;
struct xt_mark_target_info_v1 m = {
.mark = cm->mark,
.mode = cm->mode,
};
memcpy(dst, &m, sizeof(m));
}
static int compat_to_user_v1(void __user *dst, void *src)
{
struct xt_mark_target_info_v1 *m = src;
struct compat_xt_mark_target_info_v1 cm = {
.mark = m->mark,
.mode = m->mode,
};
return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
}
#endif /* CONFIG_COMPAT */
static struct xt_target xt_mark_target[] = {
{
.name = "MARK",
.family = AF_INET,
.revision = 0,
.checkentry = checkentry_v0,
.target = target_v0,
.targetsize = sizeof(struct xt_mark_target_info),
.table = "mangle",
.me = THIS_MODULE,
},
{
.name = "MARK",
.family = AF_INET,
.revision = 1,
.checkentry = checkentry_v1,
.target = target_v1,
.targetsize = sizeof(struct xt_mark_target_info_v1),
#ifdef CONFIG_COMPAT
.compatsize = sizeof(struct compat_xt_mark_target_info_v1),
.compat_from_user = compat_from_user_v1,
.compat_to_user = compat_to_user_v1,
#endif
.table = "mangle",
.me = THIS_MODULE,
},
{
.name = "MARK",
.family = AF_INET6,
.revision = 0,
.checkentry = checkentry_v0,
.target = target_v0,
.targetsize = sizeof(struct xt_mark_target_info),
.table = "mangle",
.me = THIS_MODULE,
},
};
static int __init xt_mark_init(void)
{
return xt_register_targets(xt_mark_target, ARRAY_SIZE(xt_mark_target));
}
static void __exit xt_mark_fini(void)
{
xt_unregister_targets(xt_mark_target, ARRAY_SIZE(xt_mark_target));
}
module_init(xt_mark_init);
module_exit(xt_mark_fini);

复制代码

特向高人请教不明白之处:
1.target_v0和target_v1，怎么有两个版本，其它模块都只有一个的啊？
2.#ifdef CONFIG_COMPAT
这个CONFIG_COMPAT是什么东西来的

作者: zhoutao0712 发布时间: 2010-08-06

建议到程序区问问。感觉是配置时使用的一个控制参数吧。

作者: renxiao2003 发布时间: 2010-08-06

关于 COMPAT 的文章这里提到了一点点
http://blog.chinaunix.net/u1/38994/showart_2246878.html

至于为什么同时有两个版本，可能是为了照顾不同用户态程序，v1 比 v0 功能更强大些，但为了保持兼容性，保留了 v0

作者: platinum 发布时间: 2010-08-06

xt_MARK源码请教

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