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(1)给链接跟踪设置标记(--set-mark)
实现代码如下: 53 case XT_CONNMARK_SET:
54 newmark = (*ctmark & ~markinfo->mask) | markinfo->mark;
55 if (newmark != *ctmark)
56 *ctmark = newmark;
57 break;
复制代码这里先按照markinfo->mask中所有被置位的bit,将*ctmark中对应的bit位清零,然后再与markinfo->mark进行按位或。这样就保证了mask中置位的bit位,一定为按照mark中的值重新设置。
55~57行代码的实现和我们第2部分分析的67~68代码的实现相同。
在iptables/extensions/libxt_CONNMARK.c 核心代码
/* Function which parses command options; returns true if it
ate an option */
static int
parse(int c, char **argv, int invert, unsigned int *flags,
const struct ipt_entry *entry,
struct ipt_entry_target **target)
{
struct ipt_connmark_target_info *markinfo
= (struct ipt_connmark_target_info *)(*target)->data;
markinfo->mask = 0xffffffffUL;
switch (c) {
char *end;
case '1':
markinfo->mode = IPT_CONNMARK_SET;
markinfo->mark = strtoul(optarg, &end, 0);
if (*end == '/' && end[1] != '\0')
markinfo->mask = strtoul(end+1, &end, 0);
if (*end != '\0' || end == optarg)
exit_error(PARAMETER_PROBLEM, "Bad MARK value `%s'", optarg);
if (*flags)
exit_error(PARAMETER_PROBLEM,
"CONNMARK target: Can't specify --set-mark twice");
*flags = 1;
break;
case '2':
markinfo->mode = IPT_CONNMARK_SAVE;
if (*flags)
exit_error(PARAMETER_PROBLEM,
"CONNMARK target: Can't specify --save-mark twice");
*flags = 1;
break;
case '3':
markinfo->mode = IPT_CONNMARK_RESTORE;
if (*flags)
exit_error(PARAMETER_PROBLEM,
"CONNMARK target: Can't specify --restore-mark twice");
*flags = 1;
break;
case '4':
if (!*flags)
exit_error(PARAMETER_PROBLEM,
"CONNMARK target: Can't specify --mask without a operation");
markinfo->mask = strtoul(optarg, &end, 0);
if (*end != '\0' || end == optarg)
exit_error(PARAMETER_PROBLEM, "Bad MASK value `%s'", optarg);
break;
default:
return 0;
}
return 1;
}
版主,问一下,markinfo->mark = strtoul(optarg, &end, 0);
if (*end == '/' && end[1] != '\0')
markinfo->mask = strtoul(end+1, &end, 0);
optarg是--set-mark后面的参数? --set-mark 111时, optarg=111
其中:static struct option opts[] = {
{ "set-mark", 1, 0, '1' },
{ "save-mark", 0, 0, '2' },
{ "restore-mark", 0, 0, '3' },
{ "mask", 1, 0, '4' },
{ 0 }
}; 怎么理解下命令时,markinfo->mask的值,和其作用??? |
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