Linux netfilter源码分析(6)

转贴自：http://alexanderlaw.blog.hexun.com/8968944_d.html
六、 扩展的match
 
6.1 do_match函数  ip_tables.c
do_match通过IPT_MATCH_ITERATE宏来调用,
IPT_MATCH_ITERATE是在ipt_do_table函数中调用的宏
IPT_MATCH_ITERATE(e, do_match,
                                  *pskb, in, out,
                                  offset, &hotdrop)
定义如下：
#define IPT_MATCH_ITERATE(e, fn, args...)      \
({                               \
      unsigned int __i;               \
      int __ret = 0;                    \
      struct ipt_entry_match *__match;  \
                                  \
      for (__i = sizeof(struct ipt_entry);  \
           __i < (e)->target_offset;        \
           __i += __match->u.match_size) {      \
           __match = (void *)(e) + __i;    \
      &