自定义规则链

 定义规则链时需要指定链要加入的表，默认加入Filter表
 --append  -A chain        Append to chain

 --check   -C chain        Check for the existence of a rule

 --delete  -D chain        Delete matching rule from chain

 --delete  -D chain rulenum
           Delete rule rulenum (1 = first) from chain
 --insert  -I chain [rulenum]
                Insert in chain as rulenum (default 1=first)
 --replace -R chain rulenum
                Replace rule rulenum (1 = first) in chain
 --list    -L [chain [rulenum]]
                List the rules in a chain or all chains
 --list-rules -S [chain [rulenum]]
               Print the rules in a chain or all chains
 --flush   -F [chain]        Delete all rules in  chain or all chains
 --zero    -Z [chain [rulenum]]
                Zero counters in chain or all chains
 --new     -N chain        Create a new user-defined chain
 --delete-chain
           -X [chain]        Delete a user-defined chain
  --policy  -P chain target
                Change policy on chain to target
  --rename-chain
            -E old-chain new-chain
                Change chain name, (moving any references)

    =======================================================
    iptables -t filter -N   jychain
    iptables -A jychain -s xxxxxxx -DROP
    iptables -A jychain  -m comment --comment 'dddd' -j RETURN---(返回调用主链的下一条规则)
    -j RETURN 用于自定义规则链的返回主调用链，继续执行后续的匹配
     //调用jychain
    iptables -t filter -s xxxxx -j jychain