RK3568 Debian10关于iptables_iptables: failed to initialize nft: protocol not s

平台：RK3568 Debian10系统

问题：1、iptables无法使用；        2、iptables -L没作用

iptsbles：iptables（网络 过滤器）是一个工作于用户空间的防火墙应用软件，是与 3.5 版本 Linux 内核集成的 IP 信息包过滤系统。如果 Linux 系统连接到因特网或 LAN、服务器或连接 LAN 和因特网的代理服务器，则该系统有利于在 Linux 系统上更好地控制 IP 信息包过滤和防火墙配置。

问题一：输入iptables --help会报错

root@linaro-alip:~# iptables --help
iptables/1.8.2 Failed to initialize nft: Protocol not supported

原因：Debian10的 iptables 默认是使用 nf_tables，而系统中并没有支持nf_tables。

办法：在kernel/arch/arm64/configs/rockchip_linux_defconfig添加

CONFIG_NF_TABLES=y

加完编kernel升级一下就可以了

root@linaro-alip:~# iptables
iptables v1.8.2 (nf_tables): no command specified
Try `iptables -h' or 'iptables --help' for more information.
root@linaro-alip:~# iptables --help
iptables v1.8.2
 
Usage: iptables -[ACD] chain rule-specification [options]
        iptables -I chain [rulenum] rule-specification [options]
        iptables -R chain rulenum rule-specification [options]
        iptables -D chain rulenum [options]
        iptables -[LS] [chain [rulenum]] [options]
        iptables -[FZ] [chain] [options]
        iptables -[NX] chain
        iptables -E old-chain-name new-chain-name
        iptables -P chain target [options]
        iptables -h (print this help information)
 
Commands:
Either long or short options are allowed.
  --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]]

问题二：使用iptables -L来列出系统防火墙规则，出现报错

root@linaro-alip:~# iptables -L
iptables v1.8.2 (nf_tables):  CHAIN_ADD failed (Operation not supported): chain INPUT

原因：Debian buster使用 nftables 而不是 iptables

方法：调用update-alternatives强制Debian10用iptables而不是nftables

sudo update-alternatives --set iptables /usr/sbin/iptables-legacy

解决这个问题以后iptables -L依旧不行，还是报错

root@linaro-alip:~# iptables -L
iptables v1.8.2 (legacy): can't initialize iptables table `filter': Table does not exist (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.

目测应该是缺了个内核模块（iptable_filter）导致这个filter表出不来，去源码翻了一下，不小心看见了一个kernel\net\ipv4\netfilter\iptable_filter.c(其实是拿grep去kernel底下搜)，一看没有编，估计就是少了这个模块。

办法：在kernel/arch/arm64/configs/rockchip_linux_defconfig把宏加上

CONFIG_IP_NF_FILTER=y

一般来说RK源码kernel里面有的C文件想编进去打开对应的宏就行了，kconfig里面说已经写好的，保险起见可以检查一下kernel\net\ipv4\netfilter\kconfig，当然，Makefile同理。

++ kernel\net\ipv4\netfilter\kconfig
config IP_NF_FILTER
 tristate "Packet filtering"
 default m if NETFILTER_ADVANCED=n
 help
   Packet filtering defines a table `filter', which has a series of
   rules for simple packet filtering at local input, forwarding and
   local output.  See the man page for iptables(8).
 
   To compile it as a module, choose M here.  If unsure, say N.

改完把.o文件编出来烧一下kernel就好了

root@linaro-alip:~# iptables -L  
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
 
Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         
 
Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

参考文章：RK3568 debian系统iptables命令报错_iptables/1.8.2 failed to initialize nft: protocol -CSDN博客

iptables v1.8.2 (nf_tables): CHAIN_ADD failed (No such file or directory): chain PREROUTING-CSDN博客