OpenWrt 22.03 Nftables 防火墙导出
狐狸Nomad
2022年10月07日 20:53
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共13篇

近段时间 OpenWrt 的最新版 22.03 中使用了 fw4 作为默认防火墙。

Firewall4 based on nftable

于是在简单开启了 OpenWrt 的 Drop invalid packets 以及禁用了外网 Ping 之后，通过如下命令导出了 fw4 的规则列表，用于后续研究。

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## 导出 Nftables 规则
nft -s list ruleset | tee openwrt-nft-ruleset.conf
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输出如下：

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table inet fw4 {
        chain input {
                type filter hook input priority filter; policy accept;
                iifname "lo" accept comment "!fw4: Accept traffic from loopback"
                ct state established,related accept comment "!fw4: Allow inbound established and related flows"
                ct state invalid drop comment "!fw4: Drop flows with invalid conntrack state"
                tcp flags syn / fin,syn,rst,ack jump syn_flood comment "!fw4: Rate limit TCP syn packets"
                iifname "br-lan" jump input_lan comment "!fw4: Handle lan IPv4/IPv6 input traffic"
                iifname "eth0" jump input_wan comment "!fw4: Handle wan IPv4/IPv6 input traffic"
        }

        chain forward {
                type filter hook forward priority filter; policy drop;
                ct state established,related accept comment "!fw4: Allow forwarded established and related flows"
                ct state invalid drop comment "!fw4: Drop flows with invalid conntrack state"
                iifname "br-lan" jump forward_lan comment "!fw4: Handle lan IPv4/IPv6 forward traffic"
                iifname "eth0" jump forward_wan comment "!fw4: Handle wan IPv4/IPv6 forward traffic"
                jump handle_reject
        }

        chain output {
                type filter hook output priority filter; policy accept;
                oifname "lo" accept comment "!fw4: Accept traffic towards loopback"
                ct state established,related accept comment "!fw4: Allow outbound established and related flows"
                ct state invalid drop comment "!fw4: Drop flows with invalid conntrack state"
                oifname "br-lan" jump output_lan comment "!fw4: Handle lan IPv4/IPv6 output traffic"
                oifname "eth0" jump output_wan comment "!fw4: Handle wan IPv4/IPv6 output traffic"
        }

        chain prerouting {
                type filter hook prerouting priority filter; policy accept;
                iifname "br-lan" jump helper_lan comment "!fw4: Handle lan IPv4/IPv6 helper assignment"
        }

        chain handle_reject {
                meta l4proto tcp reject with tcp reset comment "!fw4: Reject TCP traffic"
                reject comment "!fw4: Reject any other traffic"
        }

        chain syn_flood {
                limit rate 25/second burst 50 packets return comment "!fw4: Accept SYN packets below rate-limit"
                drop comment "!fw4: Drop excess packets"
        }

        chain input_lan {
                jump accept_from_lan
        }

        chain output_lan {
                jump accept_to_lan
        }

        chain forward_lan {
                jump accept_to_wan comment "!fw4: Accept lan to wan forwarding"
                jump accept_to_lan
        }

        chain helper_lan {
        }

        chain accept_from_lan {
                iifname "br-lan" counter accept comment "!fw4: accept lan IPv4/IPv6 traffic"
        }

        chain accept_to_lan {
                oifname "br-lan" counter accept comment "!fw4: accept lan IPv4/IPv6 traffic"
        }

        chain input_wan {
                meta nfproto ipv4 udp dport 68 counter accept comment "!fw4: Allow-DHCP-Renew"
                icmp type echo-request counter drop comment "!fw4: Allow-Ping"
                meta nfproto ipv4 meta l4proto igmp counter accept comment "!fw4: Allow-IGMP"
                meta nfproto ipv6 udp dport 546 counter accept comment "!fw4: Allow-DHCPv6"
                ip6 saddr fe80::/10 icmpv6 type . icmpv6 code { mld-listener-query . no-route, mld-listener-report . no-route, mld-listener-done . no-route, mld2-listener-report . no-route } counter accept comment "!fw4: Allow-MLD"
                icmpv6 type { destination-unreachable, time-exceeded, echo-request, echo-reply, nd-router-solicit, nd-router-advert } limit rate 1000/second counter accept comment "!fw4: Allow-ICMPv6-Input"
                icmpv6 type . icmpv6 code { packet-too-big . no-route, parameter-problem . no-route, nd-neighbor-solicit . no-route, nd-neighbor-advert . no-route, parameter-problem . admin-prohibited } limit rate 1000/second counter accept comment "!fw4: Allow-ICMPv6-Input"
                jump reject_from_wan
        }

        chain output_wan {
                jump accept_to_wan
        }

        chain forward_wan {
                icmpv6 type { destination-unreachable, time-exceeded, echo-request, echo-reply } limit rate 1000/second counter accept comment "!fw4: Allow-ICMPv6-Forward"
                icmpv6 type . icmpv6 code { packet-too-big . no-route, parameter-problem . no-route, parameter-problem . admin-prohibited } limit rate 1000/second counter accept comment "!fw4: Allow-ICMPv6-Forward"
                meta l4proto esp counter jump accept_to_lan comment "!fw4: Allow-IPSec-ESP"
                udp dport 500 counter jump accept_to_lan comment "!fw4: Allow-ISAKMP"
                jump reject_to_wan
        }

        chain accept_to_wan {
                oifname "eth0" counter accept comment "!fw4: accept wan IPv4/IPv6 traffic"
        }

        chain reject_from_wan {
                iifname "eth0" counter jump handle_reject comment "!fw4: reject wan IPv4/IPv6 traffic"
        }

        chain reject_to_wan {
                oifname "eth0" counter jump handle_reject comment "!fw4: reject wan IPv4/IPv6 traffic"
        }

        chain dstnat {
                type nat hook prerouting priority dstnat; policy accept;
        }

        chain srcnat {
                type nat hook postrouting priority srcnat; policy accept;
                oifname "eth0" jump srcnat_wan comment "!fw4: Handle wan IPv4/IPv6 srcnat traffic"
        }

        chain srcnat_wan {
                meta nfproto ipv4 masquerade comment "!fw4: Masquerade IPv4 wan traffic"
        }

        chain raw_prerouting {
                type filter hook prerouting priority raw; policy accept;
        }

        chain raw_output {
                type filter hook output priority raw; policy accept;
        }

        chain mangle_prerouting {
                type filter hook prerouting priority mangle; policy accept;
        }

        chain mangle_postrouting {
                type filter hook postrouting priority mangle; policy accept;
        }

        chain mangle_input {
                type filter hook input priority mangle; policy accept;
        }

        chain mangle_output {
                type route hook output priority mangle; policy accept;
        }

        chain mangle_forward {
                type filter hook forward priority mangle; policy accept;
                iifname "eth0" tcp flags syn tcp option maxseg size set rt mtu comment "!fw4: Zone wan IPv4/IPv6 ingress MTU fixing"
                oifname "eth0" tcp flags syn tcp option maxseg size set rt mtu comment "!fw4: Zone wan IPv4/IPv6 egress MTU fixing"
        }
}
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对应的 OpenWrt 防火墙配置文件 /etc/config/firewall 内容如下：

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config defaults
        option input 'ACCEPT'
        option output 'ACCEPT'
        option forward 'REJECT'
        option synflood_protect '1'
        option drop_invalid '1'

config zone
        option name 'lan'
        list network 'lan'
        option input 'ACCEPT'
        option output 'ACCEPT'
        option forward 'ACCEPT'

config zone
        option name 'wan'
        list network 'wan'
        list network 'wan6'
        option input 'REJECT'
        option output 'ACCEPT'
        option forward 'REJECT'
        option masq '1'
        option mtu_fix '1'

config forwarding
        option src 'lan'
        option dest 'wan'

config rule
        option name 'Allow-DHCP-Renew'
        option src 'wan'
        option proto 'udp'
        option dest_port '68'
        option target 'ACCEPT'
        option family 'ipv4'

config rule
        option name 'Allow-Ping'
        option src 'wan'
        option proto 'icmp'
        option family 'ipv4'
        list icmp_type 'echo-request'
        option target 'DROP'

config rule
        option name 'Allow-IGMP'
        option src 'wan'
        option proto 'igmp'
        option family 'ipv4'
        option target 'ACCEPT'

config rule
        option name 'Allow-DHCPv6'
        option src 'wan'
        option proto 'udp'
        option dest_port '546'
        option family 'ipv6'
        option target 'ACCEPT'

config rule
        option name 'Allow-MLD'
        option src 'wan'
        option proto 'icmp'
        option src_ip 'fe80::/10'
        list icmp_type '130/0'
        list icmp_type '131/0'
        list icmp_type '132/0'
        list icmp_type '143/0'
        option family 'ipv6'
        option target 'ACCEPT'

config rule
        option name 'Allow-ICMPv6-Input'
        option src 'wan'
        option proto 'icmp'
        list icmp_type 'echo-request'
        list icmp_type 'echo-reply'
        list icmp_type 'destination-unreachable'
        list icmp_type 'packet-too-big'
        list icmp_type 'time-exceeded'
        list icmp_type 'bad-header'
        list icmp_type 'unknown-header-type'
        list icmp_type 'router-solicitation'
        list icmp_type 'neighbour-solicitation'
        list icmp_type 'router-advertisement'
        list icmp_type 'neighbour-advertisement'
        option limit '1000/sec'
        option family 'ipv6'
        option target 'ACCEPT'

config rule
        option name 'Allow-ICMPv6-Forward'
        option src 'wan'
        option dest '*'
        option proto 'icmp'
        list icmp_type 'echo-request'
        list icmp_type 'echo-reply'
        list icmp_type 'destination-unreachable'
        list icmp_type 'packet-too-big'
        list icmp_type 'time-exceeded'
        list icmp_type 'bad-header'
        list icmp_type 'unknown-header-type'
        option limit '1000/sec'
        option family 'ipv6'
        option target 'ACCEPT'

config rule
        option name 'Allow-IPSec-ESP'
        option src 'wan'
        option dest 'lan'
        option proto 'esp'
        option target 'ACCEPT'

config rule
        option name 'Allow-ISAKMP'
        option src 'wan'
        option dest 'lan'
        option dest_port '500'
        option proto 'udp'
        option target 'ACCEPT'
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Linux Firewall OpenWrt Nftables
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