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提出问题:
为什么默认的nft table里的 “wan的入向”,只有tcp reject ? 难道udp流量都默认放行??
如下是标准的nft table, 在 chain input_wan { } 最后一句 jump reject_from_wan, 然后去到 chain reject_from_wan {} 最后一句jump handle_reject, 然后到chain handle_reject {}最后一句meta l4proto tcp reject with tcp reset, 这里面只有tcp reject, 没有udp reject!
root@OpenWrt:~# nft -s list ruleset
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"
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 "eth1" 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"
iifname "br-lan" jump forward_lan comment "!fw4: Handle lan IPv4/IPv6 forward traffic"
iifname "eth1" 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"
oifname "br-lan" jump output_lan comment "!fw4: Handle lan IPv4/IPv6 output traffic"
oifname "eth1" 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 accept comment "!fw4: Allow-Ping"
meta nfproto ipv4 meta l4proto igmp counter accept comment "!fw4: Allow-IGMP"
tcp dport 22 counter accept comment "!fw4: Allow-SSH"
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 "eth1" counter accept comment "!fw4: accept wan IPv4/IPv6 traffic"
}
chain reject_from_wan {
iifname "eth1" counter jump handle_reject comment "!fw4: reject wan IPv4/IPv6 traffic"
}
chain reject_to_wan {
oifname "eth1" 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 "eth1" 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 "eth1" tcp flags syn tcp option maxseg size set rt mtu comment "!fw4: Zone wan IPv4/IPv6 ingress MTU fixing"
oifname "eth1" tcp flags syn tcp option maxseg size set rt mtu comment "!fw4: Zone wan IPv4/IPv6 egress MTU fixing"
}
}
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