[FS#4239] flow_offloading_hw doesn't work with nftables (mt7621)

OpenWrt Bugs openwrt-bugs at lists.openwrt.org
Tue Jan 25 01:23:10 PST 2022


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A new Flyspray task has been opened.  Details are below. 

User who did this - amaumene (amaumene) 

Attached to Project - OpenWrt/LEDE Project
Summary - flow_offloading_hw doesn't work with nftables (mt7621)
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Medium
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - When enabling flow_offloading_hw on mt7621 device (Xiaomi Redmi Router AC2100 and Mikrotik RB760iGS) like this:
root at route2:~# grep flow_offload /etc/config/firewall 
	option flow_offloading '1'
	option flow_offloading_hw '1'

firewall4 fails to start:
root at route2:~# /etc/init.d/firewall start
/proc/self/fd/0:9:12-13: Error: Could not process rule: Not supported

/proc/self/fd/0:51:29-44: Error: Could not process rule: No such file or directory

nftables rules generated looks good:
root at route2:~# fw4 print > /tmp/fw4 
root at route2:~# cat /tmp/fw4 
table inet fw4
flush table inet fw4

table inet fw4 {
	#
	# Flowtable
	#

	flowtable ft {
		hook ingress priority 0;
		devices = { "br-lan" };
		flags offload;
	}

	#
	# Set definitions
	#


	#
	# Defines
	#

	define lan_devices = { "br-lan" }
	define lan_subnets = { 192.168.1.0/24, 302:f543:22c1:2921::/64 }

	#
	# User includes
	#

	include "/etc/nftables.d/*.nft"


	#
	# Filter rules
	#

	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 & (fin | syn | rst | ack) == syn jump syn_flood comment "!fw4: Rate limit TCP syn packets"
		iifname "br-lan" jump input_lan comment "!fw4: Handle lan IPv4/IPv6 input traffic"
	}

	chain forward {
		type filter hook forward priority filter; policy drop;

		meta l4proto { tcp, udp } flow offload @ft;
		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"
		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"
	}

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

	chain syn_flood {
		tcp flags & (fin | syn | rst | ack) == syn 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 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"
		meta nfproto ipv4 icmp type 8 counter accept comment "!fw4: Allow-Ping"
		meta nfproto ipv4 meta l4proto igmp counter accept comment "!fw4: Allow-IGMP"
		ip6 saddr fc00::/6 ip6 daddr fc00::/6 udp dport 546 counter accept comment "!fw4: Allow-DHCPv6"
		ip6 saddr fe80::/10 icmpv6 type . icmpv6 code { 130 . 0, 131 . 0, 132 . 0, 143 . 0 } counter accept comment "!fw4: Allow-MLD"
		meta nfproto ipv6 icmpv6 type { 128, 129, 1, 3, 133, 134 } limit rate 1000/second counter accept comment "!fw4: Allow-ICMPv6-Input"
		meta nfproto ipv6 icmpv6 type . icmpv6 code { 2 . 0, 4 . 0, 4 . 1, 135 . 0, 136 . 0 } 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 {
		meta nfproto ipv6 icmpv6 type { 128, 129, 1, 3 } limit rate 1000/second counter accept comment "!fw4: Allow-ICMPv6-Forward"
		meta nfproto ipv6 icmpv6 type . icmpv6 code { 2 . 0, 4 . 0, 4 . 1 } 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 {
	}

	chain reject_from_wan {
	}

	chain reject_to_wan {
	}


	#
	# NAT rules
	#

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

	chain srcnat {
		type nat hook postrouting priority srcnat; policy accept;
	}

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


	#
	# Raw rules (notrack & helper)
	#

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

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

	chain helper_lan {
	}


	#
	# Mangle rules
	#

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

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

	chain mangle_forward {
		type filter hook forward priority mangle; policy accept;
	}
}

But for some reason nftables cannot process the rules:
root at route2:~# nft -f /tmp/fw4 -c
/tmp/fw4:9:12-13: Error: Could not process rule: Not supported
	flowtable ft {
	          ^^
/tmp/fw4:51:29-44: Error: Could not process rule: No such file or directory
		meta l4proto { tcp, udp } flow offload @ft;
		                          ^^^^^^^^^^^^^^^^

This has been tested on latest trunk version:
root at route2:~# cat /etc/openwrt_version 
r18638-ebc36ebb23

When only software flow offloading is enabled (option flow_offloading '1') everything works fine (verified in /proc/net/nf_conntrack)

More information can be found at the following URL:
https://bugs.openwrt.org/index.php?do=details&task_id=4239

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