The release of the nftables 1.0.5 packet filter has been published, unifying the packet filtering interfaces for IPv4, IPv6, ARP, and network bridges (aimed at replacing iptables, ip6tables, arptables, and ebtables). At the same time, the accompanying library libnftnl 1.2.3 has been released, providing a low-level API for interacting with the nf_tables subsystem.
The nftables package includes user-space packet filter components, while the nf_tables subsystem, which is part of the Linux kernel since version 3.13, handles operations at the kernel level. At the kernel level, only a general interface is provided, which is independent of specific protocols and offers basic functions for extracting data from packets, performing data operations, and managing the flow.
The filtering rules themselves and protocol-specific handlers are compiled into bytecode in user space, after which this bytecode is loaded into the kernel via the Netlink interface and executed in the kernel in a special environment resembling BPF (Berkeley Packet Filters). This approach significantly reduces the size of the filtering code running at the kernel level and offloads all functions related to rule parsing and protocol logic into user space. virtual machineFull support for lightweight tunnel templates, such as vxlan, geneve, and erspan, has been provided: table netdev global { tunnel t1 { id 10 ip saddr 192.168.2.10 ip daddr 192.168.2.11 sport 1025 dport 20020 ttl 1 erspan { version 1 index 2 } } tunnel t2 { id 10 ip saddr 192.168.3.10 ip daddr 192.168.3.11 sport 1025 dport 21021 ttl 1 erspan { version 1 index 2 } } chain in { type filter hook ingress device veth0 priority 0; tunnel name ip saddr map { 10.141.10.12 : "t1", 10.141.10.13 : "t2" } fwd to erspan1 } } Before loading the rules, a network interface erspan1 must be created: ip link add dev erspan1 type erspan external
Key Changes:
- In the rule optimizer called with the -o/--optimize option, issues with merging rules, map, and set lists have been resolved. # cat ruleset.nft table ip x { chain y { type nat hook postrouting priority srcnat; policy drop; ip saddr 1.1.1.1 tcp dport 8000 snat to 4.4.4.4:80 ip saddr 2.2.2.2 tcp dport 8001 snat to 5.5.5.5:90 } } # nft -o -c -f ruleset.nft Merging: ruleset.nft:4:3-52: ip saddr 1.1.1.1 tcp dport 8000 snat to 4.4.4.4:80 ruleset.nft:5:3-52: ip saddr 2.2.2.2 tcp dport 8001 snat to 5.5.5.5:90 into: snat to ip saddr . tcp dport map { 1.1.1.1 . 8000 : 4.4.4.4 . 80, 2.2.2.2 . 8001 : 5.5.5.5 . 90 }
- When merging ethernet and vlan elements, the definition of a dynamic set list has been ensured, filled based on the packet path parameters. add table netdev x add chain netdev x y { type filter hook ingress device enp0s25 priority 0; } add set netdev x macset { typeof ether daddr . vlan id; flags dynamic,timeout; } add rule netdev x y update @macset { ether daddr . vlan id timeout 60s } add rule netdev x y ether saddr . vlan id { 0a:0b:0c:0d:0e:0f . 42, 0a:0b:0c:0d:0e:0f . 4095 } counter accept
- The display of rules with map lists containing masks in interface names has been established. table inet filter { chain INPUT { iifname vmap { "eth0" : jump input_lan, "wg*" : jump input_vpn } } chain input_lan {} chain input_vpn {} }
- Regression changes that led to incorrect lexical parsing of correct rules have been eliminated.
- Issues with slow processing and automatic merging of large lists with elements defining value ranges have been resolved.
- Crash upon adding elements to an invalid set list has been eliminated.
Source: opennet.ru
