Re: iptables-nft: Wrong payload merge of rule filter - "! --sport xx ! --dport xx"

[Phil Sutter <phil@nwl.cc>]

Hi Sriram,

On Fri, Mar 08, 2024 at 02:49:38PM +0530, Sriram Rajagopalan wrote:
> iptables-nft based on nftables has an issue with the way the rule
> filter - "! --sport xx ! --dport xx" is wrongly merged and rendered.

I agree with your analysis and the patches look fine. Could you please
submit them formally?

[...]
> % export IPTABLES=/usr/local/sbin/iptables-legacy; sudo $IPTABLES -A
> INPUT -p tcp ! --sport 22 ! --dport 22 -i vm2; echo -e "\n---- Before
> data ----\n"; sudo $IPTABLES -L INPUT -vvvn; sudo python -c "from
> scapy.all import *;
> sendp(Ether(dst='9e:00:fa:a3:c9:48')/IP(src='1.1.1.1',
> dst='2.2.2.2')/TCP(sport=23, dport=22), iface='vm1')"; echo -e "\n----
> After data with either one of tcp sport/dport being 22 ----\n"; sudo
> $IPTABLES -L INPUT -vn; sudo python -c "from scapy.all import *;
> sendp(Ether(dst='9e:00:fa:a3:c9:48')/IP(src='1.1.1.1',
> dst='2.2.2.2')/TCP(sport=23, dport=23), iface='vm1')"; echo -e "\n----
> After data with neither one of tcp sport/dport being 22 ----\n"; sudo
> $IPTABLES -L INPUT -vn; sudo $IPTABLES -D INPUT -p tcp ! --sport 22 !
> --dport 22 -i vm2
> 
> 
> ---- Before data ----
> 
> ip filter INPUT 41
>   [ meta load iifname => reg 1 ]
>   [ cmp eq reg 1 0x00326d76 ]
>   [ payload load 1b @ network header + 9 => reg 1 ]
>   [ cmp eq reg 1 0x00000006 ]
>   [ payload load 2b @ transport header + 0 => reg 1 ]
>   [ cmp neq reg 1 0x00001600 ]
>   [ payload load 2b @ transport header + 2 => reg 1 ]
>   [ cmp neq reg 1 0x00001600 ]
>   [ counter pkts 0 bytes 0 ]

You're fibbing here: That netlink debug output can't come from
iptables-legacy. I suspect it actually comes from your patched
iptables-nft or nft too. :)

[...]
> Author: Sriram Rajagopalan <bglsriram@gmail.com>
> Date:   Fri Mar 07 20:09:38 2024 -0800
> 
> iptables: Fixed the issue with combining the payload in case of invert
> filter for tcp src and dst ports
> 
> Signed-off-by: Sriram Rajagopalan <bglsriram@gmail.com>
> Signed-off-by: Sriram Rajagopalan <sriramr@arista.com>

Maybe avoid the double SoB? Apart from that:

Acked-by: Phil Sutter <phil@nwl.cc>

Thanks, Phil