Re: [PATCH nft] proto: add pseudo th protocol to match d/sport in generic way

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Sat, Jul 13, 2019 at 07:23:27PM +0200, Florian Westphal wrote:
> Problem: Its not possible to easily match both udp and tcp in a single
> rule.
> 
> ... input ip protocol { tcp,udp } dport 53
> 
> will not work, as bison expects "tcp dport" or "sctp dport", or any
> other transport protocol name.
> 
> Its possible to match the sport and dport via raw payload expressions,
> e.g.:
> ... input ip protocol { tcp,udp } @th,16,16 53
> 
> but its not very readable.
> Furthermore, its not possible to use this for set definitions:
> 
> table inet filter {
>         set myset {
>                 type ipv4_addr . inet_proto . inet_service
>         }
> 
>         chain forward {
>                 type filter hook forward priority filter; policy accept;
>                 ip daddr . ip protocol . @th,0,16 @myset
>         }
> }
>  # nft -f test
>  test:7:26-35: Error: can not use variable sized data types (integer) in concat expressions
> 
> During the netfilter workshop Pablo suggested to add an alias to do raw
> sport/dport matching more readable, and make it use the inet_service
> type automatically.
> 
> So, this change makes @th,0,16 work for the set definition case by
> setting the data type to inet_service.
> 
> A new "th s|dport" syntax is provided as readable alternative:
> 
> ip protocol { tcp, udp } th dport 53
> 
> As "th" is an alias for the raw expression, no dependency is
> generated -- its the users responsibility to add a suitable test to
> select the l4 header types that should be matched.
> 
> Suggested-by: Pablo Neira Ayuso <pablo@netfilter.org>
> Signed-off-by: Florian Westphal <fw@strlen.de>

Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>

Thanks Florian.