Re: [PATCH] IPv6 dnat/snat support

Jan Engelhardt wrote on Wednesday, February 06, 2008 4:33 PM:

> On Feb 6 2008 16:14, Tseng, Kuo-Lang wrote:
> 
>>>>> I would like to find out if there is any IPv6 support in ebtables
>>>>> for replacing MAC address of the Ethernet header based on TCP or
>>>>> UDP port id in IPv6 packets. I would appreciate it if there is
>>>>> anyone on this list who knows of any prior work in ebtables to
>>>>> support IPv6.
> 
> Sorry; I only monitor ebtables-devel since recently,
> an ebt_ip6 match has been posted at
> http://marc.info/?l=netfilter-devel&m=120182168424052&w=2
> 
> I am not to keen to add layer-4 parsing to ebt code; instead,
> it should (ideally) interface with Xtables.

We are not adding any new functionality. This only extends ebtables 
adding Layer 4 Port Based NAT for IPv6, which is already present for 
IPv4. This is efficient and is consistent with the current 
Functionality (this involves only few lines of code (see my patch) 
and matches the same way today ebtables is doing for v4).

A few comments to the br-netfilter patch you posted in that link:

1. 
+	if ((info->match_flags & EBT_IP6_NEXTHDR) &&
+	    (iph->nexthdr != info->nexthdr) ^
+	    !!(info->invert_flags & EBT_IP6_NEXTHDR))
+		return EBT_NOMATCH;

This is not sufficient and is broken if you got options headers in 
between the v6 header and the protocol header that you wish to match.

2. You could use the macro FWINV and same name for the mask field, 
bitmask, so that this module is consistent with other protocol 
modules in br-netfilter.  

3. The other suggestion is that next time when you post 
br-netfiler change for ebtables, please also post an email to 
ebtables-devel list so that people on that list can be aware coming 
changes/patches in ebtables (as br-netfilter is where ebtables is 
implemented) thus can avoid duplication of work. Let's folow the 
standard practice. 

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