[dpdk-dev] [PATCH] doc: refine ethernet and VLAN flow rule items

[Stephen Hemminger]

On Sun, 26 Apr 2020 09:18:54 +0000
Dekel Peled <dekelp at mellanox.com> wrote:

> Thanks, PSB.
> 
> > -----Original Message-----
> > From: Andrew Rybchenko <arybchenko at solarflare.com>
> > Sent: Saturday, April 25, 2020 5:00 PM
> > To: Dekel Peled <dekelp at mellanox.com>; Ori Kam <orika at mellanox.com>;
> > john.mcnamara at intel.com; marko.kovacevic at intel.com; Thomas Monjalon
> > <thomas at monjalon.net>; ferruh.yigit at intel.com
> > Cc: dev at dpdk.org; Asaf Penso <asafp at mellanox.com>
> > Subject: Re: [PATCH] doc: refine ethernet and VLAN flow rule items
> > 
> > On 4/23/20 9:30 PM, Dekel Peled wrote:  
> > > Specified pattern may be translated in different manner.
> > > For example the pattern "eth / ipv4" can be translated to match
> > > untagged packets only, since the pattern doesn't specify a vlan item.  
> > 
> > vlan -> VLAN  
> 
> I will change to uppercase.
> 
> >   
> > > It can also be translated to match both tagged and untagged packets,
> > > for the same reason.
> > > This patch updates the rte_flow documentation to clearly specify the
> > > required pattern to use.
> > > For example:
> > > To match tagged ipv4 packets, the pattern "eth type is 0x8100 / vlan /
> > > ipv4 / end" should be used.  
> > 
> > Isn't eth / vlan / ipv4 /end sufficient? What's the difference?
> > I guess later should allow any VLAN TPID, but it is greyish since it is HW
> > dependent.  
> 
> In the example I wanted to show explicit rule, to emphasize the importance of detailed pattern structure.
> 
> >   
> > > To match untagged ipv4 packets, the pattern "eth type is 0x0800 /
> > > ipv4 / end" should be used.  
> > 
> > What about eth / ipv4 / end?
> > Does usage of ipv4 assume that EtherType is 0x0800?  
> 
> Same as above.
> 
> >   
> > > To match both tagged and untagged packets, the pattern "eth / end"
> > > should be used.  
> > 
> > The interesting question is what should be used if I want either tagged or
> > untagged IPv4 packets. I think it worse to mention to make the picture
> > complete.  
> 
> To match any IPV4 packet, either tagged or untagged, need to apply two rules.
> One for tagged packets and the other for untagged packets.
> I will add this example as well.
> 
> >   
> > > Signed-off-by: Dekel Peled <dekelp at mellanox.com>

All this reminds me that "code is the best documentation" and there
is no working code that does a complete software implementation of the
rte_flow engine. This means the actual interpretation of what the rte_flow
means is left to documentation and hardware vendors choices in implementation.