Re: [mpls-linux-general] Looking for examples to test TC/DS/IPTABLE

[Olivier D. <Oli...@rd...>]

hi Jim,

Can you describe a little more the MPLS_OP_NF_FWD action ?

If i understand well, the sutff is :

- mark packet with iptable
- use MPLS_OP_NF_FWD to retrieve the MOI info (and so the outgoing 
label) from the nfmark value
- possibly use nfmark as filter criteria for TC as usual

It look like good for me because it made a very little change in the 
kernel and haven't to maintain an mpls_index change in case of nfmark 
change.

Just a point of clarification about the use of nfmark instead of 
mpls_index for the reason given previously (incomptability with nfmark 
route only stuff) Have you a different way to use this action and so let 
the normal nfmark  behaviour work as usual ? I suppose mplsadm need to 
be modified to set up this action with the right nfmark value ? If so, i 
suppose you can leave both normal and mpls nfmark. The difference come 
with a different value for nfmark (only value setup with mplsadm result 
in a mpls processing)

Regards,

Olivier

James R. Leu wrote:

> Hello,
> 
> I have (re)implemented my version of TC/DS enhanced mpls-linux. I would
> like to describe what I have created so I can get feed back.  Also
> I would like to get examples from people of how to use TC and iptables
> to actually excercise this new code and to show me what this implementation
> cannot do.
> 
> First this to keep in mind is that 'outgoing info' nolonger can be interpreted
> as 'outgoing label'.  A particular 'outgoing info' can fwd on to another
> 'outgoing info' which may do a 'push'.  'incoming labels', aux_proto, and
> mpls tunnels all point to 'outgoing info' (in addition 'outgoing info' can
> point to other 'outgoing info').  I will refer to 'outgoing info' as
> 'MOI' (in the code it stands for the mpls_outgoing_info structure).
> 
> Incoming labels and MOI's have an array of 'instructions' associated
> with them.  Each instruction has a 'data block' associated with it.
> The original set of instructions, have changed very little:
> 
> MPLS_OP_POP	-> IN: pop off top label (no data)
> MPLS_OP_PEEK	-> IN: make the top label the active 'incoming label' (no data)
> MPLS_OP_PUSH	-> OUT: push a label on to the top of the label stack
> 		   (label to push)
> MPLS_OP_DLV	-> IN: deliver the packet to a specify protocol handler
> 		   (protocol id to send the packet to ie IPv4 IPv6)
> MPLS_OP_FWD	-> IN: transfer control to mpls_output() (pointer to the MOI)
> 		   OUT: start processing the instructions wit the new MOI
> 			(pointer to the new MOI)
> MPLS_OP_SET	-> IN: set the incoing interface
> 		   OUT: set the dst_entry on the skb [last step before TXing a
> 		   MPLS packet] (pointer to the dst_entry)
> 
> These are the new instructions:
> 
> *nfmark comes from skb
> #dsmark comes from IP header
> *tc_index comes from the skb
> *EXP comes from the active incoming label
> 
> MPLS_OP_NF_FWD	-> IN/OUT: index into the datablock by using the (nfmark & mask)
> 		   start processing the MOI that was found. (array of MOIs)
> MPLS_OP_DS_FWD	-> IN: index into the datablock by using the (dsmark & mask)
> 		   start processing the MOI that was found. (array of MOIs)
> MPLS_OP_TC_FWD	-> OUT: index into the datablock by using the (tc_index & mask)
> 		   start processing the MOI that was found. (array of MOIs)
> MPLS_OP_EXP_FWD	-> IN: index into the datablock by using the (EXP)
> 		   start processing the MOI that was found. (array of MOIs)
> MPLS_OP_SET_TC	-> IN/OUT: set the tc_index (tc_index to use)
> MPLS_OP_SET_DS	-> IN/OUT: set the dsmark (DSCP to use)
> MPLS_OP_SET_EXP	-> IN/OUT: set EXP on the top label (EXP to use)
> MPLS_OP_EXP2TC	-> IN: index into the data block by using the (EXP) and set the
> 		   tc_index to the value found
> MPLS_OP_EXP2DS	-> IN: index into the data block by using the (EXP) and set the
> 		   dsmark to the value found
> 
> 
> 
> So here are some examples:
> 
> Egress LER:
> 
> On input of label 100 EXP 1 gets DSCP 0x4, EXP 4 gets DSCP 0x7
> 
> MII(100) -> PEEK POP EXP2DS(1->0x4,4->0x7) DLV(IPv4)
> 
> Ingress LER (DSCP):
> 
> Packets going to 11.0.0.0/16 goes out with label 100, DSCP 0x4 get EXP 1,
>     DSCP 0x7 gets EXP 4
> 
> IPROUTE(11.0.0.0/16) -> MOI(1000)
>     MOI(1000) DS_FWD(0x4->MOI(500), 0x7->MOI(2000))
> 	MOI(500) SET_EXP (1) PUSH(100) SET(next hop info)
> 	MOI(2000) SET_EXP (4) PUSH(100) SET(next hop info)
> 
> IP routing tranfer control to mpls_output and starts processing MOI(1000).
> MOI(1000) looks at the DSCP and starts processing either MOI(500) or
> MOI(2000).  MOI(500) and MOI(2000) set the EXP, puch the label,
> set the dst_entry and then send the packet)
> 
> (you could implement L-LSPs in a similar way, push differnt label in MOI(500)
> and MOI(2000) and do not set the EXP value)
> 
> Alternative:
> 
> IPROUTE(11.0.0.0/16) -> MPLS_TUNNEL(mpls0)
>     mpls0 -> MOI(1000)
> 	MOI(500) SET_EXP (1) PUSH(100) SET(next hop info)
> 	MOI(2000) SET_EXP (4) PUSH(100) SET(next hop info)
> 
> IP routing tranfer send the packet out interface mpls0.  Interface mpls0
> transfers control to mpls_output and starts processing MOI(1000).
> MOI(1000) looks at the DSCP and starts processing either MOI(500) or
> MOI(2000).  MOI(500) and MOI(2000) set the EXP, puch the label,
> set the dst_entry and then send the packet)
> 
> Ingress LER NFMARK and TCINDEX, work simlarly.
> 
> Transit:
> 
> INCOMING_LABEL(100) PEEK POP EXP2TC(1->0xF,4->0xE) -> MOI(10000)
>     MOI(10000) PUSH(100) SET(next hop info)
> 
> Incoming label 100 looks at the EXP bits and sets tc_index to 0xF when
> EXP is 1 and to 0xE when EXP is 4.  MOI(10000) is responsible for
> trasmitting the label.  It pushed on label 100 (and the same EXP bits)
> and send it on it way.  As it leaved via the physical interface a packet
> scheduler can look at the tc_index and schedule it appropriately.
> 
> If you want to translate the EXP then you could use an EXP forward
> to differnt MOIs that push on the same label, but set differnt EXP bits.
> 
> Additional intructions?
> 
> MPLS_OP_TC2EXP	-> coule be use in a MOI to translate the tc_index set on
> 		   input to differnt EXP values.  This would avoid having
> 		   to do a EXP FWD just to set differnt EXP values.
> 
> MPLS_OP_DS2EXP	-> same as above, but would look at DSCP in the IP header
> 		   and could only be execute on packet that came directly
> 		   from the IP layer.  It would avoid having to have
> 		   seperate MOIs to implement E-LSPs.
> 
> Comments, questions, political statments?
> 
> Jim
> 


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