29 lines
1.3 KiB
Markdown
29 lines
1.3 KiB
Markdown
# Resubmit
|
|
|
|
## Description
|
|
|
|
This program illustrates as simply as possible how to use the `resubmit()`
|
|
primitive. This primitive is used to make a packet go twice through the ingress
|
|
pipeline. For more information, please refer to the P4 specification.
|
|
|
|
The P4 program only consists of an ingress pipeline, with 2 tables:
|
|
`t_ingress_1` and `t_ingress_2`. When a packet enters the pipeline, the
|
|
following happens (based on the P4 program and the [commands.txt](commands.txt)
|
|
files):
|
|
- the packet hits `table_ingress_1` and the egress port is set to 2.
|
|
- the packet hits `table_ingress_2`, `mymeta.f1` is set to 1 and the
|
|
`resubmit()` primitive is called. Because `mymeta` is resubmitted along with
|
|
the packet, `mymeta.f1` will now be equal to 1 for the second pass.
|
|
- the packet hits `table_ingress_1`, this time the egress port is set to 3.
|
|
- the packet hits `table_ingress_2` which is a no-op.
|
|
|
|
### Running the demo
|
|
|
|
We provide a small demo to let you test the program. It consists of the
|
|
following scripts, which you need to run one after the other, in 2 separate
|
|
terminals:
|
|
- [run_switch.sh](run_switch.sh): compile the P4 program and starts the switch,
|
|
also configures the data plane by running the CLI [commands](commands.txt).
|
|
- [send_and_receive.py](send_and_receive.py): send a packet on port 0 (veth1),
|
|
wait for the forwarded packet on port 3 (veth7).
|