This repository contains the P4 implementation of Switcharoo for Intel Tofino. Switcharoo is a key-value data structure entirely implemented in the data plane that supports millions of modifications per second.

This implementation is tested with SDE 9.8.0 and SDE 9.9.1.

The main file is switcharoo.p4. It contains the implementation of the entire pipeline.

The cuckoo_pipe directory contains the logic for the cuckoo-hash table pipeline.

The bloom_pipe directory contains the logic for the ordering pipeline.

The include directory contains general configuration files.

The file setup.py contains a bfrt_python script that configures ports, mirroring, and other several callbacks for the program.

Example command to build the code, it can vary depending on your SDE installation:

./p4_build.sh switcharoo.p4

You can specify different compilation-time parameters:

• ENTRY_TIMEOUT: timeout of the entries in the cuckoo-hash table (in nanoseconds). Default is 50000.
• MAX_LOOPS_WAIT: number of recirculations before a WAIT packet is sent out. Default is 10.
• MAX_LOOPS_INSERT: number of recirculations of the same packet before the transient states of the corresponding flow are reset. Default is 20.
• TABLE_SIZE: number of entries in the cuckoo-hash table (minimum is 128, maximum is 65536). Default is 65536.
• BLOOM_FILTER_SIZE: number of entries in the Ordering and Flow Count bloom filters (minimum is 128, maximum is 65536). Default is 65536.
• SWAP_BLOOM_FILTER_SIZE: number of entries in the Swap and Swapped bloom filters (minimum is 128, maximum is 65536). Default is 65536.

For example, if you want to compile Switcharoo with a cuckoo-hash table of 32768 entries and an expiration timeout of 10us:

./p4_build.sh -DENTRY_TIMEOUT=10000 -DTABLE_SIZE=32768 switcharoo.p4

Example commands to run Switcharoo, they can vary depending on your SDE installation. On a terminal, run switchd:

$SDE/run_switchd.sh -p switcharoo

On another terminal, launch the setup.py script using bfshell:

$SDE/run_bfshell.sh -i -b /absolute/path/to/setup.py

By default, P4 programs are compiled using a 4-pipes layout. Hence, if you are using a 2-pipe Tofino ASIC, the program will not be launched since the mapping will fail.

In this repository, we provide a proper 2-pipes mapping file (switcharoo.conf) that has to be loaded when launching run_switchd.sh. The mapping assigns the cuckoo pipe to the first pipe of the ASIC and the bloom pipe to the second one. You can change the mapping by changing the pipe_scope key in the switcharoo.conf file.

To run switchd with the new mapping, type the following command:

$SDE/run_switchd.sh -p switcharoo -c /absolute/path/to/switcharoo.conf

The figure shows the port configuration of Switcharoo.

You can find ports configuration in the include/configuration.p4 file. Here you can set the output port and the recirculation ports. If you make changes, you need to update the ports value in the setup.py file accordingly.

The outport ports specified in the files are used to send out the traffic after being processed by Switcharoo. The current implementation sends out the packets randomly assigning an IPv4 identification in the cuckoo pipe using the select_flow_id table. The identification is then used in the bloom pipe to send out the packet using the forward table, which is filled in the setup.py file:

#########################
##### FORWARD TABLE #####
#########################
# This function setups the entries in the forward table.
# You can add/edit/remove entries to choose where output the packets based on the IPv4 identification.
def setup_forward_table():
    global switcharoo_bloom_pipe, OUTPUT_PORT_1, OUTPUT_PORT_2, OUTPUT_PORT_3, OUTPUT_PORT_4

    forward_table = switcharoo_bloom_pipe.BloomIngress.forward
    forward_table.clear()

    forward_table.add_with_send(identification=0xFFFF, port_number=OUTPUT_PORT_1)
    forward_table.add_with_send(identification=0xEEEE, port_number=OUTPUT_PORT_2)
    forward_table.add_with_send(identification=0xDDDD, port_number=OUTPUT_PORT_3)
    forward_table.add_with_send(identification=0xCCCC, port_number=OUTPUT_PORT_4)

To add a port, you need to:

• Add it in the include/configuration.p4 file;
• Add it in the setup.py file;
• Add an additional entry in the select_flow_id of the cuckoo pipe;
• Add an additional entry in the setup_forward_table in the setup.py file.

Each input port is then mapped to several recirculation ports, which are used to share packets between the cuckoo and bloom pipe. For each input port, you need three ports in the cuckoo pipe:

1. RECIRCULATE_PORT_INSERT_IP*_TO_BLOOM
2. RECIRCULATE_PORT_WAIT_IP*_TO_BLOOM
3. RECIRCULATE_PORT_NOP_IP*_TO_BLOOM

And two ports in the bloom pipe:

1. RECIRCULATE_PORT_INSERT_IP*_TO_CUCKOO
2. RECIRCULATE_PORT_LOOKUP_IP*_TO_CUCKOO

To handle traffic from a new port, you need to:

• Define the new recirculation ports in the include/configuration.p4 file;
• Define new actions in the include/recirculation_action.p4 file;
• Add the corresponding entries in the select_bloom_recirculation_port in the cuckoo pipe (you can follow the pattern of the other entries);
• Add the corresponding entries in the select_cuckoo_recirculation_port in the bloom pipe (you can follow the pattern of the other entries).

Switcharoo leverages on a mirror port (with mirroring ID=100) to perform swapping.

If you want to change the mirroring port, you have to:

• Change the RECIRCULATE_PORT_SWAP_TO_CUCKOO definition in the setup.py file;
• Change the RECIRCULATE_PORT_SWAP_TO_CUCKOO definition in the include/configuration.p4 file.

Additional modifications (e.g., the mirroring ID) can be done by changing the setup.py file setup_mirror_session_table callback:

#################################
##### MIRROR SESSIONS TABLE #####
#################################
# In this section, we setup the mirror sessions of SWITCHAROO.
# There is only one session, that is used to truncate/send swap operations to the Cuckoo Pipe.
PKT_MIN_LENGTH = 100
SWAP_MIRROR_SESSION = 100


def setup_mirror_session_table():
    global bfrt, SWAP_MIRROR_SESSION, RECIRCULATE_PORT_SWAP_TO_CUCKOO, PKT_MIN_LENGTH

    mirror_cfg = bfrt.mirror.cfg

    mirror_cfg.entry_with_normal(
        sid=SWAP_MIRROR_SESSION,
        direction="BOTH",
        session_enable=True,
        ucast_egress_port=RECIRCULATE_PORT_SWAP_TO_CUCKOO,
        ucast_egress_port_valid=1,
        max_pkt_len=PKT_MIN_LENGTH,
        packet_color="GREEN"
    ).push()

And the include/configuration.p4 file:

/* Mirror Configuration */
const MirrorType_t SWAP_MIRROR = 1;
const MirrorId_t SWAP_MIRROR_SESSION = 100;