Swap P4 program at runtime

Based on https://titanwolf.org/Network/Articles/Article?AID=14bf03b7-91f3-407e-b331-26b67139248f#gsc.tab=0, I wrote this lab

Before running this lab, you need to modify the file p4_mininet.py, which is located p4-utils/p4utils/mininetlib. Remember to run ./install.sh again.

def start(self, controllers = None):

"""Start up a new P4 switch."""

info("Starting P4 switch {}.\n".format(self.name))

args = [self.sw_path]

for port, intf in self.intfs.items():

if not intf.IP():

args.extend(['-i', str(port) + "@" + intf.name])

if self.pcap_dump:

if self.pcap_dir:

args.append("--pcap="+self.pcap_dir)

else:

args.append("--pcap")

if self.thrift_port:

args.extend(['--thrift-port', str(self.thrift_port)])

if self.nanomsg:

args.extend(['--nanolog', self.nanomsg])

args.extend(['--device-id', str(self.device_id)])

args.append(self.json_path)

#add the following line

args.append("-- --enable-swap")

if self.enable_debugger:

args.append("--debugger")

if self.log_console:

args.append("--log-console")

args.append('>' + self.log_file)

info(' '.join(args) + "\n")

………

[topology]

H1----P4Switch---H2

In the original p4 program (phy_forward.p4), P4Switch will forward the traffic from port 1 to port 2, and forward the traffic from port 2 to port 1. Then we can use the “load_new_config_file” command in simple_switch_switch to change the p4 program to mac_forward.p4. (mac-layer forward).

(phy_forward.p4)

/* -*- P4_16 -*- */

#include <core.p4>

#include <v1model.p4>

/*************************************************************************

*********************** H E A D E R S ***********************************

*************************************************************************/

struct metadata {

/* empty */

}

struct headers {

}

/*************************************************************************

*********************** P A R S E R ***********************************

*************************************************************************/

parser MyParser(packet_in packet,

out headers hdr,

inout metadata meta,

inout standard_metadata_t standard_metadata) {

state start {

transition accept;

}

}

/*************************************************************************

************ C H E C K S U M V E R I F I C A T I O N *************

*************************************************************************/

control MyVerifyChecksum(inout headers hdr, inout metadata meta) {

apply { }

}

/*************************************************************************

************** I N G R E S S P R O C E S S I N G *******************

*************************************************************************/

control MyIngress(inout headers hdr,

inout metadata meta,

inout standard_metadata_t standard_metadata) {

action drop() {

mark_to_drop(standard_metadata);

}

action forward(bit<9> port) {

standard_metadata.egress_spec = port;

}

table phy_forward {

key = {

standard_metadata.ingress_port: exact;

}

actions = {

forward;

drop;

}

size = 1024;

default_action = drop();

}

apply {

phy_forward.apply();

}

}

/*************************************************************************

**************** E G R E S S P R O C E S S I N G *******************

*************************************************************************/

control MyEgress(inout headers hdr,

inout metadata meta,

inout standard_metadata_t standard_metadata) {

apply { }

}

/*************************************************************************

************* C H E C K S U M C O M P U T A T I O N **************

*************************************************************************/

control MyComputeChecksum(inout headers hdr, inout metadata meta) {

apply {

}

}

/*************************************************************************

*********************** D E P A R S E R *******************************

*************************************************************************/

control MyDeparser(packet_out packet, in headers hdr) {

apply {

}

}

/*************************************************************************

*********************** S W I T C H *******************************

*************************************************************************/

V1Switch(

MyParser(),

MyVerifyChecksum(),

MyIngress(),

MyEgress(),

MyComputeChecksum(),

MyDeparser()

) main;

(phy_forward-cmd.txt)

table_add phy_forward forward 1 => 2

table_add phy_forward forward 2 => 1

(mac_forward.p4)

/* -*- P4_16 -*- */

#include <core.p4>

#include <v1model.p4>

/*************************************************************************

*********************** H E A D E R S ***********************************

*************************************************************************/

header ethernet_t {

bit<48> dstAddr;

bit<48> srcAddr;

bit<16> etherType;

}

struct metadata {

/* empty */

}

struct headers {

ethernet_t ethernet;

}

/*************************************************************************

*********************** P A R S E R ***********************************

*************************************************************************/

parser MyParser(packet_in packet,

out headers hdr,

inout metadata meta,

inout standard_metadata_t standard_metadata) {

state start {

transition parse_ethernet;

}

state parse_ethernet {

packet.extract(hdr.ethernet);

transition accept;

}

}

/*************************************************************************

************ C H E C K S U M V E R I F I C A T I O N *************

*************************************************************************/

control MyVerifyChecksum(inout headers hdr, inout metadata meta) {

apply { }

}

/*************************************************************************

************** I N G R E S S P R O C E S S I N G *******************

*************************************************************************/

control MyIngress(inout headers hdr,

inout metadata meta,

inout standard_metadata_t standard_metadata) {

action drop() {

mark_to_drop(standard_metadata);

}

action forward(bit<9> port) {

standard_metadata.egress_spec = port;

}

table mac_forward {

key = {

hdr.ethernet.dstAddr: exact;

}

actions = {

forward;

drop;

}

size = 1024;

default_action = drop();

}

apply {

mac_forward.apply();

}

}

/*************************************************************************

**************** E G R E S S P R O C E S S I N G *******************

*************************************************************************/

control MyEgress(inout headers hdr,

inout metadata meta,

inout standard_metadata_t standard_metadata) {

apply { }

}

/*************************************************************************

************* C H E C K S U M C O M P U T A T I O N **************

*************************************************************************/

control MyComputeChecksum(inout headers hdr, inout metadata meta) {

apply {

}

}

/*************************************************************************

*********************** D E P A R S E R *******************************

*************************************************************************/

control MyDeparser(packet_out packet, in headers hdr) {

apply {

packet.emit(hdr.ethernet);

}

}

/*************************************************************************

*********************** S W I T C H *******************************

*************************************************************************/

V1Switch(

MyParser(),

MyVerifyChecksum(),

MyIngress(),

MyEgress(),

MyComputeChecksum(),

MyDeparser()

) main;

(mac_forward-cmd.txt)

table_add mac_forward forward 00:00:0a:00:01:01 => 1

table_add mac_forward forward 00:00:0a:00:01:02 => 2

(p4app.json)

{

"program": "phy_forward.p4",

"switch": "simple_switch",

"compiler": "p4c",

"options": "--target bmv2 --arch v1model --std p4-16",

"switch_cli": "simple_switch_CLI",

"cli": true,

"pcap_dump": false,

"enable_log": false,

"topo_module": {

"file_path": "",

"module_name": "p4utils.mininetlib.apptopo",

"object_name": "AppTopoStrategies"

},

"controller_module": null,

"topodb_module": {

"file_path": "",

"module_name": "p4utils.utils.topology",

"object_name": "Topology"

},

"mininet_module": {

"file_path": "",

"module_name": "p4utils.mininetlib.p4net",

"object_name": "P4Mininet"

},

"topology": {

"links": [["h1", "s1"], ["h2", "s1"]],

"hosts": {

"h1": {

},

"h2": {

}

},

"switches": {

"s1": {

"cli_input": "phy_forward-cmd.txt",

"program": "phy_forward.p4"

}

}

}

}

[Execution]

Before we run “p4run”, we need to compile the mac_forward.p4 first.

Run “p4run”

….. (You need to see -- -- enable-swap at the end)

….

Open another terminal and run “simple_switch_CLI”

From the above figure, we can see that the current program is “phy_forward.p4”.

Now we will change the program to mac_forward.p4. (Run load_new_config_file new.json and swap_configs commands).

From the above figure we can see that the program has changed and h1 cannot ping h2. Because no rules in mac_forward table.

Add the rules to mac_forward table. And h1 can ping h2.

Dr. Chih-Heng Ke (smallko@gmail.com)

Department of Computer Science and Information Engineering,

National Quemoy University, Kinmen, Taiwan.