P4 (P4-16) Switch: lookahead and varbit example (count the number of http request (GET) and http response packets)

[Topology]

 

H1 ---- s1 (P4 switch) --- H2

 

H1 will send the packets to H2. S1 will count the number of the number of http request (GET) and http response packets.

 

[basic.p4]

/* -*- P4_16 -*- */

#include <core.p4>

#include <v1model.p4>

 

const bit<16> TYPE_IPV4 = 0x800;

const bit<32> TYPE_HTTP_REQ_GET = 0x47455420; //GET

const bit<32> TYPE_HTTP_RES = 0x48545450; //HTTP

 

register<bit<32>>(10) http_pkts;

 

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

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

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

 

typedef bit<9>  egressSpec_t;

typedef bit<48> macAddr_t;

typedef bit<32> ip4Addr_t;

 

header ethernet_t {

    macAddr_t dstAddr;

    macAddr_t srcAddr;

    bit<16>   etherType;

}

 

header ipv4_t {

    bit<4>    version;

    bit<4>    ihl;

    bit<8>    diffserv;

    bit<16>   totalLen;

    bit<16>   identification;

    bit<3>    flags;

    bit<13>   fragOffset;

    bit<8>    ttl;

    bit<8>    protocol;

    bit<16>   hdrChecksum;

    ip4Addr_t srcAddr;

    ip4Addr_t dstAddr;

}

 

header tcp_t {

    bit<16> srcPort;

    bit<16> dstPort;

    bit<32> seqNo;

    bit<32> ackNo;

    bit<4>  dataOffset;

    bit<3>  res;

    bit<3>  ecn;

    bit<6>  ctrl;

    bit<16> window;

    bit<16> checksum;

    bit<16> urgentPtr;

}

 

header tcp_options_t {

    varbit<320> options;

}

 

struct metadata {

    bit<1> flag_http_req_get;

    bit<1> flag_http_res;

}

 

struct headers {

    ethernet_t   ethernet;

    ipv4_t       ipv4;

    tcp_t           tcp;

    tcp_options_t tcp_options;

}

 

error {

  noAppLayerData,

  TcpDataOffsetTooSmall

}

 

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

*********************** 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 {

        meta.flag_http_req_get=0;

        meta.flag_http_res=0;

        transition parse_ethernet;

    }

 

    state parse_ethernet {

        packet.extract(hdr.ethernet);

        transition select(hdr.ethernet.etherType) {

            TYPE_IPV4: parse_ipv4;

            default: accept;

        }

    }

 

    state parse_ipv4 {

        packet.extract(hdr.ipv4);

        transition select(hdr.ipv4.protocol) {

            6: parse_tcp;

            default: accept;

        }

    }

 

    state parse_tcp {

        packet.extract(hdr.tcp);

        verify(hdr.tcp.dataOffset >=5, error.TcpDataOffsetTooSmall);

            transition select(hdr.tcp.dataOffset){

             5: parse_app;

                 default: parse_tcp_options;

            }      

    }

 

    state parse_tcp_options {

        bit<10> len = ((bit<10>)(hdr.tcp.dataOffset - 5) * 4 * 8);

        packet.extract(hdr.tcp_options, (bit<32>)len);

            transition parse_app;

    }

 

    state parse_app {

        transition select(hdr.tcp.dstPort) {

            80: parse_http;

            default: parse_app2;

        }

    }

 

    state parse_app2 {

        transition select(hdr.tcp.srcPort) {

            80: parse_http;

            default: accept;

        }

    }

  

    state parse_http {

            verify(hdr.ipv4.totalLen > (bit<16>)(hdr.ipv4.ihl+hdr.tcp.dataOffset)*4, error.noAppLayerData);

            transition select(packet.lookahead<bit<32>>()) {

              TYPE_HTTP_RES: parse_http_response;

              TYPE_HTTP_REQ_GET: parse_http_request_get;      

              default: parse_http_request;

            }      

    }

 

    state parse_http_response {

            meta.flag_http_res=1;

        transition accept;

    }

 

    state parse_http_request_get {

        meta.flag_http_req_get=1;

        transition accept;

    }      

 

    state parse_http_request {

        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();

    }

   

    action ipv4_forward(macAddr_t dstAddr, egressSpec_t port) {

        standard_metadata.egress_spec = port;

        hdr.ethernet.srcAddr = hdr.ethernet.dstAddr;

        hdr.ethernet.dstAddr = dstAddr;

        hdr.ipv4.ttl = hdr.ipv4.ttl - 1;

    }

   

    table ipv4_lpm {

        key = {

            hdr.ipv4.dstAddr: lpm;

        }

        actions = {

            ipv4_forward;

            drop;

            NoAction;

        }

        size = 1024;

        default_action = NoAction();

    }

   

    apply {

        if (hdr.ipv4.isValid()) {

            ipv4_lpm.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 {

        bit<32> tmp_http_req_get;

        bit<32> tmp_http_res;

            http_pkts.read( tmp_http_res, (bit<32>)0);

        http_pkts.read( tmp_http_req_get, (bit<32>)1);

        if(meta.flag_http_res==1){

            tmp_http_res=tmp_http_res+1;

            http_pkts.write((bit<32>)0, tmp_http_res);

        } 

        if(meta.flag_http_req_get==1){

            tmp_http_req_get=tmp_http_req_get+1;

            http_pkts.write((bit<32>)1, tmp_http_req_get);

        }       

    }

}

 

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

*************   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 {

        update_checksum(

            hdr.ipv4.isValid(),

            { hdr.ipv4.version,

              hdr.ipv4.ihl,

              hdr.ipv4.diffserv,

              hdr.ipv4.totalLen,

              hdr.ipv4.identification,

              hdr.ipv4.flags,

              hdr.ipv4.fragOffset,

              hdr.ipv4.ttl,

              hdr.ipv4.protocol,

              hdr.ipv4.srcAddr,

              hdr.ipv4.dstAddr },

            hdr.ipv4.hdrChecksum,

            HashAlgorithm.csum16);

    }

}

 

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

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

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

 

control MyDeparser(packet_out packet, in headers hdr) {

    apply {

        packet.emit(hdr.ethernet);

        packet.emit(hdr.ipv4);

        packet.emit(hdr.tcp);

        packet.emit(hdr.tcp_options);

    }

}

 

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

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

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

 

V1Switch(

MyParser(),

MyVerifyChecksum(),

MyIngress(),

MyEgress(),

MyComputeChecksum(),

MyDeparser()

) main;

 

[cmd.txt]

table_add ipv4_lpm ipv4_forward 10.0.0.1/32 => 00:00:00:00:00:01 1

table_add ipv4_lpm ipv4_forward 10.0.0.2/32 => 00:00:00:00:00:02 2

table_add ipv4_lpm ipv4_forward 10.0.0.3/32 => 00:00:00:00:00:03 3

 

[cmd_add.py]

import os

 

os.system('sudo /home/vagrant/behavioral-model/targets/simple_switch/simple_switch_CLI --thrift-port=9090 < cmd.txt')

 

[test_topo.py]

import os

from mininet.net import Mininet

from mininet.topo import Topo

from mininet.log import setLogLevel, info

from mininet.cli import CLI

from mininet.node import RemoteController

 

from p4_mininet import P4Switch, P4Host

 

import argparse

from time import sleep

 

parser = argparse.ArgumentParser(description='Mininet demo')

parser.add_argument('--behavioral-exe', help='Path to behavioral executable',

                    type=str, action="store", required=False, default='simple_switch' )

parser.add_argument('--thrift-port', help='Thrift server port for table updates',

                    type=int, action="store", default=9090)

parser.add_argument('--num-hosts', help='Number of hosts to connect to switch',

                    type=int, action="store", default=2)

parser.add_argument('--mode', choices=['l2', 'l3'], type=str, default='l3')

parser.add_argument('--json', help='Path to JSON config file',

                    type=str, action="store", required=True)

parser.add_argument('--pcap-dump', help='Dump packets on interfaces to pcap files',

                    type=str, action="store", required=False, default=False)

 

 

args = parser.parse_args()

 

 

class SingleSwitchTopo(Topo):

    def __init__(self, sw_path, json_path, thrift_port, pcap_dump, **opts):

        Topo.__init__(self, **opts)

 

        switch1 = self.addSwitch('s1', sw_path = sw_path, json_path = json_path, thrift_port = thrift_port,cls = P4Switch ,pcap_dump = pcap_dump)

               

        host1 = self.addHost('h1', mac = '00:00:00:00:00:01')

        host2 = self.addHost('h2', mac = '00:00:00:00:00:02')

        host3 = self.addHost('h3', mac = '00:00:00:00:00:03')

 

        self.addLink(host1, switch1, port1 = 0, port2 = 1)

        self.addLink(host2, switch1, port1 = 0, port2 = 2)

        self.addLink(host3, switch1, port1 = 0, port2 = 3)

         

       

def main():

    topo = SingleSwitchTopo(args.behavioral_exe, args.json, args.thrift_port, args.pcap_dump)

    #controller1 = RemoteController('controller1', ip = '10.108.148.148')

    net = Mininet(topo = topo, host = P4Host, controller = None)

    net.start()

    h1,h2,h3=net.get('h1','h2','h3')

    h1.cmd("arp -s 10.0.0.2 00:00:00:00:00:02")   

    h1.cmd("arp -s 10.0.0.3 00:00:00:00:00:03")

    h2.cmd("arp -s 10.0.0.1 00:00:00:00:00:01")

    h2.cmd("arp -s 10.0.0.3 00:00:00:00:00:03")

    h3.cmd("arp -s 10.0.0.1 00:00:00:00:00:01")

    h3.cmd("arp -s 10.0.0.2 00:00:00:00:00:02")

 

    sleep(1)

 

    print('\033[0;32m'),

    print "Gotcha!"

    print('\033[0m')

 

    CLI(net)

    try:

        net.stop()

    except:

        print('\033[0;31m'),

        print('Stop error! Trying sudo mn -c')

        print('\033[0m')

        os.system('sudo mn -c')

        print('\033[0;32m'),

        print ('Stop successfully!')

        print('\033[0m')

 

if __name__ == '__main__':

    setLogLevel('info')

    main()

 

[start_test_topo.py]

import os

 

os.system("sudo python test_topo.py --behavioral-exe /home/vagrant/behavioral-model/targets/simple_switch/simple_switch --json basic.json")

 

[p4_mininet.py]

# Copyright 2013-present Barefoot Networks, Inc.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

#   http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

#

 

from mininet.net import Mininet

from mininet.node import Switch, Host

from mininet.log import setLogLevel, info, error, debug

from mininet.moduledeps import pathCheck

from sys import exit

import os

import tempfile

import socket

 

class P4Host(Host):

    def config(self, **params):

        r = super(Host, self).config(**params)

 

        self.defaultIntf().rename("eth0")

 

        for off in ["rx", "tx", "sg"]:

            cmd = "/sbin/ethtool --offload eth0 %s off" % off

            self.cmd(cmd)

 

        # disable IPv6

        self.cmd("sysctl -w net.ipv6.conf.all.disable_ipv6=1")

        self.cmd("sysctl -w net.ipv6.conf.default.disable_ipv6=1")

        self.cmd("sysctl -w net.ipv6.conf.lo.disable_ipv6=1")

 

        return r

 

    def describe(self):

        print "**********"

        print self.name

        print "default interface: %s\t%s\t%s" %(

            self.defaultIntf().name,

            self.defaultIntf().IP(),

            self.defaultIntf().MAC()

        )

        print "**********"

 

class P4Switch(Switch):

    """P4 virtual switch"""

    device_id = 0

 

    def __init__(self, name, sw_path = None, json_path = None,

                 thrift_port = None,

                 pcap_dump = False,

                 log_console = True,

                 verbose = False,

                 device_id = None,

                 enable_debugger = False,

                 **kwargs):

        Switch.__init__(self, name, **kwargs)

        assert(sw_path)

        assert(json_path)

        # make sure that the provided sw_path is valid

        pathCheck(sw_path)

        # make sure that the provided JSON file exists

        if not os.path.isfile(json_path):

            error("Invalid JSON file.\n")

            exit(1)

        self.sw_path = sw_path

        self.json_path = json_path

        self.verbose = verbose

        logfile = "/tmp/p4s.{}.log".format(self.name)

        self.output = open(logfile, 'w')

        self.thrift_port = thrift_port

        self.pcap_dump = pcap_dump

        self.enable_debugger = enable_debugger

        self.log_console = log_console

        if device_id is not None:

            self.device_id = device_id

            P4Switch.device_id = max(P4Switch.device_id, device_id)

        else:

            self.device_id = P4Switch.device_id

            P4Switch.device_id += 1

        self.nanomsg = "ipc:///tmp/bm-{}-log.ipc".format(self.device_id)

 

    @classmethod

    def setup(cls):

        pass

 

    def check_switch_started(self, pid):

        """While the process is running (pid exists), we check if the Thrift

        server has been started. If the Thrift server is ready, we assume that

        the switch was started successfully. This is only reliable if the Thrift

        server is started at the end of the init process"""

        while True:

            if not os.path.exists(os.path.join("/proc", str(pid))):

                return False

            sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

            sock.settimeout(0.5)

            result = sock.connect_ex(("localhost", self.thrift_port))

            if result == 0:

                return  True

 

    def start(self, controllers):

        "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])

 

        #wuwzhs edit in 2017/11/10

        #args.extend(['-i 3@veth1'])

 

        if self.pcap_dump:

            args.append("--pcap")

            # args.append("--useFiles")

        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)])

        P4Switch.device_id += 1

        args.append(self.json_path)

        if self.enable_debugger:

            args.append("--debugger")

        if self.log_console:

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

        logfile = "/tmp/p4s.{}.log".format(self.name)

        info(' '.join(args) + "\n")

 

        pid = None

        with tempfile.NamedTemporaryFile() as f:

            # self.cmd(' '.join(args) + ' > /dev/null 2>&1 &')

            self.cmd(' '.join(args) + ' >' + logfile + ' 2>&1 & echo $! >> ' + f.name)

            pid = int(f.read())

        debug("P4 switch {} PID is {}.\n".format(self.name, pid))

        if not self.check_switch_started(pid):

            error("P4 switch {} did not start correctly.\n".format(self.name))

            exit(1)

        info("P4 switch {} has been started.\n".format(self.name))

 

    def stop(self):

        "Terminate P4 switch."

        self.output.flush()

        self.cmd('kill %' + self.sw_path)

        self.cmd('wait')

        self.deleteIntfs()

 

    def attach(self, intf):

        "Connect a data port"

        assert(0)

 

    def detach(self, intf):

        "Disconnect a data port"

        assert(0)

 

[Execution]

 

xterm h1 h1 h2 to open two terminals for h1. One of h1 terminals is to use wireshark for capturing packets. Open another terminal to setup rules for s1.

 

In h2, use “python –m SimpleHTTPServer 80” to start a http server. In h1, use “curl http://10.0.0.2” to get a webpage from h1.

We can also see the captured packets in wireshark window.

Open another terminal. Use “simple_switch_CLI” to connect to s1. We can get the register values. The first 1 indicated that there is one http response packet.

The second 1 indicated that there is one http request (GET) packet.

 

Dr. Chih-Heng Ke (smallko@gmail.com)

Department of Computer Science and Information Engineering,

National Quemoy University, Kinmen, Taiwan.