P4-16 switch: recirculate() example

[Topology]

H1-s1--s2----h2

|_s3_|

|

H3

http://lists.p4.org/pipermail/p4-dev_lists.p4.org/2016-June/002119.html Based on this post, I try to write a recirculate() example.

In this lab, h1 will ping h2 with different tos values. If the packet sent by h1 with TOS value equal to 1 to 10, the switch will decrease the value to 0. So h2 will get the packet with TOS=0. If the packet sent by h1 with other TOS values, the switch will keep the value.

[topology.p4]

{

"hosts": [

"h1",

"h2",

"h3"

],

"switches": {

"s1": { "cli_input" : "s1-commands.txt" },

"s2": { "cli_input" : "s2-commands.txt" },

"s3": { "cli_input" : "s3-commands.txt" }

},

"links": [

["h1", "s1"], ["s1", "s2"], ["s1", "s3"],

["s3", "s2"], ["s2", "h2"], ["s3", "h3"]

]

}

[s1-commands.txt]

table_set_default ipv4_lpm drop

table_add ipv4_lpm ipv4_forward 10.0.1.1/32 => 00:00:00:00:01:01 1

table_add ipv4_lpm ipv4_forward 10.0.2.2/32 => 00:00:00:02:02:00 2

table_add ipv4_lpm ipv4_forward 10.0.3.3/32 => 00:00:00:03:03:00 3

[s2-commands.txt]

table_set_default ipv4_lpm drop

table_add ipv4_lpm ipv4_forward 10.0.1.1/32 => 00:00:00:01:02:00 2

table_add ipv4_lpm ipv4_forward 10.0.2.2/32 => 00:00:00:00:02:02 1

table_add ipv4_lpm ipv4_forward 10.0.3.3/32 => 00:00:00:03:03:00 3

[s3-commands.txt]

table_set_default ipv4_lpm drop

table_add ipv4_lpm ipv4_forward 10.0.1.1/32 => 00:00:00:01:03:00 2

table_add ipv4_lpm ipv4_forward 10.0.2.2/32 => 00:00:00:02:03:00 3

table_add ipv4_lpm ipv4_forward 10.0.3.3/32 => 00:00:00:00:03:03 1

[basic.p4]

/* -*- P4_16 -*- */

#include <core.p4>

#include <v1model.p4>

const bit<16> TYPE_IPV4 = 0x800;

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

*********************** 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;

}

struct metadata {

/* empty */

}

struct headers {

ethernet_t ethernet;

ipv4_t ipv4;

}

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

*********************** 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 select(hdr.ethernet.etherType) {

TYPE_IPV4: parse_ipv4;

default: accept;

}

}

state parse_ipv4 {

packet.extract(hdr.ipv4);

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) {

action set_mytos() {

hdr.ipv4.diffserv=hdr.ipv4.diffserv-1;

recirculate<headers>(hdr);

}

table set_tos {

key = {

hdr.ipv4.diffserv: range;

}

actions = {

set_mytos;

NoAction;

}

size = 1024;

default_action = NoAction();

const entries = {

1..10 : set_mytos();

_ : NoAction();

}

}

apply {

set_tos.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 {

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);

}

}

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

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

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

V1Switch(

MyParser(),

MyVerifyChecksum(),

MyIngress(),

MyEgress(),

MyComputeChecksum(),

MyDeparser()

) main;

[Execution]

If the h1 send the packets with TOS=11, then

If the h1 send the packets with TOS=5, then

If the h1 send the packets with TOS=3, then

Dr. Chih-Heng Ke (smallko@gmail.com)

Department of Computer Science and Information Engineering,

National Quemoy University, Kinmen, Taiwan.