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This problem contains the tutorial exercises and solutions presented at SIGCOMM '17.
This commit is contained in:
Nate Foster
2017-10-03 16:30:47 -04:00
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# Implementing MRI
## Introduction
The objective of this tutorial is to extend basic L3 forwarding with a
scaled-down version of In-Band Network Telemetry (INT), which we call
Multi-Hop Route Inspection (MRI).
MRI allows users to track the path and the length of queues that every
packet travels through. To support this functionality, you will need
to write a P4 program that appends an ID and queue length to the
header stack of every packet. At the destination, the sequence of
switch IDs correspond to the path, and each ID is followed by the
queue length of the port at switch.
As before, we have already defined the control plane rules, so you
only need to implement the data plane logic of your P4 program.
> **Spoiler alert:** There is a reference solution in the `solution`
> sub-directory. Feel free to compare your implementation to the reference.
## Step 1: Run the (incomplete) starter code
The directory with this README also contains a skeleton P4 program,
`mri.p4`, which initially implements L3 forwarding. Your job (in the
next step) will be to extend it to properly prepend the MRI custom
headers.
Before that, let's compile the incomplete `mri.p4` and bring up a
switch in Mininet to test its behavior.
1. In your shell, run:
```bash
./run.sh
```
This will:
* compile `mri.p4`, and
* start a Mininet instance with three switches (`s1`, `s2`, `s3`) configured
in a triangle. There are 5 hosts. `h1` and `h11` are connected to `s1`.
`h2` and `h22` are connected to `s2` and `h3` is connected to `s3`.
* The hosts are assigned IPs of `10.0.1.10`, `10.0.2.10`, etc
(`10.0.<Switchid>.<hostID>`).
* The control plane programs the P4 tables in each switch based on
`sx-commands.txt`
2. We want to send a low rate traffic from `h1` to `h2` and a high
rate iperf traffic from `h11` to `h22`. The link between `s1` and
`s2` is common between the flows and is a bottleneck because we
reduced its bandwidth to 512kbps in p4app.json. Therefore, if we
capture packets at `h2`, we should see high queue size for that
link.
3. You should now see a Mininet command prompt. Open four terminals
for `h1`, `h11`, `h2`, `h22`, respectively:
```bash
mininet> xterm h1 h11 h2 h22
```
3. In `h2`'s xterm, start the server that captures packets:
```bash
./receive.py
```
4. in `h22`'s xterm, start the iperf UDP server:
```bash
iperf -s -u
```
5. In `h1`'s xterm, send one packet per second to `h2` using send.py
say for 30 seconds:
```bash
./send.py 10.0.2.2 "P4 is cool" 30
```
The message "P4 is cool" should be received in `h2`'s xterm,
6. In `h11`'s xterm, start iperf client sending for 15 seconds
```bash
h11 iperf -c 10.0.2.22 -t 15 -u
```
7. At `h2`, the MRI header has no hop info (`count=0`)
8. type `exit` to close each xterm window
You should see the message received at host `h2`, but without any
information about the path the message took. Your job is to extend
the code in `mri.p4` to implement the MRI logic to record the path.
### A note about the control plane
P4 programs define a packet-processing pipeline, but the rules
governing packet processing are inserted into the pipeline by the
control plane. When a rule matches a packet, its action is invoked
with parameters supplied by the control plane as part of the rule.
In this exercise, the control plane logic has already been
implemented. As part of bringing up the Mininet instance, the
`run.sh` script will install packet-processing rules in the tables of
each switch. These are defined in the `sX-commands.txt` files, where
`X` corresponds to the switch number.
## Step 2: Implement MRI
The `mri.p4` file contains a skeleton P4 program with key pieces of
logic replaced by `TODO` comments. These should guide your
implementation---replace each `TODO` with logic implementing the
missing piece.
MRI will require two custom headers. The first header, `mri_t`,
contains a single field `count`, which indicates the number of switch
IDs that follow. The second header, `switch_t`, contains switch ID and
Queue depth fields of each switch hop the packet goes through.
One of the biggest challenges in implementing MRI is handling the
recursive logic for parsing these two headers. We will use a
`parser_metadata` field, `remaining`, to keep track of how many
`switch_t` headers we need to parse. In the `parse_mri` state, this
field should be set to `hdr.mri.count`. In the `parse_swtrace` state,
this field should be decremented. The `parse_swtrace` state will
transition to itself until `remaining` is 0.
The MRI custom headers will be carried inside an IP Options
header. The IP Options header contains a field, `option`, which
indicates the type of the option. We will use a special type 31 to
indicate the presence of the MRI headers.
Beyond the parser logic, you will add a table in egress, `swtrace` to
store the switch ID and queue depth, and actions that increment the
`count` field, and append a `switch_t` header.
A complete `mri.p4` will contain the following components:
1. Header type definitions for Ethernet (`ethernet_t`), IPv4 (`ipv4_t`),
IP Options (`ipv4_option_t`), MRI (`mri_t`), and Switch (`switch_t`).
2. Parsers for Ethernet, IPv4, IP Options, MRI, and Switch that will
populate `ethernet_t`, `ipv4_t`, `ipv4_option_t`, `mri_t`, and
`switch_t`.
3. An action to drop a packet, using `mark_to_drop()`.
4. An action (called `ipv4_forward`), which will:
1. Set the egress port for the next hop.
2. Update the ethernet destination address with the address of
the next hop.
3. Update the ethernet source address with the address of the switch.
4. Decrement the TTL.
5. An ingress control that:
1. Defines a table that will read an IPv4 destination address, and
invoke either `drop` or `ipv4_forward`.
2. An `apply` block that applies the table.
6. At egress, an action (called `add_swtrace`) that will add the
switch ID and queue depth.
8. An egress control that applies a table (`swtrace`) to store the
switch ID and queue depth, and calls `add_swtrace`.
9. A deparser that selects the order in which fields inserted into the outgoing
packet.
10. A `package` instantiation supplied with the parser, control,
checksum verification and recomputation and deparser.
## Step 3: Run your solution
Follow the instructions from Step 1. This time, when your message
from `h1` is delivered to `h2`, you should see the seqeunce of
switches through which the packet traveled plus the corresponding
queue depths. The expected output will look like the following,
which shows the MRI header, with a `count` of 2, and switch ids
(`swids`) 2 and 1. The queue depth at the common link (from s1 to
s2) is high.
```
got a packet
###[ Ethernet ]###
dst = 00:04:00:02:00:02
src = f2:ed:e6:df:4e:fa
type = 0x800
###[ IP ]###
version = 4L
ihl = 10L
tos = 0x0
len = 42
id = 1
flags =
frag = 0L
ttl = 62
proto = udp
chksum = 0x60c0
src = 10.0.1.1
dst = 10.0.2.2
\options \
|###[ MRI ]###
| copy_flag = 0L
| optclass = control
| option = 31L
| length = 20
| count = 2
| \swtraces \
| |###[ SwitchTrace ]###
| | swid = 2
| | qdepth = 0
| |###[ SwitchTrace ]###
| | swid = 1
| | qdepth = 17
###[ Raw ]###
load = '\x04\xd2'
###[ Padding ]###
load = '\x10\xe1\x00\x12\x1c{P4 is cool'
```
### Troubleshooting
There are several ways that problems might manifest:
1. `mri.p4` fails to compile. In this case, `run.sh` will report the
error emitted from the compiler and stop.
2. `mri.p4` compiles but does not support the control plane rules in
the `sX-commands.txt` files that `run.sh` tries to install using the BMv2 CLI.
In this case, `run.sh` will report these errors to `stderr`. Use these error
messages to fix your `mri.p4` implementation.
3. `mri.p4` compiles, and the control plane rules are installed, but
the switch does not process packets in the desired way. The
`build/logs/<switch-name>.log` files contain trace messages describing
how each switch processes each packet. The output is detailed and can
help pinpoint logic errors in your implementation. The
`build/<switch-name>-<interface-name>.pcap` also contains the pcap of
packets on each interface. Use `tcpdump -r <filename> -xxx` to print
the hexdump of the packets.
4. `mri.p4` compiles and all rules are installed. Packets go through
and the logs show that the queue length is always 0. Then either
reduce the link bandwidth in `p4app.json`.
#### Cleaning up Mininet
In the latter two cases above, `run.sh` may leave a Mininet instance
running in the background. Use the following command to clean up
these instances:
```bash
mn -c
```
## Next Steps
Congratulations, your implementation works! Move on to [Source
Routing](../source_routing).

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/* -*- P4_16 -*- */
#include <core.p4>
#include <v1model.p4>
const bit<8> UDP_PROTOCOL = 0x11;
const bit<16> TYPE_IPV4 = 0x800;
const bit<5> IPV4_OPTION_MRI = 31;
#define MAX_HOPS 9
/*************************************************************************
*********************** H E A D E R S ***********************************
*************************************************************************/
typedef bit<9> egressSpec_t;
typedef bit<48> macAddr_t;
typedef bit<32> ip4Addr_t;
typedef bit<32> switchID_t;
typedef bit<32> qdepth_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 ipv4_option_t {
bit<1> copyFlag;
bit<2> optClass;
bit<5> option;
bit<8> optionLength;
}
header mri_t {
bit<16> count;
}
header switch_t {
switchID_t swid;
qdepth_t qdepth;
}
struct ingress_metadata_t {
bit<16> count;
}
struct parser_metadata_t {
bit<16> remaining;
}
struct metadata {
ingress_metadata_t ingress_metadata;
parser_metadata_t parser_metadata;
}
struct headers {
ethernet_t ethernet;
ipv4_t ipv4;
ipv4_option_t ipv4_option;
mri_t mri;
switch_t[MAX_HOPS] swtraces;
}
error { IPHeaderTooShort }
/*************************************************************************
*********************** 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);
verify(hdr.ipv4.ihl >= 5, error.IPHeaderTooShort);
transition select(hdr.ipv4.ihl) {
5 : accept;
default : parse_ipv4_option;
}
}
state parse_ipv4_option {
/*
* TODO: Add logic to:
* - Extract the ipv4_option header.
* - If value is equal to IPV4_OPTION_MRI, transition to parse_mri.
* - Otherwise, accept.
*/
transition accept;
}
state parse_mri {
/*
* TODO: Add logic to:
* - Extract hdr.mri.
* - Set meta.parser_metadata.remaining to hdr.mri.count
* - Select on the value of meta.parser_metadata.remaining
* - If the value is equal to 0, accept.
* - Otherwise, transition to parse_swid.
*/
transition accept;
}
state parse_swtrace {
/*
* TODO: Add logic to:
* - Extract hdr.swtraces.next.
* - Decrement meta.parser_metadata.remaining by 1
* - Select on the value of meta.parser_metadata.remaining
* - If the value is equal to 0, accept.
* - Otherwise, transition to parse_swtrace.
*/
transition accept;
}
}
/*************************************************************************
************ C H E C K S U M V E R I F I C A T I O N *************
*************************************************************************/
control MyVerifyChecksum(in 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 add_swtrace(switchID_t swid) {
/*
* TODO: add logic to:
- Increment hdr.mri.count by 1
- Add a new swtrace header by calling push_front(1) on hdr.swtraces.
- Set hdr.swtraces[0].swid to the id paremeter
- Set hdr.swtraces[0].qdepth to (qdepth_t)standard_metadata.deq_qdepth
- Incremement hdr.ipv4.ihl by 2
- Incrememtn hdr.ipv4_option.optionLength by 8
*/
}
table swtrace {
actions = {
/* TODO: add the correct action */
NoAction;
}
default_action = NoAction();
}
apply {
/*
* TODO: add logic to:
* - If hdr.mri is valid:
* - Apply table swtrace
*/
swtrace.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);
/* TODO: emit ipv4_option, mri and swtraces headers */
}
}
/*************************************************************************
*********************** S W I T C H *******************************
*************************************************************************/
V1Switch(
MyParser(),
MyVerifyChecksum(),
MyIngress(),
MyEgress(),
MyComputeChecksum(),
MyDeparser()
) main;

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{
"program": "mri.p4",
"language": "p4-16",
"targets": {
"multiswitch": {
"auto-control-plane": true,
"cli": true,
"pcap_dump": true,
"bmv2_log": true,
"links": [["h1", "s1"], ["h11", "s1"], ["s1", "s2", "0", 0.5], ["s1", "s3"], ["s3", "s2"], ["s2", "h2"], ["s2", "h22"], ["s3", "h3"]],
"hosts": {
"h1": {
},
"h2": {
},
"h3": {
},
"h11": {
},
"h22": {
}
},
"switches": {
"s1": {
"entries": "s1-commands.txt"
},
"s2": {
"entries": "s2-commands.txt"
},
"s3": {
"entries": "s3-commands.txt"
}
}
}
}
}

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#!/usr/bin/env python
import sys
import struct
from scapy.all import sniff, sendp, hexdump, get_if_list, get_if_hwaddr
from scapy.all import Packet, IPOption
from scapy.all import PacketListField, ShortField, IntField, LongField, BitField, FieldListField, FieldLenField
from scapy.all import IP, UDP, Raw
from scapy.layers.inet import _IPOption_HDR
def get_if():
ifs=get_if_list()
iface=None
for i in get_if_list():
if "eth0" in i:
iface=i
break;
if not iface:
print "Cannot find eth0 interface"
exit(1)
return iface
class SwitchTrace(Packet):
fields_desc = [ IntField("swid", 0),
IntField("qdepth", 0)]
def extract_padding(self, p):
return "", p
class IPOption_MRI(IPOption):
name = "MRI"
option = 31
fields_desc = [ _IPOption_HDR,
FieldLenField("length", None, fmt="B",
length_of="swtraces",
adjust=lambda pkt,l:l*2+4),
ShortField("count", 0),
PacketListField("swtraces",
[],
SwitchTrace,
count_from=lambda pkt:(pkt.count*1)) ]
def handle_pkt(pkt):
print "got a packet"
pkt.show2()
# hexdump(pkt)
sys.stdout.flush()
def main():
iface = 'h2-eth0'
print "sniffing on %s" % iface
sys.stdout.flush()
sniff(filter="udp and port 4321", iface = iface,
prn = lambda x: handle_pkt(x))
if __name__ == '__main__':
main()

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SIGCOMM_2017/exercises/mri/run.sh Executable file
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P4APPRUNNER=../../utils/p4apprunner.py
mkdir -p build
tar -czf build/p4app.tgz * --exclude='build'
#cd build
sudo python $P4APPRUNNER p4app.tgz --build-dir ./build

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SIGCOMM_2017/exercises/mri/s1-commands.txt Normal file
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table_set_default ipv4_lpm drop
table_set_default swtrace add_swtrace 1
table_add ipv4_lpm ipv4_forward 10.0.1.1/32 => 00:00:00:00:01:01 1
table_add ipv4_lpm ipv4_forward 10.0.1.11/32 => 00:00:00:00:01:0b 2
table_add ipv4_lpm ipv4_forward 10.0.2.0/24 => 00:00:00:02:03:00 3
table_add ipv4_lpm ipv4_forward 10.0.3.0/24 => 00:00:00:03:02:00 4

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SIGCOMM_2017/exercises/mri/s2-commands.txt Normal file
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table_set_default ipv4_lpm drop
table_set_default swtrace add_swtrace 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 10.0.2.22/32 => 00:00:00:00:02:16 2
table_add ipv4_lpm ipv4_forward 10.0.1.0/24 => 00:00:00:01:03:00 3
table_add ipv4_lpm ipv4_forward 10.0.3.0/24 => 00:00:00:03:03:00 4

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SIGCOMM_2017/exercises/mri/s3-commands.txt Normal file
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table_set_default ipv4_lpm drop
table_set_default swtrace add_swtrace 3
table_add ipv4_lpm ipv4_forward 10.0.3.3/32 => 00:00:00:00:03:01 1
table_add ipv4_lpm ipv4_forward 10.0.1.0/24 => 00:00:00:01:04:00 2
table_add ipv4_lpm ipv4_forward 10.0.2.0/24 => 00:00:00:02:04:00 3

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SIGCOMM_2017/exercises/mri/send.py Executable file
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#!/usr/bin/env python
import argparse
import sys
import socket
import random
import struct
from scapy.all import sendp, send, hexdump, get_if_list, get_if_hwaddr
from scapy.all import Packet, IPOption
from scapy.all import Ether, IP, UDP
from scapy.all import IntField, FieldListField, FieldLenField, ShortField, PacketListField
from scapy.layers.inet import _IPOption_HDR
from time import sleep
def get_if():
ifs=get_if_list()
iface=None # "h1-eth0"
for i in get_if_list():
if "eth0" in i:
iface=i
break;
if not iface:
print "Cannot find eth0 interface"
exit(1)
return iface
class SwitchTrace(Packet):
fields_desc = [ IntField("swid", 0),
IntField("qdepth", 0)]
def extract_padding(self, p):
return "", p
class IPOption_MRI(IPOption):
name = "MRI"
option = 31
fields_desc = [ _IPOption_HDR,
FieldLenField("length", None, fmt="B",
length_of="swtraces",
adjust=lambda pkt,l:l*2+4),
ShortField("count", 0),
PacketListField("swtraces",
[],
SwitchTrace,
count_from=lambda pkt:(pkt.count*1)) ]
def main():
if len(sys.argv)<3:
print 'pass 2 arguments: <destination> "<message>"'
exit(1)
addr = socket.gethostbyname(sys.argv[1])
iface = get_if()
pkt = Ether(src=get_if_hwaddr(iface), dst="ff:ff:ff:ff:ff:ff") / IP(
dst=addr, options = IPOption_MRI(count=0,
swtraces=[])) / UDP(
dport=4321, sport=1234) / sys.argv[2]
# pkt = Ether(src=get_if_hwaddr(iface), dst="ff:ff:ff:ff:ff:ff") / IP(
# dst=addr, options = IPOption_MRI(count=2,
# swtraces=[SwitchTrace(swid=0,qdepth=0), SwitchTrace(swid=1,qdepth=0)])) / UDP(
# dport=4321, sport=1234) / sys.argv[2]
pkt.show2()
#hexdump(pkt)
try:
for i in range(int(sys.argv[3])):
sendp(pkt, iface=iface)
sleep(1)
except KeyboardInterrupt:
raise
if __name__ == '__main__':
main()

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/* -*- P4_16 -*- */
#include <core.p4>
#include <v1model.p4>
const bit<8> UDP_PROTOCOL = 0x11;
const bit<16> TYPE_IPV4 = 0x800;
const bit<5> IPV4_OPTION_MRI = 31;
#define MAX_HOPS 9
/*************************************************************************
*********************** H E A D E R S ***********************************
*************************************************************************/
typedef bit<9> egressSpec_t;
typedef bit<48> macAddr_t;
typedef bit<32> ip4Addr_t;
typedef bit<32> switchID_t;
typedef bit<32> qdepth_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 ipv4_option_t {
bit<1> copyFlag;
bit<2> optClass;
bit<5> option;
bit<8> optionLength;
}
header mri_t {
bit<16> count;
}
header switch_t {
switchID_t swid;
qdepth_t qdepth;
}
struct ingress_metadata_t {
bit<16> count;
}
struct parser_metadata_t {
bit<16> remaining;
}
struct metadata {
ingress_metadata_t ingress_metadata;
parser_metadata_t parser_metadata;
}
struct headers {
ethernet_t ethernet;
ipv4_t ipv4;
ipv4_option_t ipv4_option;
mri_t mri;
switch_t[MAX_HOPS] swtraces;
}
error { IPHeaderTooShort }
/*************************************************************************
*********************** 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);
verify(hdr.ipv4.ihl >= 5, error.IPHeaderTooShort);
transition select(hdr.ipv4.ihl) {
5 : accept;
default : parse_ipv4_option;
}
}
state parse_ipv4_option {
packet.extract(hdr.ipv4_option);
transition select(hdr.ipv4_option.option) {
IPV4_OPTION_MRI: parse_mri;
default: accept;
}
}
state parse_mri {
packet.extract(hdr.mri);
meta.parser_metadata.remaining = hdr.mri.count;
transition select(meta.parser_metadata.remaining) {
0 : accept;
default: parse_swtrace;
}
}
state parse_swtrace {
packet.extract(hdr.swtraces.next);
meta.parser_metadata.remaining = meta.parser_metadata.remaining - 1;
transition select(meta.parser_metadata.remaining) {
0 : accept;
default: parse_swtrace;
}
}
}
/*************************************************************************
************ C H E C K S U M V E R I F I C A T I O N *************
*************************************************************************/
control MyVerifyChecksum(in 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 add_swtrace(switchID_t swid) {
hdr.mri.count = hdr.mri.count + 1;
hdr.swtraces.push_front(1);
hdr.swtraces[0].swid = swid;
hdr.swtraces[0].qdepth = (qdepth_t)standard_metadata.deq_qdepth;
hdr.ipv4.ihl = hdr.ipv4.ihl + 2;
hdr.ipv4_option.optionLength = hdr.ipv4_option.optionLength + 8;
}
table swtrace {
actions = {
add_swtrace;
NoAction;
}
default_action = NoAction();
}
apply {
if (hdr.mri.isValid()) {
swtrace.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);
packet.emit(hdr.ipv4_option);
packet.emit(hdr.mri);
packet.emit(hdr.swtraces);
}
}
/*************************************************************************
*********************** S W I T C H *******************************
*************************************************************************/
V1Switch(
MyParser(),
MyVerifyChecksum(),
MyIngress(),
MyEgress(),
MyComputeChecksum(),
MyDeparser()
) main;