fyb/p4tutorials-turkce
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Basic Encapsulation Example (#64)

Browse Source 
* Adding initial implementation of basic_encap example

* Updated basic_encap example to count the number of valid packets

* Updated basic_encap example to put encapsulation layer after Ethernet
header.

* Added solution file for basic_encap example

* Changed the name of the basic_encap example to basic_tunnel and called
the new header myTunnel. Also changed the myTunnel field names slightly.
This commit is contained in:
sibanez12 2017-10-25 16:22:23 -07:00 committed by Robert Soule
parent 597b5b401c
commit 7738341012
11 changed files with 757 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

163
P4D2_2017_Fall/exercises/basic_tunnel/README.md Normal file
View File

@ -0,0 +1,163 @@
# Implementing Basic Forwarding
## Introduction
The objective of this exercise is to write a P4 program that
implements basic forwarding. To keep things simple, we will just
implement forwarding for IPv4.
With IPv4 forwarding, the switch must perform the following actions
for every packet: (i) update the source and destination MAC addresses,
(ii) decrement the time-to-live (TTL) in the IP header, and (iii)
forward the packet out the appropriate port.
Your switch will have a single table, which the control plane will
populate with static rules. Each rule will map an IP address to the
MAC address and output port for the next hop. 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,
`basic.p4`, which initially drops all packets. Your job will be to
extend this skeleton program to properly forward IPv4 packets.
Before that, let's compile the incomplete `basic.p4` and bring
up a switch in Mininet to test its behavior.
1. In your shell, run:
```bash
./run.sh
```
This will:
* compile `basic.p4`, and
* start a Mininet instance with three switches (`s1`, `s2`, `s3`)
configured in a triangle, each connected to one host (`h1`, `h2`,
and `h3`).
* The hosts are assigned IPs of `10.0.1.1`, `10.0.2.2`, etc.
2. You should now see a Mininet command prompt. Open two terminals
for `h1` and `h2`, respectively:
```bash
mininet> xterm h1 h2
```
3. Each host includes a small Python-based messaging client and
server. In `h2`'s xterm, start the server:
```bash
./receive.py
```
4. In `h1`'s xterm, send a message to `h2`:
```bash
./send.py 10.0.2.2 "P4 is cool"
```
The message will not be received.
5. Type `exit` to leave each xterm and the Mininet command line.
The message was not received because each switch is programmed
according to `basic.p4`, which drops all packets on arrival.
Your job is to extend this file so it forwards packets.
### A note about the control plane
A P4 program defines a packet-processing pipeline, but the rules
within each table are inserted 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, we have already implemented the the control plane
logic for you. 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.
**Important:** A P4 program also defines the interface between the
switch pipeline and control plane. The commands in the files
`sX-commands.txt` refer to specific tables, keys, and actions by name,
and any changes in the P4 program that add or rename tables, keys, or
actions will need to be reflected in these command files.
## Step 2: Implement L3 forwarding
The `basic.p4` file contains a skeleton P4 program with key pieces of
logic replaced by `TODO` comments. Your implementation should follow
the structure given in this file---replace each `TODO` with logic
implementing the missing piece.
A complete `basic.p4` will contain the following components:
1. Header type definitions for Ethernet (`ethernet_t`) and IPv4 (`ipv4_t`).
2. **TODO:** Parsers for Ethernet and IPv4 that populate `ethernet_t` and `ipv4_t` fields.
3. An action to drop a packet, using `mark_to_drop()`.
4. **TODO:** An action (called `ipv4_forward`) that:
1. Sets the egress port for the next hop.
2. Updates the ethernet destination address with the address of the next hop.
3. Updates the ethernet source address with the address of the switch.
4. Decrements the TTL.
5. **TODO:** A 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. **TODO:** A deparser that selects the order
in which fields inserted into the outgoing packet.
7. A `package` instantiation supplied with the parser, control, and deparser.
> In general, a package also requires instances of checksum verification
> and recomputation controls. These are not necessary for this tutorial
> and are replaced with instantiations of empty controls.
## Step 3: Run your solution
Follow the instructions from Step 1. This time, your message from
`h1` should be delivered to `h2`.
### Food for thought
The "test suite" for your solution---sending a message from `h1` to
`h2`---is not very robust. What else should you test to be confident
of your implementation?
> Although the Python `scapy` library is outside the scope of this tutorial,
> it can be used to generate packets for testing. The `send.py` file shows how
> to use it.
Other questions to consider:
- How would you enhance your program to support next hops?
- Is this program enough to replace a router? What's missing?
### Troubleshooting
There are several problems that might manifest as you develop your program:
1. `basic.p4` might fails to compile. In this case, `run.sh` will
report the error emitted from the compiler and halt.
2. `basic.p4` might compile but fail to support the control plane
rules in the `s1-commands.txt` through `s3-command.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 `basic.p4` implementation.
3. `basic.p4` might compile, and the control plane rules might be
installed, but the switch might not process packets in the desired
way. The `build/logs/<switch-name>.log` files contain detailed logs
that describing how each switch processes each packet. The output is
detailed and can help pinpoint logic errors in your implementation.
#### 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 the next
exercise: implementing the [scrambler](../scrambler)!

211
P4D2_2017_Fall/exercises/basic_tunnel/basic_tunnel.p4 Normal file
View File

@ -0,0 +1,211 @@
/* -*- P4_16 -*- */
#include <core.p4>
#include <v1model.p4>
const bit<16> TYPE_MYTUNNEL = 0x1212;
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 myTunnel_t {
bit<16> proto_id;
bit<16> dst_id;
}
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;
myTunnel_t myTunnel;
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_MYTUNNEL: parse_myTunnel;
TYPE_IPV4: parse_ipv4;
default: accept;
}
}
state parse_myTunnel {
packet.extract(hdr.myTunnel);
transition select(hdr.myTunnel.proto_id) {
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(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();
}
action myTunnel_forward(egressSpec_t port) {
standard_metadata.egress_spec = port;
}
table myTunnel_exact {
key = {
hdr.myTunnel.dst_id: exact;
}
actions = {
myTunnel_forward;
drop;
}
size = 1024;
default_action = drop();
}
apply {
if (hdr.myTunnel.isValid()) {
myTunnel_exact.apply();
} else 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 { }
}
/*************************************************************************
************* 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.myTunnel);
packet.emit(hdr.ipv4);
}
}
/*************************************************************************
*********************** S W I T C H *******************************
*************************************************************************/
V1Switch(
MyParser(),
MyVerifyChecksum(),
MyIngress(),
MyEgress(),
MyComputeChecksum(),
MyDeparser()
) main;

20
P4D2_2017_Fall/exercises/basic_tunnel/myTunnel_header.py Normal file
View File

@ -0,0 +1,20 @@
from scapy.all import *
import sys, os
TYPE_MYTUNNEL = 0x1212
TYPE_IPV4 = 0x0800
class MyTunnel(Packet):
name = "MyTunnel"
fields_desc = [
ShortField("pid", 0),
ShortField("dst_id", 0)
]
def mysummary(self):
return self.sprintf("pid=%pid%, dst_id=%dst_id%")
bind_layers(Ether, MyTunnel, type=TYPE_MYTUNNEL)
bind_layers(MyTunnel, IP, pid=TYPE_IPV4)

32
P4D2_2017_Fall/exercises/basic_tunnel/p4app.json Normal file
View File

@ -0,0 +1,32 @@
{
"program": "basic_tunnel.p4",
"language": "p4-16",
"targets": {
"multiswitch": {
"auto-control-plane": true,
"cli": true,
"pcap_dump": true,
"bmv2_log": true,
"links": [["h1", "s1"], ["s1", "s2"], ["s1", "s3"], ["s3", "s2"], ["s2", "h2"], ["s3", "h3"]],
"hosts": {
"h1": {
},
"h2": {
},
"h3": {
}
},
"switches": {
"s1": {
"entries": "s1-commands.txt"
},
"s2": {
"entries": "s2-commands.txt"
},
"s3": {
"entries": "s3-commands.txt"
}
}
}
}
}

43
P4D2_2017_Fall/exercises/basic_tunnel/receive.py Executable file
View File

@ -0,0 +1,43 @@
#!/usr/bin/env python
import sys
import struct
import os
from scapy.all import sniff, sendp, hexdump, get_if_list, get_if_hwaddr
from scapy.all import Packet, IPOption
from scapy.all import ShortField, IntField, LongField, BitField, FieldListField, FieldLenField
from scapy.all import IP, UDP, Raw
from scapy.layers.inet import _IPOption_HDR
from myTunnel_header import MyTunnel
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
def handle_pkt(pkt):
if MyTunnel in pkt:
print "got a packet"
pkt.show2()
# hexdump(pkt)
# print "len(pkt) = ", len(pkt)
sys.stdout.flush()
def main():
ifaces = filter(lambda i: 'eth' in i, os.listdir('/sys/class/net/'))
iface = ifaces[0]
print "sniffing on %s" % iface
sys.stdout.flush()
sniff(iface = iface,
prn = lambda x: handle_pkt(x))
if __name__ == '__main__':
main()

5
P4D2_2017_Fall/exercises/basic_tunnel/run.sh Executable file
View File

@ -0,0 +1,5 @@
P4APPRUNNER=../../utils/p4apprunner.py
mkdir -p build
tar -czf build/p4app.tgz * --exclude='build'
#cd build
sudo python $P4APPRUNNER p4app.tgz --build-dir ./build

9
P4D2_2017_Fall/exercises/basic_tunnel/s1-commands.txt Normal file
View File

@ -0,0 +1,9 @@
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
table_set_default myTunnel_exact drop
table_add myTunnel_exact myTunnel_forward 1 => 1
table_add myTunnel_exact myTunnel_forward 2 => 2
table_add myTunnel_exact myTunnel_forward 3 => 3

9
P4D2_2017_Fall/exercises/basic_tunnel/s2-commands.txt Normal file
View File

@ -0,0 +1,9 @@
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
table_set_default myTunnel_exact drop
table_add myTunnel_exact myTunnel_forward 1 => 2
table_add myTunnel_exact myTunnel_forward 2 => 1
table_add myTunnel_exact myTunnel_forward 3 => 3

9
P4D2_2017_Fall/exercises/basic_tunnel/s3-commands.txt Normal file
View File

@ -0,0 +1,9 @@
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
table_set_default myTunnel_exact drop
table_add myTunnel_exact myTunnel_forward 1 => 2
table_add myTunnel_exact myTunnel_forward 2 => 3
table_add myTunnel_exact myTunnel_forward 3 => 1

45
P4D2_2017_Fall/exercises/basic_tunnel/send.py Executable file
View File

@ -0,0 +1,45 @@
#!/usr/bin/env python
import argparse
import sys
import socket
import random
import struct
from scapy.all import sendp, send, get_if_list, get_if_hwaddr, hexdump
from scapy.all import Packet
from scapy.all import Ether, IP, UDP, TCP
from myTunnel_header import MyTunnel
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
def main():
if len(sys.argv)<4:
print 'pass 2 arguments: <ip_addr> <dst_nid> "<message>"'
exit(1)
addr = socket.gethostbyname(sys.argv[1])
dst_id = int(sys.argv[2])
iface = get_if()
print "sending on interface %s to id %s" % (iface, str(dst_id))
pkt = Ether(src=get_if_hwaddr(iface), dst='ff:ff:ff:ff:ff:ff')
pkt = pkt / MyTunnel(dst_id=dst_id) / IP(dst=addr) / sys.argv[3]
pkt.show2()
# hexdump(pkt)
# print "len(pkt) = ", len(pkt)
sendp(pkt, iface=iface, verbose=False)
if __name__ == '__main__':
main()

211
P4D2_2017_Fall/exercises/basic_tunnel/solution/basic_tunnel.p4 Normal file
View File

@ -0,0 +1,211 @@
/* -*- P4_16 -*- */
#include <core.p4>
#include <v1model.p4>
const bit<16> TYPE_MYTUNNEL = 0x1212;
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 myTunnel_t {
bit<16> proto_id;
bit<16> dst_id;
}
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;
myTunnel_t myTunnel;
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_MYTUNNEL: parse_myTunnel;
TYPE_IPV4: parse_ipv4;
default: accept;
}
}
state parse_myTunnel {
packet.extract(hdr.myTunnel);
transition select(hdr.myTunnel.proto_id) {
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(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();
}
action myTunnel_forward(egressSpec_t port) {
standard_metadata.egress_spec = port;
}
table myTunnel_exact {
key = {
hdr.myTunnel.dst_id: exact;
}
actions = {
myTunnel_forward;
drop;
}
size = 1024;
default_action = drop();
}
apply {
if (hdr.myTunnel.isValid()) {
myTunnel_exact.apply();
} else 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 { }
}
/*************************************************************************
************* 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.myTunnel);
packet.emit(hdr.ipv4);
}
}
/*************************************************************************
*********************** S W I T C H *******************************
*************************************************************************/
V1Switch(
MyParser(),
MyVerifyChecksum(),
MyIngress(),
MyEgress(),
MyComputeChecksum(),
MyDeparser()
) main;