VPP/How To Use The Packet Generator and Packet Tracer
Introduction
The VPP platform includes packet generation and packet tracing facilities.
The following example shows steps that you might typically use to run a debug version of the vpp executable file, generate packets, and to analyze results.
Example with IP4 ARP Messages
In the following steps, the VPP executable does not need to be started with superuser permissions. The VPP executable will not discover physical devices when run as a normal user.
Step 1. Start a debug version of vpp
From the command line, make the build-root directory the working directory and run vpp from the /bin directory as shown in the following example.
In the following example, including the dpdk argument means that no physical interfaces will be discovered.
$ cd ../build-root
$ ./install-vpp_debug-native/vpp/bin/vpp unix interactive dpdk {no-pci no-huge num-mbufs 8192}
Step 2. Execute the arp4 setup script
From the vpp debug command-line, execute the arp4 script.
DBGvpp# exec /vpp/vnet/etc/scripts/arp4
Step 3. Examine the setup script
Let's tale a look at the contents of the setup script that you just executed. The script .../vpp/vnet/etc/scripts/arp4 contains:
packet-generator new {
name x
limit 1
node ip4-input
size 64-64
no-recycle
data {
ICMP: 1.0.0.2 -> 2.0.0.2
ICMP echo_request
incrementing 100
}
}
trace add pg-input 100 loop create loop create set int state loop0 up set int state loop1 up set int ip address loop0 1.0.0.1/24 set int ip address loop1 2.0.0.1/24
The first stanza creates a packet generator stream called "x" which sends a single ipv4 icmp echo-request when enabled. The trace add command arranges to trace 100 packets originating at the pg-input graph node. If you want to trace packets originating at the "dpdk-input" node - which is probably the most typical real-world use-case - make the substitution for that graph node.
Finally, the script configures a couple of loopback interfaces; primarily, so that ip4-input / ip4-lookup won't immediately ditch the generated packet.
Step 4. Generate packets
On the vpp debug command-line, enable the packet generator.
DBGvpp# packet-generator enable
Step 5. Run the packet tracer
Use the show trace command to run the packet tracer.
DBGvpp# show trace
DBGvpp# show trace
------------------- Start of thread 0 -------------------
Packet 1
00:02:37:928917: pg-input
stream x, 64 bytes
current data 0, length 64, free-list 2, trace 0x0
ICMP: 1.0.0.2 -> 2.0.0.2
tos 0x00, ttl 64, length 64, checksum 0x77ba
fragment id 0x0000
ICMP echo_request checksum 0x7a6e
00:02:37:928960: ip4-input
ICMP: 1.0.0.2 -> 2.0.0.2
tos 0x00, ttl 64, length 64, checksum 0x77ba
fragment id 0x0000
ICMP echo_request checksum 0x7a6e
00:02:37:928979: ip4-arp
fib: 0 adjacency: arp loop1 2.0.0.1/24 flow hash: 0x00000000
00:02:37:929005: loop1-output
loop1
ARP: de:ad:00:00:00:01 -> ff:ff:ff:ff:ff:ff
request, type ethernet/IP4, address size 6/4
de:ad:00:00:00:01/2.0.0.1 -> 00:00:00:00:00:00/2.0.0.2
00:02:37:929010: error-drop
ip4-arp: ARP requests sent
loop1-output: interface is down
Step 6. Examine the IPv4 default VRF table
Use the show ip fib command to see the VRF table.
Here's the contents of the IPv4 default VRF table after the arp4 script was executed:
DBGvpp# show ip fib
Table 0, fib_index 0, flow hash: src dst sport dport proto
Destination Packets Bytes Adjacency
1.0.0.0/24 0 0 weight 1, index 3
arp loop0 1.0.0.1/24
1.0.0.1/32 0 0 weight 1, index 4
local 1.0.0.1/24
2.0.0.0/24 0 0 weight 1, index 5
arp loop1 2.0.0.1/24
2.0.0.1/32 0 0 weight 1, index 6
local 2.0.0.1/24
When we enable the packet generator stream, we observe a lookup hit on 2.0.0.0/24:
DBGvpp# sh ip fib
Table 0, fib_index 0, flow hash: src dst sport dport proto
Destination Packets Bytes Adjacency
1.0.0.0/24 0 0 weight 1, index 3
arp loop0 1.0.0.1/24
1.0.0.1/32 0 0 weight 1, index 4
local 1.0.0.1/24
2.0.0.0/24 1 78 weight 1, index 5
arp loop1 2.0.0.1/24
2.0.0.1/32 0 0 weight 1, index 6
local 2.0.0.1/24
Step 7. Analyze the information
Inspecting the error counters you see what we might expect in light of the packet tracer output:
DBGvpp# sh err
Count Node Reason
1 ip4-arp ARP requests sent
1 loop1-output interface is down
=== Convert a PCAP file to a PG file
The below is a ping PCAP capture converted into Packet Generator (PG) format.
1. Use the PCAP2PG converter utility in the source tree
cd /vpp/build-root/build-vpp_debug-native/vnet/ ./pcap2pg -i vpp1.pcap > vpp1.pg edit vpp1.pg
2. Each line in the PCAP file is wrapped in Packet-Generator specific information:
packet-generator new {
name s0
limit 1
size 98-98
node ethernet-input
data {
0x0800: b66a.2a78.efb3 -> 02fe.6613.e729
hex 0x45000054c622400040011962ac100102ac1002020800cb807f4f00016cf0f756000000008514050000000000101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f3031323334353637 }
}
packet-generator new {
name s1
limit 1
size 98-98
node ethernet-input
data {
0x0800: 02fe.6613.e729 -> b66a.2a78.efb3
hex 0x450000543fee00003f01e096ac100202ac1001020000d3807f4f00016cf0f756000000008514050000000000101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f3031323334353637 }
}
packet-generator new {
name s2
limit 1
size 98-98
node ethernet-input
data {
0x0800: b66a.2a78.efb3 -> 02fe.6613.e729
hex 0x45000054c63540004001194fac100102ac10020208006d837f4f00026df0f75600000000e210050000000000101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f3031323334353637 }
}
3. Remove any lines of text and add an interface:
packet-generator new {
name s0
limit 1
size 98-98
node ethernet-input
interface GigabitEthernet0/8/0
data {
0x0800: b66a.2a78.efb3 -> 02fe.6613.e729
hex 0x45000054c622400040011962ac100102ac1002020800cb807f4f00016cf0f756000000008514050000000000101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f3031323334353637 }
}
