See README-using-bmv2.md for some things that are common across different P4 programs executed using bmv2.
This program is a modification of the demo3 code, with additions intended not because they make sense, but because they help demonstrate some P4_16 language features that test the p4c-bm2-ss compiler's ability to include source info (P4 source file names and line numbers) for a variety of language constructs.
To compile the P4_16 version of the code:
p4c --target bmv2 --arch v1model demo5.p4_16.p4
To compile the P4_14 version of the code:
p4c --std p4-14 --target bmv2 --arch v1model demo5.p4_14.p4
The .dot and .png files in the subdirectory 'graphs' were created with the p4c-graphs program, which is also installed when you build and install p4c-bm2-ss:
p4c-graphs -I $HOME/p4c/p4include demo5.p4_16.p4
The '-I' option is only necessary if you did not install the P4 compiler in your system-wide /usr/local/bin directory.
To run the behavioral model with 8 ports numbered 0 through 7:
sudo simple_switch --log-console --dump-packet-data 10000 -i 0@veth0 -i 1@veth2 -i 2@veth4 -i 3@veth6 -i 4@veth8 -i 5@veth10 -i 6@veth12 -i 7@veth14 demo5.p4_16.json
To run CLI for controlling and examining simple_switch's table contents:
simple_switch_CLI
General syntax for table_add commands at simple_switch_CLI prompt:
RuntimeCmd: help table_add
Add entry to a match table: table_add <table name> <action name> <match fields> => <action parameters> [priority]
All of these, except for the counter-specific ones, also work for demo1.
# These should be unnecessary for P4_16 program, which defines
# these default actions with default_action assignments in its
# table definitions.
table_set_default compute_ipv4_hashes compute_lkp_ipv4_hash
table_set_default ipv4_da_lpm my_drop
table_set_default mac_da my_drop
table_set_default send_frame my_drop
Add both sets of entries below:
# For P4_16 program, set_l2ptr action name for table ipv4_da_lpm
# is changed to set_l2ptr_with_stat.
table_add ipv4_da_lpm set_l2ptr_with_stat 10.1.0.1/32 => 58
table_add mac_da set_bd_dmac_intf 58 => 9 02:13:57:ab:cd:ef 2
table_add send_frame rewrite_mac 9 => 00:11:22:33:44:55
table_add ipv4_da_lpm set_l2ptr_with_stat 10.1.0.200/32 => 81
table_add mac_da set_bd_dmac_intf 81 => 15 08:de:ad:be:ef:00 1
table_add send_frame rewrite_mac 15 => ca:fe:ba:be:d0:0d
# For P4_14 program, use this
table_add ipv4_da_lpm set_l2ptr 10.1.0.1/32 => 58
table_add mac_da set_bd_dmac_intf 58 => 9 02:13:57:ab:cd:ef 2
table_add send_frame rewrite_mac 9 => 00:11:22:33:44:55
table_add ipv4_da_lpm set_l2ptr 10.1.0.200/32 => 81
table_add mac_da set_bd_dmac_intf 81 => 15 08:de:ad:be:ef:00 1
table_add send_frame rewrite_mac 15 => ca:fe:ba:be:d0:0d
The entries above with action set_l2ptr on table ipv4_da_lpm work exactly as they did before. They avoid needing to do a lookup in the new ecmp_group table.
Here is a first try at using the ecmp_group and ecmp_path tables for forwarding packets. It assumes that the table entries above are already added.
I want all packets that match 11.1.0.1/32 to go through a 3-way ECMP table to output ports 1, 2, and 3, where ports 1 and 2 reuse the mac_da table entries added above.
# mac_da and send_frame table entries for output port 3
table_add mac_da set_bd_dmac_intf 101 => 22 08:de:ad:be:ef:00 3
table_add send_frame rewrite_mac 22 => ca:fe:ba:be:d0:0d
# LPM entry pointing at ecmp group idx 67.
# Then ecmp_group entry for ecmp group idx 67 that returns num_paths=3.
# Then 3 ecmp_path entries with ecmp group idx 67, and
# ecmp_path_selector values in the range [0,2], each giving a
# result with a different l2ptr value.
table_add ipv4_da_lpm set_ecmp_group_idx 11.1.0.1/32 => 67
table_add ecmp_group set_ecmp_path_idx 67 => 3
table_add ecmp_path set_l2ptr 67 0 => 81
table_add ecmp_path set_l2ptr 67 1 => 58
table_add ecmp_path set_l2ptr 67 2 => 101
I believe we must run scapy as root for it to have permission to send packets on veth interfaces.
sudo PATH=$PATH VIRTUAL_ENV=$VIRTUAL_ENV python3
from scapy.all import *
fwd_to_p1=Ether() / IP(dst='10.1.0.200') / TCP(sport=5793, dport=80) / Raw('The quick brown fox jumped over the lazy dog.')
fwd_to_p2=Ether() / IP(dst='10.1.0.1') / TCP(sport=5793, dport=80)
drop_pkt1=Ether() / IP(dst='10.1.0.34') / TCP(sport=5793, dport=80)
# Send packet at layer2, specifying interface
sendp(fwd_to_p1, iface="veth0")
sendp(fwd_to_p2, iface="veth0")
sendp(drop_pkt1, iface="veth0")
# For packets going to the ECMP group, vary the source IP address
# so that each will likely get different hash values.
# The hash value for this one caused it to go out port 2 in my
# testing.
fwd_to_ecmp_grp1=Ether() / IP(dst='11.1.0.1', src='1.2.3.4') / TCP(sport=5793, dport=80)
# output port 1 for this packet
fwd_to_ecmp_grp2=Ether() / IP(dst='11.1.0.1', src='1.2.3.5') / TCP(sport=5793, dport=80)
# output port 3 for this packet
fwd_to_ecmp_grp3=Ether() / IP(dst='11.1.0.1', src='1.2.3.7') / TCP(sport=5793, dport=80)