Commit 7df5e3db authored by Peter Oskolkov's avatar Peter Oskolkov Committed by Alexei Starovoitov
Browse files

selftests: bpf: tc-bpf flow shaping with EDT 



Add a small test that shows how to shape a TCP flow in tc-bpf
with EDT and ECN.

Signed-off-by: default avatarPeter Oskolkov <posk@google.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 315a2029

tools/testing/selftests/bpf/Makefile

+2 −1
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@@ -53,7 +53,8 @@ TEST_PROGS := test_kmod.sh \ 
	test_xdp_vlan.sh \

	test_lwt_ip_encap.sh \

	test_tcp_check_syncookie.sh \

	test_tc_tunnel.sh

	test_tc_tunnel.sh \

	test_tc_edt.sh



TEST_PROGS_EXTENDED := with_addr.sh \

	with_tunnels.sh \

tools/testing/selftests/bpf/progs/test_tc_edt.c

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+109 −0
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// SPDX-License-Identifier: GPL-2.0

#include <stdint.h>

#include <linux/bpf.h>

#include <linux/if_ether.h>

#include <linux/in.h>

#include <linux/ip.h>

#include <linux/pkt_cls.h>

#include <linux/tcp.h>

#include "bpf_helpers.h"

#include "bpf_endian.h"



/* the maximum delay we are willing to add (drop packets beyond that) */

#define TIME_HORIZON_NS (2000 * 1000 * 1000)

#define NS_PER_SEC 1000000000

#define ECN_HORIZON_NS 5000000

#define THROTTLE_RATE_BPS (5 * 1000 * 1000)



/* flow_key => last_tstamp timestamp used */

struct bpf_map_def SEC("maps") flow_map = {

	.type = BPF_MAP_TYPE_HASH,

	.key_size = sizeof(uint32_t),

	.value_size = sizeof(uint64_t),

	.max_entries = 1,

};



static inline int throttle_flow(struct __sk_buff *skb)

{

	int key = 0;

	uint64_t *last_tstamp = bpf_map_lookup_elem(&flow_map, &key);

	uint64_t delay_ns = ((uint64_t)skb->len) * NS_PER_SEC /

			THROTTLE_RATE_BPS;

	uint64_t now = bpf_ktime_get_ns();

	uint64_t tstamp, next_tstamp = 0;



	if (last_tstamp)

		next_tstamp = *last_tstamp + delay_ns;



	tstamp = skb->tstamp;

	if (tstamp < now)

		tstamp = now;



	/* should we throttle? */

	if (next_tstamp <= tstamp) {

		if (bpf_map_update_elem(&flow_map, &key, &tstamp, BPF_ANY))

			return TC_ACT_SHOT;

		return TC_ACT_OK;

	}



	/* do not queue past the time horizon */

	if (next_tstamp - now >= TIME_HORIZON_NS)

		return TC_ACT_SHOT;



	/* set ecn bit, if needed */

	if (next_tstamp - now >= ECN_HORIZON_NS)

		bpf_skb_ecn_set_ce(skb);



	if (bpf_map_update_elem(&flow_map, &key, &next_tstamp, BPF_EXIST))

		return TC_ACT_SHOT;

	skb->tstamp = next_tstamp;



	return TC_ACT_OK;

}



static inline int handle_tcp(struct __sk_buff *skb, struct tcphdr *tcp)

{

	void *data_end = (void *)(long)skb->data_end;



	/* drop malformed packets */

	if ((void *)(tcp + 1) > data_end)

		return TC_ACT_SHOT;



	if (tcp->dest == bpf_htons(9000))

		return throttle_flow(skb);



	return TC_ACT_OK;

}



static inline int handle_ipv4(struct __sk_buff *skb)

{

	void *data_end = (void *)(long)skb->data_end;

	void *data = (void *)(long)skb->data;

	struct iphdr *iph;

	uint32_t ihl;



	/* drop malformed packets */

	if (data + sizeof(struct ethhdr) > data_end)

		return TC_ACT_SHOT;

	iph = (struct iphdr *)(data + sizeof(struct ethhdr));

	if ((void *)(iph + 1) > data_end)

		return TC_ACT_SHOT;

	ihl = iph->ihl * 4;

	if (((void *)iph) + ihl > data_end)

		return TC_ACT_SHOT;



	if (iph->protocol == IPPROTO_TCP)

		return handle_tcp(skb, (struct tcphdr *)(((void *)iph) + ihl));



	return TC_ACT_OK;

}



SEC("cls_test") int tc_prog(struct __sk_buff *skb)

{

	if (skb->protocol == bpf_htons(ETH_P_IP))

		return handle_ipv4(skb);



	return TC_ACT_OK;

}



char __license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/test_tc_edt.sh

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#!/bin/bash

# SPDX-License-Identifier: GPL-2.0

#

# This test installs a TC bpf program that throttles a TCP flow

# with dst port = 9000 down to 5MBps. Then it measures actual

# throughput of the flow.



if [[ $EUID -ne 0 ]]; then

	echo "This script must be run as root"

	echo "FAIL"

	exit 1

fi



# check that nc, dd, and timeout are present

command -v nc >/dev/null 2>&1 || \

	{ echo >&2 "nc is not available"; exit 1; }

command -v dd >/dev/null 2>&1 || \

	{ echo >&2 "nc is not available"; exit 1; }

command -v timeout >/dev/null 2>&1 || \

	{ echo >&2 "timeout is not available"; exit 1; }



readonly NS_SRC="ns-src-$(mktemp -u XXXXXX)"

readonly NS_DST="ns-dst-$(mktemp -u XXXXXX)"



readonly IP_SRC="172.16.1.100"

readonly IP_DST="172.16.2.100"



cleanup()

{

	ip netns del ${NS_SRC}

	ip netns del ${NS_DST}

}



trap cleanup EXIT



set -e  # exit on error



ip netns add "${NS_SRC}"

ip netns add "${NS_DST}"

ip link add veth_src type veth peer name veth_dst

ip link set veth_src netns ${NS_SRC}

ip link set veth_dst netns ${NS_DST}



ip -netns ${NS_SRC} addr add ${IP_SRC}/24  dev veth_src

ip -netns ${NS_DST} addr add ${IP_DST}/24  dev veth_dst



ip -netns ${NS_SRC} link set dev veth_src up

ip -netns ${NS_DST} link set dev veth_dst up



ip -netns ${NS_SRC} route add ${IP_DST}/32  dev veth_src

ip -netns ${NS_DST} route add ${IP_SRC}/32  dev veth_dst



# set up TC on TX

ip netns exec ${NS_SRC} tc qdisc add dev veth_src root fq

ip netns exec ${NS_SRC} tc qdisc add dev veth_src clsact

ip netns exec ${NS_SRC} tc filter add dev veth_src egress \

	bpf da obj test_tc_edt.o sec cls_test





# start the listener

ip netns exec ${NS_DST} bash -c \

	"nc -4 -l -s ${IP_DST} -p 9000 >/dev/null &"

declare -i NC_PID=$!

sleep 1



declare -ir TIMEOUT=20

declare -ir EXPECTED_BPS=5000000



# run the load, capture RX bytes on DST

declare -ir RX_BYTES_START=$( ip netns exec ${NS_DST} \

	cat /sys/class/net/veth_dst/statistics/rx_bytes )



set +e

ip netns exec ${NS_SRC} bash -c "timeout ${TIMEOUT} dd if=/dev/zero \

	bs=1000 count=1000000 > /dev/tcp/${IP_DST}/9000 2>/dev/null"

set -e



declare -ir RX_BYTES_END=$( ip netns exec ${NS_DST} \

	cat /sys/class/net/veth_dst/statistics/rx_bytes )



declare -ir ACTUAL_BPS=$(( ($RX_BYTES_END - $RX_BYTES_START) / $TIMEOUT ))



echo $TIMEOUT $ACTUAL_BPS $EXPECTED_BPS | \

	awk '{printf "elapsed: %d sec; bps difference: %.2f%%\n",

		$1, ($2-$3)*100.0/$3}'



# Pass the test if the actual bps is within 1% of the expected bps.

# The difference is usually about 0.1% on a 20-sec test, and ==> zero

# the longer the test runs.

declare -ir RES=$( echo $ACTUAL_BPS $EXPECTED_BPS | \

	 awk 'function abs(x){return ((x < 0.0) ? -x : x)}

	      {if (abs(($1-$2)*100.0/$2) > 1.0) { print "1" }

		else { print "0"} }' )

if [ "${RES}" == "0" ] ; then

	echo "PASS"

else

	echo "FAIL"

	exit 1

fi