selftests/bpf: measure RTT from xdp using xdping

xdping allows us to get latency estimates from XDP.  Output looks
like this:

./xdping -I eth4 192.168.55.8
Setting up XDP for eth4, please wait...
XDP setup disrupts network connectivity, hit Ctrl+C to quit

Normal ping RTT data
[Ignore final RTT; it is distorted by XDP using the reply]
PING 192.168.55.8 (192.168.55.8) from 192.168.55.7 eth4: 56(84) bytes of data.
64 bytes from 192.168.55.8: icmp_seq=1 ttl=64 time=0.302 ms
64 bytes from 192.168.55.8: icmp_seq=2 ttl=64 time=0.208 ms
64 bytes from 192.168.55.8: icmp_seq=3 ttl=64 time=0.163 ms
64 bytes from 192.168.55.8: icmp_seq=8 ttl=64 time=0.275 ms

4 packets transmitted, 4 received, 0% packet loss, time 3079ms
rtt min/avg/max/mdev = 0.163/0.237/0.302/0.054 ms

XDP RTT data:
64 bytes from 192.168.55.8: icmp_seq=5 ttl=64 time=0.02808 ms
64 bytes from 192.168.55.8: icmp_seq=6 ttl=64 time=0.02804 ms
64 bytes from 192.168.55.8: icmp_seq=7 ttl=64 time=0.02815 ms
64 bytes from 192.168.55.8: icmp_seq=8 ttl=64 time=0.02805 ms

The xdping program loads the associated xdping_kern.o BPF program
and attaches it to the specified interface.  If run in client
mode (the default), it will add a map entry keyed by the
target IP address; this map will store RTT measurements, current
sequence number etc.  Finally in client mode the ping command
is executed, and the xdping BPF program will use the last ICMP
reply, reformulate it as an ICMP request with the next sequence
number and XDP_TX it.  After the reply to that request is received
we can measure RTT and repeat until the desired number of
measurements is made.  This is why the sequence numbers in the
normal ping are 1, 2, 3 and 8.  We XDP_TX a modified version
of ICMP reply 4 and keep doing this until we get the 4 replies
we need; hence the networking stack only sees reply 8, where
we have XDP_PASSed it upstream since we are done.

In server mode (-s), xdping simply takes ICMP requests and replies
to them in XDP rather than passing the request up to the networking
stack.  No map entry is required.

xdping can be run in native XDP mode (the default, or specified
via -N) or in skb mode (-S).

A test program test_xdping.sh exercises some of these options.

Note that native XDP does not seem to XDP_TX for veths, hence -N
is not tested.  Looking at the code, it looks like XDP_TX is
supported so I'm not sure if that's expected.  Running xdping in
native mode for ixgbe as both client and server works fine.

Changes since v4

- close fds on cleanup (Song Liu)

Changes since v3

- fixed seq to be __be16 (Song Liu)
- fixed fd checks in xdping.c (Song Liu)

Changes since v2

- updated commit message to explain why seq number of last
  ICMP reply is 8 not 4 (Song Liu)
- updated types of seq number, raddr and eliminated csum variable
  in xdpclient/xdpserver functions as it was not needed (Song Liu)
- added XDPING_DEFAULT_COUNT definition and usage specification of
  default/max counts (Song Liu)

Changes since v1
 - moved from RFC to PATCH
 - removed unused variable in ipv4_csum() (Song Liu)
 - refactored ICMP checks into icmp_check() function called by client
   and server programs and reworked client and server programs due
   to lack of shared code (Song Liu)
 - added checks to ensure that SKB and native mode are not requested
   together (Song Liu)

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 99 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/test_xdping.sh b/tools/testing/selftests/bpf/test_xdping.sh
new file mode 100755
index 000000000000..c2f0ddb45531
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_xdping.sh
@@ -0,0 +1,99 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+# xdping tests
+#   Here we setup and teardown configuration required to run
+#   xdping, exercising its options.
+#
+#   Setup is similar to test_tunnel tests but without the tunnel.
+#
+# Topology:
+# ---------
+#     root namespace   |     tc_ns0 namespace
+#                      |
+#      ----------      |     ----------
+#      |  veth1  | --------- |  veth0  |
+#      ----------    peer    ----------
+#
+# Device Configuration
+# --------------------
+# Root namespace with BPF
+# Device names and addresses:
+#	veth1 IP: 10.1.1.200
+#	xdp added to veth1, xdpings originate from here.
+#
+# Namespace tc_ns0 with BPF
+# Device names and addresses:
+#       veth0 IPv4: 10.1.1.100
+#	For some tests xdping run in server mode here.
+#
+
+readonly TARGET_IP="10.1.1.100"
+readonly TARGET_NS="xdp_ns0"
+
+readonly LOCAL_IP="10.1.1.200"
+
+setup()
+{
+	ip netns add $TARGET_NS
+	ip link add veth0 type veth peer name veth1
+	ip link set veth0 netns $TARGET_NS
+	ip netns exec $TARGET_NS ip addr add ${TARGET_IP}/24 dev veth0
+	ip addr add ${LOCAL_IP}/24 dev veth1
+	ip netns exec $TARGET_NS ip link set veth0 up
+	ip link set veth1 up
+}
+
+cleanup()
+{
+	set +e
+	ip netns delete $TARGET_NS 2>/dev/null
+	ip link del veth1 2>/dev/null
+	if [[ $server_pid -ne 0 ]]; then
+		kill -TERM $server_pid
+	fi
+}
+
+test()
+{
+	client_args="$1"
+	server_args="$2"
+
+	echo "Test client args '$client_args'; server args '$server_args'"
+
+	server_pid=0
+	if [[ -n "$server_args" ]]; then
+		ip netns exec $TARGET_NS ./xdping $server_args &
+		server_pid=$!
+		sleep 10
+	fi
+	./xdping $client_args $TARGET_IP
+
+	if [[ $server_pid -ne 0 ]]; then
+		kill -TERM $server_pid
+		server_pid=0
+	fi
+
+	echo "Test client args '$client_args'; server args '$server_args': PASS"
+}
+
+set -e
+
+server_pid=0
+
+trap cleanup EXIT
+
+setup
+
+for server_args in "" "-I veth0 -s -S" ; do
+	# client in skb mode
+	client_args="-I veth1 -S"
+	test "$client_args" "$server_args"
+
+	# client with count of 10 RTT measurements.
+	client_args="-I veth1 -S -c 10"
+	test "$client_args" "$server_args"
+done
+
+echo "OK. All tests passed"
+exit 0