Merge branch 'selftest-rds'

Allison Henderson says:

====================
selftests: rds selftest

This series is a new selftest that Vegard, Chuck and myself have been
working on to provide some test coverage for rds.  I've modified the
scripts to include the feedback from the last version, but let me know
if there's anything missed.  Questions and comments appreciated.

Thanks everyone!

Allison

Changes in v2:
- Removed qemu vm creation and related code
- Updated README.txt with examples of running the test with virtme
- Removed init.sh. run.sh now directly calls test.py
- Some clean up done with the return code handling since there is no
  vm between the scripts anymore
- Imported ip python function in
tools/testing/selftests/net/lib/py/utils.py into test.py
- Adapted test.py to use the imported ip function, and removed the
local ip wrapper
- Some line wrap clean up
- Link to v1:
https://lore.kernel.org/netdev/20240626012834.5678-3-allison.henderson@oracle.com/T
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

11 files changed, 620 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
index 7902adf4f7f1..38b7ab9e7dc4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -24,6 +24,7 @@
 *.dwo
 *.elf
 *.gcno
+*.gcda
 *.gz
 *.i
 *.ko
diff --git a/Documentation/dev-tools/gcov.rst b/Documentation/dev-tools/gcov.rst
index 5fce2b06f229..dbd26b02ff3c 100644
--- a/Documentation/dev-tools/gcov.rst
+++ b/Documentation/dev-tools/gcov.rst
@@ -75,6 +75,17 @@ Only files which are linked to the main kernel image or are compiled as
 kernel modules are supported by this mechanism.
 
 
+Module specific configs
+-----------------------
+
+Gcov kernel configs for specific modules are described below:
+
+CONFIG_GCOV_PROFILE_RDS:
+        Enables GCOV profiling on RDS for checking which functions or
+        lines are executed. This config is used by the rds selftest to
+        generate coverage reports. If left unset the report is omitted.
+
+
 Files
 -----
 
diff --git a/MAINTAINERS b/MAINTAINERS
index 1a7ea5c7c710..7b291c3a9aa4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -19197,6 +19197,7 @@ S:	Supported
 W:	https://oss.oracle.com/projects/rds/
 F:	Documentation/networking/rds.rst
 F:	net/rds/
+F:	tools/testing/selftests/net/rds/
 
 RDT - RESOURCE ALLOCATION
 M:	Fenghua Yu <fenghua.yu@intel.com>
diff --git a/net/rds/Kconfig b/net/rds/Kconfig
index 75cd696963b2..f007730aa2bb 100644
--- a/net/rds/Kconfig
+++ b/net/rds/Kconfig
@@ -26,3 +26,12 @@ config RDS_DEBUG
 	bool "RDS debugging messages"
 	depends on RDS
 	default n
+
+config GCOV_PROFILE_RDS
+	bool "Enable GCOV profiling on RDS"
+	depends on GCOV_KERNEL
+	help
+	  Enable GCOV profiling on RDS for checking which functions/lines
+	  are executed.
+
+	  If unsure, say N.
diff --git a/net/rds/Makefile b/net/rds/Makefile
index 8fdc118e2927..3af1ca1d965c 100644
--- a/net/rds/Makefile
+++ b/net/rds/Makefile
@@ -15,3 +15,8 @@ rds_tcp-y :=		tcp.o tcp_connect.o tcp_listen.o tcp_recv.o \
 			tcp_send.o tcp_stats.o
 
 ccflags-$(CONFIG_RDS_DEBUG)	:=	-DRDS_DEBUG
+
+# for GCOV coverage profiling
+ifdef CONFIG_GCOV_PROFILE_RDS
+GCOV_PROFILE := y
+endif
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index bc8fe9e8f7f2..a5f1c0c27dff 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -68,6 +68,7 @@ TARGETS += net/mptcp
 TARGETS += net/openvswitch
 TARGETS += net/tcp_ao
 TARGETS += net/netfilter
+TARGETS += net/rds
 TARGETS += nsfs
 TARGETS += perf_events
 TARGETS += pidfd
diff --git a/tools/testing/selftests/net/rds/Makefile b/tools/testing/selftests/net/rds/Makefile
new file mode 100644
index 000000000000..da9714bc7aad
--- /dev/null
+++ b/tools/testing/selftests/net/rds/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+
+all:
+	@echo mk_build_dir="$(shell pwd)" > include.sh
+
+TEST_PROGS := run.sh \
+	include.sh \
+	test.py
+
+EXTRA_CLEAN := /tmp/rds_logs
+
+include ../../lib.mk
diff --git a/tools/testing/selftests/net/rds/README.txt b/tools/testing/selftests/net/rds/README.txt
new file mode 100644
index 000000000000..cbde2951ab13
--- /dev/null
+++ b/tools/testing/selftests/net/rds/README.txt
@@ -0,0 +1,41 @@
+RDS self-tests
+==============
+
+These scripts provide a coverage test for RDS-TCP by creating two
+network namespaces and running rds packets between them. A loopback
+network is provisioned with optional probability of packet loss or
+corruption. A workload of 50000 hashes, each 64 characters in size,
+are passed over an RDS socket on this test network. A passing test means
+the RDS-TCP stack was able to recover properly.  The provided config.sh
+can be used to compile the kernel with the necessary gcov options.  The
+kernel may optionally be configured to omit the coverage report as well.
+
+USAGE:
+	run.sh [-d logdir] [-l packet_loss] [-c packet_corruption]
+	       [-u packet_duplcate]
+
+OPTIONS:
+	-d	Log directory.  Defaults to tools/testing/selftests/net/rds/rds_logs
+
+	-l	Simulates a percentage of packet loss
+
+	-c	Simulates a percentage of packet corruption
+
+	-u	Simulates a percentage of packet duplication.
+
+EXAMPLE:
+
+    # Create a suitable gcov enabled .config
+    tools/testing/selftests/net/rds/config.sh -g
+
+    # Alternatly create a gcov disabled .config
+    tools/testing/selftests/net/rds/config.sh
+
+    # build the kernel
+    vng --build  --config tools/testing/selftests/net/config
+
+    # launch the tests in a VM
+    vng -v --rwdir ./ --run . --user root --cpus 4 -- \
+        "export PYTHONPATH=tools/testing/selftests/net/; tools/testing/selftests/net/rds/run.sh"
+
+An HTML coverage report will be output in tools/testing/selftests/net/rds/rds_logs/coverage/.
diff --git a/tools/testing/selftests/net/rds/config.sh b/tools/testing/selftests/net/rds/config.sh
new file mode 100755
index 000000000000..791c8dbe1095
--- /dev/null
+++ b/tools/testing/selftests/net/rds/config.sh
@@ -0,0 +1,53 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+set -u
+set -x
+
+unset KBUILD_OUTPUT
+
+GENERATE_GCOV_REPORT=0
+while getopts "g" opt; do
+  case ${opt} in
+    g)
+      GENERATE_GCOV_REPORT=1
+      ;;
+    :)
+      echo "USAGE: config.sh [-g]"
+      exit 1
+      ;;
+    ?)
+      echo "Invalid option: -${OPTARG}."
+      exit 1
+      ;;
+  esac
+done
+
+CONF_FILE="tools/testing/selftests/net/config"
+
+# no modules
+scripts/config --file "$CONF_FILE" --disable CONFIG_MODULES
+
+# enable RDS
+scripts/config --file "$CONF_FILE" --enable CONFIG_RDS
+scripts/config --file "$CONF_FILE" --enable CONFIG_RDS_TCP
+
+if [ "$GENERATE_GCOV_REPORT" -eq 1 ]; then
+	# instrument RDS and only RDS
+	scripts/config --file "$CONF_FILE" --enable CONFIG_GCOV_KERNEL
+	scripts/config --file "$CONF_FILE" --disable GCOV_PROFILE_ALL
+	scripts/config --file "$CONF_FILE" --enable GCOV_PROFILE_RDS
+else
+	scripts/config --file "$CONF_FILE" --disable CONFIG_GCOV_KERNEL
+	scripts/config --file "$CONF_FILE" --disable GCOV_PROFILE_ALL
+	scripts/config --file "$CONF_FILE" --disable GCOV_PROFILE_RDS
+fi
+
+# need network namespaces to run tests with veth network interfaces
+scripts/config --file "$CONF_FILE" --enable CONFIG_NET_NS
+scripts/config --file "$CONF_FILE" --enable CONFIG_VETH
+
+# simulate packet loss
+scripts/config --file "$CONF_FILE" --enable CONFIG_NET_SCH_NETEM
+
diff --git a/tools/testing/selftests/net/rds/run.sh b/tools/testing/selftests/net/rds/run.sh
new file mode 100755
index 000000000000..8aee244f582a
--- /dev/null
+++ b/tools/testing/selftests/net/rds/run.sh
@@ -0,0 +1,224 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+set -u
+
+unset KBUILD_OUTPUT
+
+current_dir="$(realpath "$(dirname "$0")")"
+build_dir="$current_dir"
+
+build_include="$current_dir/include.sh"
+if test -f "$build_include"; then
+	# this include will define "$mk_build_dir" as the location the test was
+	# built.  We will need this if the tests are installed in a location
+	# other than the kernel source
+
+	source "$build_include"
+	build_dir="$mk_build_dir"
+fi
+
+# This test requires kernel source and the *.gcda data therein
+# Locate the top level of the kernel source, and the net/rds
+# subfolder with the appropriate *.gcno object files
+ksrc_dir="$(realpath "$build_dir"/../../../../../)"
+kconfig="$ksrc_dir/.config"
+obj_dir="$ksrc_dir/net/rds"
+
+GCOV_CMD=gcov
+
+#check to see if the host has the required packages to generate a gcov report
+check_gcov_env()
+{
+	if ! which "$GCOV_CMD" > /dev/null 2>&1; then
+		echo "Warning: Could not find gcov. "
+		GENERATE_GCOV_REPORT=0
+		return
+	fi
+
+	# the gcov version must match the gcc version
+	GCC_VER=$(gcc -dumpfullversion)
+	GCOV_VER=$($GCOV_CMD -v | grep gcov | awk '{print $3}'| awk 'BEGIN {FS="-"}{print $1}')
+	if [ "$GCOV_VER" != "$GCC_VER" ]; then
+		#attempt to find a matching gcov version
+		GCOV_CMD=gcov-$(gcc -dumpversion)
+
+		if ! which "$GCOV_CMD" > /dev/null 2>&1; then
+			echo "Warning: Could not find an appropriate gcov installation. \
+				gcov version must match gcc version"
+			GENERATE_GCOV_REPORT=0
+			return
+		fi
+
+		#recheck version number of found gcov executable
+		GCOV_VER=$($GCOV_CMD -v | grep gcov | awk '{print $3}'| \
+			awk 'BEGIN {FS="-"}{print $1}')
+		if [ "$GCOV_VER" != "$GCC_VER" ]; then
+			echo "Warning: Could not find an appropriate gcov installation. \
+				gcov version must match gcc version"
+			GENERATE_GCOV_REPORT=0
+		else
+			echo "Warning: Mismatched gcc and gcov detected.  Using $GCOV_CMD"
+		fi
+	fi
+}
+
+# Check to see if the kconfig has the required configs to generate a coverage report
+check_gcov_conf()
+{
+	if ! grep -x "CONFIG_GCOV_PROFILE_RDS=y" "$kconfig" > /dev/null 2>&1; then
+		echo "INFO: CONFIG_GCOV_PROFILE_RDS should be enabled for coverage reports"
+		GENERATE_GCOV_REPORT=0
+	fi
+	if ! grep -x "CONFIG_GCOV_KERNEL=y" "$kconfig" > /dev/null 2>&1; then
+		echo "INFO: CONFIG_GCOV_KERNEL should be enabled for coverage reports"
+		GENERATE_GCOV_REPORT=0
+	fi
+	if grep -x "CONFIG_GCOV_PROFILE_ALL=y" "$kconfig" > /dev/null 2>&1; then
+		echo "INFO: CONFIG_GCOV_PROFILE_ALL should be disabled for coverage reports"
+		GENERATE_GCOV_REPORT=0
+	fi
+
+	if [ "$GENERATE_GCOV_REPORT" -eq 0 ]; then
+		echo "To enable gcov reports, please run "\
+			"\"tools/testing/selftests/net/rds/config.sh -g\" and rebuild the kernel"
+	else
+		# if we have the required kernel configs, proceed to check the environment to
+		# ensure we have the required gcov packages
+		check_gcov_env
+	fi
+}
+
+# Kselftest framework requirement - SKIP code is 4.
+check_conf_enabled() {
+	if ! grep -x "$1=y" "$kconfig" > /dev/null 2>&1; then
+		echo "selftests: [SKIP] This test requires $1 enabled"
+		echo "Please run tools/testing/selftests/net/rds/config.sh and rebuild the kernel"
+		exit 4
+	fi
+}
+check_conf_disabled() {
+	if grep -x "$1=y" "$kconfig" > /dev/null 2>&1; then
+		echo "selftests: [SKIP] This test requires $1 disabled"
+		echo "Please run tools/testing/selftests/net/rds/config.sh and rebuild the kernel"
+		exit 4
+	fi
+}
+check_conf() {
+	check_conf_enabled CONFIG_NET_SCH_NETEM
+	check_conf_enabled CONFIG_VETH
+	check_conf_enabled CONFIG_NET_NS
+	check_conf_enabled CONFIG_RDS_TCP
+	check_conf_enabled CONFIG_RDS
+	check_conf_disabled CONFIG_MODULES
+}
+
+check_env()
+{
+	if ! test -d "$obj_dir"; then
+		echo "selftests: [SKIP] This test requires a kernel source tree"
+		exit 4
+	fi
+	if ! test -e "$kconfig"; then
+		echo "selftests: [SKIP] This test requires a configured kernel source tree"
+		exit 4
+	fi
+	if ! which strace > /dev/null 2>&1; then
+		echo "selftests: [SKIP] Could not run test without strace"
+		exit 4
+	fi
+	if ! which tcpdump > /dev/null 2>&1; then
+		echo "selftests: [SKIP] Could not run test without tcpdump"
+		exit 4
+	fi
+
+	if ! which python3 > /dev/null 2>&1; then
+		echo "selftests: [SKIP] Could not run test without python3"
+		exit 4
+	fi
+
+	python_major=$(python3 -c "import sys; print(sys.version_info[0])")
+	python_minor=$(python3 -c "import sys; print(sys.version_info[1])")
+	if [[ python_major -lt 3 || ( python_major -eq 3 && python_minor -lt 9 ) ]] ; then
+		echo "selftests: [SKIP] Could not run test without at least python3.9"
+		python3 -V
+		exit 4
+	fi
+}
+
+LOG_DIR="$current_dir"/rds_logs
+PLOSS=0
+PCORRUPT=0
+PDUP=0
+GENERATE_GCOV_REPORT=1
+while getopts "d:l:c:u:" opt; do
+  case ${opt} in
+    d)
+      LOG_DIR=${OPTARG}
+      ;;
+    l)
+      PLOSS=${OPTARG}
+      ;;
+    c)
+      PCORRUPT=${OPTARG}
+      ;;
+    u)
+      PDUP=${OPTARG}
+      ;;
+    :)
+      echo "USAGE: run.sh [-d logdir] [-l packet_loss] [-c packet_corruption]" \
+           "[-u packet_duplcate] [-g]"
+      exit 1
+      ;;
+    ?)
+      echo "Invalid option: -${OPTARG}."
+      exit 1
+      ;;
+  esac
+done
+
+
+check_env
+check_conf
+check_gcov_conf
+
+
+rm -fr "$LOG_DIR"
+TRACE_FILE="${LOG_DIR}/rds-strace.txt"
+COVR_DIR="${LOG_DIR}/coverage/"
+mkdir -p  "$LOG_DIR"
+mkdir -p "$COVR_DIR"
+
+set +e
+echo running RDS tests...
+echo Traces will be logged to "$TRACE_FILE"
+rm -f "$TRACE_FILE"
+strace -T -tt -o "$TRACE_FILE" python3 "$(dirname "$0")/test.py" --timeout 400 -d "$LOG_DIR" \
+       -l "$PLOSS" -c "$PCORRUPT" -u "$PDUP"
+
+test_rc=$?
+dmesg > "${LOG_DIR}/dmesg.out"
+
+if [ "$GENERATE_GCOV_REPORT" -eq 1 ]; then
+       echo saving coverage data...
+       (set +x; cd /sys/kernel/debug/gcov; find ./* -name '*.gcda' | \
+       while read -r f
+       do
+               cat < "/sys/kernel/debug/gcov/$f" > "/$f"
+       done)
+
+       echo running gcovr...
+       gcovr -s --html-details --gcov-executable "$GCOV_CMD" --gcov-ignore-parse-errors \
+             -o "${COVR_DIR}/gcovr" "${ksrc_dir}/net/rds/"
+else
+       echo "Coverage report will be skipped"
+fi
+
+if [ "$test_rc" -eq 0 ]; then
+	echo "PASS: Test completed successfully"
+else
+	echo "FAIL: Test failed"
+fi
+
+exit "$test_rc"
diff --git a/tools/testing/selftests/net/rds/test.py b/tools/testing/selftests/net/rds/test.py
new file mode 100644
index 000000000000..e6bb109bcead
--- /dev/null
+++ b/tools/testing/selftests/net/rds/test.py
@@ -0,0 +1,262 @@
+#! /usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import argparse
+import ctypes
+import errno
+import hashlib
+import os
+import select
+import signal
+import socket
+import subprocess
+import sys
+import atexit
+from pwd import getpwuid
+from os import stat
+from lib.py import ip
+
+
+libc = ctypes.cdll.LoadLibrary('libc.so.6')
+setns = libc.setns
+
+net0 = 'net0'
+net1 = 'net1'
+
+veth0 = 'veth0'
+veth1 = 'veth1'
+
+# Helper function for creating a socket inside a network namespace.
+# We need this because otherwise RDS will detect that the two TCP
+# sockets are on the same interface and use the loop transport instead
+# of the TCP transport.
+def netns_socket(netns, *args):
+    u0, u1 = socket.socketpair(socket.AF_UNIX, socket.SOCK_SEQPACKET)
+
+    child = os.fork()
+    if child == 0:
+        # change network namespace
+        with open(f'/var/run/netns/{netns}') as f:
+            try:
+                ret = setns(f.fileno(), 0)
+            except IOError as e:
+                print(e.errno)
+                print(e)
+
+        # create socket in target namespace
+        s = socket.socket(*args)
+
+        # send resulting socket to parent
+        socket.send_fds(u0, [], [s.fileno()])
+
+        sys.exit(0)
+
+    # receive socket from child
+    _, s, _, _ = socket.recv_fds(u1, 0, 1)
+    os.waitpid(child, 0)
+    u0.close()
+    u1.close()
+    return socket.fromfd(s[0], *args)
+
+def signal_handler(sig, frame):
+    print('Test timed out')
+    sys.exit(1)
+
+#Parse out command line arguments.  We take an optional
+# timeout parameter and an optional log output folder
+parser = argparse.ArgumentParser(description="init script args",
+                  formatter_class=argparse.ArgumentDefaultsHelpFormatter)
+parser.add_argument("-d", "--logdir", action="store",
+                    help="directory to store logs", default="/tmp")
+parser.add_argument('--timeout', help="timeout to terminate hung test",
+                    type=int, default=0)
+parser.add_argument('-l', '--loss', help="Simulate tcp packet loss",
+                    type=int, default=0)
+parser.add_argument('-c', '--corruption', help="Simulate tcp packet corruption",
+                    type=int, default=0)
+parser.add_argument('-u', '--duplicate', help="Simulate tcp packet duplication",
+                    type=int, default=0)
+args = parser.parse_args()
+logdir=args.logdir
+packet_loss=str(args.loss)+'%'
+packet_corruption=str(args.corruption)+'%'
+packet_duplicate=str(args.duplicate)+'%'
+
+ip(f"netns add {net0}")
+ip(f"netns add {net1}")
+ip(f"link add type veth")
+
+addrs = [
+    # we technically don't need different port numbers, but this will
+    # help identify traffic in the network analyzer
+    ('10.0.0.1', 10000),
+    ('10.0.0.2', 20000),
+]
+
+# move interfaces to separate namespaces so they can no longer be
+# bound directly; this prevents rds from switching over from the tcp
+# transport to the loop transport.
+ip(f"link set {veth0} netns {net0} up")
+ip(f"link set {veth1} netns {net1} up")
+
+
+
+# add addresses
+ip(f"-n {net0} addr add {addrs[0][0]}/32 dev {veth0}")
+ip(f"-n {net1} addr add {addrs[1][0]}/32 dev {veth1}")
+
+# add routes
+ip(f"-n {net0} route add {addrs[1][0]}/32 dev {veth0}")
+ip(f"-n {net1} route add {addrs[0][0]}/32 dev {veth1}")
+
+# sanity check that our two interfaces/addresses are correctly set up
+# and communicating by doing a single ping
+ip(f"netns exec {net0} ping -c 1 {addrs[1][0]}")
+
+# Start a packet capture on each network
+for net in [net0, net1]:
+    tcpdump_pid = os.fork()
+    if tcpdump_pid == 0:
+        pcap = logdir+'/'+net+'.pcap'
+        subprocess.check_call(['touch', pcap])
+        user = getpwuid(stat(pcap).st_uid).pw_name
+        ip(f"netns exec {net} /usr/sbin/tcpdump -Z {user} -i any -w {pcap}")
+        sys.exit(0)
+
+# simulate packet loss, duplication and corruption
+for net, iface in [(net0, veth0), (net1, veth1)]:
+    ip(f"netns exec {net} /usr/sbin/tc qdisc add dev {iface} root netem  \
+         corrupt {packet_corruption} loss {packet_loss} duplicate  \
+         {packet_duplicate}")
+
+# add a timeout
+if args.timeout > 0:
+    signal.alarm(args.timeout)
+    signal.signal(signal.SIGALRM, signal_handler)
+
+sockets = [
+    netns_socket(net0, socket.AF_RDS, socket.SOCK_SEQPACKET),
+    netns_socket(net1, socket.AF_RDS, socket.SOCK_SEQPACKET),
+]
+
+for s, addr in zip(sockets, addrs):
+    s.bind(addr)
+    s.setblocking(0)
+
+fileno_to_socket = {
+    s.fileno(): s for s in sockets
+}
+
+addr_to_socket = {
+    addr: s for addr, s in zip(addrs, sockets)
+}
+
+socket_to_addr = {
+    s: addr for addr, s in zip(addrs, sockets)
+}
+
+send_hashes = {}
+recv_hashes = {}
+
+ep = select.epoll()
+
+for s in sockets:
+    ep.register(s, select.EPOLLRDNORM)
+
+n = 50000
+nr_send = 0
+nr_recv = 0
+
+while nr_send < n:
+    # Send as much as we can without blocking
+    print("sending...", nr_send, nr_recv)
+    while nr_send < n:
+        send_data = hashlib.sha256(
+            f'packet {nr_send}'.encode('utf-8')).hexdigest().encode('utf-8')
+
+        # pseudo-random send/receive pattern
+        sender = sockets[nr_send % 2]
+        receiver = sockets[1 - (nr_send % 3) % 2]
+
+        try:
+            sender.sendto(send_data, socket_to_addr[receiver])
+            send_hashes.setdefault((sender.fileno(), receiver.fileno()),
+                    hashlib.sha256()).update(f'<{send_data}>'.encode('utf-8'))
+            nr_send = nr_send + 1
+        except BlockingIOError as e:
+            break
+        except OSError as e:
+            if e.errno in [errno.ENOBUFS, errno.ECONNRESET, errno.EPIPE]:
+                break
+            raise
+
+    # Receive as much as we can without blocking
+    print("receiving...", nr_send, nr_recv)
+    while nr_recv < nr_send:
+        for fileno, eventmask in ep.poll():
+            receiver = fileno_to_socket[fileno]
+
+            if eventmask & select.EPOLLRDNORM:
+                while True:
+                    try:
+                        recv_data, address = receiver.recvfrom(1024)
+                        sender = addr_to_socket[address]
+                        recv_hashes.setdefault((sender.fileno(),
+                            receiver.fileno()), hashlib.sha256()).update(
+                                    f'<{recv_data}>'.encode('utf-8'))
+                        nr_recv = nr_recv + 1
+                    except BlockingIOError as e:
+                        break
+
+    # exercise net/rds/tcp.c:rds_tcp_sysctl_reset()
+    for net in [net0, net1]:
+        ip(f"netns exec {net} /usr/sbin/sysctl net.rds.tcp.rds_tcp_rcvbuf=10000")
+        ip(f"netns exec {net} /usr/sbin/sysctl net.rds.tcp.rds_tcp_sndbuf=10000")
+
+print("done", nr_send, nr_recv)
+
+# the Python socket module doesn't know these
+RDS_INFO_FIRST = 10000
+RDS_INFO_LAST = 10017
+
+nr_success = 0
+nr_error = 0
+
+for s in sockets:
+    for optname in range(RDS_INFO_FIRST, RDS_INFO_LAST + 1):
+        # Sigh, the Python socket module doesn't allow us to pass
+        # buffer lengths greater than 1024 for some reason. RDS
+        # wants multiple pages.
+        try:
+            s.getsockopt(socket.SOL_RDS, optname, 1024)
+            nr_success = nr_success + 1
+        except OSError as e:
+            nr_error = nr_error + 1
+            if e.errno == errno.ENOSPC:
+                # ignore
+                pass
+
+print(f"getsockopt(): {nr_success}/{nr_error}")
+
+print("Stopping network packet captures")
+subprocess.check_call(['killall', '-q', 'tcpdump'])
+
+# We're done sending and receiving stuff, now let's check if what
+# we received is what we sent.
+for (sender, receiver), send_hash in send_hashes.items():
+    recv_hash = recv_hashes.get((sender, receiver))
+
+    if recv_hash is None:
+        print("FAIL: No data received")
+        sys.exit(1)
+
+    if send_hash.hexdigest() != recv_hash.hexdigest():
+        print("FAIL: Send/recv mismatch")
+        print("hash expected:", send_hash.hexdigest())
+        print("hash received:", recv_hash.hexdigest())
+        sys.exit(1)
+
+    print(f"{sender}/{receiver}: ok")
+
+print("Success")
+sys.exit(0)