Subject: [PATCH net-next v1 1/2] selftests: rds: Refactor test.py

From: Allison Henderson <[email-masked]>
Date: Sun, 1 Mar 2026 22:55:17 -0700

From: Allison Henderson <[email-masked]>

This patch hoists the send and recv logic from test.py into a helper
module rds_basic.py, keeping the namespace and networking configurations
in the calling test.py script.  This will allow us to reuse the test.py
infrastructure to add additional rds tests.  No functional changes are
added in this initial refactor.

Signed-off-by: Allison Henderson <[email-masked]>
---
 tools/testing/selftests/net/rds/Makefile     |   1 +
 tools/testing/selftests/net/rds/rds_basic.py | 183 +++++++++++++++++++
 tools/testing/selftests/net/rds/test.py      | 169 +----------------
 3 files changed, 191 insertions(+), 162 deletions(-)

diff --git a/tools/testing/selftests/net/rds/Makefile b/tools/testing/selftests/net/rds/Makefile
index 762845cc973c..611ed6f2bf91 100644
--- a/tools/testing/selftests/net/rds/Makefile
+++ b/tools/testing/selftests/net/rds/Makefile
@@ -8,6 +8,7 @@ TEST_PROGS := run.sh
 TEST_FILES := \
 	include.sh \
 	test.py \
+	rds_basic.py \
 # end of TEST_FILES
 
 EXTRA_CLEAN := \
diff --git a/tools/testing/selftests/net/rds/rds_basic.py b/tools/testing/selftests/net/rds/rds_basic.py
new file mode 100755
index 000000000000..49c524e2c72a
--- /dev/null
+++ b/tools/testing/selftests/net/rds/rds_basic.py
@@ -0,0 +1,183 @@
+#! /usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import ctypes
+import errno
+import hashlib
+import os
+import select
+import socket
+import sys
+
+# Allow utils module to be imported from different directory
+this_dir = os.path.dirname(os.path.realpath(__file__))
+sys.path.append(os.path.join(this_dir, "../"))
+from lib.py.utils import ip
+
+libc = ctypes.cdll.LoadLibrary('libc.so.6')
+setns = libc.setns
+
+# 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):
+    """Create a socket inside a network namespace."""
+    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}', encoding='utf-8') as f:
+            try:
+                setns(f.fileno(), 0)
+            except IOError as ioe:
+                print(ioe.errno)
+                print(ioe)
+
+        # 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 run_test(env):
+    """Run basic RDS selftest.
+
+    env is a dictionary provided by test.py and is expected to contain:
+      - 'addrs':   list of (ip, port) tuples matching the sockets
+      - 'netns':   list of network namespace names (for sysctl exercises)
+    """
+    addrs = env['addrs']        # [('10.0.0.1', 10000), ('10.0.0.2', 20000)]
+    netns_list = env['netns']   # ['net0', 'net1']
+
+    sockets = [
+        netns_socket(netns_list[0], socket.AF_RDS, socket.SOCK_SEQPACKET),
+        netns_socket(netns_list[1], 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 = dict(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:
+                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:
+                            break
+
+        # exercise net/rds/tcp.c:rds_tcp_sysctl_reset()
+        for net in netns_list:
+            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 ose:
+                nr_error = nr_error + 1
+                if ose.errno == errno.ENOSPC:
+                    # ignore
+                    pass
+
+    print(f"getsockopt(): {nr_success}/{nr_error}")
+
+    # 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")
+            return 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())
+            return 1
+
+        print(f"{sender}/{receiver}: ok")
+
+    print("Success")
+    return 0
diff --git a/tools/testing/selftests/net/rds/test.py b/tools/testing/selftests/net/rds/test.py
index 4a7178d11193..0cb060073f6d 100755
--- a/tools/testing/selftests/net/rds/test.py
+++ b/tools/testing/selftests/net/rds/test.py
@@ -2,65 +2,25 @@
 # 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
+import rds_basic
 
 # Allow utils module to be imported from different directory
 this_dir = os.path.dirname(os.path.realpath(__file__))
 sys.path.append(os.path.join(this_dir, "../"))
 from lib.py.utils 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)
@@ -87,7 +47,7 @@ packet_duplicate=str(args.duplicate)+'%'
 
 ip(f"netns add {net0}")
 ip(f"netns add {net1}")
-ip(f"link add type veth")
+ip("link add type veth")
 
 addrs = [
     # we technically don't need different port numbers, but this will
@@ -137,129 +97,14 @@ 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)
+env = {
+    'addrs': addrs,
+    'netns': [net0, net1],
 }
 
-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}")
+ret = rds_basic.run_test(env)
 
 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)
+sys.exit(ret)
-- 
2.43.0