Add a test for NLM_F_DUMP_INTR on RTM_GETQDISC. A qdisc dump spans several netlink batches once a few devices carry a full set of qdiscs, and RTNL is only held while a single batch is filled, so the device list can change in between and entries can be missed.
Netlink dumps are driven by the reader, so rather than racing against a dump the test unregisters a device at a known point: it receives the first batch, unregisters a dummy, then drains the rest. This is deterministic -- one flagged message, every run. A second case dumps without disturbing anything and requires that the flag stays clear, so the test cannot be satisfied by a kernel that raises it unconditionally. Four dummy devices with mq + 16 fq + clsact each, read with a 4KiB buffer, give 12 batches and run in about a second. The test skips if dummy, mq, fq or clsact are unavailable. Signed-off-by: Reshma Sreekumar <[email protected]> --- tools/testing/selftests/net/Makefile | 1 + .../testing/selftests/net/qdisc_dump_intr.py | 123 ++++++++++++++++++ 2 files changed, 124 insertions(+) create mode 100755 tools/testing/selftests/net/qdisc_dump_intr.py diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile index 708d960ae..769ee26ae 100644 --- a/tools/testing/selftests/net/Makefile +++ b/tools/testing/selftests/net/Makefile @@ -72,6 +72,7 @@ TEST_PROGS := \ pmtu.sh \ protodown.sh \ psock_snd.sh \ + qdisc_dump_intr.py \ reuseaddr_ports_exhausted.sh \ reuseport_addr_any.sh \ route_hint.sh \ diff --git a/tools/testing/selftests/net/qdisc_dump_intr.py b/tools/testing/selftests/net/qdisc_dump_intr.py new file mode 100755 index 000000000..9623847f4 --- /dev/null +++ b/tools/testing/selftests/net/qdisc_dump_intr.py @@ -0,0 +1,123 @@ +#!/usr/bin/env python3 +# SPDX-License-Identifier: GPL-2.0 + +""" +Check that a qdisc dump disturbed by a device unregister reports +NLM_F_DUMP_INTR. + +tc_dump_qdisc() walks every netdev in the netns and spans several netlink +batches once there are more than a handful of qdiscs. RTNL is only held +while a single batch is filled, so the device list can change in between and +the reply can miss entries. Netlink dumps are driven by the reader, so this +test unregisters a device at a known point between two batches rather than +racing against one. +""" + +import socket +import struct + +from lib.py import ksft_run, ksft_exit, ksft_true, ksft_pr, KsftSkipEx +from lib.py import CmdExitFailure, NetNS, NetNSEnter, ip, tc + +NETLINK_ROUTE = 0 +RTM_NEWQDISC = 36 +RTM_GETQDISC = 38 +NLMSG_DONE = 3 +NLM_F_REQUEST = 0x001 +NLM_F_DUMP = 0x300 +NLM_F_DUMP_INTR = 0x010 + +NLMSGHDR = "=IHHII" +TCMSG_LEN = 20 # struct tcmsg + +# tc parses handles as hex; 64: keeps the mq root clear of the fq children +MQ_HANDLE = "64" +CHANNELS = 16 # fq children per device +NDEVS = 4 # 4 * (mq + 16 fq + clsact) is several batches worth +BUFSZ = 4096 # small recv buffer keeps the kernel's batches small + + +def _setup(): + """Devices carrying enough qdiscs that a dump has to paginate.""" + try: + for i in range(NDEVS): + ip(f"link add d{i} numtxqueues {CHANNELS} type dummy") + ip(f"link set d{i} up") + tc(f"qdisc replace dev d{i} root handle {MQ_HANDLE}: mq") + for q in range(1, CHANNELS + 1): + tc(f"qdisc replace dev d{i} parent {MQ_HANDLE}:{q:x} " + f"handle {q:x}: fq") + tc(f"qdisc replace dev d{i} clsact") + except CmdExitFailure as exc: + raise KsftSkipEx("dummy, mq, fq or clsact unavailable") from exc + + +def _dump(between_batches=None): + """ + Walk an RTM_GETQDISC dump one batch at a time, optionally running + `between_batches` after the first batch. Returns (batches, qdiscs, + messages carrying NLM_F_DUMP_INTR). + """ + sk = socket.socket(socket.AF_NETLINK, socket.SOCK_RAW, NETLINK_ROUTE) + try: + sk.bind((0, 0)) + hdr = struct.pack(NLMSGHDR, struct.calcsize(NLMSGHDR) + TCMSG_LEN, + RTM_GETQDISC, NLM_F_REQUEST | NLM_F_DUMP, 1, 0) + sk.send(hdr + bytes(TCMSG_LEN)) + + batches = qdiscs = intr = 0 + done = False + while not done: + buf = sk.recv(BUFSZ) + batches += 1 + off = 0 + while off + 16 <= len(buf): + mlen, mtype, flags = struct.unpack_from("=IHH", buf, off) + if mlen < 16: + break + if flags & NLM_F_DUMP_INTR: + intr += 1 + if mtype == NLMSG_DONE: + done = True + elif mtype == RTM_NEWQDISC: + qdiscs += 1 + off += (mlen + 3) & ~3 + if batches == 1 and not done and between_batches: + between_batches() + return batches, qdiscs, intr + finally: + sk.close() + + +def dump_intr_on_unregister() -> None: + """Unregistering a device mid-dump must raise NLM_F_DUMP_INTR.""" + ip("link add victim type dummy") + + batches, qdiscs, intr = _dump(lambda: ip("link del victim")) + + ksft_pr(f"{batches} batches, {qdiscs} qdiscs, {intr} flagged messages") + ksft_true(batches > 1, "dump did not paginate, nothing to disturb") + ksft_true(intr > 0, + "NLM_F_DUMP_INTR not set although a device was unregistered " + "while the dump was in flight") + + +def dump_intr_absent_when_stable() -> None: + """An undisturbed dump must not raise NLM_F_DUMP_INTR.""" + batches, qdiscs, intr = _dump() + + ksft_pr(f"{batches} batches, {qdiscs} qdiscs, {intr} flagged messages") + ksft_true(batches > 1, "dump did not paginate, test is not meaningful") + ksft_true(intr == 0, "NLM_F_DUMP_INTR set on an undisturbed dump") + + +def main() -> None: + with NetNS() as ns: + with NetNSEnter(str(ns)): + _setup() + ksft_run(globs=globals(), case_pfx={"dump_"}) + ksft_exit() + + +if __name__ == "__main__": + main() -- 2.43.0
