[PATCH net 0/2] net/sched: flag inconsistent qdisc dumps

[Reshma Sreekumar <reshmaisat@gmail.com>]

tc_dump_qdisc() walks every netdev in the netns and spans many netlink
batches on any busy host.  RTNL is only held while a single batch is filled,
so the device list can change in between and the reply can miss entries --
but nothing under net/sched sets cb->seq, so NLM_F_DUMP_INTR is never raised
and userspace cannot tell a partial listing from a complete one.
rtnl_dump_ifinfo() already pairs for_each_netdev_dump() with
cb->seq = dev_base_seq and nl_dump_check_consistent(); patch 1 does the same
for the qdisc dump.

Patch 2 adds a selftest.  Netlink dumps are driven by the reader, so it
unregisters a device at a known point between two batches instead of racing
against one, and a second case requires the flag to stay clear on an
undisturbed dump.  It fails on net/main and passes with patch 1.

Build coverage: allmodconfig builds clean with W=1 -- vmlinux and all
modules link, no new warnings, none in net/sched.  allyesconfig compiles
clean with W=1, including net/sched/sch_api.o with no diagnostics in
net/sched, but the final LD of vmlinux.o exceeds the memory of the machine
used here, so that link was not completed.

Reshma Sreekumar (2):
  net/sched: flag inconsistent qdisc dumps
  selftests: net: check that a disturbed qdisc dump is flagged

 net/sched/sch_api.c                           |  16 ++-
 tools/testing/selftests/net/Makefile          |   1 +
 .../testing/selftests/net/qdisc_dump_intr.py  | 123 ++++++++++++++++++
 3 files changed, 139 insertions(+), 1 deletion(-)
 create mode 100755 tools/testing/selftests/net/qdisc_dump_intr.py


base-commit: 51b093a7ba27476e1f639455f005e8d2e75390e4
-- 
2.43.0