linux.git/drivers/net/tun.c, branch v7.2

Revert "tun/tap: add ptr_ring consume helper with netdev queue wakeup"

2026-07-30T00:12:27+00:00

This reverts commit d4c22d70d7253dd727c71484c58d504f6c630343.

There is no netdev queue left to wake after reverting
commit 1d6e569b7d0c ("tun/tap & vhost-net: avoid ptr_ring tail-drop
when a qdisc is present").

Signed-off-by: Simon Schippers 
Acked-by: Michael S. Tsirkin 
Link: https://patch.msgid.link/20260728092240.250257-5-simon.schippers@tu-dortmund.de
Signed-off-by: Jakub Kicinski

Revert "vhost-net: wake queue of tun/tap after ptr_ring consume"

2026-07-30T00:12:27+00:00

This reverts commit baf808fe4fcd35767ab732b4ab2ea80dabfd97a6.

There is no netdev queue left to wake after reverting
commit 1d6e569b7d0c ("tun/tap & vhost-net: avoid ptr_ring tail-drop
when a qdisc is present").

Signed-off-by: Simon Schippers 
Acked-by: Michael S. Tsirkin 
Link: https://patch.msgid.link/20260728092240.250257-4-simon.schippers@tu-dortmund.de
Signed-off-by: Jakub Kicinski

Revert "tun/tap & vhost-net: avoid ptr_ring tail-drop when a qdisc is present"

2026-07-30T00:12:26+00:00

This reverts commit 1d6e569b7d0c0b2736636749e4be0a27f3cefcb3.

The commit stops the netdev queue when the ptr_ring is full instead of
dropping the packet. My own tests showed no relevant regression, but on
Brett Sheffield's librecast testbed an IPv6 multicast testcase got
slower. With 8 iperf3 TCP threads sending, the throughput dropped from
13.5 Gbit/s to 9.13 Gbit/s.

Reported-by: Brett Sheffield 
Closes: https://lore.kernel.org/netdev/akVnoOYQOrt8k-Gu@karahi.librecast.net/
Signed-off-by: Simon Schippers 
Acked-by: Michael S. Tsirkin 
Link: https://patch.msgid.link/20260728092240.250257-2-simon.schippers@tu-dortmund.de
Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2026-06-11T21:33:35+00:00

Cross-merge networking fixes after downstream PR (net-7.1-rc8).

Conflicts:

drivers/net/ethernet/wangxun/txgbe/txgbe_aml.c
  f67aead16e85 ("net: txgbe: rework service event handling")
  57d39faed4c9 ("net: txgbe: improve functions of AML 40G devices")

net/rds/info.c
  512db8267b73 ("rds: mark snapshot pages dirty in rds_info_getsockopt()")
  6e94eeb2a2a6 ("rds: convert to getsockopt_iter")

Adjacent changes:

include/net/sock.h
  1ee90b77b727 ("net: guard timestamp cmsgs to real error queue skbs")
  f0de88303d5e ("net: make is_skb_wmem() available to modules")

Signed-off-by: Jakub Kicinski

tun: zero the whole vnet header in tun_put_user()

2026-06-10T01:33:18+00:00

tun_put_user() declares an on-stack struct virtio_net_hdr_v1_hash_tunnel
without zeroing it. For a non-tunnel skb, virtio_net_hdr_tnl_from_skb()
only initializes the first 10 bytes (sizeof(struct virtio_net_hdr)),
leaving bytes 10..23 (num_buffers and the hash/tunnel fields) as stack
garbage.

An unprivileged user can set the vnet header size to 24 with
TUNSETVNETHDRSZ, so __tun_vnet_hdr_put() copies all 24 bytes of the
partially-initialized struct to userspace, leaking 14 bytes of kernel
stack on every read of a non-tunnel packet.

Fix it the same way tun_get_user() already does by zeroing the whole
header right after declaration.

Fixes: 288f30435132 ("tun: enable gso over UDP tunnel support.")
Reported-by: Weiming Shi 
Signed-off-by: Xiang Mei 
Reviewed-by: Willem de Bruijn 
Link: https://patch.msgid.link/20260607054428.3050243-1-xmei5@asu.edu
Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2026-05-28T21:02:21+00:00

Cross-merge networking fixes after downstream PR (net-7.1-rc6).

Conflicts:

drivers/net/phy/air_en8811h.c
  d895767c33781 ("net: phy: air_en8811h: add AN8811HB MCU assert/deassert support")
  dddfadd75197e ("net: phy: Add Airoha phy library for shared code")
  5226bb6634cdf ("net: phy: air_phy_lib: Factorize BuckPBus register accessors")
  e08f0ea6daf2e ("net: phy: Rename Airoha common BuckPBus register accessors")

net/sched/sch_netem.c
  a2f6ed7b4873 ("net/sched: netem: add per-impairment extended statistics")
  9552b11e3eda ("net/sched: fix packet loop on netem when duplicate is on")

Adjacent changes:

drivers/dpll/zl3073x/core.c
  c1224569cef0 ("dpll: zl3073x: make frequency monitor a per-device attribute")
  54e65df8cf18 ("dpll: zl3073x: report FFO as DPLL vs input reference offset")

net/iucv/af_iucv.c
  347fdd4df85f ("af_iucv: convert to getsockopt_iter")
  3589d20a666c ("net/iucv: fix locking in .getsockopt")

Signed-off-by: Jakub Kicinski

tun: free page on build_skb failure in tun_xdp_one()

2026-05-22T17:10:07+00:00

When build_skb() fails in tun_xdp_one(), the function sets ret to
-ENOMEM and jumps to the out label, which returns without freeing the
page that vhost_net_build_xdp() allocated for the frame. As with the
short-frame rejection path, tun_sendmsg() discards the per-buffer error
and still returns total_len, so vhost_tx_batch() takes the success path
and never frees the page. Each build_skb() failure in a batch leaks one
page-frag chunk.

Free the page before taking the error path, matching the put_page() the
other error exits of tun_xdp_one() already perform.

Fixes: 043d222f93ab ("tuntap: accept an array of XDP buffs through sendmsg()")
Reported-by: Xiang Mei 
Signed-off-by: Weiming Shi 
Reviewed-by: Dongli Zhang 
Reviewed-by: Willem de Bruijn 
Link: https://patch.msgid.link/20260521163312.1479805-2-bestswngs@gmail.com
Signed-off-by: Jakub Kicinski

tun: free page on short-frame rejection in tun_xdp_one()

2026-05-22T14:56:27+00:00

tun_xdp_one() returns -EINVAL on a frame shorter than ETH_HLEN without
freeing the page that vhost_net_build_xdp() allocated for it.
tun_sendmsg() discards that -EINVAL and still returns total_len, so
vhost_tx_batch() takes the success path and never frees the page; each
short frame in a batch leaks one page-frag chunk.

A local process that can open /dev/net/tun and /dev/vhost-net can hit
this path: it attaches a tun/tap device as the vhost-net backend and
feeds TX descriptors whose length minus the virtio-net header is below
ETH_HLEN. Each kick leaks the page-frag chunks for that batch, and a
tight submission loop exhausts host memory and triggers an OOM panic.
Free the page before returning -EINVAL, matching the XDP-program error
path in the same function.

Fixes: 049584807f1d ("tun: add missing verification for short frame")
Reported-by: Xiang Mei 
Signed-off-by: Weiming Shi 
Reviewed-by: Dongli Zhang 
Reviewed-by: Willem de Bruijn 
Link: https://patch.msgid.link/20260520160020.375349-2-bestswngs@gmail.com
Signed-off-by: Jakub Kicinski

tun/tap & vhost-net: avoid ptr_ring tail-drop when a qdisc is present

2026-05-14T00:52:55+00:00

This commit prevents tail-drop when a qdisc is present and the ptr_ring
becomes full. Once the ring reaches capacity after a produce attempt,
the netdev queue is stopped instead of dropping subsequent packets.
If no qdisc is present, the previous tail-drop behavior is preserved.

If producing an entry fails anyway due to a race, tun_net_xmit() drops
the packet. Such races are expected because LLTX is enabled and the
transmit path operates without the usual locking.

The __tun_wake_queue() function of the consumer races with the producer
for waking/stopping the netdev queue, which could result in a stalled
queue. Therefore, an smp_mb__after_atomic() is introduced that pairs
with the smp_mb() of the consumer. It follows the principle of store
buffering described in tools/memory-model/Documentation/recipes.txt:

- The producer in tun_net_xmit() first sets __QUEUE_STATE_DRV_XOFF,
  followed by an smp_mb__after_atomic() (= smp_mb()), and then reads the
  ring with __ptr_ring_check_produce().

- The consumer in __tun_wake_queue() first writes zero to the ring in
  __ptr_ring_consume(), followed by an smp_mb(), and then reads the queue
  status with netif_tx_queue_stopped().

=> Following the aforementioned principle, it is impossible for the
   producer to see a full ring (and therefore not wake the queue on the
   re-check) while the consumer simultaneously fails to see a stopped
   queue (and therefore also does not wake it).

Benchmarks:
The benchmarks show a slight regression in raw transmission performance
when using two sending threads. Packet loss also occurs only in the
two-thread sending case; no packet loss was observed with a single
sending thread.

Test setup:
AMD Ryzen 5 5600X at 4.3 GHz, 3200 MHz RAM, isolated QEMU threads;
Average over 50 runs @ 100,000,000 packets. SRSO and spectre v2
mitigations disabled.

Note for tap+vhost-net:
XDP drop program active in VM -> ~2.5x faster; slower for tap due to
more syscalls (high utilization of entry_SYSRETQ_unsafe_stack in perf)

+--------------------------+--------------+----------------+----------+
| 1 thread                 | Stock        | Patched with   | diff     |
| sending                  |              | fq_codel qdisc |          |
+------------+-------------+--------------+----------------+----------+
| TAP        | Received    | 1.132 Mpps   | 1.123 Mpps     | -0.8%    |
|            +-------------+--------------+----------------+----------+
|            | Lost/s      | 3.765 Mpps   | 0 pps          |          |
+------------+-------------+--------------+----------------+----------+
| TAP        | Received    | 3.857 Mpps   | 3.901 Mpps     | +1.1%    |
|            +-------------+--------------+----------------+----------+
| +vhost-net | Lost/s      | 0.802 Mpps   | 0 pps          |          |
+------------+-------------+--------------+----------------+----------+

+--------------------------+--------------+----------------+----------+
| 2 threads                | Stock        | Patched with   | diff     |
| sending                  |              | fq_codel qdisc |          |
+------------+-------------+--------------+----------------+----------+
| TAP        | Received    | 1.115 Mpps   | 1.081 Mpps     | -3.0%    |
|            +-------------+--------------+----------------+----------+
|            | Lost/s      | 8.490 Mpps   | 391 pps        |          |
+------------+-------------+--------------+----------------+----------+
| TAP        | Received    | 3.664 Mpps   | 3.555 Mpps     | -3.0%    |
|            +-------------+--------------+----------------+----------+
| +vhost-net | Lost/s      | 5.330 Mpps   | 938 pps        |          |
+------------+-------------+--------------+----------------+----------+

Co-developed-by: Tim Gebauer 
Signed-off-by: Tim Gebauer 
Signed-off-by: Simon Schippers 
Acked-by: Michael S. Tsirkin 
Link: https://patch.msgid.link/20260510151529.43895-5-simon.schippers@tu-dortmund.de
Signed-off-by: Jakub Kicinski

vhost-net: wake queue of tun/tap after ptr_ring consume

2026-05-14T00:52:55+00:00

Add tun_wake_queue() to tun.c and export it for use by vhost-net. The
function validates that the file belongs to a tun/tap device and that
the tfile exists, dereferences the tun_struct under RCU, and delegates
to __tun_wake_queue().

vhost_net_buf_produce() now calls tun_wake_queue() after a successful
batched consume of the ring to allow the netdev subqueue to be woken up.
The point is to allow the queue to be stopped when it gets full, which
is required for traffic shaping - implemented by the following
"avoid ptr_ring tail-drop when a qdisc is present".

Without the corresponding queue stopping, this patch alone causes no
throughput regression for a tap+vhost-net setup sending to a qemu VM:
3.857 Mpps to 3.891 Mpps.

Details: AMD Ryzen 5 5600X at 4.3 GHz, 3200 MHz RAM, isolated QEMU
threads, XDP drop program active in VM, pktgen sender; Avg over
50 runs @ 100,000,000 packets. SRSO and spectre v2 mitigations disabled.

Co-developed-by: Tim Gebauer 
Signed-off-by: Tim Gebauer 
Signed-off-by: Simon Schippers 
Acked-by: Michael S. Tsirkin 
Link: https://patch.msgid.link/20260510151529.43895-3-simon.schippers@tu-dortmund.de
Signed-off-by: Jakub Kicinski