linux.git/include/linux/netpoll.h, branch v7.2-rc1

netconsole: do not dequeue pooled skbs that cannot satisfy len

2026-06-09T10:42:20+00:00

find_skb() falls back to np->skb_pool when the GFP_ATOMIC alloc_skb()
fails. The pool is refilled by refill_skbs(), which always allocates
buffers of MAX_SKB_SIZE (ethhdr + iphdr + udphdr + MAX_UDP_CHUNK ==
1502 bytes).

netconsole, however, computes the requested length dynamically as

        total_len + np->dev->needed_tailroom

If the egress device declares a non-zero needed_tailroom (e.g. some
tunnel or hardware accelerator devices), the required length can exceed
MAX_SKB_SIZE. The pooled skb is then handed back to the caller, which
immediately performs skb_put(skb, len), trips the tail > end check, and
triggers skb_over_panic().

Leave the normal alloc_skb(len, GFP_ATOMIC) path untouched -- the slab
allocator can still satisfy oversized requests when memory is available,
so senders to devices with non-zero needed_tailroom keep working in the
common case. Only the pool fallback is gated: when alloc_skb() failed
and len exceeds the pool buffer size, skip the skb_dequeue() instead of
burning a pre-allocated skb on a request that would later trip
skb_over_panic(). Reserving pool entries for requests they can actually
satisfy also keeps the panic path, which depends on the pool being
primed, intact.

When that drop happens, emit a rate-limited net_warn() so the user
notices that netconsole is unable to push messages on the egress device.
The warn is skipped under in_nmi() for the same reason schedule_work()
is: printk machinery taken by net_warn_ratelimited() is not NMI-safe and
would risk recursing into the same nbcon console we are servicing.

MAX_SKB_SIZE / MAX_UDP_CHUNK were private to net/core/netpoll.c. Move
them to include/linux/netpoll.h so netconsole can reference the same
definition that refill_skbs() uses, keeping the two in sync by
construction. The header now pulls in  and 
explicitly so MAX_SKB_SIZE remains self-contained for any future user.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20260604-netcons_fix_before_move-v3-2-ab055b3a6aa5@debian.org
Signed-off-by: Paolo Abeni

netconsole: move find_skb() from netpoll

2026-05-14T01:09:13+00:00

find_skb() is the netconsole-specific entry into the netpoll skb
pool: every other netpoll consumer (bonding, team, vlan, bridge,
macvlan, dsa) builds its own sk_buff and never touches the pool.
With netpoll_send_udp() (its only caller) now living in netconsole,
find_skb() can join it.

Move find_skb() into drivers/net/netconsole.c as a file-static
helper, drop EXPORT_SYMBOL_GPL(find_skb) and remove its prototype
from include/linux/netpoll.h. find_skb() drains TX completions via
netpoll_zap_completion_queue(), which is already exported in the
NETDEV_INTERNAL namespace, so netconsole picks up
MODULE_IMPORT_NS("NETDEV_INTERNAL") to consume it.

The skb pool's lifecycle (np->skb_pool, np->refill_wq, refill_skbs(),
refill_skbs_work_handler(), skb_pool_flush()) stays in netpoll: it
is initialised in __netpoll_setup() and torn down in
__netpoll_cleanup(), both of which remain netpoll's responsibility.
The refill work queued via schedule_work(&np->refill_wq) from the
moved find_skb() runs refill_skbs_work_handler() in netpoll without
any further plumbing.

This is pure code motion: the function body is unchanged and its
sole caller (netpoll_send_udp(), already moved by an earlier patch)
keeps invoking it the same way. Pre-existing concerns about
find_skb() running from NMI/printk context (zap_completion_queue()
re-entry, skb_pool spinlocks, GFP_ATOMIC allocation, fallback skb
sizing vs. MAX_SKB_SIZE, PREEMPT_RT semantics of __kfree_skb()) are
inherited as-is and are not addressed here; they predate this
series and are out of scope. Fixing them is left for follow-up
work.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20260512-netconsole_split-v2-9-1191d14ad66d@debian.org
Signed-off-by: Jakub Kicinski

netpoll: rename and export netpoll_zap_completion_queue()

2026-05-14T01:09:13+00:00

zap_completion_queue() drains the per-CPU softnet completion queue.
Rename it with the netpoll_ prefix shared by the rest of the
subsystem's public API, and promote it from file-static to
EXPORT_SYMBOL_NS_GPL in the NETDEV_INTERNAL namespace so the upcoming
netconsole-side find_skb() can call it once the function moves out.
A forward declaration is added to include/linux/netpoll.h, and the
old file-static forward declaration is dropped.

No functional change.

Suggested-by: Jakub Kicinski 
Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20260512-netconsole_split-v2-8-1191d14ad66d@debian.org
Signed-off-by: Jakub Kicinski

netconsole: move netpoll_udp_checksum() from netpoll

2026-05-14T01:09:13+00:00

netpoll_udp_checksum() computes the UDP checksum for netconsole's
packets. Move it into drivers/net/netconsole.c as a file-static
helper; drop its EXPORT_SYMBOL_GPL and remove the prototype from
include/linux/netpoll.h.

This was the last csum_ipv6_magic() consumer in net/core/netpoll.c,
so drop the now-stale  include there. Pull it
into netconsole.c so the moved code keeps building.

It was also the last udp_hdr() consumer in net/core/netpoll.c. The
file no longer needs anything from  (the UDP socket-layer
helpers); MAX_SKB_SIZE only needs struct udphdr, which is provided
by the lighter . Swap the include accordingly.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20260512-netconsole_split-v2-7-1191d14ad66d@debian.org
Signed-off-by: Jakub Kicinski

netconsole: move push_udp() from netpoll

2026-05-14T01:09:13+00:00

push_udp() builds the UDP header (and triggers the checksum) for
netconsole's UDP packets. Move it into drivers/net/netconsole.c as
a file-static helper; drop its EXPORT_SYMBOL_GPL and remove the
prototype from include/linux/netpoll.h.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20260512-netconsole_split-v2-6-1191d14ad66d@debian.org
Signed-off-by: Jakub Kicinski

netconsole: move push_eth() from netpoll

2026-05-14T01:09:12+00:00

push_eth() builds the Ethernet header for netconsole's UDP packets.
Move it into drivers/net/netconsole.c as a file-static helper; drop
its EXPORT_SYMBOL_GPL and remove the prototype from
include/linux/netpoll.h.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20260512-netconsole_split-v2-5-1191d14ad66d@debian.org
Signed-off-by: Jakub Kicinski

netconsole: move push_ipv4() from netpoll

2026-05-14T01:09:12+00:00

push_ipv4() builds the IPv4 header for netconsole's UDP packets.
Move it into drivers/net/netconsole.c as a file-static helper; drop
its EXPORT_SYMBOL_GPL and remove the prototype from
include/linux/netpoll.h.

put_unaligned() is no longer used in net/core/netpoll.c, so drop
the now-stale  include from there. Pull it into
netconsole.c so the moved code keeps building.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20260512-netconsole_split-v2-4-1191d14ad66d@debian.org
Signed-off-by: Jakub Kicinski

netconsole: move push_ipv6() from netpoll

2026-05-14T01:09:12+00:00

push_ipv6() builds the IPv6 header for netconsole's UDP packets.
Its only caller, netpoll_send_udp(), now lives in netconsole, so
the helper can move there as a file-static function. Drop its
EXPORT_SYMBOL_GPL and remove the prototype from
include/linux/netpoll.h.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20260512-netconsole_split-v2-3-1191d14ad66d@debian.org
Signed-off-by: Jakub Kicinski

netconsole: move netpoll_send_udp() from netpoll

2026-05-14T01:09:12+00:00

Move netpoll_send_udp() from net/core/netpoll.c into
drivers/net/netconsole.c as a static helper, drop EXPORT_SYMBOL(),
and remove the prototype from include/linux/netpoll.h.

netconsole was the only in-tree caller of this entry point. Every
other netpoll consumer (bonding, team, vlan, bridge, macvlan, dsa)
already builds its own sk_buff and hands it to netpoll_send_skb(),
so the netpoll send-side interface is now skb-only.

The helpers it depends on (find_skb(), push_ipv6(), push_ipv4(),
push_udp(), push_eth(), netpoll_udp_checksum()) were exposed in
the previous patches and stay in net/core/netpoll.c for now.
Subsequent patches move each of them into netconsole one at a time
and drop the corresponding EXPORT_SYMBOL_GPL.

Pull ,  and  into netconsole.c
so the moved code can name the header structures.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20260512-netconsole_split-v2-2-1191d14ad66d@debian.org
Signed-off-by: Jakub Kicinski

netpoll: expose UDP packet builder helpers for netconsole

2026-05-14T01:09:12+00:00

Promote each from file-static to EXPORT_SYMBOL_GPL and forward-
declare them in include/linux/netpoll.h so netconsole can call
them once netpoll_send_udp() moves out.

These exports are kept until the end of the series, when
al of them move into netconsole.

No functional change.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20260512-netconsole_split-v2-1-1191d14ad66d@debian.org
Signed-off-by: Jakub Kicinski