kernel/linux.git/include/linux/skbuff.h, branch v7.0.12

net: Introduce skb tc depth field to track packet loops

2026-06-09T10:32:26+00:00

[ Upstream commit 98b34f3e8c3492cfc89ff943c9d92b4d52863d1d ] Add a 2-bit per-skb tc depth field to track packet loops across the stack. The previous per-CPU loop counters like MIRRED_NEST_LIMIT assume a single call stack and lose state in two cases: 1) When a packet is queued and reprocessed later (e.g., egress->ingress via backlog), the per-cpu state is gone by the time it is dequeued. 2) With XPS/RPS a packet may arrive on one CPU and be processed on another. A per-skb field solves both by travelling with the packet itself. The field fits in existing padding, using 2 bits that were previously a hole: pahole before(-) and after (+) diff looks like: __u8 slow_gro:1; /* 132: 3 1 */ __u8 csum_not_inet:1; /* 132: 4 1 */ __u8 unreadable:1; /* 132: 5 1 */ + __u8 tc_depth:2; /* 132: 6 1 */ - /* XXX 2 bits hole, try to pack */ /* XXX 1 byte hole, try to pack */ __u16 tc_index; /* 134 2 */ There used to be a ttl field which was removed as part of tc_verd in commit aec745e2c520 ("net-tc: remove unused tc_verd fields"). It was already unused by that time, due to remove earlier in commit c19ae86a510c ("tc: remove unused redirect ttl"). The first user of this field is netem, which increments tc_depth on duplicated packets before re-enqueueing them at the root qdisc. On re-entry, netem skips duplication for any skb with tc_depth already set, bounding recursion to a single level regardless of tree topology. The other user is mirred which increments it on each pass and limits to depth to MIRRED_DEFER_LIMIT (3). The new field was called ttl in earlier versions of this patch but renamed to tc_depth to avoid confusion with IP ttl. Note (looking at you Sashiko! Dont ignore me and continue bringing this up): 1. Since both mirred and netem utilize the same 2-bit tc_depth field it is possible when netem and mirred are used together that netem qdisc to skip the duplication step. This is a known trade-off, as a 2-bit field cannot independently track both features' recursion depths and it is not considered sane to have a setup that addresses both features on at the same time. 2. skb_scrub_packet does not clear tc_depth. This means a packet's loop history is preserved even across namespaces. While this might be restrictive for some topologies, it is also design intent to provide robustness against loops across namespaces. Reviewed-by: Stephen Hemminger Signed-off-by: Jamal Hadi Salim Link: https://patch.msgid.link/20260525122556.973584-2-jhs@mojatatu.com Signed-off-by: Paolo Abeni Stable-dep-of: db875221ab08 ("net/sched: Fix ethx:ingress -> ethy:egress -> ethx:ingress mirred loop") Signed-off-by: Sasha Levin

netdevsim: fix build if SKB_EXTENSIONS=n

2026-03-27T03:08:58+00:00

__skb_ext_put() is not declared if SKB_EXTENSIONS is not enabled, which causes a build error: drivers/net/netdevsim/netdev.c: In function 'nsim_forward_skb': drivers/net/netdevsim/netdev.c:114:25: error: implicit declaration of function '__skb_ext_put'; did you mean 'skb_ext_put'? [-Werror=implicit-function-declaration] 114 | __skb_ext_put(psp_ext); | ^~~~~~~~~~~~~ | skb_ext_put cc1: some warnings being treated as errors Add a stub to fix the build. Fixes: 7d9351435ebb ("netdevsim: drop PSP ext ref on forward failure") Signed-off-by: Qingfang Deng Link: https://patch.msgid.link/20260324140857.783-1-dqfext@gmail.com Signed-off-by: Jakub Kicinski

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

2026-02-05T17:54:08+00:00

Cross-merge networking fixes after downstream PR (net-6.19-rc9). No adjacent changes, conflicts: drivers/net/ethernet/spacemit/k1_emac.c 3125fc1701694 ("net: spacemit: k1-emac: fix jumbo frame support") f66086798f91f ("net: spacemit: Remove broken flow control support") https://lore.kernel.org/aYIysFIE9ooavWia@sirena.org.uk Signed-off-by: Jakub Kicinski

can: add CAN skb extension infrastructure

2026-02-05T10:58:39+00:00

To remove the private CAN bus skb headroom infrastructure 8 bytes need to be stored in the skb. The skb extensions are a common pattern and an easy and efficient way to hold private data travelling along with the skb. We only need the skb_ext_add() and skb_ext_find() functions to allocate and access CAN specific content as the skb helpers to copy/clone/free skbs automatically take care of skb extensions and their final removal. This patch introduces the complete CAN skb extensions infrastructure: - add struct can_skb_ext in new file include/net/can.h - add include/net/can.h in MAINTAINERS - add SKB_EXT_CAN to skbuff.c and skbuff.h - select SKB_EXTENSIONS in Kconfig when CONFIG_CAN is enabled - check for existing CAN skb extensions in can_rcv() in af_can.c - add CAN skb extensions allocation at every skb_alloc() location - duplicate the skb extensions if cloning outgoing skbs (framelen/gw_hops) - introduce can_skb_ext_add() and can_skb_ext_find() helpers The patch also corrects an indention issue in the original code from 2018: Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202602010426.PnGrYAk3-lkp@intel.com/ Signed-off-by: Marc Kleine-Budde Signed-off-by: Oliver Hartkopp Link: https://patch.msgid.link/20260201-can_skb_ext-v8-2-3635d790fe8b@hartkopp.net Signed-off-by: Paolo Abeni

net: add a debug check in __skb_push()

2026-02-03T01:24:14+00:00

Add the following check, to detect bugs sooner for CONFIG_DEBUG_NET=y builds. DEBUG_NET_WARN_ON_ONCE(skb->data < skb->head); Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260130160253.2936789-1-edumazet@google.com Signed-off-by: Jakub Kicinski

net: add skb_header_pointer_careful() helper

2026-01-30T02:25:22+00:00

This variant of skb_header_pointer() should be used in contexts where @offset argument is user-controlled and could be negative. Negative offsets are supported, as long as the zone starts between skb->head and skb->data. Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260128141539.3404400-2-edumazet@google.com Signed-off-by: Jakub Kicinski

net: always inline __skb_incr_checksum_unnecessary()

2026-01-22T03:28:32+00:00

clang does not inline this helper in GRO fast path. We can save space and cpu cycles. $ scripts/bloat-o-meter -t vmlinux.0 vmlinux.1 add/remove: 0/2 grow/shrink: 2/0 up/down: 156/-218 (-62) Function old new delta tcp6_gro_complete 227 311 +84 tcp4_gro_complete 325 397 +72 __pfx___skb_incr_checksum_unnecessary 32 - -32 __skb_incr_checksum_unnecessary 186 - -186 Total: Before=22592724, After=22592662, chg -0.00% Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260120164903.1912995-2-edumazet@google.com Signed-off-by: Jakub Kicinski

netmem, devmem, tcp: access pp fields through @desc in net_iov

2025-11-28T01:41:51+00:00

Convert all the legacy code directly accessing the pp fields in net_iov to access them through @desc in net_iov. Signed-off-by: Byungchul Park Signed-off-by: Jakub Kicinski

net: Helper to move packet data and metadata after skb_push/pull

2025-11-10T18:52:31+00:00

Lay groundwork for fixing BPF helpers available to TC(X) programs. When skb_push() or skb_pull() is called in a TC(X) ingress BPF program, the skb metadata must be kept in front of the MAC header. Otherwise, BPF programs using the __sk_buff->data_meta pseudo-pointer lose access to it. Introduce a helper that moves both metadata and a specified number of packet data bytes together, suitable as a drop-in replacement for memmove(). Signed-off-by: Jakub Sitnicki Signed-off-by: Martin KaFai Lau Link: https://patch.msgid.link/20251105-skb-meta-rx-path-v4-1-5ceb08a9b37b@cloudflare.com

net: datagram: introduce datagram_poll_queue for custom receive queues

2025-10-23T13:46:04+00:00

Some protocols using TCP encapsulation (e.g., espintcp, openvpn) deliver userspace-bound packets through a custom skb queue rather than the standard sk_receive_queue. Introduce datagram_poll_queue that accepts an explicit receive queue, and convert datagram_poll into a wrapper around datagram_poll_queue. This allows protocols with custom skb queues to reuse the core polling logic without relying on sk_receive_queue. Cc: Sabrina Dubroca Cc: Antonio Quartulli Signed-off-by: Ralf Lici Reviewed-by: Sabrina Dubroca Reviewed-by: Antonio Quartulli Link: https://patch.msgid.link/20251021100942.195010-2-ralf@mandelbit.com Signed-off-by: Paolo Abeni