From: Fernando Fernandez Mancera <fmancera@suse.de>
To: netdev@vger.kernel.org
Cc: Fernando Fernandez Mancera <fmancera@suse.de>,
davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com, horms@kernel.org, dsahern@kernel.org,
rbm@suse.com, linux-kernel@vger.kernel.org
Subject: [PATCH 00/11 net-next v5] Convert CONFIG_IPV6 to built-in and remove stubs
Date: Wed, 25 Mar 2026 13:08:41 +0100 [thread overview]
Message-ID: <20260325120928.15848-1-fmancera@suse.de> (raw)
Historically, the Linux kernel has supported compiling the IPv6 stack as
a loadable module. While this made sense in the early days of IPv6
adoption, modern deployments and distributions overwhelmingly either
build IPv6 directly into the kernel (CONFIG_IPV6=y) or disable it
entirely (CONFIG_IPV6=n). The modular IPv6 use-case offers image size
and memory savings for specific setups, this benefit is outweighed by
the architectural burden it imposes on the subsystems on implementation
and maintenance.
In addition, most of the distributions are already using CONFIG_IPV6=y
by default [1], including openWRT [2] and Android gki_defconfig [3]. So
this won't have an impact on them. The most impacted architecture would
probably be arm64 as their default config is still using CONFIG_IPV6=m.
To allow core networking, BPF, Netfilter, and various device drivers to
safely interact with a potentially unloaded IPv6 module, the kernel
relies on indirect call structures like ipv6_stub, ipv6_bpf_stub, and
nf_ipv6_ops, along with dynamic RCU registrations for things like ICMPv6
senders.
This patch series addresses this by changing CONFIG_IPV6 from a tristate
to a boolean, enforcing that IPv6 is either built-in or disabled. This
allows us to completely rip out the stub infrastructures and safely
replace them with direct function calls.
The bloat-o-meter report the following results for m68k, arm64, x86_64
defconfig.
m68k (keep on mind that CONFIG_IPV6 is disabled now):
add/remove: 65/938 grow/shrink: 36/254 up/down: 3022/-49692 (-46670)
arm64:
add/remove: 1251/265 grow/shrink: 81/46 up/down: 448740/-71519 (377221)
x86_64:
add/remove: 62/98 grow/shrink: 10/39 up/down: 2497/-4357 (-1860)
Considering that each new kernel release increases sizes by 30-40KiB on
average, this size increase isn't a huge jump for the distributions that
are still using CONFIG_IPV6=m. For the ones that are already using
CONFIG_IPV6=y, the size is reduced actually.
All the patches has been independently build tested. With allmodconfig
and allmodconfig + CONFIG_IPV6=n. In addition, net selftest has been run
against them on virtme-ng.
The series applied as a whole as been tested with allyesconfig and also
allyesconfig + CONFIG_IPV6=n but not all patches has been independently
tested this way.
[1] https://github.com/nyrahul/linux-kernel-configs
[2] https://github.com/openwrt/openwrt/commit/832e7b817221d288df76b763ca12c585365db5d8
[3] https://android.googlesource.com/kernel/common/+/refs/heads/android-mainline/arch/arm64/configs/gki_defconfig
Changes:
v5:
Patch 3: drop all IS_BUILTIN(IPV6) on files compiled only when IPV6=y
Patch 5: drop the skb in ip6_fragment() before returning -EAFNOSUPPORT
Patch 4, 6, 10: drop ipv6_get_nd_tbl() and use &nd_tbl directly always guarded by IS_ENABLED(CONFIG_IPV6) check
v4: https://lore.kernel.org/netdev/20260320185649.5411-1-fmancera@suse.de/
Patch 2: new patch introduced on this revision
Patch 3: drop some IS_BUILTIN(IPV6) on files compiled only when IPV6=y
Patch 5: introduce ipv6_mod_enabled() checks on fib6_nh_init(), ip6_dst_lookup_flow() and ip6_fragment() to avoid crash when ipv6.disable=1 during boot
Patch 6: use &nd_tbl on code guarded by IS_ENABLED(CONFIG_IPV6)
Patch 7: ipv6_stub->fib6_update_sernum() is replaced by fib6_update_sernum_upto_root() variant and guarded by spinlocks as it was on the ipv6_stub variant. This fixes the RCU warnings.
v3: https://lore.kernel.org/netdev/20260317140141.5723-1-fmancera@suse.de/
Patch 1: bring back CONFIG_NET_FOU_IP_TUNNELS on m68k defconfigs and drop unrelated changes.
Patch 4: add missing netlink error message indicating IPv6 is disabled
Patch 8: use __inet6_bind() instead the alias that was just created.
v2: https://lore.kernel.org/netdev/20260310153506.5181-1-fmancera@suse.de/
Patch 1: change fs_initcall() to device_initcall() to avoid race condition and disable CONFIG_IPV6 on m68k defconfigs.
v1: https://lore.kernel.org/netdev/20260309022013.5199-1-fmancera@suse.de/
Fernando Fernandez Mancera (11):
ipv6: convert CONFIG_IPV6 to built-in only and clean up Kconfigs
net: remove EXPORT_IPV6_MOD() and EXPORT_IPV6_MOD_GPL() macros
ipv6: replace IS_BUILTIN(CONFIG_IPV6) with IS_ENABLED(CONFIG_IPV6)
ipv6: remove dynamic ICMPv6 sender registration infrastructure
ipv6: prepare headers for ipv6_stub removal
drivers: net: drop ipv6_stub usage and use direct function calls
ipv4: drop ipv6_stub usage and use direct function calls
net: convert remaining ipv6_stub users to direct function calls
bpf: remove ipv6_bpf_stub completely and use direct function calls
ipv6: remove ipv6_stub infrastructure completely
netfilter: remove nf_ipv6_ops and use direct function calls
arch/arm64/configs/defconfig | 2 +-
arch/m68k/configs/amiga_defconfig | 44 +-------
arch/m68k/configs/apollo_defconfig | 44 +-------
arch/m68k/configs/atari_defconfig | 44 +-------
arch/m68k/configs/bvme6000_defconfig | 44 +-------
arch/m68k/configs/hp300_defconfig | 44 +-------
arch/m68k/configs/mac_defconfig | 44 +-------
arch/m68k/configs/multi_defconfig | 44 +-------
arch/m68k/configs/mvme147_defconfig | 44 +-------
arch/m68k/configs/mvme16x_defconfig | 44 +-------
arch/m68k/configs/q40_defconfig | 44 +-------
arch/m68k/configs/sun3_defconfig | 44 +-------
arch/m68k/configs/sun3x_defconfig | 44 +-------
drivers/infiniband/Kconfig | 1 -
drivers/infiniband/core/addr.c | 3 +-
drivers/infiniband/hw/ocrdma/Kconfig | 2 +-
drivers/infiniband/sw/rxe/rxe_net.c | 6 +-
drivers/infiniband/ulp/ipoib/Kconfig | 2 +-
drivers/net/Kconfig | 9 --
drivers/net/ethernet/broadcom/Kconfig | 2 +-
drivers/net/ethernet/chelsio/Kconfig | 2 +-
.../mellanox/mlx5/core/en/rep/neigh.c | 9 +-
.../ethernet/mellanox/mlx5/core/en/tc_tun.c | 3 +-
.../mellanox/mlx5/core/en/tc_tun_encap.c | 2 +-
.../mellanox/mlx5/core/en_accel/ipsec.c | 1 -
.../net/ethernet/mellanox/mlx5/core/en_rep.c | 1 -
.../net/ethernet/mellanox/mlx5/core/en_tc.c | 1 -
drivers/net/ethernet/mellanox/mlxsw/Kconfig | 1 -
drivers/net/ethernet/netronome/Kconfig | 1 -
.../ethernet/netronome/nfp/flower/action.c | 2 +-
.../netronome/nfp/flower/tunnel_conf.c | 7 +-
drivers/net/ethernet/sfc/tc_counters.c | 2 +-
drivers/net/ethernet/sfc/tc_encap_actions.c | 5 +-
drivers/net/geneve.c | 1 -
drivers/net/gtp.c | 2 +-
drivers/net/ovpn/peer.c | 3 +-
drivers/net/ovpn/udp.c | 3 +-
drivers/net/usb/cdc_mbim.c | 17 +--
drivers/net/vxlan/vxlan_core.c | 11 +-
drivers/net/vxlan/vxlan_multicast.c | 6 +-
drivers/net/wireguard/socket.c | 3 +-
drivers/net/wireless/intel/ipw2x00/ipw2100.c | 2 +-
drivers/scsi/bnx2fc/Kconfig | 1 -
drivers/scsi/bnx2i/Kconfig | 1 -
drivers/scsi/cxgbi/cxgb3i/Kconfig | 2 +-
drivers/scsi/cxgbi/cxgb4i/Kconfig | 2 +-
fs/dlm/Kconfig | 2 +-
fs/gfs2/Kconfig | 2 +-
include/linux/icmpv6.h | 29 +----
include/linux/indirect_call_wrapper.h | 2 +-
include/linux/netfilter_ipv6.h | 102 ++----------------
include/net/ip.h | 8 --
include/net/ip6_fib.h | 35 +++++-
include/net/ip6_route.h | 26 +++++
include/net/ipv6.h | 12 +++
include/net/ipv6_stubs.h | 101 -----------------
include/net/ndisc.h | 31 ++----
include/net/udp_tunnel.h | 3 +-
net/bridge/Kconfig | 1 -
net/bridge/br_arp_nd_proxy.c | 3 +-
net/bridge/br_netfilter_hooks.c | 12 +--
net/bridge/br_netfilter_ipv6.c | 7 +-
net/core/dev.c | 3 -
net/core/filter.c | 72 ++++++-------
net/core/hotdata.c | 1 -
net/core/lwt_bpf.c | 10 +-
net/core/neighbour.c | 1 -
net/ipv4/Kconfig | 9 +-
net/ipv4/fib_semantics.c | 16 +--
net/ipv4/icmp.c | 2 +-
net/ipv4/inet_connection_sock.c | 2 -
net/ipv4/inet_hashtables.c | 5 -
net/ipv4/inetpeer.c | 4 -
net/ipv4/metrics.c | 1 -
net/ipv4/nexthop.c | 28 ++---
net/ipv4/ping.c | 16 ---
net/ipv4/route.c | 4 +-
net/ipv4/syncookies.c | 4 -
net/ipv4/tcp.c | 23 ----
net/ipv4/tcp_fastopen.c | 1 -
net/ipv4/tcp_input.c | 7 --
net/ipv4/tcp_ipv4.c | 21 ----
net/ipv4/tcp_minisocks.c | 4 -
net/ipv4/tcp_output.c | 6 --
net/ipv4/tcp_timer.c | 1 -
net/ipv4/udp.c | 36 +------
net/ipv6/Kconfig | 6 +-
net/ipv6/addrconf_core.c | 91 ----------------
net/ipv6/af_inet6.c | 67 +-----------
net/ipv6/icmp.c | 6 --
net/ipv6/ip6_fib.c | 10 +-
net/ipv6/ip6_icmp.c | 46 +-------
net/ipv6/ip6_offload.c | 4 +-
net/ipv6/ip6_output.c | 8 ++
net/ipv6/ip6_udp_tunnel.c | 3 +-
net/ipv6/ndisc.c | 1 +
net/ipv6/netfilter.c | 48 ---------
net/ipv6/route.c | 12 +--
net/l2tp/Kconfig | 1 -
net/mpls/af_mpls.c | 3 +-
net/netfilter/Kconfig | 8 --
net/netfilter/core.c | 3 -
net/netfilter/nf_nat_masquerade.c | 21 +---
net/netfilter/nfnetlink_queue.c | 22 +++-
net/netfilter/utils.c | 1 -
net/openvswitch/actions.c | 3 +-
net/psp/psp_sock.c | 1 -
net/rxrpc/Kconfig | 2 +-
net/sched/sch_frag.c | 4 +-
net/sctp/Kconfig | 1 -
net/tipc/Kconfig | 1 -
net/tipc/udp_media.c | 9 +-
net/xfrm/espintcp.c | 5 +-
net/xfrm/xfrm_nat_keepalive.c | 4 +-
net/xfrm/xfrm_output.c | 3 +-
115 files changed, 296 insertions(+), 1397 deletions(-)
delete mode 100644 include/net/ipv6_stubs.h
--
2.53.0
next reply other threads:[~2026-03-25 12:09 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-25 12:08 Fernando Fernandez Mancera [this message]
2026-03-25 12:08 ` [PATCH 01/11 net-next v5] ipv6: convert CONFIG_IPV6 to built-in only and clean up Kconfigs Fernando Fernandez Mancera
2026-03-25 12:08 ` [PATCH 02/11 net-next v5] net: remove EXPORT_IPV6_MOD() and EXPORT_IPV6_MOD_GPL() macros Fernando Fernandez Mancera
2026-03-25 12:08 ` [PATCH 03/11 net-next v5] ipv6: replace IS_BUILTIN(CONFIG_IPV6) with IS_ENABLED(CONFIG_IPV6) Fernando Fernandez Mancera
2026-03-25 17:33 ` Martin KaFai Lau
2026-03-25 12:08 ` [PATCH 04/11 net-next v5] ipv6: remove dynamic ICMPv6 sender registration infrastructure Fernando Fernandez Mancera
2026-03-25 12:08 ` [PATCH 05/11 net-next v5] ipv6: prepare headers for ipv6_stub removal Fernando Fernandez Mancera
2026-03-25 12:08 ` [PATCH 06/11 net-next v5] drivers: net: drop ipv6_stub usage and use direct function calls Fernando Fernandez Mancera
2026-03-25 12:08 ` [PATCH 07/11 net-next v5] ipv4: " Fernando Fernandez Mancera
2026-03-25 12:08 ` [PATCH 08/11 net-next v5] net: convert remaining ipv6_stub users to " Fernando Fernandez Mancera
2026-03-25 12:08 ` [PATCH 09/11 net-next v5] bpf: remove ipv6_bpf_stub completely and use " Fernando Fernandez Mancera
2026-03-25 19:11 ` Martin KaFai Lau
2026-03-25 20:29 ` Fernando Fernandez Mancera
2026-03-25 21:36 ` Martin KaFai Lau
2026-03-25 22:40 ` David Ahern
2026-03-25 23:41 ` Fernando Fernandez Mancera
2026-03-26 16:27 ` David Ahern
2026-03-25 12:08 ` [PATCH 10/11 net-next v5] ipv6: remove ipv6_stub infrastructure completely Fernando Fernandez Mancera
2026-03-25 12:08 ` [PATCH 11/11 net-next v5] netfilter: remove nf_ipv6_ops and use direct function calls Fernando Fernandez Mancera
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