Re: [PATCH 00/11 net-next v4] Convert CONFIG_IPV6 to built-in and remove stubs
From: Fernando Fernandez Mancera
Date: Mon Mar 23 2026 - 11:34:02 EST
On 3/23/26 3:38 PM, David Ahern wrote:
On 3/23/26 6:19 AM, Fernando Fernandez Mancera wrote:
On 3/22/26 6:27 PM, Ido Schimmel wrote:
On Fri, Mar 20, 2026 at 07:55:52PM +0100, Fernando Fernandez ManceraHi Ido, the main reason why ipv6_get_nd_tbl() is used on IPv6 code is
wrote:
Changes:
v4:
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)
The IPv6 code is still using ipv6_get_nd_tbl() for some reason. If you
remove it from there (it's not needed), then we are only left with
handful of users that can be converted to use '&nd_tbl' when IPv6 is
enabled. Something like the patch below.
due to inlined functions. __ipv6_neigh_lookup_noref() is used in several
places not guarded by IS_ENABLED(CONFIG_IPV6) preprocessor directive.
That leads to undefined references when compiling with CONFIG_IPV6=n.
ld: vmlinux.o: in function `bpf_ipv4_fib_lookup':
filter.c:(.text+0x322b9dc): undefined reference to `nd_tbl'
ld: filter.c:(.text+0x322b9fb): undefined reference to `nd_tbl'
ld: filter.c:(.text+0x322ce1a): undefined reference to `nd_tbl'
ld: vmlinux.o: in function `ipv4_confirm_neigh':
route.c:(.text+0x345ade7): undefined reference to `nd_tbl'
ld: route.c:(.text+0x345ae06): undefined reference to `nd_tbl'
ld: vmlinux.o:route.c:(.text+0x345b74f): more undefined references to
`nd_tbl' follow
are these errors with Ido's suggested additional change?
Actually no. I missed the Dead-code elimination optimization. Never mind my reply, it makes sense to follow Ido's suggestion.
Thanks and sorry for the back-and-forth. *facepalm*
Fernando.