On 3/2/26 3:43 PM, Sabrina Dubroca wrote:
2026-03-02, 15:08:47 +0100, Fernando Fernandez Mancera wrote:
When booting with the 'ipv6.disable=1' parameter, the nd_tbl is never
initialized because inet6_init() exits before ndisc_init() is called
which initializes it. If an IPv6 packet is injected into the interface,
route_shortcircuit() is called and a NULL pointer dereference happens on
neigh_lookup().
VXLAN can be built-in even when IPv6 is built as a module, and then
ipv6_mod_enabled can't be used in VXLAN:
ld: drivers/net/vxlan/vxlan_core.o: in function `route_shortcircuit':
drivers/net/vxlan/vxlan_core.c:2133:(.text+0x116e0): undefined reference to
`ipv6_mod_enabled'
GENEVE has a Kconfig tweak to prevent this since 094be0927ff3
("geneve: fix build with modular IPV6"):
depends on IPV6 || !IPV6
but VXLAN doesn't.
Ugh, good catch. Thanks Sabrina.
But then I think we don't need to use ipv6_stub at all.
If we enforce "depends on IPV6 || IPV6=n" on VXLAN we could get rid of
ipv6_stub completely and use direct calls instead.
Would you agree to do as Ido mentioned on v1 and follow neigh_reduce()
approach (__in6_dev_get()), then on net-next follow-up getting rid of
ipv6_stub? I think this could be good.
Thanks,
Fernando.
