bareudp: use ipv6_mod_enabled to check if IPv6 enabled

stable inclusion
from stable-v5.10.110
commit ac1ec6f319c02faebce514d07c11d2cac939c078
bugzilla: https://gitee.com/openeuler/kernel/issues/I574AL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ac1ec6f319c02faebce514d07c11d2cac939c078



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[ Upstream commit e077ed58 ]

bareudp_create_sock() use AF_INET6 by default if IPv6 CONFIG enabled.
But if user start kernel with ipv6.disable=1, the bareudp sock will
created failed, which cause the interface open failed even with ethertype
ip. e.g.

 # ip link add bareudp1 type bareudp dstport 2 ethertype ip
 # ip link set bareudp1 up
 RTNETLINK answers: Address family not supported by protocol

Fix it by using ipv6_mod_enabled() to check if IPv6 enabled. There is
no need to check IS_ENABLED(CONFIG_IPV6) as ipv6_mod_enabled() will
return false when CONFIG_IPV6 no enabled in include/linux/ipv6.h.

Reported-by: Jianlin Shi <jishi@redhat.com>
Fixes: 571912c6 ("net: UDP tunnel encapsulation module for tunnelling different protocols like MPLS, IP, NSH etc.")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://lore.kernel.org/r/20220315062618.156230-1-liuhangbin@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>