ip/geneve: fix ttl inherit behavior
Currently when we add geneve with "ttl inherit", we only set ttl to 0, which
is actually use whatever default value instead of inherit the inner protocol's
ttl value.
To make a difference with ttl inherit and ttl == 0, we add an attribute
IFLA_GENEVE_TTL_INHERIT in kernel commit
52d0d404d39dd ("geneve: add ttl
inherit support"). Now let's use "ttl inherit" to inherit the inner
protocol's ttl, and use "ttl auto" to means "use whatever default value",
the same behavior with ttl == 0.
v2:
1) remove IFLA_GENEVE_TTL_INHERIT defination in if_link.h as it's already
updated.
2) Still use addattr8() so we can enable/disable ttl inherit, as Michal
suggested.
v3: Update man page
Reported-by: Jianlin Shi <jishi@redhat.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David Ahern <dsahern@gmail.com>