mptcp: fix opt size when sending DSS + MP_FAIL

When these two options had to be sent -- which is not common -- the DSS
size was not being taken into account in the remaining size.

Additionally in this situation, the reported size was only the one of
the MP_FAIL which can cause issue if at the end, we need to write more
in the TCP options than previously said.

Here we use a dedicated variable for MP_FAIL size to keep the
WARN_ON_ONCE() just after.

Fixes: c25aeb4e0953 ("mptcp: MP_FAIL suboption sending")
Acked-and-tested-by: Geliang Tang <>
Signed-off-by: Matthieu Baerts <>
Signed-off-by: Mat Martineau <>
Signed-off-by: David S. Miller <>
1 file changed