StrongSwan 5.1.0 will segfault if you have any IKEv2 peers with a closeaction of restart or route. A workaround of course is to disable the closeaction, but that would then result in IKEv2 CHILD_SAs remaining closed if the remote side closes it, which in the vast majority of cases is undesirable, hence making closeaction a rather significant option. Strongswan 5.1.0 should definitely not be stabilised without this. Patch upstream is here: http://git.strongswan.org/?p=strongswan.git;a=commit;h=e42ab08a737b41b3ba56e7db1f8ab719a2d8ae58
Fixed, since we have 5.1.1 in the tree now.