Hello
StrongSwan's charon (v4.5.2) has some problems.
# 1. Collision occurs at rekey, VPN keep disconnected.
when keylife is short , Collision occurs at rekey.
```
IKEv2 05[IKE] CHILD_SA rekey collision lost, deleting rekeyed child
```
I'd backport this issue.
[bug report at StrongSwan](https://wiki.strongswan.org/issues/853)
[source code](https://wiki.strongswan.org/projects/strongswan/repository/revisions/7f2a20a4f45dc1a1806aa4fd2ef39ce21d586ba4/diff/src/libcharon/sa/ikev2/tasks/child_rekey.c)
# 2. Collision occurs at rekey, segmentation fault occurs with IPsec VTI
```
ipsec_starter[17127]: charon has died -- restart scheduled (5sec)
```
A null pointer is referenced and a segmentation fault occurs.
The above problems can be reproduced by bellow setting.
```
ipsec.conf
---
keylife=10s
rekeymargin=5s
rekeyfuzz=0%
```
# Test status
working fine at [nifcloud VPN Gateway](https://cloud.nifty.com/service/vpngw.htm).
Best regards.