Hello Steffen,

Checking further with printk's, I can see

vti_tunnel_init being called for both ip_vti0 and vtil tunnels. But,
when vti_tunnel_xmit is called, it is called with ip_vti0 tunnel and
not the vtil tunnel. I am not sure if I am setting the route wrong. I
saw a comment that vti_tunnel_xmit is called by dev_queue_xmit
function. I could not figure out what dev_queue_xmit does though. 

master# echo "1" | sudo tee /proc/sys/net/ipv4/ip_forward
1
master# modprobe ip_vti
master# ipsec start
Starting strongSwan 5.2.0 IPsec [starter]...
master# ip tunnel add vtil mode vti local 192.168.0.11 remote 192.168.1.232 ikey 1 okey 1
master# ip link set vtil up
master# sleep 10
master# ip route add 192.168.1.0/24 dev vtil
master# ip route list
default via 192.168.0.1 dev enp4s0  metric 202
127.0.0.0/8 dev lo  scope host
192.168.0.0/24 dev enp4s0  proto kernel  scope link  src 192.168.0.11  metric 202
192.168.1.0/24 dev vtil  scope link

ip link list
.
.
.
13: ip_vti0@NONE: <NOARP,UP,LOWER_UP> mtu 1428 qdisc noqueue state UNKNOWN mode DEFAULT group default
    link/ipip 0.0.0.0 brd 0.0.0.0
14: vtil@NONE: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1428 qdisc noqueue state UNKNOWN mode DEFAULT group default
    link/ipip 192.168.0.11 peer 192.168.1.232
master# ip tunnel list
ip_vti0: ip/ip  remote any  local any  ttl inherit  nopmtudisc key 0
vtil: ip/ip  remote 192.168.1.232  local 192.168.0.11  ttl inherit  key 1

Just wanted to check if you have any suggestions to go about debugging
this.

Thanks
Joe