Can I use tailscale interface as gateway?

Let’s say I have three computers, A, B and C.

A and B are connected via tailscale, whereas C is not and cannot be (e.g. embedded device). C is however on the same network as B, so my idea is to use B as some kind of gateway to get access from A to C.

So we have the following IPs and NICs.

A (tailscale0): 100.a.b.c
B (tailscale0): 100.x.y.z
B (eth1):
C (eth0):

I tried following:

B:  iptables -t nat -A POSTROUTING -o tailscale0 -j MASQUERADE
B:  iptables -A FORWARD -i tailscale0 -o eth1 -m state --state RELATED,ESTABLISHED -j ACCEPT
B:  iptables -A FORWARD -i eth1 -o tailscale0 -j ACCEPT
B:  echo 1 > /proc/sys/net/ipv4/ip_forward
A:  ip route add via 100.x.y.z dev tailscale0

However, when I try to ping on A, all packages are lost.
Am I missing something or do the rules listed above conflict with some other rules created by tailscale? Is there a better way to achieve the desired result?

Does it maybe matter that in this particular case eth1 on B also serves as connection with WAN-access (i.e. tailscale uses it)? Would it be different if B had a separate eth0 as WAN and eth1 only as LAN?

From what I understand if your setup, you should be able to use a tailscale subnet router.

So B would have to advertise-routes and A would have to accept-routes