Does anyone have a working procedure for routing/bridging an ethernet interface to a wifi interface?

My SBC is running Yocto Linux 4.1.15 which is using systemd (very important).
I've tried using parprouted but I haven't gotten it to work. All the google references assume you are using init instead of systemd but even trying this manually, no soap, Doc.

Basically, what I want to be able to do is connect something like an IP camera to an ethernet port on a single-board computer, then have the SBC's wifi connect to a regular wifi router and then be able to view the camera feed on a laptop.

No, I don't want to use OpenWRT to do this.

On the client machine:

# ifconfig eth0 192.168.3.3 netmask 255.255.255.0 mtu 1440 up
# route add default gw 192.168.3.1

or

# ip link set eth0 up mtu 1440
# ip addr add 192.168.3.3/24 dev eth0
# ip route add default via 192.168.3.1 dev eth0

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On the bridge machine

# dhclient -4 -v eth0
(connect to the internet / router, replace the device name as needed like wlan0 for wireless or wlp1s0)


# ifconfig eth2 192.168.3.1 netmask 255.255.255.0 mtu 1440 up

or

# ip link set eth2 up mtu 1440
# ip addr add 192.168.3.1/24 dev eth2
(note, no route needed since the gateway of the client is the route, plus a different subnet)

Then

# echo 1 > /proc/sys/net/ipv4/ip_forward
# iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
(where eth0 is the internet facing interface)

Of course this is the double NAT route, assuming the router also NATs. Which is why there's a modification to the MTU. It helps to keep speed up by keeping packet fragmentation down. Technically you only need 40 bytes per tcp/ip header, but I do 60.