Hi, how can I develop L2 Forwarding function in linux? I have to add and remove VLAN Tags for traffic of user coming to and from untagged vlan. Is there a way to do this?

Yes, there are many. Read the "Question Guidelines" link in my posting signature; doing basic research (i.e. searching) should be done before posting. Just putting "l2 forwarding linux" into Google pulls up MANY hits, several from this very site:
https://goyalankit.com/blog/linux-bridge
https://wiki.debian.org/BridgeNetwor...ctionsProxyArp

You can 'develop' something by writing a program. But you say nothing about the language you want to use, network environment, goals, etc. Without details all you can hope for is a generic answer.

Thank you for reply. I am using embedded Linux system so bash scripting or C language is preferable. What i want to do is that Packets coming from Client1 bridged to lets say eth0 having bridged interface br-wan. I have one VLAN eth0.2 having bridged interface br-vlan_2. What i want dynamically is that whenever any packet from Client1 coming to br-wan should go to br-vlan_2 and out by tagged 2. In reply that packet will come to br-vlan_2 so it will passed it to br-wan so that it can again reach it to the client1 via br-wan. I have read your links but not able to achieve this. Though i got idea from ebtables but didnt able to achieve it. Any suggestions in this regard?

Thanks

Yes; write your code to perform whatever task you want. Not sure what 'suggestions' anyone can give you past that, since YOU are the software developer.

check out links below, it might give you some ideas.

https://www.kernel.org/doc/Documenta...orking/vrf.txt

https://github.com/torvalds/linux/bl...orking/vrf.txt

https://www.netfilter.org/documentat...king-HOWTO.txt

http://www.citi.umich.edu/u/provos/p...cnet-spoof.txt