How to set VLAN priority for socket (not for interface)

Hello,

After browsing Internet for a while I could not find any code
on how to set VLAN priority for outgoing packets from program and for
program.
The priority can change from socket to socket.

I have read about IP_TOS, SO_PRIORITY options but I am not sure I can
do anything with that.
Are there any fuctions/ioctls to set VLAN priority not going into
PF_PACKET level programmming :)

Many thanks in advance,
Vlad.

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