How to make ssh tunnel for 2 gray ip?

Question

SSH

Given:
1) provider A and a working computer for Nat
2) provider B and a router with a white ip
3) provider C and a home computer for Nat
Work and home computers can connect via ssh to the router.
Is it possible to make (and if possible, how) a tunnel between the work and home machines using ssh.
IMPORTANT! None of the computers (home and work) are in the local network of the router.

Answer 1

Have a working SSH server on the router.
From one machine A
ssh -NL 8080:127.0.0.1:8080 hostB
From another machine C
ssh -NR 8080:127.0.0.1:8080 hostB
then a knock on A on port 8080 will be forwarded on C port 8080