Why my setting does not work?

lab mypc server
7000 -> 5900
1080 -> 10800
10800 -> internet
15900 -> 5900
22 -> github:22

rinitd runs at lab pc
1081 -> 1080
17000 -> 7000

test

pcx --VNC-> lab:17000 to connect mypc ok

pcx: VNC connect lab:17000 VNC client protocal
lab: rinitd redirect 17000 to 7000 rinitd tunnel
lab: 7000 redirect via ssh tunnel to mypc:5900 ssh tunnel
mypc: 5900 is VNC server VNC server protocal

lab --firefox (using socks 1080) to access internet ok
lab: firefox connect to lab:1080 socks client protocal
lab: 1080 redirect via ssh tunnel to mypc:10800 ssh tunnel
mypc: 10800 is socks server socks server protocal
putty decode socks request and redirect data to myhome via ssh tunnel

lab --firefox (using socks 10800) to access internet fail
lab: firefox connect to lab:10800 socks client protocal
lab: 10800 is redirected to lab:1080 via rinetd rinitd tunnel
lab: 1080 redirect via ssh tunnel to mypc:10800 ssh tunnel
mypc: 10800 is socks server socks server protocal
putty decode socks request and redirect data to myhome via ssh tunnel