Accepts all incoming TCP connections , and forwards the connections through a SOCKS server
+---------------+
+--->| tcp_conn_cb |---+
| +---------------+ |
+----------------+ -----> +-----------+ | +---------------+ | +-----------------+ -----> +---------------+
|ip packet frames| |tcp segment+--+--->| tcp_read_cb |---+->>| virtual program | | socks proxy |
+----------------+ <----- +-----------+ +---------------+ +---+-----------------+ <----- +---------------+
^ +---------------+ |
+-------------| tcp_write |<--+
+---------------+
this layer has to reassemble the datagram and pass it to the higher protocol layer.
if ip packet frames come from host apps, and because of it not recv or send data by network, so it don't need set timeout and retransmission