shutdown should send TCP_FIN packet.
close should send TCP_RST packet when the data in readahead has not been
read and NEW_DATA has arrived.
send TCP_FIN packet when in other cases.
Signed-off-by: zhanghongyu <zhanghongyu@xiaomi.com>
CLOSE-WAIT - represents waiting for a connection termination request
from the local user.
TCP A TCP B
1. ESTABLISHED ESTABLISHED
2. (Close)
FIN-WAIT-1 --> <SEQ=100><ACK=300><CTL=FIN,ACK> --> CLOSE-WAIT
3. FIN-WAIT-2 <-- <SEQ=300><ACK=101><CTL=ACK> <-- CLOSE-WAIT
4. (Close)
TIME-WAIT <-- <SEQ=300><ACK=101><CTL=FIN,ACK> <-- LAST-ACK
5. TIME-WAIT --> <SEQ=101><ACK=301><CTL=ACK> --> CLOSED
6. (2 MSL)
CLOSED
in the current state, we can continue to send data until the user
calls shutdown or close, then directly enter the TCP_LAST_ACK state
Signed-off-by: zhanghongyu <zhanghongyu@xiaomi.com>
