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From: hanoh haim <hhaim.hanoh@gmail.com>
Date: Fri, 4 May 2018 18:28:30 +0300
Message-ID: <CA+YxBoL3DOKO7g9X0_QhamURkPRPGv69a4o5+JDJbUDY416ieA@mail.gmail.com>
Subject: TCP keepalive does not work for half-close connections
To: freebsd-net@freebsd.org
Cc: hhaim.hanoh@gamil.com
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Hi Expert,

Regarding the folwoing code,
Is there a reason that keepalive timer does not protect from half-close
socket (e.g. other side crash after this step)?

example

C    S

FIN->
  <-ACK

server crash here, the Client is not protected by keepalive

     <-FIN
 ->ACK


I think that this condition should be removed.
"tp->t_state <= TCPS_CLOSIN "


if ((tcp_always_keepalive ||
inp->inp_socket->so_options & SO_KEEPALIVE) &&
tp->t_state <= TCPS_CLOSING) {
thanks
Hanoh