Date: Thu, 22 Mar 2001 16:10:21 +0000 From: thinker <thinker@branda.to> To: freebsd-security@freebsd.org Subject: Hang forever at LAST_ACK Message-ID: <20010322161021.A45575@hell.branda.to>
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Hi,
Few days ago, my friend has a FreeBSD 4.2-stable server be hanged
totally for socket being exhausted. He found there are many sockets
stay at LAST_ACK state and never been dropped. We don't know whether
it is a DDoS attack, but it could be a DDoS way. I don't know whether
there is people to fix it up, and I make a patch file for it following.
It seems work fine. Kernel patch is following.
--------- begin patch file of sys/netinet/tcp_usrreq.c ----------
--- tcp_usrreq.c.orig Thu Mar 22 14:59:45 2001
+++ tcp_usrreq.c Thu Mar 22 15:04:49 2001
@@ -1139,13 +1139,15 @@
tp->t_state = TCPS_LAST_ACK;
break;
}
- if (tp && tp->t_state >= TCPS_FIN_WAIT_2) {
+ if (tp && tp->t_state >= TCPS_FIN_WAIT_2)
soisdisconnected(tp->t_inpcb->inp_socket);
- /* To prevent the connection hanging in FIN_WAIT_2 forever. */
- if (tp->t_state == TCPS_FIN_WAIT_2)
- callout_reset(tp->tt_2msl, tcp_maxidle,
- tcp_timer_2msl, tp);
- }
+ /*
+ * To prevent the connection hanging in FIN_WAIT_2 &
+ * TCPS_LAST_ACK forever.
+ */
+ if (tp->t_state == TCPS_FIN_WAIT_2 || tp->t_state == TCPS_LAST_ACK)
+ callout_reset(tp->tt_2msl, tcp_maxidle,
+ tcp_timer_2msl, tp);
return (tp);
}
--------- end patch file of sys/netinet/tcp_usrreq.c ------------
--
thinker@branda.to Branda Open Site (BOS)
thinker.bbs@bbs.yzu.edu.tw http://www.branda.to/
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