From 0eda2a9c26fce9efca9185306e14fe4e4cadf637 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Mon, 24 Apr 2000 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 2000-04-24

---
 ip/devip.c |  3 +++
 ip/icmp.c  |  1 +
 ip/il.c    |  1 +
 ip/ip.h    |  3 ++-
 ip/tcp.c   | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 ip/udp.c   |  1 +
 6 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/ip/devip.c b/ip/devip.c
index 5829142959de5e69aea57d622247c6b24af4c5a7..256b2fe31539f8d2dfbbeb07ddb69cd3fc059eac 100644
--- a/ip/devip.c
+++ b/ip/devip.c
@@ -1084,6 +1084,7 @@ Fsprotoclone(Proto *p, char *user)
 {
 	Conv *c, **pp, **ep;
 
+retry:
 	c = nil;
 	ep = &p->conv[p->nc];
 	for(pp = p->conv; pp < ep; pp++) {
@@ -1120,6 +1121,8 @@ Fsprotoclone(Proto *p, char *user)
 		}
 	}
 	if(pp >= ep) {
+		if(p->gc != nil && (*p->gc)(p))
+			goto retry;
 		return nil;
 	}
 
diff --git a/ip/icmp.c b/ip/icmp.c
index 6a515f0cc6a4f4e81360a2933d5d7d6b628468f7..7df64cfbf11dc95a73c5f188bf3aeaf5538e48b3 100644
--- a/ip/icmp.c
+++ b/ip/icmp.c
@@ -465,6 +465,7 @@ icmpinit(Fs *fs)
 	icmp->stats = icmpstats;
 	icmp->ctl = nil;
 	icmp->advise = icmpadvise;
+	icmp->gc = nil;
 	icmp->ipproto = IP_ICMPPROTO;
 	icmp->nc = 16;
 	icmp->ptclsize = 0;
diff --git a/ip/il.c b/ip/il.c
index 33391b729a4fdc83f6939aca7b579f8beaa7d85b..33ec6df9a770f9fe1550bafddccc2a1c328808d7 100644
--- a/ip/il.c
+++ b/ip/il.c
@@ -1341,6 +1341,7 @@ ilinit(Fs *f)
 	il->advise = iladvise;
 	il->stats = ilxstats;
 	il->inuse = ilinuse;
+	il->gc = nil;
 	il->ipproto = IP_ILPROTO;
 	il->nc = Nchans;
 	il->ptclsize = sizeof(Ilcb);
diff --git a/ip/ip.h b/ip/ip.h
index e10fc09806fe9239161a1210873ec4037a130090..ef1b2f8887d5a75aa63c2437bf44e6048af48923 100644
--- a/ip/ip.h
+++ b/ip/ip.h
@@ -27,7 +27,7 @@ enum
 	Maxproto=	20,
 	Nhash=		64,
 	Maxincall=	5,
-	Nchans=		256,
+	Nchans=		512,
 	MAClen=		16,		/* longest mac address */
 
 	MAXTTL=		255,
@@ -218,6 +218,7 @@ struct Proto
 	int		(*local)(Conv*, char*, int);
 	int		(*remote)(Conv*, char*, int);
 	int		(*inuse)(Conv*);
+	int		(*gc)(Proto*);	/* returns true if any conversations are freed */
 
 	Fs		*f;		/* file system this proto is part of */
 	Conv		**conv;		/* array of conversations */
diff --git a/ip/tcp.c b/ip/tcp.c
index 0c65ef3024a0874c4ef659b77e0b2e80a9b61466..33051c536dc30355b346690c3a7789a5a34f9c40 100644
--- a/ip/tcp.c
+++ b/ip/tcp.c
@@ -123,7 +123,7 @@ struct	Tcp
 	ushort	wnd;
 	ushort	urg;
 	ushort	mss;
-        ushort  len;  /* size of data */
+        ushort  len;	/* size of data */
 };
 
 typedef struct Reseq Reseq;
@@ -188,6 +188,7 @@ struct Tcpctl
 	int	mdev;			/* Mean deviation of round trip */
 	int	kacounter;		/* count down for keep alive */
 	uint	sndsyntime;		/* time syn sent */
+	ulong	time;			/* time Finwait2 or Syn_received was sent */
 
 	Tcphdr	protohdr;		/* prototype header */
 };
@@ -1340,6 +1341,7 @@ tcpiput(Proto *tcp, uchar*, Block *bp)
 		if(seg.flags & SYN) {
 			procsyn(s, &seg);
 			tcpsndsyn(tcb);
+			tcb->time = msec;
 			tcpsetstate(s, Syn_received);
 			if(length != 0 || (seg.flags & FIN))
 				break;
@@ -1365,8 +1367,10 @@ tcpiput(Proto *tcp, uchar*, Block *bp)
 				tcpsynackrtt(s);
 				tcpsetstate(s, Established);
 			}
-			else
+			else {
+				tcb->time = msec;
 				tcpsetstate(s, Syn_received);
+			}
 
 			if(length != 0 || (seg.flags & FIN))
 				break;
@@ -1460,6 +1464,7 @@ tcpiput(Proto *tcp, uchar*, Block *bp)
 				tcphalt(tpriv, &tcb->rtt_timer);
 				tcphalt(tpriv, &tcb->acktimer);
 				tcpsetkacounter(tcb);
+				tcb->time = msec;
 				tcpsetstate(s, Finwait2);
 				tcb->katimer.start = MSL2 * (1000 / MSPTICK);
 				tcpgo(tpriv, &tcb->katimer);
@@ -2238,6 +2243,51 @@ tcpstats(Proto *tcp, char *buf, int len)
 		tpriv->tstats.OutRsts);
 }
 
+/*
+ *  garbage collect any stale conversations:
+ *	- SYN received but no SYN-ACK after 5 seconds (could be the SYN attack)
+ *	- Finwait2 after 5 minutes
+ *
+ *  this is called whenever we run out of channels.  Both checks are
+ *  of questionable validity so we try to use them only when we're
+ *  up against the wall.
+ */
+int
+tcpgc(Proto *tcp)
+{
+	Conv *c, **pp, **ep;
+	int n;
+	Tcpctl *tcb;
+
+
+	n = 0;
+	ep = &tcp->conv[tcp->nc];
+	for(pp = tcp->conv; pp < ep; pp++) {
+		c = *pp;
+		if(c == nil)
+			break;
+		if(!canqlock(c))
+			continue;
+		tcb = (Tcpctl*)c->ptcl;
+		switch(tcb->state){
+		case Syn_received:
+			if(msec - tcb->time > 5000){
+				localclose(c, "timed out");
+				n++;
+			}
+			break;
+		case Finwait2:
+			if(msec - tcb->time > 5*60*1000){
+				localclose(c, "timed out");
+				n++;
+			}
+			break;
+		}
+		qunlock(c);
+	}
+	return n;
+}
+
 void
 tcpinit(Fs *fs)
 {
@@ -2258,6 +2308,7 @@ tcpinit(Fs *fs)
 	tcp->advise = tcpadvise;
 	tcp->stats = tcpstats;
 	tcp->inuse = tcpinuse;
+	tcp->gc = tcpgc;
 	tcp->ipproto = IP_TCPPROTO;
 	tcp->nc = Nchans;
 	tcp->ptclsize = sizeof(Tcpctl);
diff --git a/ip/udp.c b/ip/udp.c
index d7eff2ae775dffcedee4b0b6113cbd2cda9db46e..ea3217654b193fa2320cb873dce3aa588177e813 100644
--- a/ip/udp.c
+++ b/ip/udp.c
@@ -497,6 +497,7 @@ udpinit(Fs *fs)
 	udp->rcv = udpiput;
 	udp->advise = udpadvise;
 	udp->stats = udpstats;
+	udp->gc = nil;
 	udp->ipproto = IP_UDPPROTO;
 	udp->nc = Nchans;
 	udp->ptclsize = sizeof(Udpcb);