From c5ce870ef3f5ab1593349511574b3f041a00fed5 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Thu, 4 Jul 2002 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 2002-07-04

---
 ip/ethermedium.c   | 13 ++++++++----
 ip/tcp.c           | 51 ++++++++++++++++++++++++++--------------------
 port/devrealtime.c | 24 ++++++++++++----------
 port/edf.c         | 36 ++++++++++++++++++++++----------
 port/edf.h         |  8 ++++----
 port/nulledf.c     | 45 ++++++++++++++++++++++++++++++++++------
 port/portclock.c   |  2 +-
 port/portdat.h     | 16 +++++++++++++++
 port/portfns.h     | 12 -----------
 port/proc.c        | 32 ++++++++++++++++-------------
 port/qlock.c       | 12 +++++------
 port/sysproc.c     |  4 ++--
 12 files changed, 162 insertions(+), 93 deletions(-)

diff --git a/ip/ethermedium.c b/ip/ethermedium.c
index 2d736d610b70b3a3bc5c4d622c9f26b171afe318..b8afe066c5bc7a5bcaafb8f9b144329988a296d3 100644
--- a/ip/ethermedium.c
+++ b/ip/ethermedium.c
@@ -115,7 +115,7 @@ struct Etherarp
 static void
 etherbind(Ipifc *ifc, int argc, char **argv)
 {
-	Chan *mchan4, *cchan4, *achan, *mchan6, *cchan6;
+	Chan *mchan4, *cchan4, *achan, *mchan6, *cchan6, *schan;
 	char addr[Maxpath];	//char addr[2*KNAMELEN];
 	char dir[Maxpath];	//char dir[2*KNAMELEN];
 	char *buf;
@@ -158,9 +158,14 @@ etherbind(Ipifc *ifc, int argc, char **argv)
 	 */
 	snprint(addr, sizeof(addr), "%s/stats", dir);
 	buf = smalloc(512);
-	achan = namec(addr, Aopen, OREAD, 0);
-	n = devtab[achan->type]->read(achan, buf, 511, 0);
-	cclose(achan);
+	schan = namec(addr, Aopen, OREAD, 0);
+	if(waserror()){
+		cclose(schan);
+		nexterror();
+	}
+	n = devtab[schan->type]->read(schan, buf, 511, 0);
+	cclose(schan);
+	poperror();
 	buf[n] = 0;
 
 	ptr = strstr(buf, "addr: ");
diff --git a/ip/tcp.c b/ip/tcp.c
index 9f8433700e2b10bc7739bc3dcfea839543d8ad53..6d9c4d059cc35255eb52b83d2e338c8d9a04feab 100644
--- a/ip/tcp.c
+++ b/ip/tcp.c
@@ -679,23 +679,19 @@ tcpmtu(Conv *s)
 	uchar version;
 
 	version = s->ipversion;
-	mtu = 0;
 	ifc = findipifc(s->p->f, s->raddr, 0);
-	if(ifc != nil) {
-		switch(version){
-		case V4:
+	switch(version){
+	default:
+	case V4:
+		mtu = DEF_MSS;
+		if(ifc != nil)
 			mtu = ifc->maxmtu - ifc->m->hsize - (TCP4_PKT + TCP4_HDRSIZE);
-			break;
-		case V6:
+		break;
+	case V6:
+		mtu = DEF_MSS6;
+		if(ifc != nil)
 			mtu = ifc->maxmtu - ifc->m->hsize - (TCP6_PKT + TCP6_HDRSIZE);
-			break;
-		default:
-			panic("tcpmtu: version %d", version);
-		}
-	}
-
-	if(mtu < 32) {
-		mtu = 1280;
+		break;
 	}
 
 	return mtu;
@@ -1665,6 +1661,19 @@ reset:
 		break;
 	}
 
+	if(tcb->state != Syn_received){
+		/*
+		 *  One DOS attack is to open connections to us and then forget about them,
+		 *  thereby tying up a conv at no long term cost to the attacker.
+		 *  This is an attempt to defeat these stateless DOS attacks.  See
+		 *  corresponding code in tcpsendka().
+		 */
+		if(seq_within(seg.ack, tcb->snd.una-(1<<31), tcb->snd.una-(1<<29))){
+			print("stateless hog %lux - %lux - %lux\n", tcb->snd.una-(1<<31), seg.ack, tcb->snd.una-(1<<29));
+			localclose(s, "stateless hog");
+		}
+	}
+
 	/* Cut the data to fit the receive window */
 	if(tcptrim(tcb, &seg, &bp, &length) == -1) {
 		netlog(f, Logtcp, "tcp len < 0, %lux\n", seg.seq);
@@ -2122,6 +2131,10 @@ tcpoutput(Conv *s)
 
 /*
  *  the BSD convention (hack?) for keep alives.  resend last uchar acked.
+ *
+ *  To avoid stateless Conv hogs, we pick a sequence number at random.  If
+ *  it that number gets acked by the other end, we shut down the connection.
+ *  See the equivalent code in tcpiput().
  */
 void
 tcpsendka(Conv *s)
@@ -2138,7 +2151,7 @@ tcpsendka(Conv *s)
 	seg.dest = s->rport;
 	seg.flags = ACK|PSH;
 	seg.mss = 0;
-	seg.seq = tcb->snd.una-1;
+	seg.seq = tcb->snd.una-(1<<30)-nrand(1<<20);
 	seg.ack = tcb->rcv.nxt;
 	seg.wnd = tcb->rcv.wnd;
 	tcb->last_ack = tcb->rcv.nxt;
@@ -2320,7 +2333,6 @@ void
 procsyn(Conv *s, Tcp *seg)
 {
 	Tcpctl *tcb;
-	int mtu;
 
 	tcb = (Tcpctl*)s->ptcl;
 	tcb->flags |= FORCE;
@@ -2330,14 +2342,9 @@ procsyn(Conv *s, Tcp *seg)
 	tcb->irs = seg->seq;
 	tcb->snd.wnd = seg->wnd;
 
-	if(seg->mss != 0)
+	if(seg->mss != 0 && seg->mss < tcb->mss)
 		tcb->mss = seg->mss;
-
 	tcb->max_snd = seg->wnd;
-
-	mtu = tcpmtu(s);
-	if(tcb->mss > mtu)
-		tcb->mss = mtu;
 	tcb->cwind = tcb->mss;
 }
 
diff --git a/port/devrealtime.c b/port/devrealtime.c
index f52508001677b2c20c0f73682de70c814ba16a7d..249406889729e05f6baf7dcfb5a8d9d94596e784 100644
--- a/port/devrealtime.c
+++ b/port/devrealtime.c
@@ -13,6 +13,7 @@
 
 /* debugging */
 extern int			edfprint;
+extern Edfinterface	realedf, *edf;
 
 static Schedevent *events;
 static int nevents, revent, wevent;
@@ -219,6 +220,7 @@ devrtinit(void)
 	events = (Schedevent *)malloc(sizeof(Schedevent) * Nevents);
 	assert(events);
 	nevents = revent = wevent = 0;
+	edf = &realedf;
 }
 
 static Chan *
@@ -286,7 +288,7 @@ devrtopen(Chan *c, int mode)
 	case Qclone:
 		if (mode == OREAD) 
 			error(Eperm);
-		edfinit();
+		edf->edfinit();
 		/* open a new task */
 		for (t = tasks; t< tasks + Maxtasks; t++){
 			qlock(t);
@@ -638,7 +640,7 @@ removetask(Task *t)
 	Resource *r;
 
 	qlock(t);
-	edfexpel(t);
+	edf->edfexpel(t);
 	for (pp = t->procs; pp < t->procs + nelem(t->procs); pp++)
 		if (p = *pp)
 			p->task = nil;
@@ -724,7 +726,7 @@ devrtwrite(Chan *c, void *va, long n, vlong)
 				if (e=parsetime(&time, v))
 					error(e);
 				ticks = time2ticks(time);
-				edfexpel(t);
+				edf->edfexpel(t);
 				switch(add){
 				case -1:
 					if (ticks > t->T)
@@ -745,7 +747,7 @@ devrtwrite(Chan *c, void *va, long n, vlong)
 				if (e=parsetime(&time, v))
 					error(e);
 				ticks = time2ticks(time);
-				edfexpel(t);
+				edf->edfexpel(t);
 				switch(add){
 				case -1:
 					if (ticks > t->D)
@@ -764,7 +766,7 @@ devrtwrite(Chan *c, void *va, long n, vlong)
 				if (e=parsetime(&time, v))
 					error(e);
 				ticks = time2ticks(time);
-				edfexpel(t);
+				edf->edfexpel(t);
 				switch(add){
 				case -1:
 					if (ticks > t->C)
@@ -784,7 +786,7 @@ devrtwrite(Chan *c, void *va, long n, vlong)
 			}else if (strcmp(a, "resources") == 0){
 				if (v == nil)
 					error("resources: value missing");
-				edfexpel(t);
+				edf->edfexpel(t);
 				if (add == 0){
 					for (rp = t->res; rp < t->res + nelem(t->res); rp++)
 						if (*rp){
@@ -809,7 +811,7 @@ devrtwrite(Chan *c, void *va, long n, vlong)
 				if (v == nil)
 					error("procs: value missing");
 				if (add <= 0){
-					edfexpel(t);
+					edf->edfexpel(t);
 				}
 				if (add == 0){
 					for (pp = t->procs; pp < t->procs + nelem(t->procs); pp++)
@@ -835,10 +837,10 @@ devrtwrite(Chan *c, void *va, long n, vlong)
 						error(e);
 				}
 			}else if (strcmp(a, "admit") == 0){
-				if (e = edfadmit(t))
+				if (e = edf->edfadmit(t))
 					error(e);
 			}else if (strcmp(a, "expel") == 0){
-				edfexpel(t);
+				edf->edfexpel(t);
 			}else if (strcmp(a, "remove") == 0){
 				removetask(t);
 				return n;	/* Ignore any subsequent commands */
@@ -857,8 +859,8 @@ devrtwrite(Chan *c, void *va, long n, vlong)
 				else
 					t->flags |= Useblocking;
 			}else if (strcmp(a, "yield") == 0){
-				if (isedf(up) && up->task == t){
-					edfdeadline(up);	/* schedule next release */
+				if (edf->isedf(up) && up->task == t){
+					edf->edfdeadline(up);	/* schedule next release */
 					sched();
 				}else
 					error("yield outside task");
diff --git a/port/edf.c b/port/edf.c
index 0b1263c32cf9569458bf060200b40a61bd5e444d..d0d6d1c5d794dd6e2486eddf2a3bacb827e10786 100644
--- a/port/edf.c
+++ b/port/edf.c
@@ -49,6 +49,7 @@ enum{
 
 static int earlierrelease(Task *t1, Task *t2) {return t1->r < t2->r;}
 static int earlierdeadline(Task *t1, Task *t2) {return t1->d < t2->d;}
+static void	edfrelease(Task *t);
 
 /* Tasks waiting for release, head earliest release time */
 Taskq		qwaitrelease =	{{0}, nil, earlierrelease};
@@ -71,7 +72,7 @@ static void		edfreleaseintr(Ureg *, Timer *cy);
 static void		edfdeadlineintr(Ureg*, Timer*);
 static char *	edftestschedulability(Task *thetask);
 
-void
+static void
 edfinit(void)
 {
 	int i;
@@ -96,13 +97,13 @@ edfinit(void)
 	iunlock(&edflock);
 }
 
-int
+static int
 isedf(Proc *p)
 {
 	return p && p->task && p->task->state >= EdfIdle;
 }
 
-int
+static int
 edfanyready(void)
 {
 	return edfstack[m->machno].head || qreleased.head;
@@ -220,7 +221,7 @@ edfreleasetimer(void)
 	timeradd(&releasetimer[m->machno]);
 }
 
-void
+static void
 edfblock(Proc *p)
 {
 	Task *t, *pt;
@@ -284,7 +285,7 @@ deadline(Proc *p, SEvent why)
 	edfresched(t);
 }
 
-void
+static void
 edfdeadline(Proc *p)
 {
 	DPRINT("%d edfdeadline\n", m->machno);
@@ -295,7 +296,7 @@ edfdeadline(Proc *p)
 	iunlock(&edflock);
 }
 
-char *
+static char *
 edfadmit(Task *t)
 {
 	char *err;
@@ -361,7 +362,7 @@ edfadmit(Task *t)
 	return nil;
 }
 
-void
+static void
 edfexpel(Task *t)
 {
 	Task *tt;
@@ -492,7 +493,7 @@ edfdeadlineintr(Ureg*, Timer*)
 	splhi();
 }
 
-void
+static void
 edfbury(Proc *p)
 {
 	Task *t;
@@ -526,7 +527,7 @@ edfbury(Proc *p)
 	iunlock(&edflock);
 }
 
-void
+static void
 edfready(Proc *p)
 {
 	Task *t;
@@ -671,7 +672,7 @@ edfresched(Task *t)
 	}
 }
 
-void
+static void
 edfrelease(Task *t)
 {
 	DPRINT("%d edfrelease, %s, %d\n", m->machno, edfstatename[t->state], t->runq.n);
@@ -685,7 +686,7 @@ edfrelease(Task *t)
 	if(devrt) devrt(t, now, SRelease);
 }
 
-Proc *
+static Proc *
 edfrunproc(void)
 {
 	/* Return an edf proc to run or nil */
@@ -961,3 +962,16 @@ time2ticks(Time time)
 	assert(time >= 0);
 	return uvmuldiv(time, fasthz, Onesecond);
 }
+
+Edfinterface realedf = {
+	.isedf		= isedf,
+	.edfbury		= edfbury,
+	.edfanyready	= edfanyready,
+	.edfready		= edfready,
+	.edfrunproc	= edfrunproc,
+	.edfblock		= edfblock,
+	.edfinit		= edfinit,
+	.edfexpel		= edfexpel,
+	.edfadmit		= edfadmit,
+	.edfdeadline	= edfdeadline,
+};
diff --git a/port/edf.h b/port/edf.h
index a8e1f399b5e7369d87783e9eb697b48e0fd7203f..03ba40b4670d8a38005927426b33998107a8061f 100644
--- a/port/edf.h
+++ b/port/edf.h
@@ -14,10 +14,10 @@ enum {
 typedef vlong	Time;
 typedef uvlong	Ticks;
 
-typedef struct Task		Task;
-typedef struct Resource	Resource;
-typedef struct Edf		Edf;
-typedef struct Taskq		Taskq;
+typedef struct Task			Task;
+typedef struct Resource		Resource;
+typedef struct Edf			Edf;
+typedef struct Taskq			Taskq;
 
 enum Edfstate {
 	EdfUnused,		/* task structure not in use */
diff --git a/port/nulledf.c b/port/nulledf.c
index 7ab36fc3152edbe2a5c3d1812f5934b3578b84ed..db630b20ee238e3a5dd7e43cb8d27a4c1c17021a 100644
--- a/port/nulledf.c
+++ b/port/nulledf.c
@@ -6,36 +6,69 @@
 #include	"../port/error.h"
 #include	"../port/edf.h"
 
-int
+static int
 isedf(Proc*)
 {
 	return 0;
 }
 
-void
+static void
 edfbury(Proc*)
 {
 }
 
-int
+static int
 edfanyready(void)
 {
 	return 0;
 }
 
-void
+static void
 edfready(Proc*)
 {
 }
 
-Proc*
+static Proc*
 edfrunproc(void)
 {
 	return nil;
 }
 
-void
+static void
 edfblock(Proc*)
 {
 }
 
+static void
+edfinit(void)
+{
+}
+
+static void
+edfexpel(Task*)
+{
+}
+
+static char *
+edfadmit(Task*)
+{
+	return "No edf";
+}
+
+static void
+edfdeadline(Proc*)
+{
+}
+
+Edfinterface nulledf = {
+	.isedf		= isedf,
+	.edfbury		= edfbury,
+	.edfanyready	= edfanyready,
+	.edfready		= edfready,
+	.edfrunproc	= edfrunproc,
+	.edfblock		= edfblock,
+	.edfinit		= edfinit,
+	.edfexpel		= edfexpel,
+	.edfadmit		= edfadmit,
+	.edfdeadline	= edfdeadline,
+};
diff --git a/port/portclock.c b/port/portclock.c
index 04761203c0c95772369e8ba907436a9ba74028a7..fec208181cafc2fee3374d30efe537ff4a8176fe 100644
--- a/port/portclock.c
+++ b/port/portclock.c
@@ -122,7 +122,7 @@ hzclock(Ureg *ur)
 		return;
 
 	/* i.e. don't deschedule an EDF process here! */
-	if(anyready() && !isedf(up)){
+	if(anyready() && !edf->isedf(up)){
 		sched();
 		splhi();
 	}
diff --git a/port/portdat.h b/port/portdat.h
index 619cf34f7feca8d4e958463308038a0d4622b7d2..8da75534ea090205dc409c778f9d413e3b3dd288 100644
--- a/port/portdat.h
+++ b/port/portdat.h
@@ -6,6 +6,7 @@ typedef struct Cmdtab	Cmdtab;
 typedef struct Cname	Cname;
 typedef struct Dev	Dev;
 typedef struct Dirtab	Dirtab;
+typedef struct Edfinterface	Edfinterface;
 typedef struct Egrp	Egrp;
 typedef struct Evalue	Evalue;
 typedef struct Fgrp	Fgrp;
@@ -846,6 +847,21 @@ struct Timer
 	ulong	period;
 };
 
+struct Edfinterface {
+	int		(*isedf)(Proc*);
+	void		(*edfbury)(Proc*);
+	int		(*edfanyready)(void);
+	void		(*edfready)(Proc*);
+	Proc*	(*edfrunproc)(void);
+	void		(*edfblock)(Proc*);
+	void		(*edfinit)(void);
+	void		(*edfexpel)(Task *t);
+	char *	(*edfadmit)(Task *t);
+	void		(*edfdeadline)(Proc *p);
+};
+
+extern Edfinterface *edf;
+
 #define DEVDOTDOT -1
 
 #pragma	varargck	argpos	print	1
diff --git a/port/portfns.h b/port/portfns.h
index b0cd038bbf254915dfd6fc01f1877d996764fd85..ee8b9bd19a6a4520500d81cebc67a19139b8c9ba 100644
--- a/port/portfns.h
+++ b/port/portfns.h
@@ -87,17 +87,6 @@ void		dumpstack(void);
 Fgrp*		dupfgrp(Fgrp*);
 void		duppage(Page*);
 void		dupswap(Page*);
-void		edfdeadline(Proc*);
-void		edfrelease(Task*);
-char*		edfadmit(Task*);
-void		edfexpel(Task*);
-void		edfbury(Proc*);
-void		edfsched(Task*);
-int		edfanyready(void);
-void		edfready(Proc*);
-Proc*		edfrunproc(void);
-void		edfblock(Proc*);
-void		edfinit(void);
 int		emptystr(char*);
 int		encrypt(void*, void*, int);
 void		envcpy(Egrp*, Egrp*);
@@ -140,7 +129,6 @@ int		incref(Ref*);
 void		initseg(void);
 int		iprint(char*, ...);
 void		isdir(Chan*);
-int		isedf(Proc*);
 int		iseve(void);
 int		islo(void);
 Segment*	isoverlap(Proc*, ulong, int);
diff --git a/port/proc.c b/port/proc.c
index 6844083d743276930a7ef0efd84d26049e7fc481..6d3d727dda84a35696e292702f6bfebcf21661f1 100644
--- a/port/proc.c
+++ b/port/proc.c
@@ -22,6 +22,10 @@ static struct Procalloc
 
 static Schedq	runq[Nrq];
 
+extern Edfinterface	nulledf;
+
+Edfinterface *edf = &nulledf;
+
 char *statename[] =
 {	/* BUG: generate automatically */
 	"Dead",
@@ -57,8 +61,8 @@ schedinit(void)		/* never returns */
 			break;
 		case Moribund:
 			up->state = Dead;
-			if (isedf(up))
-				edfbury(up);
+			if (edf->isedf(up))
+				edf->edfbury(up);
 
 			/*
 			 * Holding locks from pexit:
@@ -122,7 +126,7 @@ sched(void)
 int
 anyready(void)
 {
-	return nrdy || edfanyready();
+	return nrdy || edf->edfanyready();
 }
 
 int
@@ -153,8 +157,8 @@ ready(Proc *p)
 
 	s = splhi();
 
-	if(isedf(p)){
-		edfready(p);
+	if(edf->isedf(p)){
+		edf->edfready(p);
 		splx(s);
 		return;
 	}
@@ -208,7 +212,7 @@ runproc(void)
 	Proc *p, *l;
 	ulong rt;
 
-	if ((p = edfrunproc()) != nil)
+	if ((p = edf->edfrunproc()) != nil)
 		return p;
 
 loop:
@@ -503,8 +507,8 @@ sleep(Rendez *r, int (*f)(void*), void *arg)
 			unlock(r);
 			// Behind unlock, we may call wakeup on ourselves.
 
-			if (isedf(up))
-				edfblock(up);
+			if (edf->isedf(up))
+				edf->edfblock(up);
 
 			gotolabel(&m->sched);
 		}
@@ -713,8 +717,8 @@ addbroken(Proc *p)
 	broken.p[broken.n++] = p;
 	qunlock(&broken);
 
-	if (isedf(up))
-		edfbury(up);
+	if (edf->isedf(up))
+		edf->edfbury(up);
 	p->state = Broken;
 	p->psstate = 0;
 	sched();
@@ -884,8 +888,8 @@ pexit(char *exitstr, int freemem)
 	lock(&procalloc);
 	lock(&palloc);
 
-	if (isedf(up))
-		edfbury(up);
+	if (edf->isedf(up))
+		edf->edfbury(up);
 	up->state = Moribund;
 	sched();
 	panic("pexit");
@@ -1139,8 +1143,8 @@ procctl(Proc *p)
 		qunlock(&p->debug);
 		splhi();
 		p->state = Stopped;
-		if (isedf(up))
-			edfblock(up);
+		if (edf->isedf(up))
+			edf->edfblock(up);
 		sched();
 		p->psstate = state;
 		splx(s);
diff --git a/port/qlock.c b/port/qlock.c
index 629fcd4d6b5a7dedb9427d5c8843dc6dd909a476..0f14c41e71055fcd2fe385beeace44b50d9cb82c 100644
--- a/port/qlock.c
+++ b/port/qlock.c
@@ -43,8 +43,8 @@ qlock(QLock *q)
 	up->state = Queueing;
 	up->qpc = getcallerpc(&q);
 	unlock(&q->use);
-	if(isedf(up))
-		edfblock(up);
+	if(edf->isedf(up))
+		edf->edfblock(up);
 	sched();
 }
 
@@ -107,8 +107,8 @@ rlock(RWlock *q)
 	up->qnext = 0;
 	up->state = QueueingR;
 	unlock(&q->use);
-	if (isedf(up))
-		edfblock(up);
+	if (edf->isedf(up))
+		edf->edfblock(up);
 	sched();
 }
 
@@ -164,8 +164,8 @@ wlock(RWlock *q)
 	up->qnext = 0;
 	up->state = QueueingW;
 	unlock(&q->use);
-	if (isedf(up))
-		edfblock(up);
+	if (edf->isedf(up))
+		edf->edfblock(up);
 	sched();
 }
 
diff --git a/port/sysproc.c b/port/sysproc.c
index 73d10bed3d0e14c587a2402debca7ec6f1f5a4cb..c23d205790aa7e547b9cd81db81a0b5887efc50c 100644
--- a/port/sysproc.c
+++ b/port/sysproc.c
@@ -839,8 +839,8 @@ sysrendezvous(ulong *arg)
 	*l = up;
 	up->state = Rendezvous;
 	unlock(up->rgrp);
-	if (isedf(up))
-		edfblock(up);
+	if (edf->isedf(up))
+		edf->edfblock(up);
 
 	sched();