From 2251ef7a32f881ae2c80989d5285db943aa2073b Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Wed, 3 Apr 2019 13:45:54 +0200
Subject: sshnet: pass on open failure error message, simplify

return the error message from MSG_CHANNEL_OPEN_FAILURE
in the "connect" control write.

use a extra state "Finished" to distinguish server from client
initiated teardown. that way we do not need to track if we
send the MSG_CHANNEL_CLOSE message in closeclient(). this way
we also cannot be fooled by misbehaving server.

simplify hangupclient() by removing state transitions and doing
them in the caller explicitely. that way we can use hangupclient()
instead of dialedclient().
---
 sys/src/cmd/sshnet.c | 81 ++++++++++++++++++++++++++--------------------------
 1 file changed, 40 insertions(+), 41 deletions(-)

diff --git a/sys/src/cmd/sshnet.c b/sys/src/cmd/sshnet.c
index 6c28144e5..993f16021 100755
--- a/sys/src/cmd/sshnet.c
+++ b/sys/src/cmd/sshnet.c
@@ -46,6 +46,7 @@ enum
 	Dialing,
 	Established,
 	Teardown,
+	Finished,
 };
 
 char *statestr[] = {
@@ -53,6 +54,7 @@ char *statestr[] = {
 	"Dialing",
 	"Established",
 	"Teardown",
+	"Finished",
 };
 
 struct Client
@@ -61,7 +63,6 @@ struct Client
 	int state;
 	int num;
 	int servernum;
-	int sentclose;
 	char *connect;
 
 	int sendpkt;
@@ -120,7 +121,6 @@ char *mtpt;
 int sshfd;
 int localport;
 char localip[] = "::";
-char Ehangup[] = "hangup on network connection";
 
 int
 vpack(uchar *p, int n, char *fmt, va_list a)
@@ -434,23 +434,7 @@ findreq(Client *c, Req *r)
 }
 
 void
-dialedclient(Client *c)
-{
-	Req *r;
-
-	if(r=c->wq){
-		if(r->aux != nil)
-			sysfatal("more than one outstanding dial request (BUG)");
-		if(c->state == Established)
-			respond(r, nil);
-		else
-			respond(r, "connect failed");
-	}
-	c->wq = nil;
-}
-
-void
-hangupclient(Client *c)
+hangupclient(Client *c, char *err)
 {
 	Req *r;
 
@@ -460,22 +444,17 @@ hangupclient(Client *c)
 	while((r = c->wq) != nil){
 		c->wq = r->aux;
 		r->aux = nil;
-		respond(r, Ehangup);
-	}
-	if(c->state == Established){
-		c->state = Teardown;
-		matchrmsgs(c);
-		return;
+		respond(r, err);
 	}
-	c->state = Closed;
+	matchrmsgs(c);
 }
 
 void
 teardownclient(Client *c)
 {
-	hangupclient(c);
-	if(c->sentclose++ == 0)
-		sendmsg(pack(nil, "bu", MSG_CHANNEL_CLOSE, c->servernum));
+	c->state = Teardown;
+	hangupclient(c, "i/o on hungup channel");
+	sendmsg(pack(nil, "bu", MSG_CHANNEL_CLOSE, c->servernum));
 }
 
 void
@@ -485,14 +464,21 @@ closeclient(Client *c)
 
 	if(--c->ref)
 		return;
-	if(c->state >= Established)
+	switch(c->state){
+	case Established:
 		teardownclient(c);
+		break;
+	case Finished:
+		c->state = Closed;
+		sendmsg(pack(nil, "bu", MSG_CHANNEL_CLOSE, c->servernum));
+		break;
+	}
 	while((m = c->mq) != nil){
 		c->mq = m->link;
 		free(m);
 	}
 }
-	
+
 void
 sshreadproc(void*)
 {
@@ -813,9 +799,7 @@ ctlwrite(Req *r, Client *c)
 		nf = getfields(f[1], f, nelem(f), 0, "!");
 		if(nf != 2)
 			goto Badarg;
-		c->eof = 0;
-		c->sendwin = MaxPacket;
-		c->recvwin = WinPackets * MaxPacket;
+		c->recvwin = WinPackets*MaxPacket;
 		c->recvacc = 0;
 		c->state = Dialing;
 		queuewreq(c, r);
@@ -1074,8 +1058,17 @@ handlemsg(Msg *m)
 		if(unpack(m, "_u", &chan) < 0)
 			break;
 		c = getclient(chan);
-		if(c != nil && c->state >= Established)
-			hangupclient(c);
+		if(c == nil)
+			break;
+		switch(c->state){
+		case Established:
+			c->state = Finished;
+			hangupclient(c, "connection closed");
+			break;
+		case Teardown:
+			c->state = Closed;
+			break;
+		}
 		break;
 	case MSG_CHANNEL_OPEN_CONFIRMATION:
 		if(unpack(m, "_uuuu", &chan, &n, &win, &pkt) < 0)
@@ -1089,25 +1082,31 @@ handlemsg(Msg *m)
 			break;
 		if(pkt <= 0 || pkt > MaxPacket)
 			pkt = MaxPacket;
+		c->eof = 0;
 		c->sendpkt = pkt;
 		c->sendwin = win;
 		c->servernum = n;
-		c->sentclose = 0;
 		c->state = Established;
-		dialedclient(c);
+		if(c->wq != nil){
+			respond(c->wq, nil);
+			c->wq = nil;
+		}
 		break;
 	case MSG_CHANNEL_OPEN_FAILURE:
 		if(unpack(m, "_u____s", &chan, &s, &n) < 0)
 			break;
+		s = smprint("%.*s", utfnlen(s, n), s);
 		if(chan == SESSIONCHAN){
-			sendp(ssherrchan, smprint("%.*s", utfnlen(s, n), s));
+			sendp(ssherrchan, s);
 			break;
 		}
 		c = getclient(chan);
-		if(c == nil || c->state != Dialing)
+		if(c == nil || c->state != Dialing){
+			free(s);
 			break;
+		}
 		c->state = Closed;
-		dialedclient(c);
+		hangupclient(c, s);
 		break;
 	}
 	free(m);
-- 
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