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sshnet: fix fork race conditions

sshreadproc() needs to be started after opening the sshfd file
descriptor.

fsnetproc() needs to run in the same filedescriptor group as
the fileserver.

--- a/sys/src/cmd/sshnet.c

+++ b/sys/src/cmd/sshnet.c

@@ -33,7 +33,7 @@

 #define TYPE(path)		((int)(path) & 0xFF)

 #define NUM(path)		((uint)(path)>>8)

-Channel *ssherrchan;		/* chan(char*) */

+int sessionopen = 0;

 Channel *sshmsgchan;		/* chan(Msg*) */

 Channel *fsreqchan;		/* chan(Req*) */

 Channel *fsreqwaitchan;		/* chan(nil) */

@@ -125,7 +125,7 @@

 int nclient;

 Client **client;

-char *mtpt;

+char *mtpt, *service;

 int sshfd;

 int

@@ -1148,7 +1148,7 @@

 		if(unpack(m, "_uuuu", &chan, &n, &win, &pkt) < 0)

 			break;

 		if(chan == SESSIONCHAN){

-			sendp(ssherrchan, nil);

+			sessionopen++;

 			break;

 		}

 		c = getclient(chan);

@@ -1173,7 +1173,7 @@

 			break;

 		s = smprint("%.*s", utfnlen(s, n), s);

 		if(chan == SESSIONCHAN){

-			sendp(ssherrchan, s);

+			sysfatal("ssh failed: %s", s);

 			break;

 		}

 		c = getclient(chan);

@@ -1313,6 +1313,12 @@

 	recvp(fsclunkwaitchan);

 }

+static void

+startup(Srv*)

+{

+	proccreate(fsnetproc, nil, 8*1024);

+}

+

 void

 takedown(Srv*)

 {

@@ -1321,7 +1327,7 @@

 Srv fs = 

 {

-.attach=		fssend,

+.attach=	fssend,

 .destroyfid=	fsdestroyfid,

 .walk1=		fswalk1,

 .open=		fssend,

@@ -1329,6 +1335,7 @@

 .write=		fssend,

 .stat=		fssend,

 .flush=		fssend,

+.start=		startup,

 .end=		takedown,

 };

@@ -1356,9 +1363,9 @@

 void

 ssh(int argc, char *argv[])

 {

-	Alt a[3];

+	Alt a[4];

 	Waitmsg *w;

-	char *e;

+	Msg *m;

 	sshargc = argc + 2;

 	sshargv = emalloc9p(sizeof(char *) * (sshargc + 1));

@@ -1366,11 +1373,14 @@

 	sshargv[1] = "-X";

 	memcpy(sshargv + 2, argv, argc * sizeof(char *));

-	pipe(pfd);

+	if(pipe(pfd) < 0)

+		sysfatal("pipe: %r");

 	sshfd = pfd[0];

-	procrfork(startssh, nil, 8*1024, RFFDG|RFNOTEG|RFNAMEG);

+	procrfork(startssh, nil, 8*1024, RFFDG|RFNOTEG);

 	close(pfd[1]);

+	procrfork(sshreadproc, nil, 8*1024, RFFDG|RFNOTEG);

+

 	sendmsg(pack(nil, "bsuuu", MSG_CHANNEL_OPEN,

 		"session", 7,

 		SESSIONCHAN,

@@ -1381,18 +1391,18 @@

 	a[0].c = threadwaitchan();

 	a[0].v = &w;

 	a[1].op = CHANRCV;

-	a[1].c = ssherrchan;

-	a[1].v = &e;

+	a[1].c = sshmsgchan;

+	a[1].v = &m;

 	a[2].op = CHANEND;

-	switch(alt(a)){

-	case 0:

-		sysfatal("ssh failed: %s", w->msg);

-	case 1:

-		if(e != nil)

-			sysfatal("ssh failed: %s", e);

+	while(!sessionopen){

+		switch(alt(a)){

+		case 0:

+			sysfatal("ssh failed: %s", w->msg);

+		case 1:

+			handlemsg(m);

+		}

 	}

-	chanclose(ssherrchan);

 }

 void

@@ -1405,8 +1415,6 @@

 void

 threadmain(int argc, char **argv)

 {

-	char *service;

-

 	fmtinstall('H', encodefmt);

 	mtpt = "/net";

@@ -1429,17 +1437,15 @@

 		usage();

 	time0 = time(0);

-	ssherrchan = chancreate(sizeof(char*), 0);

 	sshmsgchan = chancreate(sizeof(Msg*), 16);

 	fsreqchan = chancreate(sizeof(Req*), 0);

 	fsreqwaitchan = chancreate(sizeof(void*), 0);

 	fsclunkchan = chancreate(sizeof(Fid*), 0);

 	fsclunkwaitchan = chancreate(sizeof(void*), 0);

-	procrfork(fsnetproc, nil, 8*1024, RFNAMEG|RFNOTEG);

-	procrfork(sshreadproc, nil, 8*1024, RFNAMEG|RFNOTEG);

 	ssh(argc, argv);

 	threadpostmountsrv(&fs, service, mtpt, MREPL);

-	exits(0);

+

+	threadexits(nil);

 }