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auth/newns: add chdev command

--- a/sys/man/6/namespace

+++ b/sys/man/6/namespace

@@ -59,6 +59,12 @@

 .I new

 is missing.

 .TP

+.BR chdev \ [ -nr "] \fIdevmask

+.I Devmask

+defines a string of driver characters to restrict

+the current namespace to. Existing binds

+of drivers are left unaffected.

+.TP

 .BR clear

 Clear the name space with

 .BR rfork(RFCNAMEG) .

@@ -80,4 +86,5 @@

 .SH "SEE ALSO"

 .IR bind (1),

 .IR namespace (4),

-.IR init (8)

+.IR init (8),

+.IR chdev (1)

--- a/sys/src/libauth/newns.c

+++ b/sys/src/libauth/newns.c

@@ -14,8 +14,8 @@

 static int	setenv(char*, char*);

 static char	*expandarg(char*, char*);

 static int	splitargs(char*, char*[], char*, int);

-static int	nsfile(char*, Biobuf *, AuthRpc *);

-static int	nsop(char*, int, char*[], AuthRpc*);

+static int	nsfile(char*, Biobuf *, AuthRpc *, int);

+static int	nsop(char*, int, char*[], AuthRpc*, int);

 static int	catch(void*, char*);

 int newnsdebug;

@@ -35,7 +35,7 @@

 {

 	Biobuf *b;

 	char home[4*ANAMELEN];

-	int afd, cdroot;

+	int afd, cdroot, dfd;

 	char *path;

 	AuthRpc *rpc;

@@ -51,8 +51,13 @@

 	}

 	/* rpc != nil iff afd >= 0 */

+	dfd = open("#c/drivers", OWRITE|OCEXEC);

+	if(dfd < 0 && newnsdebug)

+		fprint(2, "open #c/drivers: %r\n");

+

 	if(file == nil){

 		if(!newns){

+			close(dfd);

 			werrstr("no namespace file specified");

 			return freecloserpc(rpc);

 		}

@@ -60,6 +65,7 @@

 	}

 	b = Bopen(file, OREAD|OCEXEC);

 	if(b == nil){

+		close(dfd);

 		werrstr("can't open %s: %r", file);

 		return freecloserpc(rpc);

 	}

@@ -70,7 +76,8 @@

 		setenv("home", home);

 	}

-	cdroot = nsfile(newns ? "newns" : "addns", b, rpc);

+	cdroot = nsfile(newns ? "newns" : "addns", b, rpc, dfd);

+	close(dfd);

 	Bterm(b);

 	freecloserpc(rpc);

@@ -87,7 +94,7 @@

 }

 static int

-nsfile(char *fn, Biobuf *b, AuthRpc *rpc)

+nsfile(char *fn, Biobuf *b, AuthRpc *rpc, int dfd)

 {

 	int argc;

 	char *cmd, *argv[NARG+1], argbuf[MAXARG*NARG];

@@ -103,7 +110,7 @@

 			continue;

 		argc = splitargs(cmd, argv, argbuf, NARG);

 		if(argc)

-			cdroot |= nsop(fn, argc, argv, rpc);

+			cdroot |= nsop(fn, argc, argv, rpc, dfd);

 	}

 	atnotify(catch, 0);

 	return cdroot;

@@ -143,10 +150,11 @@

 }

 static int

-nsop(char *fn, int argc, char *argv[], AuthRpc *rpc)

+nsop(char *fn, int argc, char *argv[], AuthRpc *rpc, int dfd)

 {

 	char *argv0;

 	ulong flags;

+	char *devop;

 	int fd, i;

 	Biobuf *b;

 	int cdroot;

@@ -153,6 +161,7 @@

 	cdroot = 0;

 	flags = 0;

+	devop = "&";

 	argv0 = nil;

 	if(newnsdebug){

 		for (i = 0; i < argc; i++)

@@ -172,6 +181,12 @@

 	case 'C':

 		flags |= MCACHE;

 		break;

+	case 'r':

+		devop = "&~";

+		break;

+	case 'n':

+		devop = "~";

+		break;

 	}ARGEND

 	if(!(flags & (MAFTER|MBEFORE)))

@@ -181,7 +196,7 @@

 		b = Bopen(argv[0], OREAD|OCEXEC);

 		if(b == nil)

 			return 0;

-		cdroot |= nsfile(fn, b, rpc);

+		cdroot |= nsfile(fn, b, rpc, dfd);

 		Bterm(b);

 	}else if(strcmp(argv0, "clear") == 0 && argc == 0){

 		rfork(RFCNAMEG);

@@ -212,6 +227,18 @@

 	}else if(strcmp(argv0, "cd") == 0 && argc == 1){

 		if(chdir(argv[0]) == 0 && *argv[0] == '/')

 			cdroot = 1;

+	}else if(strcmp(argv0, "chdev") == 0){

+		//We should not silently fail if we can not honor a chdev

+		//due to the parent namespace missing #c/drivers.

+		if(dfd <= 0)

+			sysfatal("chdev requested, but could not open #c/drivers");

+		if(argc == 0 && devop[0] == '~'){

+			if(fprint(dfd, "chdev ~") < 0 && newnsdebug)

+				fprint(2, "%s: chdev ~: %r\n", fn);

+		}else if(argc == 1){

+			if(fprint(dfd, "chdev %s %s", devop, argv[0]) < 0 && newnsdebug)

+				fprint(2, "%s: chdev %s %s: %r\n", fn, devop, argv[0]);

+		}

 	}

 	return cdroot;

 }