Adds kexportfs and ksrvfs used by syscall-exportfs patch.  This work
was done by rsc in 2005 for 9Netics.

Reference: /n/sources/patch/kexportfs
Date: Fri Mar 18 22:39:23 CET 2016
Signed-off-by: skip.tavakkolian@gmail.com

--- /sys/src/cmd/kexportfs/kexportfs.c	Thu Jan  1 00:00:00 1970
+++ /sys/src/cmd/kexportfs/kexportfs.c	Fri Mar 18 22:36:49 2016
@@ -0,0 +1,463 @@
+/*
+ * exportfs - Export a plan 9 name space across a network
+ */
+#include <u.h>
+#include <libc.h>
+#include <auth.h>
+#include <fcall.h>
+#include <libsec.h>
+
+enum {
+	Encnone,
+	Encssl,
+	Enctls,
+};
+
+#define DEBUG if(dbg)fprint
+#define DFD 2
+
+int	dbg;
+int	netfd;
+int	srvfd = -1;
+int	nonone = 1;
+char	*filterp;
+char	*ealgs = "rc4_256 sha1";
+char	*aanfilter = "/bin/aan";
+int	encproto = Encnone;
+
+static void	mksecret(char *, uchar *);
+static int localread9pmsg(int, void *, uint, ulong *);
+static char *anstring  = "tcp!*!0";
+int	filter(int, char *);
+void	fatal(char*, ...);
+void copylog(int, int, char*);
+
+int	export(int, char*, int);
+
+void
+usage(void)
+{
+	fprint(2, "usage:	%s [-ads] [-f dbgfile] [-m msize] [-r root] [-S srvfile] [-e 'crypt hash'] [-A announce-string]\n", argv0);
+	fprint(2, "	%s -B address\n", argv0);
+	fatal("usage");
+}
+
+void
+main(int argc, char **argv)
+{
+	char buf[ERRMAX], ebuf[ERRMAX];
+	int n, fd;
+	char *dbfile, *srv, *file, *na, *nsfile, *keyspec;
+	AuthInfo *ai;
+	ulong initial;
+	int negotiate;
+
+	dbfile = "/tmp/exportdb";
+	srv = nil;
+	srvfd = -1;
+	na = nil;
+	nsfile = nil;
+	keyspec = "";
+	
+	netfd = 0;
+	dup(2, 1);
+
+	negotiate = 1;
+	ai = nil;
+	fmtinstall('F', fcallfmt);
+	fmtinstall('D', dirmodefmt);
+	fmtinstall('H', encodefmt);
+	
+	ARGBEGIN{
+	case 'a':
+		/*
+		 * We use p9any so we don't have to visit this code again, with the
+		 * cost that this code is incompatible with the old world, which
+		 * requires p9sk2. (The two differ in who talks first, so compatibility
+		 * is awkward.)
+		 */
+		ai = auth_proxy(0, auth_getkey, "proto=p9any role=server %s", keyspec);
+		if(ai == nil)
+			fatal("auth_proxy: %r");
+		if(nonone && strcmp(ai->cuid, "none") == 0)
+			fatal("exportfs by none disallowed");
+		if(auth_chuid(ai, nsfile) < 0)
+			fatal("auth_chuid: %r");
+		putenv("service", "exportfs");
+		break;
+
+	case 'k':
+		keyspec = EARGF(usage());
+		break;
+
+	case 'e':
+		ealgs = ARGF();
+		if(ealgs == nil)
+			usage();
+		if(*ealgs == 0 || strcmp(ealgs, "clear") == 0)
+			ealgs = nil;
+		break;
+
+	case 'S':
+		if(srvfd != -1)
+			usage();
+		file = EARGF(usage());
+		if((srvfd = open(file, ORDWR)) < 0)
+			sysfatal("open '%s': %r", file);
+		break;
+
+	case 'd':
+		dbg++;
+		break;
+
+	case 'f':
+		dbfile = EARGF(usage());
+		break;
+
+	case 'n':
+		nonone = 0;
+		break;
+
+	case 'N':
+		nsfile = EARGF(usage());
+		break;
+
+	case 'r':
+		srv = EARGF(usage());
+		break;
+
+	case 's':
+		srv = "/";
+		break;
+
+	case 'A':
+		anstring = EARGF(usage());
+		break;
+
+	case 'Z':
+		negotiate = 0;
+		break;
+
+	default:
+		usage();
+	}ARGEND
+	USED(argc, argv);
+
+	if(na){
+		if(srv == nil)
+			sysfatal("-B requires -s");
+
+		if((fd = dial(netmkaddr(na, 0, "importfs"), 0, 0, 0)) < 0)
+			sysfatal("can't dial %s: %r", na);
+	
+		ai = auth_proxy(fd, auth_getkey, "proto=p9any role=client %s", keyspec);
+		if(ai == nil)
+			sysfatal("%r: %s", na);
+
+		dup(fd, 0);
+		dup(fd, 1);
+		close(fd);
+	}
+
+	if(dbg){
+		n = create(dbfile, OWRITE|OTRUNC, 0666);
+		dup(n, 2);
+		dup(2, 1);
+		if(n > 2)
+			close(n);
+	}
+	
+	if(srvfd >= 0 && srv){
+		fprint(2, "exportfs: -S cannot be used with -r or -s\n");
+		usage();
+	}
+
+	DEBUG(DFD, "exportfs: started\n");
+
+	rfork(RFNOTEG);
+
+	/*
+	 * Get tree to serve from network connection,
+	 * check we can get there and ack the connection
+ 	 */
+	if(srvfd != -1) {
+		/* do nothing */
+	}
+	else if(srv) {
+		chdir(srv);
+		DEBUG(DFD, "invoked as server for %s", srv);
+		strncpy(buf, srv, sizeof buf);
+	}
+	else {
+		buf[0] = 0;
+		n = read(0, buf, sizeof(buf)-1);
+		if(n < 0) {
+			errstr(buf, sizeof buf);
+			fprint(0, "read(0): %s", buf);
+			DEBUG(DFD, "read(0): %s", buf);
+			exits(buf);
+		}
+		buf[n] = 0;
+		if(chdir(buf) < 0) {
+			errstr(ebuf, sizeof ebuf);
+			fprint(0, "chdir(%d:\"%s\"): %s", n, buf, ebuf);
+			DEBUG(DFD, "chdir(%d:\"%s\"): %s", n, buf, ebuf);
+			exits(ebuf);
+		}
+	}
+
+	DEBUG(DFD, "exportfs: %s\n", buf);
+
+	if(srv == nil && srvfd == -1 && write(0, "OK", 2) != 2)
+		fatal("open ack write");
+
+	if(!negotiate)
+		goto serve;
+		
+	if(readn(netfd, &initial, sizeof(ulong)) < sizeof(ulong))
+		fatal("can't read initial string: %r\n");
+
+	if (strncmp((char *)&initial, "impo", sizeof(ulong)) != 0)
+		fatal("cannot negotiate");
+
+	{
+		char buf[128], *p, *args[3];
+
+		// New import.  Read import's parameters...
+		initial = 0;
+
+		p = buf;
+		while (p - buf < sizeof buf) {
+			if ((n = read(netfd, p, 1)) < 0)
+				fatal("can't read impo arguments: %r\n");
+
+			if (n == 0)
+				fatal("connection closed while reading arguments\n");
+
+			if (*p == '\n') 
+				*p = '\0';
+			if (*p++ == '\0')
+				break;
+		}
+		
+		if (tokenize(buf, args, nelem(args)) != 2)
+			fatal("impo arguments invalid: impo%s...\n", buf);
+
+		if (!strcmp(args[0], "aan"))
+			filterp = aanfilter;
+		else if (strcmp(args[0], "nofilter"))
+			fatal("import filter argument unsupported: %s\n", args[0]);
+
+		if (!strcmp(args[1], "ssl"))
+			encproto = Encssl;
+		else if (!strcmp(args[1], "tls"))
+			encproto = Enctls;
+		else if (strcmp(args[1], "clear"))
+			fatal("import encryption proto unsupported: %s\n", args[1]);
+
+		if (encproto == Enctls)
+			sysfatal("%s: tls has not yet been implemented\n", argv[0]);
+	}
+
+	if (encproto != Encnone && ealgs && ai) {
+		uchar key[16];
+		uchar digest[SHA1dlen];
+		char fromclientsecret[21];
+		char fromserversecret[21];
+		int i;
+
+		memmove(key+4, ai->secret, ai->nsecret);
+
+		/* exchange random numbers */
+		srand(truerand());
+		for(i = 0; i < 4; i++)
+			key[i+12] = rand();
+
+		if (initial) 
+			fatal("Protocol botch: old import\n");
+		if(readn(netfd, key, 4) != 4)
+			fatal("can't read key part; %r\n");
+
+		if(write(netfd, key+12, 4) != 4)
+			fatal("can't write key part; %r\n");
+
+		/* scramble into two secrets */
+		sha1(key, sizeof(key), digest, nil);
+		mksecret(fromclientsecret, digest);
+		mksecret(fromserversecret, digest+10);
+
+		if (filterp)
+			netfd = filter(netfd, filterp);
+
+		switch (encproto) {
+		case Encssl:
+			netfd = pushssl(netfd, ealgs, fromserversecret, 
+						fromclientsecret, nil);
+			break;
+		case Enctls:
+		default:
+			fatal("Unsupported encryption protocol\n");
+		}
+
+		if(netfd < 0)
+			fatal("can't establish ssl connection: %r");
+	}
+	else if (filterp) {
+		if (initial) 
+			fatal("Protocol botch: don't know how to deal with this\n");
+		netfd = filter(netfd, filterp);
+	}
+
+serve:
+	
+	if(dbg){
+		int p[2];
+		
+		pipe(p);
+		switch(fork()){
+		case -1:
+			fatal("fork");
+		case 0:
+			close(p[0]);
+			switch(fork()){
+			case -1:
+				fatal("fork");
+			case 0:
+				fprint(2, "%d: copylog\n", getpid());
+				copylog(netfd, p[1], "");
+				postnote(PNGROUP, getpid(), "die");
+				break;
+			default:
+				fprint(2, "%d: copylog\n", getpid());
+				copylog(p[1], netfd, "  ");
+				postnote(PNGROUP, getpid(), "die");
+				break;
+			}
+			_exits(nil);
+		default:
+			close(p[1]);
+			close(netfd);
+			netfd = p[0];
+		}
+	}		
+	
+	fprint(2, "%d: export\n", getpid());
+	export(netfd, ".", 0);
+	postnote(PNGROUP, getpid(), "die");
+	fprint(2, "%d: export finished\n", getpid());
+	fatal(nil);
+}
+
+void
+copylog(int r, int w, char *prefix)
+{
+	int n;
+	static uchar buf[16384], buf0[16384];
+	Fcall f;
+	vlong t;
+	Tm *tm;
+	
+	for(;;){
+		n = read9pmsg(r, buf, sizeof buf);
+		if(n <= 0)
+			break;
+		memmove(buf0, buf, n);
+		t = nsec();
+		tm = localtime(t/1000000000);
+		if(convM2S(buf0, n, &f) < 0){
+			fprint(2, "%s%02d:%02d:%02d.%06d convM2S failed\n", 
+				prefix, tm->hour, tm->min, tm->sec, 
+				(int)((t/1000)%1000000));
+			break;
+		}
+		fprint(2, "%s%02d:%02d:%02d.%06d %F\n", 
+			prefix, tm->hour, tm->min, tm->sec, 
+			(int)((t/1000)%1000000), &f);
+		if(write(w, buf, n) < 0)
+			break;
+	}
+}
+
+
+void
+fatal(char *s, ...)
+{
+	char buf[ERRMAX];
+	va_list arg;
+
+	if (s) {
+		va_start(arg, s);
+		vsnprint(buf, ERRMAX, s, arg);
+		va_end(arg);
+	}
+
+	if (s) 
+		sysfatal(buf);
+	else
+		exits(nil);
+}
+
+/* Network on fd1, mount driver on fd0 */
+int
+filter(int fd, char *cmd)
+{
+	int p[2], lfd, len, nb, argc;
+	char newport[128], buf[128], devdir[40], *s, *file, *argv[16];
+
+	// Get a free port and post it to the client.
+	if (announce(anstring, devdir) < 0)
+		sysfatal("filter: Cannot announce %s: %r\n", anstring);
+
+	snprint(buf, sizeof(buf), "%s/local", devdir);
+	buf[sizeof buf - 1] = '\0';
+	if ((lfd = open(buf, OREAD)) < 0)
+		sysfatal("filter: Cannot open %s: %r\n", buf);
+	if ((len = read(lfd, newport, sizeof newport - 1)) < 0)
+		sysfatal("filter: Cannot read %s: %r\n", buf);
+	close(lfd);
+	newport[len] = '\0';
+
+	if ((s = strchr(newport, '\n')) != nil)
+		*s = '\0';
+
+	if ((nb = write(fd, newport, len)) < 0) 
+		sysfatal("getport; cannot write port; %r");
+	assert(nb == len);
+
+	argc = tokenize(cmd, argv, nelem(argv)-2);
+	if (argc == 0)
+		sysfatal("filter: empty command");
+	argv[argc++] = buf;
+	argv[argc] = nil;
+	file = argv[0];
+	if (s = strrchr(argv[0], '/'))
+		argv[0] = s+1;
+
+	if(pipe(p) < 0)
+		fatal("pipe");
+
+	switch(rfork(RFNOWAIT|RFPROC|RFFDG)) {
+	case -1:
+		fatal("rfork record module");
+	case 0:
+		if (dup(p[0], 1) < 0)
+			fatal("filter: Cannot dup to 1; %r\n");
+		if (dup(p[0], 0) < 0)
+			fatal("filter: Cannot dup to 0; %r\n");
+		close(p[0]);
+		close(p[1]);
+		exec(file, argv);
+		fatal("exec record module");
+	default:
+		close(fd);
+		close(p[0]);
+	}
+	return p[1];	
+}
+
+static void
+mksecret(char *t, uchar *f)
+{
+	sprint(t, "%2.2ux%2.2ux%2.2ux%2.2ux%2.2ux%2.2ux%2.2ux%2.2ux%2.2ux%2.2ux",
+		f[0], f[1], f[2], f[3], f[4], f[5], f[6], f[7], f[8], f[9]);
+}
--- /sys/src/cmd/kexportfs/ksrvfs.c	Thu Jan  1 00:00:00 1970
+++ /sys/src/cmd/kexportfs/ksrvfs.c	Fri Mar 18 22:36:50 2016
@@ -0,0 +1,100 @@
+#include <u.h>
+#include <libc.h>
+
+static void
+usage(void)
+{
+	fprint(2, "usage: %s [-dR] [-p perm] [-P patternfile] [-e exportfs] srvname path\n", argv0);
+	exits("usage");
+}
+
+void
+main(int argc, char **argv)
+{
+	char *ename, *arglist[16], **argp;
+	int n, fd, pipefd[2];
+	char buf[64];
+	int perm = 0600;
+
+	argp = arglist;
+	ename = "/bin/sns/kexportfs";
+	*argp++ = "kexportfs";
+	*argp++ = "-Z";
+	
+	ARGBEGIN{
+	default:
+		usage();
+	case 'd':
+		*argp++ = "-d";
+		break;
+	case 'e':
+		ename = ARGF();
+		break;
+	case 'f':
+		*argp++ = "-f";
+		*argp++ = EARGF(usage());
+		break;
+	case 'p':
+		perm = strtol(ARGF(), 0, 8);
+		break;
+	case 'P':
+		*argp++ = "-P";
+		*argp++ = ARGF();
+		break;
+	case 'R':
+		*argp++ = "-R";
+		 break;
+	}ARGEND
+	*argp = 0;
+	if(argc != 2)
+		usage();
+
+	if(pipe(pipefd) < 0){
+		fprint(2, "can't pipe: %r\n");
+		exits("pipe");
+	}
+
+	if(argv[0][0] == '/')
+		strcpy(buf, argv[0]);
+	else
+		sprint(buf, "/srv/%s", argv[0]);
+	fd = create(buf, ORCLOSE|OWRITE, perm);
+	if(fd < 0){
+		fprint(2, "can't create %s: %r\n", buf);
+		exits("create");
+	}
+
+	switch(rfork(RFPROC|RFNOWAIT|RFNOTEG|RFFDG)){
+	case -1:
+		fprint(2, "can't rfork: %r\n");
+		exits("rfork");
+	case 0:
+		dup(pipefd[0], 0);
+		dup(pipefd[0], 1);
+		close(pipefd[0]);
+		close(pipefd[1]);
+		exec(ename, arglist);
+		fprint(2, "can't exec exportfs: %r\n");
+		exits("exec");
+	default:
+		break;
+	}
+	close(pipefd[0]);
+	if(fprint(pipefd[1], "%s", argv[1]) < 0){
+		fprint(2, "can't write pipe: %r\n");
+		exits("write");
+	}
+	n = read(pipefd[1], buf, sizeof buf-1);
+	if(n < 0){
+		fprint(2, "can't read pipe: %r\n");
+		exits("read");
+	}
+	buf[n] = 0;
+	if(n != 2 || strcmp(buf, "OK") != 0){
+		fprint(2, "not OK (%d): %s\n", n, buf);
+		exits("OK");
+	}
+	fprint(fd, "%d", pipefd[1]);
+	close(pipefd[1]);
+	exits(0);
+}
--- /sys/src/cmd/kexportfs/mkfile	Thu Jan  1 00:00:00 1970
+++ /sys/src/cmd/kexportfs/mkfile	Fri Mar 18 22:36:52 2016
@@ -0,0 +1,20 @@
+</$objtype/mkfile
+
+BIN=/$objtype/bin/sns
+TARG=ksrvfs kexportfs
+OFILES=
+HFILES=
+
+</sys/src/cmd/mkmany
+
+installnet:V: ${TARG:%=$O.%}
+	import 9netics.net / /n/net
+	for(i in $TARG){
+		fcp $O.$i /n/net/$BIN/$i &
+	}
+	wait
+
+%.installnet:V: $O.%
+	import 9netics.net / /n/net
+	fcp $O.$stem /n/net/$BIN/$stem
+
--- /sys/src/cmd/kexportfs/xtest	Thu Jan  1 00:00:00 1970
+++ /sys/src/cmd/kexportfs/xtest	Fri Mar 18 22:36:53 2016
@@ -0,0 +1,22 @@
+#!/bin/rc
+
+rfork n
+rm -f /srv/a /srv/b
+k=''
+if(~ $1 -k){
+	k=sns/k
+	shift
+}
+if(~ $#* 0){
+	echo usage: xtest [-k] cmd >[1=2]
+	exit usage
+}
+
+@{rfork n; srvfs -df /tmp/a a /}
+mount /srv/a /n/a
+@{rfork n; $k^srvfs -df /tmp/b b /}
+mount /srv/b /n/b
+@{rfork n; bind /n/b/n/a /; $* >/dev/null}
+grep -c '^([0-9:.]+ )?T' /tmp/[ab]
+rm -f /srv/[ab]
+