src/cmd: Add a repurposed import(4), called `9import', to the ports.

The code is adapted from Plan 9's import(4); this allows us to speak
that protocol. We don't currently support AAN (in the works) or
TLS/SSL.

Thanks to David for help with the man page, testing, and development.

R=0intro, rsc
CC=plan9port.codebot
http://codereview.appspot.com/6458100

CONTRIBUTORS

@@ -5,6 +5,7 @@
 
 Abhishek Kulkarni <adkulkar@umail.iu.edu>
 Albert Lee <trisk@acm.jhu.edu>
+Akshat Kumar <seed@mail.nanosouffle.net>
 André Günther <Andre.G@gmx.de>
 Anthony Martin <ality@pbrane.org>
 Anthony Sorace <a@9srv.net>

man/man4/9import.4

@@ -0,0 +1,79 @@
+.TH 9IMPORT 4
+.SH NAME
+9import \- import a name space from a remote system
+.SH SYNOPSIS
+.B 9import
+[
+.I options
+]
+.I system
+.I file
+[
+.I mountpoint
+]
+.SH DESCRIPTION
+The
+.I 9import
+tool allows an arbitrary
+.I file
+on a remote
+.I system,
+with the capability of running the Plan 9
+.IR exportfs (4)
+service,
+to be imported into the local name space.
+Usually
+.I file
+is a directory, so the complete
+file tree under the directory is made available.
+.PP
+A process is started on the
+remote machine, with authority of the user of
+.IR 9import ,
+to perform work for the local machine using the
+.IR exportfs (4)
+service.
+The default port used is TCP 17007.
+If
+.I mountpoint
+is omitted, then
+.I 9import
+uses the name of the remote
+.I file
+as the local mount point.
+.PP
+The options are:
+.TF "-s namexxx"
+.PD
+.TP
+.B -A
+Skip the authentication protocol.
+This is useful for connecting to foreign systems like Inferno.
+.TP
+.B -k \fIkeypattern
+Use
+.I keypattern
+to select a key to authenticate to the remote side
+(see
+.IR auth (2)).
+.TP
+.B -p
+Push the
+.IR aan (8)
+filter onto the connection to protect against
+temporary network outages.
+.TP
+.B -s \fIname
+Post the connection's mountable file descriptor as
+.BI /srv/ name\fR.
+.SH SOURCE
+.B \*9/src/cmd/9import.c
+.SH SEE ALSO
+.IR srv (4),
+.IR aan (8),
+.IR listen1 (8),
+.B cs
+in
+.IR ndb (7)
+.SH BUGS
+Encryption is not implemented.

src/cmd/9import.c

@@ -0,0 +1,239 @@
+#include <u.h>
+#include <libc.h>
+#include <auth.h>
+#include <thread.h>
+
+enum {
+	Encnone,
+	Encssl,
+	Enctls,
+};
+
+static char *encprotos[] = {
+	[Encnone] =	"clear",
+	[Encssl] =	"ssl",
+	[Enctls] = 	"tls",
+			nil,
+};
+
+char		*keyspec = "";
+char		*filterp;
+char		*ealgs = "rc4_256 sha1";
+int		encproto = Encnone;
+AuthInfo 	*ai;
+int		debug;
+int		doauth = 1;
+int		timedout;
+
+int	connectez(char*, char*);
+void	sysfatal(char*, ...);
+void	usage(void);
+int	filter(int, char *, char *);
+
+int
+catcher(void *v, char *msg)
+{
+	timedout = 1;
+	if(strcmp(msg, "alarm") == 0)
+		return 1;
+	return 0;
+}
+
+static int
+lookup(char *s, char *l[])
+{
+	int i;
+
+	for (i = 0; l[i] != 0; i++)
+		if (strcmp(l[i], s) == 0)
+			return i;
+	return -1;
+}
+
+static char*
+srvname(char *addr)
+{
+	int i;
+
+	for(i=0; i<strlen(addr); i++){
+		if(addr[i] == '!')
+			addr[i] = ':';
+	}
+	return addr;
+}
+
+void
+threadmain(int argc, char **argv)
+{
+	char *mntpt, *srvpost, srvfile[64];
+	int fd;
+
+	quotefmtinstall();
+	srvpost = nil;
+	ARGBEGIN{
+	case 'A':
+		doauth = 0;
+		break;
+	case 'd':
+		debug++;
+		break;
+	case 'E':
+		if ((encproto = lookup(EARGF(usage()), encprotos)) < 0)
+			usage();
+		break;
+	case 'e':
+		ealgs = EARGF(usage());
+		if(*ealgs == 0 || strcmp(ealgs, "clear") == 0)
+			ealgs = nil;
+		break;
+	case 'k':
+		keyspec = EARGF(usage());
+		break;
+	case 'p':
+		filterp = unsharp("#9/bin/aan");
+		break;
+	case 's':
+		srvpost = EARGF(usage());
+		break;
+	default:
+		usage();
+	}ARGEND;
+
+	mntpt = 0;		/* to shut up compiler */
+	switch(argc) {
+	case 2:
+		mntpt = argv[1];
+		break;
+	case 3:
+		mntpt = argv[2];
+		break;
+	default:
+		usage();
+	}
+
+	if(encproto != Encnone)
+		sysfatal("%s: tls and ssl have not yet been implemented", argv[0]);
+
+	threadnotify(catcher, 1);
+	alarm(60*1000);
+
+	fd = connectez(argv[0], argv[1]);
+
+	fprint(fd, "impo %s %s\n", filterp? "aan": "nofilter",
+		encprotos[encproto]);
+
+	if (filterp)
+		fd = filter(fd, filterp, argv[0]);
+
+	if(srvpost == nil)
+		 srvpost = srvname(argv[0]);
+	sprint(srvfile, "%s", srvpost);
+
+	if(post9pservice(fd, srvfile, mntpt) < 0)
+		sysfatal("can't post %s: %r", argv[1]);
+	alarm(0);
+
+	threadexitsall(0);
+}
+
+/* the name "connect" is special */
+int
+connectez(char *system, char *tree)
+{
+	char buf[ERRMAX], *na;
+	int fd, n;
+	char *authp;
+
+	na = netmkaddr(system, "tcp", "exportfs");
+	threadsetname("dial %s", na);
+	if((fd = dial(na, nil, nil, nil)) < 0)
+		sysfatal("can't dial %s: %r", system);
+
+	if(doauth){
+		authp = "p9any";
+		threadsetname("auth_proxy auth_getkey proto=%q role=client %s",
+			authp, keyspec);
+		ai = auth_proxy(fd, auth_getkey, "proto=%q role=client %s",
+			authp, keyspec);
+		if(ai == nil)
+			sysfatal("%r: %s", system);
+	}
+
+	threadsetname("writing tree name %s", tree);
+	n = write(fd, tree, strlen(tree));
+	if(n < 0)
+		sysfatal("can't write tree: %r");
+
+	strcpy(buf, "can't read tree");
+
+	threadsetname("awaiting OK for %s", tree);
+	n = read(fd, buf, sizeof buf - 1);
+	if(n!=2 || buf[0]!='O' || buf[1]!='K'){
+		if (timedout)
+			sysfatal("timed out connecting to %s", na);
+		buf[sizeof buf - 1] = '\0';
+		sysfatal("bad remote tree: %s", buf);
+	}
+
+	return fd;
+}
+
+void
+usage(void)
+{
+	fprint(2, "usage: 9import [-A] [-E clear|ssl|tls] "
+"[-e 'crypt auth'|clear] [-k keypattern] [-p] [-s srv] host remotefs [mountpoint]\n");
+	threadexitsall("usage");
+}
+
+/* Network on fd1, mount driver on fd0 */
+int
+filter(int fd, char *cmd, char *host)
+{
+	int p[2], len, argc;
+	char newport[256], buf[256], *s;
+	char *argv[16], *file, *pbuf;
+
+	if ((len = read(fd, newport, sizeof newport - 1)) < 0)
+		sysfatal("filter: cannot write port; %r");
+	newport[len] = '\0';
+
+	if ((s = strchr(newport, '!')) == nil)
+		sysfatal("filter: illegally formatted port %s", newport);
+
+	strecpy(buf, buf+sizeof buf, netmkaddr(host, "tcp", "0"));
+	pbuf = strrchr(buf, '!');
+	strecpy(pbuf, buf+sizeof buf, s);
+
+	if(debug)
+		fprint(2, "filter: remote port %s\n", newport);
+
+	argc = tokenize(cmd, argv, nelem(argv)-2);
+	if (argc == 0)
+		sysfatal("filter: empty command");
+	argv[argc++] = "-c";
+	argv[argc++] = buf;
+	argv[argc] = nil;
+	file = argv[0];
+	if (s = strrchr(argv[0], '/'))
+		argv[0] = s+1;
+
+	if(pipe(p) < 0)
+		sysfatal("pipe: %r");
+
+	switch(rfork(RFNOWAIT|RFPROC|RFFDG)) {
+	case -1:
+		sysfatal("rfork record module: %r");
+	case 0:
+		dup(p[0], 1);
+		dup(p[0], 0);
+		close(p[0]);
+		close(p[1]);
+		exec(file, argv);
+		sysfatal("exec record module: %r");
+	default:
+		close(fd);
+		close(p[0]);
+	}
+	return p[1];
+}