Correct an out-by-one error when earlying out ustar filenames that

are too long.  Filenames escaping this test are caught later on,
so the bug doesn't cause any breakage.

Document the correct ustar limitations in pax.  As I have no access
to the IEEE 1003.2 spec, I can only assume that the limitations
imposed are in fact correct.

Add regression tests for the filename limitations imposed by pax.

MFC after:	3 weeks

bin/pax/pax.1

@@ -748,7 +748,9 @@ The extended tar interchange format specified in the
 .St -p1003.2
 standard.
 The default blocksize for this format is 10240 bytes.
-Pathnames stored by this format must be 250 characters or less in length.
+Pathnames stored by this format must be 255 characters or less in length.
+The directory part may be at most 155 characters and each path component
+must be less than 100 characters.
 .El
 .Pp
 The

bin/pax/tar.c

@@ -1086,7 +1086,7 @@ name_split(char *name, int len)
 	 */
 	if (len <= TNMSZ)
 		return(name);
-	if (len > (TPFSZ + TNMSZ + 1))
+	if (len > TPFSZ + TNMSZ)
 		return(NULL);
 
 	/*

tools/regression/bin/pax/Makefile

@@ -0,0 +1,8 @@
+# $FreeBSD$
+
+test:
+	prove -vmw regress.t
+
+clean:
+	rm -rf ustar-pathnames-[12]
+	rm -f ustar.ok ustar.fail*

tools/regression/bin/pax/regress.t

@@ -0,0 +1,91 @@
+#! /usr/bin/perl
+#
+# $FreeBSD$
+
+use strict;
+use warnings;
+
+use Test::More tests => 6;
+use File::Path qw(rmtree mkpath);
+use Cwd;
+
+my $n = 0;
+sub create_file {
+    my $fn = shift;
+
+    $n++;
+    (my $dir = $fn) =~ s,/[^/]+$,,;
+    mkpath $dir;
+    open my $fd, ">", $fn or die "$fn: $!";
+    print $fd "file $n\n";
+}
+
+
+ustar_pathnames: { SKIP: {
+    # Prove that pax breaks up ustar pathnames properly
+
+    my $top = getcwd . "/ustar-pathnames-1";
+    skip "Current path is too long", 6 if length $top > 92;
+    rmtree $top;
+    my $subdir = "x" . "x" x (92 - length $top);
+    my $work94 = "$top/$subdir";
+    mkpath $work94;		# $work is 94 characters long
+
+    my $x49 = "x" x 49;
+    my $x50 = "x" x 50;
+    my $x60 = "x" x 60;
+    my $x95 = "x" x 95;
+
+    my @paths = (
+	"$work94/x099",		# 99 chars
+	"$work94/xx100",		# 100 chars
+	"$work94/xxx101",		# 101 chars
+	"$work94/$x49/${x50}x199",	# 199 chars
+	"$work94/$x49/${x50}xx200",	# 200 chars
+	"$work94/$x49/${x50}xxx201",	# 201 chars
+	"$work94/$x60/${x95}254",	# 254 chars
+	"$work94/$x60/${x95}x255",	# 255 chars
+    );
+
+    my @l = map { length } @paths;
+
+    my $n = 0;
+    create_file $_ for @paths;
+    system "pax -wf ustar.ok $work94";
+    ok($? == 0, "Wrote 'ustar.ok' containing files with lengths @l");
+
+    (my $orig = $top) =~ s,1$,2,;
+    rmtree $orig;
+    rename $top, $orig;
+
+    system "pax -rf ustar.ok";
+    ok($? == 0, "Restored 'ustar.ok' containing files with lengths @l");
+
+    system "diff -ru $orig $top";
+    ok($? == 0, "Restored files are identical");
+
+    rmtree $top;
+    rename $orig, $top;
+
+    # 256 chars (with components < 100 chars) should not work
+    push @paths, "$work94/x$x60/${x95}x256";	# 256 chars
+    push @l, length $paths[-1];
+    create_file $paths[-1];
+    system "pax -wf ustar.fail1 $work94";
+    ok($?, "Failed to write 'ustar.fail1' containing files with lengths @l");
+
+    # Components with 100 chars shouldn't work
+    unlink $paths[-1];
+    $paths[-1] = "$work94/${x95}xc100";		# 100 char filename
+    $l[-1] = length $paths[-1];
+    create_file $paths[-1];
+    system "pax -wf ustar.fail2 $work94";
+    ok($?, "Failed to write 'ustar.fail2' with a 100 char filename");
+
+    unlink $paths[-1];
+    $paths[-1] = "$work94/${x95}xc100/x";	# 100 char component
+    $l[-1] = length $paths[-1];
+    create_file $paths[-1];
+    system "pax -wf ustar.fail3 $work94";
+    ok($?, "Failed to write 'ustar.fail3' with a 100 char component");
+}}