systemd: add a generator for the rpc_pipefs mountpoint

The nfs.conf has config options for the rpc_pipefs mountpoint.
Currently, changing these from the default also requires manually
overriding the systemd unit files that are hard-coded to mount the
filesystem on /var/lib/nfs/rpc_pipefs.

This patch adds a generator that creates a mount unit file for the
rpc_pipefs when a non-default value is specified in /etc/nfs.conf, as
well as a target unit file to override the dependencies for the systemd
units using the rpc_pipefs.  The blkmapd, idmapd, and gssd service unit
files have been modified to define their dependencies on the rpc_pipefs
mountpoint indirectly via the rpc_pipefs target unit file.  Since both
rpc-pipefs-generator.c and nfs-server-generator.c need to convert path
names to unit file names, that functionality has been moved to
systemd.c.

This patch also removes the dependency on the rpc_pipefs from the
rpc-svcgssd.service unit file.  rpc.svcgssd uses the sunrpc cache
mechanism to exchange data with the kernel, not the rpc_pipefs.

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: Steve Dickson <steved@redhat.com>

1 files changed, 133 insertions, 0 deletions

diff --git a/systemd/systemd.c b/systemd/systemd.c
new file mode 100644
index 0000000..17820d4
--- /dev/null
+++ b/systemd/systemd.c
@@ -0,0 +1,133 @@
+/*
+ * Helper functions for systemd generators in nfs-utils.
+ *
+ * Currently just systemd_escape().
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <string.h>
+
+static const char hex[16] =
+{
+  '0', '1', '2', '3', '4', '5', '6', '7',
+  '8', '9', 'a', 'b', 'c', 'd', 'e', 'f',
+};
+
+/*
+ * determine length of the string that systemd_escape() needs to allocate
+ */
+static int systemd_len(char *path)
+{
+	char *p;
+	int len = 0;
+
+	p = path;
+	while (*p == '/')
+		/* multiple leading "/" are ignored */
+		p++;
+
+	if (!*p)
+		/* root directory "/" becomes is encoded as a single "-" */
+		return 1;
+
+	if (*p == '.')
+		/*
+		 * replace "." with "\x2d" escape sequence if
+		 * it's the first character in escaped path
+		 * */
+		len += 4;
+
+	while (*p) {
+		unsigned char c = *p++;
+
+		if (c == '/') {
+			/* multiple non-trailing slashes become '-' */
+			while (*p == '/')
+				p++;
+			if (*p)
+				len++;
+		} else if (isalnum(c) || c == ':' || c == '.' || c == '_')
+			/* these characters are not replaced */
+			len++;
+		else
+			/* replace with "\x2d" escape sequence */
+			len += 4;
+	}
+
+	return len;
+}
+
+/*
+ * convert c to "\x2d" escape sequence and append to string
+ * at position p, advancing p
+ */
+static char *hexify(unsigned char c, char *p)
+{
+	*p++ = '\\';
+	*p++ = 'x';
+	*p++ = hex[c >> 4];
+	*p++ = hex[c & 0xf];
+	return p;
+}
+
+/*
+ * convert a path to a unit name according to the logic in systemd.unit(5):
+ *
+ *     Basically, given a path, "/" is replaced by "-", and all other
+ *     characters which are not ASCII alphanumerics are replaced by C-style
+ *     "\x2d" escapes (except that "_" is never replaced and "." is only
+ *     replaced when it would be the first character in the escaped path).
+ *     The root directory "/" is encoded as single dash, while otherwise the
+ *     initial and ending "/" are removed from all paths during
+ *     transformation.
+ *
+ * NB: Although the systemd.unit(5) doesn't mention it, the ':' character
+ * is not escaped.
+ */
+char *systemd_escape(char *path, char *suffix)
+{
+	char *result;
+	char *p;
+	int len;
+
+	len = systemd_len(path);
+	result = malloc(len + strlen(suffix) + 1);
+	p = result;
+	while (*path == '/')
+		/* multiple leading "/" are ignored */
+		path++;
+	if (!*path) {
+		/* root directory "/" becomes is encoded as a single "-" */
+		*p++ = '-';
+		goto out;
+	}
+	if (*path == '.')
+		/*
+		 * replace "." with "\x2d" escape sequence if
+		 * it's the first character in escaped path
+		 * */
+		p = hexify(*path++, p);
+
+	while (*path) {
+		unsigned char c = *path++;
+
+		if (c == '/') {
+			/* multiple non-trailing slashes become '-' */
+			while (*path == '/')
+				path++;
+			if (*path)
+				*p++ = '-';
+		} else if (isalnum(c) || c == ':' || c == '.' || c == '_')
+			/* these characters are not replaced */
+			*p++ = c;
+		else
+			/* replace with "\x2d" escape sequence */
+			p = hexify(c, p);
+	}
+
+out:
+	sprintf(p, "%s", suffix);
+	return result;
+}