cli: add 'validate', or '-n', dry run to copy command

This commit adds config file validation to the copy command, discussed
in #373.  Allowing users to test their config files before restoring a
backup.  The feature could also be used for the automatic rollback when
downgrading to an earlier version of the OS.

Fixes #373

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

doc/cli/introduction.md

@@ -191,4 +191,12 @@ change that, e.g., breaks networking, it is trivial to revert back by:
 admin@host-12-34-56:/> copy startup-config running-config
 ```
 
-Or restarting the device.
+Or restart the device, for example if the change to the configuration
+caused you to lose contact with the system (it happens to the best of
+us).  The system will start up from the last "save gave".
+
+> **Tip:** when restoring a backup of a configuration, or having manually
+> edited a config file, you can validate it using system's YANG models,
+> it is *not* applied if validation is successful:
+>
+> `copy /media/backup/old.cfg running-config validate`

src/bin/copy.c

@@ -34,6 +34,8 @@ struct infix_ds infix_config[] = {
 
 static const char *prognm = "copy";
 static int timeout;
+static int dry_run;
+static int quiet;
 
 
 /*
@@ -180,11 +182,12 @@ static const char *infix_ds(const char *text, struct infix_ds **ds)
 /*
  * Load configuration from a file and replace running datastore.
  * This triggers all sysrepo change callbacks, unlike sr_copy_config().
+ * In dry-run mode, only validates the configuration without applying.
  */
 static int replace_running(sr_conn_ctx_t *conn, sr_session_ctx_t *sess,
 			   const char *file, int timeout)
 {
-	uint32_t flags = LYD_PARSE_NO_STATE | LYD_PARSE_ONLY;
+	uint32_t flags = LYD_PARSE_NO_STATE | LYD_PARSE_ONLY | LYD_PARSE_STORE_ONLY | LYD_PARSE_STRICT;
 	struct lyd_node *data = NULL;
 	const struct ly_ctx *ctx;
 	LY_ERR err;
@@ -199,18 +202,26 @@ static int replace_running(sr_conn_ctx_t *conn, sr_session_ctx_t *sess,
 		return 1;
 	}
 
-	/* Replace running config (triggers callbacks, takes ownership on success) */
-	rc = sr_replace_config(sess, NULL, data, timeout * 1000);
-	if (rc) {
-		emsg(sess, ERRMSG "unable to replace configuration, err %d: %s\n",
-		     rc, sr_strerror(rc));
+	if (dry_run) {
+		if (!quiet) {
+			printf("Configuration validated, %s: OK\n", file);
+			fflush(stdout);
+		}
 		lyd_free_all(data);
+		rc = 0;
+	} else {
+		/* Replace running config, assumes ownership of 'data' */
+		rc = sr_replace_config(sess, NULL, data, timeout * 1000);
+		if (rc) {
+			emsg(sess, ERRMSG "unable to replace configuration, err %d: %s\n",
+			     rc, sr_strerror(rc));
+			lyd_free_all(data);
+		}
 	}
 
 	return rc;
 }
 
-
 static int copy(const char *src, const char *dst, const char *remote_user)
 {
 	struct infix_ds *srcds = NULL, *dstds = NULL;
@@ -450,6 +461,8 @@ static int usage(int rc)
 	       "\n"
 	       "Options:\n"
 	       "  -h         This help text\n"
+	       "  -n         Dry-run, validate configuration without applying\n"
+	       "  -q         Quiet mode, suppress informational messages\n"
 	       "  -u USER    Username for remote commands, like scp\n"
 	       "  -t SEEC    Timeout for the operation, or default %d sec\n"
 	       "  -v         Show version\n", prognm, timeout);
@@ -464,10 +477,16 @@ int main(int argc, char *argv[])
 
 	timeout = fgetint("/etc/default/confd", "=", "CONFD_TIMEOUT");
 
-	while ((c = getopt(argc, argv, "ht:u:v")) != EOF) {
+	while ((c = getopt(argc, argv, "hnqt:u:v")) != EOF) {
 		switch(c) {
 		case 'h':
 			return usage(0);
+		case 'n':
+			dry_run = 1;
+			break;
+		case 'q':
+			quiet = 1;
+			break;
 		case 't':
 			timeout = atoi(optarg);
 			break;

src/klish-plugin-infix/src/infix.c

@@ -28,7 +28,7 @@
 const uint8_t kplugin_infix_major = 1;
 const uint8_t kplugin_infix_minor = 0;
 
-static void cd_home(kcontext_t *ctx)
+static const char *cd_home(kcontext_t *ctx)
 {
 	const char *user = "root";
 	ksession_t *session;
@@ -43,6 +43,8 @@ static void cd_home(kcontext_t *ctx)
 
 	pw = getpwnam(user);
 	chdir(pw->pw_dir);
+
+	return user;
 }
 
 static int systemf(const char *fmt, ...)
@@ -201,8 +203,8 @@ int infix_copy(kcontext_t *ctx)
 {
 	kpargv_t *pargv = kcontext_pargv(ctx);
 	const char *src, *dst;
-	const char *username;
 	char user[256] = "";
+	char validate[8] = "";
 	kparg_t *parg;
 
 	src = kparg_value(kpargv_find(pargv, "src"));
@@ -214,26 +216,20 @@ int infix_copy(kcontext_t *ctx)
 	if (parg)
 		snprintf(user, sizeof(user), "-u %s", kparg_value(parg));
 
-	cd_home(ctx);
-	username = ksession_user(kcontext_session(ctx));
+	parg = kpargv_find(pargv, "validate");
+	if (parg)
+		strlcpy(validate, "-n", sizeof(validate));
 
-	return systemf("sudo -u %s copy %s %s %s", username, user, src, dst);
+	/* Ensure we run the copy command as the logged-in user, not root (klishd) */
+	return systemf("doas -u %s copy %s %s %s %s", cd_home(ctx), validate, user, src, dst);
 }
 
 int infix_shell(kcontext_t *ctx)
 {
-	const char *user = "root";
-	ksession_t *session;
+	const char *user = cd_home(ctx);
 	pid_t pid;
 	int rc;
 
-	session = kcontext_session(ctx);
-	if (session) {
-		user = ksession_user(session);
-		if (!user)
-			user = "root";
-	}
-
 	pid = fork();
 	if (pid == -1)
 		return -1;

src/klish-plugin-infix/xml/infix.xml

@@ -188,6 +188,7 @@
   <PARAM name="src" ptype="/DATASTORE"    help="Source datastore or file, e.g., tftp://ip/file"/>
   <PARAM name="dst" ptype="/RW_DATASTORE" help="Destination datastore or file, e.g., scp://ip/file"/>
   <SWITCH name="optional" min="0">
+    <COMMAND name="validate"              help="Validate configuration without applying"/>
     <PARAM name="user" ptype="/STRING"    help="Remote username (interactive password)"/>
   </SWITCH>
   <ACTION sym="copy@infix" in="tty" out="tty" interrupt="true"/>