Clean up and rename conf_ns_open()

conf_ns_open() opens file descriptors for the namespaces pasta needs, but
it doesnt really have anything to do with configuration any more.  For
better clarity, move it to pasta.c and rename it pasta_open_ns().  This
makes the symmetry between it and pasta_start_ns() more clear, since these
represent the two basic ways that pasta can operate, either attaching to
an existing namespace/process or spawning a new one.

Since its no longer validating options, the errors it could return
shouldn't cause a usage message.  Just exit directly with an error instead.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

conf.c

@@ -20,7 +20,6 @@
 #include <sched.h>
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <libgen.h>
 #include <limits.h>
 #include <grp.h>
 #include <pwd.h>
@@ -574,73 +573,6 @@ static int conf_pasta_ns(int *netns_only, char *userns, char *netns,
 	return 0;
 }
 
-/**
- * conf_ns_check() - Check if we can enter configured namespaces
- * @arg:	Execution context
- *
- * Return: 0
- */
-static int conf_ns_check(void *arg)
-{
-	struct ctx *c = (struct ctx *)arg;
-
-	if ((!c->netns_only && setns(c->pasta_userns_fd, CLONE_NEWUSER)) ||
-	    setns(c->pasta_netns_fd, CLONE_NEWNET))
-		c->pasta_userns_fd = c->pasta_netns_fd = -1;
-
-	return 0;
-
-}
-
-/**
- * conf_ns_open() - Open network, user namespaces descriptors from configuration
- * @c:		Execution context
- * @userns:	--userns argument, can be an empty string
- * @netns:	network namespace path
- *
- * Return: 0 on success, negative error code otherwise
- */
-static int conf_ns_open(struct ctx *c, const char *userns, const char *netns)
-{
-	int ufd = -1, nfd = -1;
-
-	nfd = open(netns, O_RDONLY | O_CLOEXEC);
-	if (nfd < 0) {
-		err("Couldn't open network namespace %s", netns);
-		return -ENOENT;
-	}
-
-	if (!c->netns_only && *userns) {
-		ufd = open(userns, O_RDONLY | O_CLOEXEC);
-		if (ufd < 0) {
-			close(nfd);
-			err("Couldn't open user namespace %s", userns);
-			return -ENOENT;
-		}
-	}
-
-	c->pasta_netns_fd = nfd;
-	c->pasta_userns_fd = ufd;
-
-	NS_CALL(conf_ns_check, c);
-
-	if (c->pasta_netns_fd < 0) {
-		err("Couldn't switch to pasta namespaces");
-		return -ENOENT;
-	}
-
-	if (!c->no_netns_quit) {
-		char buf[PATH_MAX];
-
-		strncpy(buf, netns, PATH_MAX);
-		strncpy(c->netns_base, basename(buf), PATH_MAX - 1);
-		strncpy(buf, netns, PATH_MAX);
-		strncpy(c->netns_dir, dirname(buf), PATH_MAX - 1);
-	}
-
-	return 0;
-}
-
 /**
  * conf_ip4() - Verify or detect IPv4 support, get relevant addresses
  * @ifi:	Host interface to attempt (0 to determine one)
@@ -1598,9 +1530,7 @@ void conf(struct ctx *c, int argc, char **argv)
 
 	if (c->mode == MODE_PASTA) {
 		if (*netns) {
-			ret = conf_ns_open(c, userns, netns);
+			pasta_open_ns(c, userns, netns);
-			if (ret < 0)
-				usage(argv[0]);
 		} else {
 			pasta_start_ns(c, argc - optind, argv + optind);
 		}

pasta.c

@@ -20,6 +20,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <errno.h>
+#include <libgen.h>
 #include <limits.h>
 #include <stdlib.h>
 #include <stdint.h>
@@ -101,6 +102,71 @@ netns:
 	return 0;
 }
 
+/**
+ * ns_check() - Check if we can enter configured namespaces
+ * @arg:	Execution context
+ *
+ * Return: 0
+ */
+static int ns_check(void *arg)
+{
+	struct ctx *c = (struct ctx *)arg;
+
+	if ((!c->netns_only && setns(c->pasta_userns_fd, CLONE_NEWUSER)) ||
+	    setns(c->pasta_netns_fd, CLONE_NEWNET))
+		c->pasta_userns_fd = c->pasta_netns_fd = -1;
+
+	return 0;
+
+}
+
+/**
+ * pasta_open_ns() - Open network, user namespaces descriptors
+ * @c:		Execution context
+ * @userns:	--userns argument, can be an empty string
+ * @netns:	network namespace path
+ *
+ * Return: 0 on success, negative error code otherwise
+ */
+void pasta_open_ns(struct ctx *c, const char *userns, const char *netns)
+{
+	int ufd = -1, nfd = -1;
+
+	nfd = open(netns, O_RDONLY | O_CLOEXEC);
+	if (nfd < 0) {
+		err("Couldn't open network namespace %s", netns);
+		exit(EXIT_FAILURE);
+	}
+
+	if (!c->netns_only && *userns) {
+		ufd = open(userns, O_RDONLY | O_CLOEXEC);
+		if (ufd < 0) {
+			close(nfd);
+			err("Couldn't open user namespace %s", userns);
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	c->pasta_netns_fd = nfd;
+	c->pasta_userns_fd = ufd;
+
+	NS_CALL(ns_check, c);
+
+	if (c->pasta_netns_fd < 0) {
+		err("Couldn't switch to pasta namespaces");
+		exit(EXIT_FAILURE);
+	}
+
+	if (!c->no_netns_quit) {
+		char buf[PATH_MAX] = { 0 };
+
+		strncpy(buf, netns, PATH_MAX - 1);
+		strncpy(c->netns_base, basename(buf), PATH_MAX - 1);
+		strncpy(buf, netns, PATH_MAX - 1);
+		strncpy(c->netns_dir, dirname(buf), PATH_MAX - 1);
+	}
+}
+
 /**
  * struct pasta_setup_ns_arg - Argument for pasta_setup_ns()
  * @c:		Execution context

pasta.h

@@ -6,6 +6,7 @@
 #ifndef PASTA_H
 #define PASTA_H
 
+void pasta_open_ns(struct ctx *c, const char *userns, const char *netns);
 void pasta_start_ns(struct ctx *c, int argc, char *argv[]);
 void pasta_ns_conf(struct ctx *c);
 void pasta_child_handler(int signal);