Move list_cloners to libifconfig

Move list_cloners() from ifconfig(8) to libifconfig(3) where it can be
reused by other consumers.

Reviewed by:	kp
Differential Revision:	https://reviews.freebsd.org/D26858

lib/libifconfig/libifconfig.c

@@ -628,3 +628,35 @@ ifconfig_set_vlantag(ifconfig_handle_t *h, const char *name,
 	}
 	return (0);
 }
+
+int
+ifconfig_list_cloners(ifconfig_handle_t *h, char **bufp, size_t *lenp)
+{
+	struct if_clonereq ifcr;
+	char *buf;
+
+	memset(&ifcr, 0, sizeof(ifcr));
+	*bufp = NULL;
+	*lenp = 0;
+
+	if (ifconfig_ioctlwrap(h, AF_LOCAL, SIOCIFGCLONERS, &ifcr) < 0)
+		return (-1);
+
+	buf = malloc(ifcr.ifcr_total * IFNAMSIZ);
+	if (buf == NULL) {
+		h->error.errtype = OTHER;
+		h->error.errcode = ENOMEM;
+		return (-1);
+	}
+
+	ifcr.ifcr_count = ifcr.ifcr_total;
+	ifcr.ifcr_buffer = buf;
+	if (ifconfig_ioctlwrap(h, AF_LOCAL, SIOCIFGCLONERS, &ifcr) < 0) {
+		free(buf);
+		return (-1);
+	}
+
+	*bufp = buf;
+	*lenp = ifcr.ifcr_total;
+	return (0);
+}

lib/libifconfig/libifconfig.h

@@ -279,3 +279,13 @@ int ifconfig_create_interface_vlan(ifconfig_handle_t *h, const char *name,
 
 int ifconfig_set_vlantag(ifconfig_handle_t *h, const char *name,
     const char *vlandev, const unsigned short vlantag);
+
+/** Gets the names of all interface cloners available on the system
+ * @param bufp	Set to the address of the names buffer on success or NULL
+ *              if an error occurs.  This buffer must be freed when done.
+ * @param lenp	Set to the number of names in the returned buffer or 0
+ * 		if an error occurs.  Each name is contained within an
+ * 		IFNAMSIZ length slice of the buffer, for a total buffer
+ * 		length of *lenp * IFNAMSIZ bytes.
+ */
+int ifconfig_list_cloners(ifconfig_handle_t *h, char **bufp, size_t *lenp);

sbin/ifconfig/ifclone.c

@@ -41,6 +41,7 @@ static const char rcsid[] =
 #include <net/if.h>
 
 #include <err.h>
+#include <libifconfig.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -51,45 +52,27 @@ static const char rcsid[] =
 static void
 list_cloners(void)
 {
-	struct if_clonereq ifcr;
-	char *cp, *buf;
-	int idx;
-	int s;
+	ifconfig_handle_t *lifh;
+	char *cloners;
+	size_t cloners_count;
 
-	s = socket(AF_LOCAL, SOCK_DGRAM, 0);
-	if (s == -1)
-		err(1, "socket(AF_LOCAL,SOCK_DGRAM)");
+	lifh = ifconfig_open();
+	if (lifh == NULL)
+		return;
 
-	memset(&ifcr, 0, sizeof(ifcr));
+	if (ifconfig_list_cloners(lifh, &cloners, &cloners_count) < 0)
+		errc(1, ifconfig_err_errno(lifh), "unable to list cloners");
+	ifconfig_close(lifh);
 
-	if (ioctl(s, SIOCIFGCLONERS, &ifcr) < 0)
-		err(1, "SIOCIFGCLONERS for count");
-
-	buf = malloc(ifcr.ifcr_total * IFNAMSIZ);
-	if (buf == NULL)
-		err(1, "unable to allocate cloner name buffer");
-
-	ifcr.ifcr_count = ifcr.ifcr_total;
-	ifcr.ifcr_buffer = buf;
-
-	if (ioctl(s, SIOCIFGCLONERS, &ifcr) < 0)
-		err(1, "SIOCIFGCLONERS for names");
-
-	/*
-	 * In case some disappeared in the mean time, clamp it down.
-	 */
-	if (ifcr.ifcr_count > ifcr.ifcr_total)
-		ifcr.ifcr_count = ifcr.ifcr_total;
-
-	for (cp = buf, idx = 0; idx < ifcr.ifcr_count; idx++, cp += IFNAMSIZ) {
-		if (idx > 0)
+	for (const char *name = cloners;
+	    name < cloners + cloners_count * IFNAMSIZ;
+	    name += IFNAMSIZ) {
+		if (name > cloners)
 			putchar(' ');
-		printf("%s", cp);
+		printf("%s", name);
 	}
-
 	putchar('\n');
-	free(buf);
-	close(s);
+	free(cloners);
 }
 
 struct clone_defcb {