classid auto generation if provided tc name does not exist

Manually editing etc/libnl/classid before adding tc objects is a pain.
This patch adds code to attempt auto generating a unique tc id which
will then be assigned to the provided name and added to the classid
file.

This will make the following commands work with prior definitions of
the names "top" and "test"
	sudo sbin/nl-qdisc-add --dev eth0 --parent root --id top htb
	sudo sbin/nl-class-add --dev eth0 --parent top --id test htb --rate 100mbit

It will generate the following ids automatically:
4001:			top
4001:1			test

1 files changed, 110 insertions, 28 deletions

diff --git a/lib/route/classid.c b/lib/route/classid.c
index 5650a20..0cb89b5 100644
--- a/lib/route/classid.c
+++ b/lib/route/classid.c
@@ -75,6 +75,20 @@ static int classid_lookup(const char *name, uint32_t *result)
 	return -NLE_OBJ_NOTFOUND;
 }
 
+static char *name_lookup(const uint32_t classid)
+{
+	void *res;
+	struct classid_map cm = {
+		.classid = classid,
+		.name = "search entry",
+	};
+
+	if ((res = tfind(&cm, &id_root, &compare_id)))
+		return (*(struct classid_map **) res)->name;
+
+	return NULL;
+}
+
 /**
  * @name Traffic Control Handle Translations
  * @{
@@ -101,14 +115,10 @@ char * rtnl_tc_handle2str(uint32_t handle, char *buf, size_t len)
 	else if (TC_H_INGRESS == handle)
 		snprintf(buf, len, "ingress");
 	else {
-		void *res;
-		struct classid_map cm = {
-			.classid = handle,
-			.name = "search entry",
-		};
-
-		if ((res = tfind(&cm, &id_root, &compare_id)))
-			snprintf(buf, len, "%s", (*(struct classid_map **) res)->name);
+		char *name;
+
+		if ((name = name_lookup(handle)))
+			snprintf(buf, len, "%s", name);
 		else if (0 == TC_H_MAJ(handle))
 			snprintf(buf, len, ":%02x", TC_H_MIN(handle));
 		else if (0 == TC_H_MIN(handle))
@@ -232,6 +242,15 @@ static void free_nothing(void *arg)
 {
 }
 
+static void classid_map_free(struct classid_map *map)
+{
+	if (!map)
+		return;
+
+	free(map->name);
+	free(map);
+}
+
 static void clear_hashtable(void)
 {
 	int i;
@@ -239,10 +258,8 @@ static void clear_hashtable(void)
 	for (i = 0; i < CLASSID_NAME_HT_SIZ; i++) {
 		struct classid_map *map, *n;
 
-		nl_list_for_each_entry_safe(map, n, &tbl_name[i], name_list) {
-			free(map->name);
-			free(map);
-		}
+		nl_list_for_each_entry_safe(map, n, &tbl_name[i], name_list)
+			classid_map_free(map);
 
 		nl_init_list_head(&tbl_name[i]);
 
@@ -254,6 +271,28 @@ static void clear_hashtable(void)
 	}
 }
 
+static int classid_map_add(uint32_t classid, const char *name)
+{
+	struct classid_map *map;
+	int n;
+
+	if (!(map = calloc(1, sizeof(*map))))
+		return -NLE_NOMEM;
+
+	map->classid = classid;
+	map->name = strdup(name);
+
+	n = classid_tbl_hash(map->name);
+	nl_list_add_tail(&map->name_list, &tbl_name[n]);
+
+	if (!tsearch((void *) map, &id_root, &compare_id)) {
+		classid_map_free(map);
+		return -NLE_NOMEM;
+	}
+
+	return 0;
+}
+
 /**
  * (Re-)read classid file
  * 
@@ -289,10 +328,8 @@ int rtnl_tc_read_classid_file(void)
 	clear_hashtable();
 
 	while (fgets(buf, sizeof(buf), fd)) {
-		struct classid_map *map;
 		uint32_t classid;
 		char *ptr, *tok;
-		int n;
 
 		/* ignore comments and empty lines */
 		if (*buf == '#' || *buf == '\n' || *buf == '\r')
@@ -312,21 +349,8 @@ int rtnl_tc_read_classid_file(void)
 			goto errout_close;
 		}
 
-		if (!(map = calloc(1, sizeof(*map)))) {
-			err = -NLE_NOMEM;
+		if ((err = classid_map_add(classid, tok)) < 0)
 			goto errout_close;
-		}
-
-		map->classid = classid;
-		map->name = strdup(tok);
-
-		n = classid_tbl_hash(map->name);
-		nl_list_add_tail(&map->name_list, &tbl_name[n]);
-
-		if (!tsearch((void *) map, &id_root, &compare_id)) {
-			err = -NLE_NOMEM;
-			goto errout_close;
-		}
 	}
 
 	err = 0;
@@ -341,6 +365,64 @@ errout:
 
 }
 
+int rtnl_classid_generate(const char *name, uint32_t *result, uint32_t parent)
+{
+	static uint32_t base = 0x4000 << 16;
+	uint32_t classid;
+	char *path;
+	FILE *fd;
+	int err = 0;
+
+	if (parent == TC_H_ROOT || parent == TC_H_INGRESS) {
+		do {
+			base += (1 << 16);
+			if (base == TC_H_MAJ(TC_H_ROOT))
+				base = 0x4000 << 16;
+		} while (name_lookup(base));
+
+		classid = base;
+	} else {
+		classid = TC_H_MAJ(parent);
+		do {
+			if (++classid == TC_H_MIN(TC_H_ROOT))
+				return -NLE_RANGE;
+		} while (name_lookup(base));
+	}
+
+	NL_DBG(2, "Generated new classid %#x\n", classid);
+
+	if (asprintf(&path, "%s/classid", SYSCONFDIR) < 0)
+		return -NLE_NOMEM;
+
+	if (!(fd = fopen(path, "a"))) {
+		err = -nl_syserr2nlerr(errno);
+		goto errout;
+	}
+
+	fprintf(fd, "%x:", TC_H_MAJ(classid) >> 16);
+	if (TC_H_MIN(classid))
+		fprintf(fd, "%x", TC_H_MIN(classid));
+	fprintf(fd, "\t\t\t%s\n", name);
+
+	fclose(fd);
+
+	if ((err = classid_map_add(classid, name)) < 0) {
+		/* 
+		 * Error adding classid map, re-read classid file is best
+		 * option here. It is likely to fail as well but better
+		 * than nothing, entry was added to the file already anyway.
+		 */
+		rtnl_tc_read_classid_file();
+	}
+
+	*result = classid;
+	err = 0;
+errout:
+	free(path);
+
+	return err;
+}
+
 /** @} */
 
 static void __init classid_init(void)