utils: add lxc_nic_exists()

src/lxc/lxc_user_nic.c

@@ -397,26 +397,6 @@ static char *find_line(char *p, char *e, char *u, char *t, char *l)
 	return NULL;
 }
 
-static bool nic_exists(char *nic)
-{
-	char path[MAXPATHLEN];
-	int ret;
-	struct stat sb;
-
-	if (!strcmp(nic, "none"))
-		return true;
-
-	ret = snprintf(path, MAXPATHLEN, "/sys/class/net/%s", nic);
-	if (ret < 0 || (size_t)ret >= MAXPATHLEN)
-		return false;
-
-	ret = stat(path, &sb);
-	if (ret < 0)
-		return false;
-
-	return true;
-}
-
 static int instantiate_veth(char *n1, char **n2)
 {
 	int err;
@@ -625,7 +605,7 @@ static bool cull_entries(int fd, char *me, char *t, char *br, char *nicname,
 			continue;
 
 		if (nic[0] != '\0')
-			exists = nic_exists(nic);
+			exists = lxc_nic_exists(nic);
 
 		if (!exists)
 			entry_lines[n - 1].keep = false;

src/lxc/utils.c

@@ -2409,3 +2409,24 @@ bool has_fs_type(const char *path, fs_type_magic magic_val)
 
 	return has_type;
 }
+
+bool lxc_nic_exists(char *nic)
+{
+#define __LXC_SYS_CLASS_NET_LEN 15 + IFNAMSIZ + 1
+	char path[__LXC_SYS_CLASS_NET_LEN];
+	int ret;
+	struct stat sb;
+
+	if (!strcmp(nic, "none"))
+		return true;
+
+	ret = snprintf(path, __LXC_SYS_CLASS_NET_LEN, "/sys/class/net/%s", nic);
+	if (ret < 0 || (size_t)ret >= __LXC_SYS_CLASS_NET_LEN)
+		return false;
+
+	ret = stat(path, &sb);
+	if (ret < 0)
+		return false;
+
+	return true;
+}

src/lxc/utils.h

@@ -402,5 +402,6 @@ extern void *must_realloc(void *orig, size_t sz);
 typedef __typeof__(((struct statfs *)NULL)->f_type) fs_type_magic;
 extern bool has_fs_type(const char *path, fs_type_magic magic_val);
 extern bool is_fs_type(const struct statfs *fs, fs_type_magic magic_val);
+extern bool lxc_nic_exists(char *nic);
 
 #endif /* __LXC_UTILS_H */