use {get,list,set}xattr to modify runtime

TODO

@@ -7,4 +7,3 @@
   * newest
 * unit tests
 * add more to ioctl
-* use {list,set}xattr for setting runtime values via .mergerfs pseudofile

src/getxattr.cpp

@@ -27,6 +27,7 @@
 
 #include <errno.h>
 #include <sys/types.h>
+#include <string.h>
 
 #include "config.hpp"
 #include "fs.hpp"
@@ -38,6 +39,45 @@ using std::string;
 using std::vector;
 using mergerfs::Policy;
 
+static
+int
+_getxattr_controlfile(const Policy &policy,
+                      const string  attrname,
+                      char         *buf,
+                      const size_t  count)
+{
+#ifndef WITHOUT_XATTR
+  size_t len;
+  string attrvalue;
+
+  if(attrname == "user.mergerfs.action")
+    attrvalue = policy.action.str();
+  else if(attrname == "user.mergerfs.create")
+    attrvalue = policy.create.str();
+  else if(attrname == "user.mergerfs.search")
+    attrvalue = policy.search.str();
+  else if(attrname == "user.mergerfs.statfs")
+    attrvalue = policy.statfs.str();
+
+  if(attrvalue.empty())
+    return -ENOATTR;
+
+  len = attrvalue.size() + 1;
+
+  if(count == 0)
+    return len;
+
+  if(count < len)
+    return -ERANGE;
+
+  memcpy(buf,attrvalue.c_str(),len);
+
+  return (int)len;
+#else
+  return -ENOTSUP;
+#endif
+}
+
 static
 int
 _getxattr(const Policy::Search::Func  searchFunc,
@@ -77,7 +117,10 @@ namespace mergerfs
       const config::Config      &config = config::get();
 
       if(fusepath == config.controlfile)
-        return -ENOTSUP;
+        return _getxattr_controlfile(config.policy,
+                                     attrname,
+                                     buf,
+                                     count);
 
       return _getxattr(config.policy.search,
                        config.srcmounts,

src/listxattr.cpp

@@ -27,6 +27,7 @@
 
 #include <sys/types.h>
 #include <errno.h>
+#include <string.h>
 
 #include "config.hpp"
 #include "fs.hpp"
@@ -37,6 +38,33 @@
 using std::string;
 using std::vector;
 using mergerfs::Policy;
+using namespace mergerfs;
+
+static
+int
+_listxattr_controlfile(char         *list,
+                       const size_t  size)
+{
+#ifndef WITHOUT_XATTR
+  const char xattrs[] =
+    "user.mergerfs.action\0"
+    "user.mergerfs.create\0"
+    "user.mergerfs.search\0"
+    "user.mergerfs.statfs\0";
+
+  if(size == 0)
+    return sizeof(xattrs);
+
+  if(size < sizeof(xattrs))
+    return -ERANGE;
+
+  memcpy(list,xattrs,sizeof(xattrs));
+
+  return sizeof(xattrs);
+#else
+  return -ENOTSUP;
+#endif
+}
 
 static
 int
@@ -75,7 +103,8 @@ namespace mergerfs
       const config::Config      &config = config::get();
 
       if(fusepath == config.controlfile)
-        return -ENOTSUP;
+        return _listxattr_controlfile(list,
+                                      size);
 
       return _listxattr(config.policy.search,
                         config.srcmounts,

src/setxattr.cpp

@@ -37,6 +37,65 @@
 using std::string;
 using std::vector;
 using mergerfs::Policy;
+using namespace mergerfs;
+
+static
+int
+_setxattr_controlfile(config::Config &config,
+                      const string    attrname,
+                      const string    attrval,
+                      const size_t    attrvalsize,
+                      const int       flags)
+{
+#ifndef WITHOUT_XATTR
+  if(attrname == "user.mergerfs.action")
+    {
+      if((flags & XATTR_CREATE) == XATTR_CREATE)
+        return -EEXIST;
+      if(Policy::Action::fromString(attrval) != -1)
+        config.policy.action = attrval;
+      else
+        return -ENOSPC;
+    }
+  else if(attrname == "user.mergerfs.create")
+    {
+      if((flags & XATTR_CREATE) == XATTR_CREATE)
+        return -EEXIST;
+      if(Policy::Create::fromString(attrval) != -1)
+        config.policy.create = attrval;
+      else
+        return -ENOSPC;
+    }
+  else if(attrname == "user.mergerfs.search")
+    {
+      if((flags & XATTR_CREATE) == XATTR_CREATE)
+        return -EEXIST;
+      if(Policy::Search::fromString(attrval) != -1)
+        config.policy.search = attrval;
+      else
+        return -ENOSPC;
+    }
+  else if(attrname == "user.mergerfs.statfs")
+    {
+      if((flags & XATTR_CREATE) == XATTR_CREATE)
+        return -EEXIST;
+      if(Policy::StatFS::fromString(attrval) != -1)
+        config.policy.statfs = attrval;
+      else
+        return -ENOSPC;
+    }
+  else
+    {
+      return -ENOATTR;
+    }
+
+  config.updateReadStr();
+
+  return 0;
+#else
+  return -ENOTSUP;
+#endif
+}
 
 static
 int
@@ -87,7 +146,11 @@ namespace mergerfs
       const config::Config      &config = config::get();
 
       if(fusepath == config.controlfile)
-        return -ENOTSUP;
+        return _setxattr_controlfile(config::get_writable(),
+                                     attrname,
+                                     string(attrval,attrvalsize),
+                                     attrvalsize,
+                                     flags);
 
       return _setxattr(config.policy.action,
                        config.srcmounts,