ramfs: Add support for "special" nodes.

Like S_IFIFO. It doesn't support ones with "sub-vnodes", but FIFOs
and UNIX sockets don't seem to use those (does anything, actually?)

Fixes #19261.

Change-Id: I9eeac4efcbe74e9084653c77d883dbb44e6f1d2c
Reviewed-on: https://review.haiku-os.org/c/haiku/+/8830
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

src/add-ons/kernel/file_systems/ramfs/Jamfile

@@ -30,6 +30,7 @@ KernelAddon ramfs
 	NodeListener.cpp
 	NodeTable.cpp
 	Query.cpp
+	SpecialNode.cpp
 	SizeIndex.cpp
 	SymLink.cpp
 	Volume.cpp

src/add-ons/kernel/file_systems/ramfs/Node.cpp

@@ -15,20 +15,21 @@
 
 
 Node::Node(Volume *volume, uint8 type)
-	: fVolume(volume),
-	  fID(fVolume->NextNodeID()),
-	  fRefCount(0),
-	  fMode(0),
-	  fUID(0),
-	  fGID(0),
-	  fATime(0),
-	  fMTime(0),
-	  fCTime(0),
-	  fCrTime(0),
-	  fModified(0),
-	  fIsKnownToVFS(false),
-	  fAttributes(),
-	  fReferrers()
+	:
+	fVolume(volume),
+	fID(fVolume->NextNodeID()),
+	fRefCount(0),
+	fMode(0),
+	fUID(0),
+	fGID(0),
+	fATime(0),
+	fMTime(0),
+	fCTime(0),
+	fCrTime(0),
+	fModified(0),
+	fIsKnownToVFS(false),
+	fAttributes(),
+	fReferrers()
 {
 	// set file type
 	switch (type) {

src/add-ons/kernel/file_systems/ramfs/Node.h

@@ -22,6 +22,7 @@ enum {
 	NODE_TYPE_DIRECTORY,
 	NODE_TYPE_FILE,
 	NODE_TYPE_SYMLINK,
+	NODE_TYPE_SPECIAL,
 };
 
 // access modes
@@ -115,6 +116,8 @@ private:
 	Volume					*fVolume;
 	ino_t					fID;
 	int32					fRefCount;
+
+protected:
 	mode_t					fMode;
 	uid_t					fUID;
 	uid_t					fGID;

src/add-ons/kernel/file_systems/ramfs/SpecialNode.cpp

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2025, Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT license.
+ */
+
+#include "SpecialNode.h"
+
+#include "Volume.h"
+
+
+SpecialNode::SpecialNode(Volume *volume, mode_t mode)
+	:
+	Node(volume, NODE_TYPE_SPECIAL)
+{
+	fMode = mode;
+}
+
+
+SpecialNode::~SpecialNode()
+{
+}
+
+
+status_t
+SpecialNode::SetSize(off_t newSize)
+{
+	return B_UNSUPPORTED;
+}
+
+
+off_t
+SpecialNode::GetSize() const
+{
+	return 0;
+}

src/add-ons/kernel/file_systems/ramfs/SpecialNode.h

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2025, Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT license.
+ */
+#ifndef SPECIAL_NODE_H
+#define SPECIAL_NODE_H
+
+
+#include "Node.h"
+
+
+class SpecialNode : public Node {
+public:
+	SpecialNode(Volume *volume, mode_t mode);
+	virtual ~SpecialNode();
+
+	virtual status_t SetSize(off_t newSize);
+	virtual off_t GetSize() const;
+};
+
+
+#endif	// SPECIAL_NODE_H

src/add-ons/kernel/file_systems/ramfs/kernel_interface.cpp

@@ -58,6 +58,7 @@
 #include "Node.h"
 #include "Query.h"
 #include "ramfs_ioctl.h"
+#include "SpecialNode.h"
 #include "SymLink.h"
 #include "Volume.h"
 
@@ -876,6 +877,71 @@ ramfs_create(fs_volume* _volume, fs_vnode* _dir, const char *name, int openMode,
 }
 
 
+static status_t
+ramfs_create_special_node(fs_volume *_volume, fs_vnode *_dir, const char *name,
+	fs_vnode *subVnode, mode_t mode, uint32 flags, fs_vnode *_superVnode,
+	ino_t *vnid)
+{
+	FUNCTION(("name: `%s', mode: %x\n", name, mode));
+	Volume* volume = (Volume*)_volume->private_volume;
+	Directory* dir = dynamic_cast<Directory*>((Node*)_dir->private_node);
+
+	if (name == NULL || subVnode != NULL)
+		RETURN_ERROR(B_UNSUPPORTED);
+	if (strcmp(name, ".") == 0 || strcmp(name, "..") == 0)
+		RETURN_ERROR(B_FILE_EXISTS);
+
+	VolumeWriteLocker locker(volume);
+	if (!locker.IsLocked())
+		RETURN_ERROR(B_ERROR);
+
+	NodeMTimeUpdater mTimeUpdater(dir);
+	status_t error = B_OK;
+
+	// directory deleted?
+	bool removed;
+	if (get_vnode_removed(volume->FSVolume(), dir->GetID(), &removed)
+			!= B_OK || removed) {
+		SET_ERROR(error, B_NOT_ALLOWED);
+	}
+
+	Node *existingNode = NULL;
+	if (dir->FindNode(name, &existingNode) == B_OK)
+		RETURN_ERROR(B_FILE_EXISTS);
+
+	error = dir->CheckPermissions(ACCESS_W);
+	if (error != B_OK)
+		RETURN_ERROR(error);
+
+	SpecialNode* node = new(std::nothrow) SpecialNode(volume, mode);
+	if (node == NULL)
+		RETURN_ERROR(B_NO_MEMORY);
+
+	*vnid = node->GetID();
+
+	node->SetUID(geteuid());
+	node->SetGID(getegid());
+
+	Entry* entry;
+	error = node->InitCheck();
+	if (error == B_OK) {
+		// add node to directory
+		error = dir->CreateEntry(node, name, &entry);
+	}
+	if (error != B_OK) {
+		delete node;
+		RETURN_ERROR(error);
+	}
+
+	NodeMTimeUpdater mTimeUpdater2(node);
+
+	// notify listeners
+	notify_entry_created(volume->GetID(), dir->GetID(), name, *vnid);
+
+	return B_OK;
+}
+
+
 static status_t
 ramfs_open(fs_volume* _volume, fs_vnode* _node, int openMode, void** _cookie)
 {
@@ -2248,7 +2314,7 @@ fs_vnode_ops gRamFSVnodeOps = {
 	&ramfs_remove_attr,
 
 	/* special nodes */
-	NULL	// create_special_node
+	&ramfs_create_special_node,
 };
 
 static file_system_module_info sRamFSModuleInfo = {