fusego/server.go

// Copyright 2015 Google Inc. All Rights Reserved.
// Author: jacobsa@google.com (Aaron Jacobs)

package fuse

import (
	"fmt"
	"io"
	"log"

	"github.com/jacobsa/gcsfuse/timeutil"
	"golang.org/x/net/context"

	bazilfuse "bazil.org/fuse"
)

// An object that terminates one end of the userspace <-> FUSE VFS connection.
type server struct {
	logger *log.Logger
	clock  timeutil.Clock
	fs     FileSystem
}

// Create a server that relays requests to the supplied file system.
func newServer(fs FileSystem) (s *server, err error) {
	s = &server{
		logger: getLogger(),
		clock:  timeutil.RealClock(),
		fs:     fs,
	}

	return
}

// Serve the fuse connection by repeatedly reading requests from the supplied
// FUSE connection, responding as dictated by the file system. Return when the
// connection is closed or an unexpected error occurs.
func (s *server) Serve(c *bazilfuse.Conn) (err error) {
	// Read a message at a time, dispatching to goroutines doing the actual
	// processing.
	for {
		var fuseReq bazilfuse.Request
		fuseReq, err = c.ReadRequest()

		// ReadRequest returns EOF when the connection has been closed.
		if err == io.EOF {
			err = nil
			return
		}

		// Otherwise, forward on errors.
		if err != nil {
			err = fmt.Errorf("Conn.ReadRequest: %v", err)
			return
		}

		go s.handleFuseRequest(fuseReq)
	}
}

func (s *server) handleFuseRequest(fuseReq bazilfuse.Request) {
	// Log the request.
	s.logger.Println("Received:", fuseReq)

	// TODO(jacobsa): Support cancellation when interrupted, if we can coax the
	// system into reproducing such requests.
	ctx := context.Background()

	// Attempt to handle it.
	switch typed := fuseReq.(type) {
	case *bazilfuse.InitRequest:
		// Convert the request.
		req := &InitRequest{
			Uid: typed.Header.Uid,
			Gid: typed.Header.Gid,
		}

		// Call the file system.
		_, err := s.fs.Init(ctx, req)
		if err != nil {
			s.logger.Print("Responding:", err)
			typed.RespondError(err)
			return
		}

		// Convert the response.
		fuseResp := &bazilfuse.InitResponse{}
		s.logger.Print("Responding:", fuseResp)
		typed.Respond(fuseResp)

	case *bazilfuse.StatfsRequest:
		// Responding to this is required to make mounting work, at least on OS X.
		// We don't currently expose the capability for the file system to
		// intercept this.
		fuseResp := &bazilfuse.StatfsResponse{}
		s.logger.Println("Responding:", fuseResp)
		typed.Respond(fuseResp)

	case *bazilfuse.LookupRequest:
		// Convert the request.
		req := &LookUpInodeRequest{
			Parent: InodeID(typed.Header.Node),
			Name:   typed.Name,
		}

		// Call the file system.
		resp, err := s.fs.LookUpInode(ctx, req)
		if err != nil {
			s.logger.Print("Responding:", err)
			typed.RespondError(err)
			return
		}

		// Convert the response.
		fuseResp := &bazilfuse.LookupResponse{
			Node:       bazilfuse.NodeID(resp.Child),
			Generation: uint64(resp.Generation),
			Attr:       convertAttributes(resp.Child, resp.Attributes),
			AttrValid:  resp.AttributesExpiration.Sub(s.clock.Now()),
			EntryValid: resp.EntryExpiration.Sub(s.clock.Now()),
		}

		s.logger.Print("Responding:", fuseResp)
		typed.Respond(fuseResp)

	case *bazilfuse.GetattrRequest:
		// Convert the request.
		req := &GetInodeAttributesRequest{
			Inode: InodeID(typed.Header.Node),
		}

		// Call the file system.
		resp, err := s.fs.GetInodeAttributes(ctx, req)
		if err != nil {
			s.logger.Print("Responding:", err)
			typed.RespondError(err)
			return
		}

		// Convert the response.
		fuseResp := &bazilfuse.GetattrResponse{
			Attr:      convertAttributes(req.Inode, resp.Attributes),
			AttrValid: resp.AttributesExpiration.Sub(s.clock.Now()),
		}

		s.logger.Print("Responding:", fuseResp)
		typed.Respond(fuseResp)

	case *bazilfuse.OpenRequest:
		// Directory or file?
		if typed.Dir {
			// Convert the request.
			req := &OpenDirRequest{
				Inode: InodeID(typed.Header.Node),
				Flags: typed.Flags,
			}

			// Call the file system.
			resp, err := s.fs.OpenDir(ctx, req)
			if err != nil {
				s.logger.Print("Responding:", err)
				typed.RespondError(err)
				return
			}

			// Convert the response.
			fuseResp := &bazilfuse.OpenResponse{
				Handle: bazilfuse.HandleID(resp.Handle),
			}

			s.logger.Print("Responding:", fuseResp)
			typed.Respond(fuseResp)
		} else {
			// Convert the request.
			req := &OpenFileRequest{
				Inode: InodeID(typed.Header.Node),
				Flags: typed.Flags,
			}

			// Call the file system.
			resp, err := s.fs.OpenFile(ctx, req)
			if err != nil {
				s.logger.Print("Responding:", err)
				typed.RespondError(err)
				return
			}

			// Convert the response.
			fuseResp := &bazilfuse.OpenResponse{
				Handle: bazilfuse.HandleID(resp.Handle),
			}

			s.logger.Print("Responding:", fuseResp)
			typed.Respond(fuseResp)
		}

	case *bazilfuse.ReadRequest:
		// Directory or file?
		if typed.Dir {
			// Convert the request.
			req := &ReadDirRequest{
				Inode:  InodeID(typed.Header.Node),
				Handle: HandleID(typed.Handle),
				Offset: DirOffset(typed.Offset),
				Size:   typed.Size,
			}

			// Call the file system.
			resp, err := s.fs.ReadDir(ctx, req)
			if err != nil {
				s.logger.Print("Responding:", err)
				typed.RespondError(err)
				return
			}

			// Convert the response.
			fuseResp := &bazilfuse.ReadResponse{
				Data: resp.Data,
			}

			s.logger.Print("Responding:", fuseResp)
			typed.Respond(fuseResp)
		} else {
			// Convert the request.
			req := &ReadFileRequest{
				Inode:  InodeID(typed.Header.Node),
				Handle: HandleID(typed.Handle),
				Offset: typed.Offset,
				Size:   typed.Size,
			}

			// Call the file system.
			resp, err := s.fs.ReadFile(ctx, req)
			if err != nil {
				s.logger.Print("Responding:", err)
				typed.RespondError(err)
				return
			}

			// Convert the response.
			fuseResp := &bazilfuse.ReadResponse{
				Data: resp.Data,
			}

			s.logger.Print("Responding:", fuseResp)
			typed.Respond(fuseResp)
		}

	default:
		s.logger.Println("Unhandled type. Returning ENOSYS.")
		typed.RespondError(ENOSYS)
	}
}

func convertAttributes(inode InodeID, attr InodeAttributes) bazilfuse.Attr {
	return bazilfuse.Attr{
		Inode:  uint64(inode),
		Size:   attr.Size,
		Mode:   attr.Mode,
		Atime:  attr.Atime,
		Mtime:  attr.Mtime,
		Crtime: attr.Crtime,
		Uid:    attr.Uid,
		Gid:    attr.Gid,
	}
}