1 files changed, 113 insertions, 0 deletions
diff --git a/pkg/lisafs/server.go b/pkg/lisafs/server.go
new file mode 100644
index 000000000..7515355ec
--- /dev/null
+++ b/pkg/lisafs/server.go
@@ -0,0 +1,113 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package lisafs
+
+import (
+	"gvisor.dev/gvisor/pkg/sync"
+)
+
+// Server serves a filesystem tree. Multiple connections on different mount
+// points can be started on a server. The server provides utilities to safely
+// modify the filesystem tree across its connections (mount points). Note that
+// it does not support synchronizing filesystem tree mutations across other
+// servers serving the same filesystem subtree. Server also manages the
+// lifecycle of all connections.
+type Server struct {
+	// connWg counts the number of active connections being tracked.
+	connWg sync.WaitGroup
+
+	// RenameMu synchronizes rename operations within this filesystem tree.
+	RenameMu sync.RWMutex
+
+	// handlers is a list of RPC handlers which can be indexed by the handler's
+	// corresponding MID.
+	handlers []RPCHandler
+
+	// mountPoints keeps track of all the mount points this server serves.
+	mpMu        sync.RWMutex
+	mountPoints []*ControlFD
+
+	// impl is the server implementation which embeds this server.
+	impl ServerImpl
+}
+
+// Init must be called before first use of server.
+func (s *Server) Init(impl ServerImpl) {
+	s.impl = impl
+	s.handlers = handlers[:]
+}
+
+// InitTestOnly is the same as Init except that it allows to swap out the
+// underlying handlers with something custom. This is for test only.
+func (s *Server) InitTestOnly(impl ServerImpl, handlers []RPCHandler) {
+	s.impl = impl
+	s.handlers = handlers
+}
+
+// WithRenameReadLock invokes fn with the server's rename mutex locked for
+// reading. This ensures that no rename operations occur concurrently.
+func (s *Server) WithRenameReadLock(fn func() error) error {
+	s.RenameMu.RLock()
+	err := fn()
+	s.RenameMu.RUnlock()
+	return err
+}
+
+// StartConnection starts the connection on a separate goroutine and tracks it.
+func (s *Server) StartConnection(c *Connection) {
+	s.connWg.Add(1)
+	go func() {
+		c.Run()
+		s.connWg.Done()
+	}()
+}
+
+// Wait waits for all connections started via StartConnection() to terminate.
+func (s *Server) Wait() {
+	s.connWg.Wait()
+}
+
+func (s *Server) addMountPoint(root *ControlFD) {
+	s.mpMu.Lock()
+	defer s.mpMu.Unlock()
+	s.mountPoints = append(s.mountPoints, root)
+}
+
+func (s *Server) forEachMountPoint(fn func(root *ControlFD)) {
+	s.mpMu.RLock()
+	defer s.mpMu.RUnlock()
+	for _, mp := range s.mountPoints {
+		fn(mp)
+	}
+}
+
+// ServerImpl contains the implementation details for a Server.
+// Implementations of ServerImpl should contain their associated Server by
+// value as their first field.
+type ServerImpl interface {
+	// Mount is called when a Mount RPC is made. It mounts the connection at
+	// mountPath.
+	//
+	// Precondition: mountPath == path.Clean(mountPath).
+	Mount(c *Connection, mountPath string) (ControlFDImpl, Inode, error)
+
+	// SupportedMessages returns a list of messages that the server
+	// implementation supports.
+	SupportedMessages() []MID
+
+	// MaxMessageSize is the maximum payload length (in bytes) that can be sent
+	// to this server implementation.
+	MaxMessageSize() uint32
+}