1 files changed, 166 insertions, 0 deletions
diff --git a/pkg/sentry/fsimpl/fuse/init.go b/pkg/sentry/fsimpl/fuse/init.go
new file mode 100644
index 000000000..779c2bd3f
--- /dev/null
+++ b/pkg/sentry/fsimpl/fuse/init.go
@@ -0,0 +1,166 @@
+// Copyright 2020 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 fuse
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+)
+
+// consts used by FUSE_INIT negotiation.
+const (
+	// fuseMaxMaxPages is the maximum value for MaxPages received in InitOut.
+	// Follow the same behavior as unix fuse implementation.
+	fuseMaxMaxPages = 256
+
+	// Maximum value for the time granularity for file time stamps, 1s.
+	// Follow the same behavior as unix fuse implementation.
+	fuseMaxTimeGranNs = 1000000000
+
+	// Minimum value for MaxWrite.
+	// Follow the same behavior as unix fuse implementation.
+	fuseMinMaxWrite = 4096
+
+	// Temporary default value for max readahead, 128kb.
+	fuseDefaultMaxReadahead = 131072
+
+	// The FUSE_INIT_IN flags sent to the daemon.
+	// TODO(gvisor.dev/issue/3199): complete the flags.
+	fuseDefaultInitFlags = linux.FUSE_MAX_PAGES
+)
+
+// Adjustable maximums for Connection's cogestion control parameters.
+// Used as the upperbound of the config values.
+// Currently we do not support adjustment to them.
+var (
+	MaxUserBackgroundRequest   uint16 = fuseDefaultMaxBackground
+	MaxUserCongestionThreshold uint16 = fuseDefaultCongestionThreshold
+)
+
+// InitSend sends a FUSE_INIT request.
+func (conn *connection) InitSend(creds *auth.Credentials, pid uint32) error {
+	in := linux.FUSEInitIn{
+		Major: linux.FUSE_KERNEL_VERSION,
+		Minor: linux.FUSE_KERNEL_MINOR_VERSION,
+		// TODO(gvisor.dev/issue/3196): find appropriate way to calculate this
+		MaxReadahead: fuseDefaultMaxReadahead,
+		Flags:        fuseDefaultInitFlags,
+	}
+
+	req, err := conn.NewRequest(creds, pid, 0, linux.FUSE_INIT, &in)
+	if err != nil {
+		return err
+	}
+
+	// Since there is no task to block on and FUSE_INIT is the request
+	// to unblock other requests, use nil.
+	return conn.CallAsync(nil, req)
+}
+
+// InitRecv receives a FUSE_INIT reply and process it.
+func (conn *connection) InitRecv(res *Response, hasSysAdminCap bool) error {
+	if err := res.Error(); err != nil {
+		return err
+	}
+
+	var out linux.FUSEInitOut
+	if err := res.UnmarshalPayload(&out); err != nil {
+		return err
+	}
+
+	return conn.initProcessReply(&out, hasSysAdminCap)
+}
+
+// Process the FUSE_INIT reply from the FUSE server.
+func (conn *connection) initProcessReply(out *linux.FUSEInitOut, hasSysAdminCap bool) error {
+	// No support for old major fuse versions.
+	if out.Major != linux.FUSE_KERNEL_VERSION {
+		conn.connInitError = true
+
+		// Set the connection as initialized and unblock the blocked requests
+		// (i.e. return error for them).
+		conn.SetInitialized()
+
+		return nil
+	}
+
+	// Start processing the reply.
+	conn.connInitSuccess = true
+	conn.minor = out.Minor
+
+	// No support for limits before minor version 13.
+	if out.Minor >= 13 {
+		conn.bgLock.Lock()
+
+		if out.MaxBackground > 0 {
+			conn.maxBackground = out.MaxBackground
+
+			if !hasSysAdminCap &&
+				conn.maxBackground > MaxUserBackgroundRequest {
+				conn.maxBackground = MaxUserBackgroundRequest
+			}
+		}
+
+		if out.CongestionThreshold > 0 {
+			conn.congestionThreshold = out.CongestionThreshold
+
+			if !hasSysAdminCap &&
+				conn.congestionThreshold > MaxUserCongestionThreshold {
+				conn.congestionThreshold = MaxUserCongestionThreshold
+			}
+		}
+
+		conn.bgLock.Unlock()
+	}
+
+	// No support for the following flags before minor version 6.
+	if out.Minor >= 6 {
+		conn.asyncRead = out.Flags&linux.FUSE_ASYNC_READ != 0
+		conn.bigWrites = out.Flags&linux.FUSE_BIG_WRITES != 0
+		conn.dontMask = out.Flags&linux.FUSE_DONT_MASK != 0
+		conn.writebackCache = out.Flags&linux.FUSE_WRITEBACK_CACHE != 0
+		conn.cacheSymlinks = out.Flags&linux.FUSE_CACHE_SYMLINKS != 0
+		conn.abortErr = out.Flags&linux.FUSE_ABORT_ERROR != 0
+
+		// TODO(gvisor.dev/issue/3195): figure out how to use TimeGran (0 < TimeGran <= fuseMaxTimeGranNs).
+
+		if out.Flags&linux.FUSE_MAX_PAGES != 0 {
+			maxPages := out.MaxPages
+			if maxPages < 1 {
+				maxPages = 1
+			}
+			if maxPages > fuseMaxMaxPages {
+				maxPages = fuseMaxMaxPages
+			}
+			conn.maxPages = maxPages
+		}
+	}
+
+	// No support for negotiating MaxWrite before minor version 5.
+	if out.Minor >= 5 {
+		conn.maxWrite = out.MaxWrite
+	} else {
+		conn.maxWrite = fuseMinMaxWrite
+	}
+	if conn.maxWrite < fuseMinMaxWrite {
+		conn.maxWrite = fuseMinMaxWrite
+	}
+
+	// Set connection as initialized and unblock the requests
+	// issued before init.
+	conn.SetInitialized()
+
+	return nil
+}