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// 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 and MaxRead.
// Follow the same behavior as unix fuse implementation.
fuseMinMaxWrite = 4096
fuseMinMaxRead = 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
}
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