1 files changed, 258 insertions, 0 deletions
diff --git a/pkg/lisafs/message.go b/pkg/lisafs/message.go
new file mode 100644
index 000000000..55fd2c0b1
--- /dev/null
+++ b/pkg/lisafs/message.go
@@ -0,0 +1,258 @@
+// 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 (
+	"math"
+	"os"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/hostarch"
+	"gvisor.dev/gvisor/pkg/marshal/primitive"
+)
+
+// Messages have two parts:
+//  * A transport header used to decipher received messages.
+//  * A byte array referred to as "payload" which contains the actual message.
+//
+// "dataLen" refers to the size of both combined.
+
+// MID (message ID) is used to identify messages to parse from payload.
+//
+// +marshal slice:MIDSlice
+type MID uint16
+
+// These constants are used to identify their corresponding message types.
+const (
+	// Error is only used in responses to pass errors to client.
+	Error MID = 0
+
+	// Mount is used to establish connection between the client and server mount
+	// point. lisafs requires that the client makes a successful Mount RPC before
+	// making other RPCs.
+	Mount MID = 1
+
+	// Channel requests to start a new communicational channel.
+	Channel MID = 2
+)
+
+const (
+	// NoUID is a sentinel used to indicate no valid UID.
+	NoUID UID = math.MaxUint32
+
+	// NoGID is a sentinel used to indicate no valid GID.
+	NoGID GID = math.MaxUint32
+)
+
+// MaxMessageSize is the recommended max message size that can be used by
+// connections. Server implementations may choose to use other values.
+func MaxMessageSize() uint32 {
+	// Return HugePageSize - PageSize so that when flipcall packet window is
+	// created with MaxMessageSize() + flipcall header size + channel header
+	// size, HugePageSize is allocated and can be backed by a single huge page
+	// if supported by the underlying memfd.
+	return uint32(hostarch.HugePageSize - os.Getpagesize())
+}
+
+// TODO(gvisor.dev/issue/6450): Once this is resolved:
+// * Update manual implementations and function signatures.
+// * Update RPC handlers and appropriate callers to handle errors correctly.
+// * Update manual implementations to get rid of buffer shifting.
+
+// UID represents a user ID.
+//
+// +marshal
+type UID uint32
+
+// Ok returns true if uid is not NoUID.
+func (uid UID) Ok() bool {
+	return uid != NoUID
+}
+
+// GID represents a group ID.
+//
+// +marshal
+type GID uint32
+
+// Ok returns true if gid is not NoGID.
+func (gid GID) Ok() bool {
+	return gid != NoGID
+}
+
+// NoopMarshal is a noop implementation of marshal.Marshallable.MarshalBytes.
+func NoopMarshal([]byte) {}
+
+// NoopUnmarshal is a noop implementation of marshal.Marshallable.UnmarshalBytes.
+func NoopUnmarshal([]byte) {}
+
+// SizedString represents a string in memory. The marshalled string bytes are
+// preceded by a uint32 signifying the string length.
+type SizedString string
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
+func (s *SizedString) SizeBytes() int {
+	return (*primitive.Uint32)(nil).SizeBytes() + len(*s)
+}
+
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
+func (s *SizedString) MarshalBytes(dst []byte) {
+	strLen := primitive.Uint32(len(*s))
+	strLen.MarshalUnsafe(dst)
+	dst = dst[strLen.SizeBytes():]
+	// Copy without any allocation.
+	copy(dst[:strLen], *s)
+}
+
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (s *SizedString) UnmarshalBytes(src []byte) {
+	var strLen primitive.Uint32
+	strLen.UnmarshalUnsafe(src)
+	src = src[strLen.SizeBytes():]
+	// Take the hit, this leads to an allocation + memcpy. No way around it.
+	*s = SizedString(src[:strLen])
+}
+
+// StringArray represents an array of SizedStrings in memory. The marshalled
+// array data is preceded by a uint32 signifying the array length.
+type StringArray []string
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
+func (s *StringArray) SizeBytes() int {
+	size := (*primitive.Uint32)(nil).SizeBytes()
+	for _, str := range *s {
+		sstr := SizedString(str)
+		size += sstr.SizeBytes()
+	}
+	return size
+}
+
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
+func (s *StringArray) MarshalBytes(dst []byte) {
+	arrLen := primitive.Uint32(len(*s))
+	arrLen.MarshalUnsafe(dst)
+	dst = dst[arrLen.SizeBytes():]
+	for _, str := range *s {
+		sstr := SizedString(str)
+		sstr.MarshalBytes(dst)
+		dst = dst[sstr.SizeBytes():]
+	}
+}
+
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (s *StringArray) UnmarshalBytes(src []byte) {
+	var arrLen primitive.Uint32
+	arrLen.UnmarshalUnsafe(src)
+	src = src[arrLen.SizeBytes():]
+
+	if cap(*s) < int(arrLen) {
+		*s = make([]string, arrLen)
+	} else {
+		*s = (*s)[:arrLen]
+	}
+
+	for i := primitive.Uint32(0); i < arrLen; i++ {
+		var sstr SizedString
+		sstr.UnmarshalBytes(src)
+		src = src[sstr.SizeBytes():]
+		(*s)[i] = string(sstr)
+	}
+}
+
+// Inode represents an inode on the remote filesystem.
+//
+// +marshal slice:InodeSlice
+type Inode struct {
+	ControlFD FDID
+	_         uint32 // Need to make struct packed.
+	Stat      linux.Statx
+}
+
+// MountReq represents a Mount request.
+type MountReq struct {
+	MountPath SizedString
+}
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
+func (m *MountReq) SizeBytes() int {
+	return m.MountPath.SizeBytes()
+}
+
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
+func (m *MountReq) MarshalBytes(dst []byte) {
+	m.MountPath.MarshalBytes(dst)
+}
+
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (m *MountReq) UnmarshalBytes(src []byte) {
+	m.MountPath.UnmarshalBytes(src)
+}
+
+// MountResp represents a Mount response.
+type MountResp struct {
+	Root Inode
+	// MaxMessageSize is the maximum size of messages communicated between the
+	// client and server in bytes. This includes the communication header.
+	MaxMessageSize primitive.Uint32
+	// SupportedMs holds all the supported messages.
+	SupportedMs []MID
+}
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
+func (m *MountResp) SizeBytes() int {
+	return m.Root.SizeBytes() +
+		m.MaxMessageSize.SizeBytes() +
+		(*primitive.Uint16)(nil).SizeBytes() +
+		(len(m.SupportedMs) * (*MID)(nil).SizeBytes())
+}
+
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
+func (m *MountResp) MarshalBytes(dst []byte) {
+	m.Root.MarshalUnsafe(dst)
+	dst = dst[m.Root.SizeBytes():]
+	m.MaxMessageSize.MarshalUnsafe(dst)
+	dst = dst[m.MaxMessageSize.SizeBytes():]
+	numSupported := primitive.Uint16(len(m.SupportedMs))
+	numSupported.MarshalBytes(dst)
+	dst = dst[numSupported.SizeBytes():]
+	MarshalUnsafeMIDSlice(m.SupportedMs, dst)
+}
+
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (m *MountResp) UnmarshalBytes(src []byte) {
+	m.Root.UnmarshalUnsafe(src)
+	src = src[m.Root.SizeBytes():]
+	m.MaxMessageSize.UnmarshalUnsafe(src)
+	src = src[m.MaxMessageSize.SizeBytes():]
+	var numSupported primitive.Uint16
+	numSupported.UnmarshalBytes(src)
+	src = src[numSupported.SizeBytes():]
+	m.SupportedMs = make([]MID, numSupported)
+	UnmarshalUnsafeMIDSlice(m.SupportedMs, src)
+}
+
+// ChannelResp is the response to the create channel request.
+//
+// +marshal
+type ChannelResp struct {
+	dataOffset int64
+	dataLength uint64
+}
+
+// ErrorResp is returned to represent an error while handling a request.
+//
+// +marshal
+type ErrorResp struct {
+	errno uint32
+}