Merge pull request #9551 from amysaq2023:support-external-stack

PiperOrigin-RevId: 677933413

pkg/sentry/socket/plugin/stack/readwriter.go

@@ -0,0 +1,110 @@
+// Copyright 2023 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 stack
+
+import (
+	"sync"
+	"syscall"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/safemem"
+	"gvisor.dev/gvisor/pkg/sentry/socket/plugin/cgo"
+)
+
+type pluginStackRW struct {
+	handle uint32
+
+	// Represent both input and output flags.
+	flags uint32
+
+	// Reused as msg_control for read.
+	to []byte
+
+	iovs [3]syscall.Iovec
+}
+
+var pluginStackRWPool = sync.Pool{
+	New: func() any {
+		return &pluginStackRW{}
+	},
+}
+
+func getReadWriter(handle uint32) *pluginStackRW {
+	rw := pluginStackRWPool.Get().(*pluginStackRW)
+	rw.handle = handle
+	return rw
+}
+
+func putReadWriter(rw *pluginStackRW) {
+	*rw = pluginStackRW{}
+	pluginStackRWPool.Put(rw)
+}
+
+// ReadToBlocks implements safemem.Reader.ReadToBlocks.
+func (rw *pluginStackRW) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) {
+	// Set MSG_DONTWAIT flag to avoid blocking in plugin stack.
+	flags := int(rw.flags) & ^linux.MSG_DONTWAIT
+	if len(rw.to) != 0 || flags != 0 {
+		iovs := iovecsFromBlockSeq(dsts, rw)
+		rc, _, lc, mflags := cgo.Recvmsg(rw.handle, iovs, nil, rw.to, int(rw.flags))
+		if rc >= 0 {
+			rw.to = rw.to[:lc]
+			rw.flags = uint32(mflags)
+		}
+		return translateReturn(rc)
+	}
+
+	var rc int64
+	if dsts.IsEmpty() {
+		rc = 0
+	} else if dsts.NumBlocks() == 1 {
+		rc = cgo.Read(rw.handle, dsts.Head().Addr(), dsts.Head().Len())
+	} else {
+		rc = cgo.Readv(rw.handle, iovecsFromBlockSeq(dsts, rw))
+	}
+
+	return translateReturn(rc)
+}
+
+// WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
+//
+// Preconditions: rw.d.metadataMu must be locked.
+func (rw *pluginStackRW) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
+	var rc int64
+
+	if rw.to != nil {
+		if srcs.IsEmpty() {
+			// Invoke plugin stack checking whether there is any error to report
+			// on target socket which sends 0-length data.
+			rc = cgo.Sendto(rw.handle, 0, 0, 0, rw.to)
+		} else if srcs.NumBlocks() == 1 {
+			rc = cgo.Sendto(rw.handle, srcs.Head().Addr(), srcs.Head().Len(), 0, rw.to)
+		} else {
+			iovs := iovecsFromBlockSeq(srcs, rw)
+			rc = cgo.Sendmsg(rw.handle, iovs, rw.to, 0)
+		}
+	} else {
+		if srcs.IsEmpty() {
+			// Invoke plugin stack checking whether there is any error to report
+			// on target socket which sends 0-length data.
+			rc = cgo.Write(rw.handle, 0, 0)
+		} else if srcs.NumBlocks() == 1 {
+			rc = cgo.Write(rw.handle, srcs.Head().Addr(), srcs.Head().Len())
+		} else {
+			rc = cgo.Writev(rw.handle, iovecsFromBlockSeq(srcs, rw))
+		}
+	}
+	return translateReturn(rc)
+}