ipv4: add {Read,Write}Batch methods to {Packet,Raw}Conn
This change provides message IO functionality that may support the
construction of modern datagram transport protocols.
The modern datagram transport protocols on a multihomed node basically
need to control each packet path for traffic engineering by using
information belongs to network- or link-layer implementation. In
addtion, it's desirable to be able to do simultaneous transmission
across multiple network- or link-layer adjacencies wihtout any
additional cost.
The ReadBatch and WriteBatch methods of PacketConn and RawConn can be
used to read and write an IO message that contains the information of
network- or link-layer implementation, and read and write a batch of
IO messages on Linux. The Marshal and Parse methods of ControlMessage
and Header can help to marshal and parse information contained in IO
messages.
Updates golang/go#3661.
Change-Id: Ia84a9d3bc51641406eaaf4258f2a3066945cc323
Reviewed-on: https://go-review.googlesource.com/38275
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/ipv4/batch.go b/ipv4/batch.go
new file mode 100644
index 0000000..b445499
--- /dev/null
+++ b/ipv4/batch.go
@@ -0,0 +1,191 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.9
+
+package ipv4
+
+import (
+ "net"
+ "runtime"
+ "syscall"
+
+ "golang.org/x/net/internal/socket"
+)
+
+// BUG(mikio): On Windows, the ReadBatch and WriteBatch methods of
+// PacketConn are not implemented.
+
+// BUG(mikio): On Windows, the ReadBatch and WriteBatch methods of
+// RawConn are not implemented.
+
+// A Message represents an IO message.
+//
+// type Message struct {
+// Buffers [][]byte
+// OOB []byte
+// Addr net.Addr
+// N int
+// NN int
+// Flags int
+// }
+//
+// The Buffers fields represents a list of contiguous buffers, which
+// can be used for vectored IO, for example, putting a header and a
+// payload in each slice.
+// When writing, the Buffers field must contain at least one byte to
+// write.
+// When reading, the Buffers field will always contain a byte to read.
+//
+// The OOB field contains protocol-specific control or miscellaneous
+// ancillary data known as out-of-band data.
+// It can be nil when not required.
+//
+// The Addr field specifies a destination address when writing.
+// It can be nil when the underlying protocol of the endpoint uses
+// connection-oriented communication.
+// After a successful read, it may contain the source address on the
+// received packet.
+//
+// The N field indicates the number of bytes read or written from/to
+// Buffers.
+//
+// The NN field indicates the number of bytes read or written from/to
+// OOB.
+//
+// The Flags field contains protocol-specific information on the
+// received message.
+type Message = socket.Message
+
+// ReadBatch reads a batch of messages.
+//
+// The provided flags is a set of platform-dependent flags, such as
+// syscall.MSG_PEEK.
+//
+// On a successful read it returns the number of messages received, up
+// to len(ms).
+//
+// On Linux, a batch read will be optimized.
+// On other platforms, this method will read only a single message.
+//
+// Unlike the ReadFrom method, it doesn't strip the IPv4 header
+// followed by option headers from the received IPv4 datagram when the
+// underlying transport is net.IPConn. Each Buffers field of Message
+// must be large enough to accommodate an IPv4 header and option
+// headers.
+func (c *payloadHandler) ReadBatch(ms []Message, flags int) (int, error) {
+ if !c.ok() {
+ return 0, syscall.EINVAL
+ }
+ switch runtime.GOOS {
+ case "linux":
+ n, err := c.RecvMsgs([]socket.Message(ms), flags)
+ if err != nil {
+ err = &net.OpError{Op: "read", Net: c.PacketConn.LocalAddr().Network(), Source: c.PacketConn.LocalAddr(), Err: err}
+ }
+ return n, err
+ default:
+ n := 1
+ err := c.RecvMsg(&ms[0], flags)
+ if err != nil {
+ n = 0
+ err = &net.OpError{Op: "read", Net: c.PacketConn.LocalAddr().Network(), Source: c.PacketConn.LocalAddr(), Err: err}
+ }
+ return n, err
+ }
+}
+
+// WriteBatch writes a batch of messages.
+//
+// The provided flags is a set of platform-dependent flags, such as
+// syscall.MSG_DONTROUTE.
+//
+// It returns the number of messages written on a successful write.
+//
+// On Linux, a batch write will be optimized.
+// On other platforms, this method will write only a single message.
+func (c *payloadHandler) WriteBatch(ms []Message, flags int) (int, error) {
+ if !c.ok() {
+ return 0, syscall.EINVAL
+ }
+ switch runtime.GOOS {
+ case "linux":
+ n, err := c.SendMsgs([]socket.Message(ms), flags)
+ if err != nil {
+ err = &net.OpError{Op: "write", Net: c.PacketConn.LocalAddr().Network(), Source: c.PacketConn.LocalAddr(), Err: err}
+ }
+ return n, err
+ default:
+ n := 1
+ err := c.SendMsg(&ms[0], flags)
+ if err != nil {
+ n = 0
+ err = &net.OpError{Op: "write", Net: c.PacketConn.LocalAddr().Network(), Source: c.PacketConn.LocalAddr(), Err: err}
+ }
+ return n, err
+ }
+}
+
+// ReadBatch reads a batch of messages.
+//
+// The provided flags is a set of platform-dependent flags, such as
+// syscall.MSG_PEEK.
+//
+// On a successful read it returns the number of messages received, up
+// to len(ms).
+//
+// On Linux, a batch read will be optimized.
+// On other platforms, this method will read only a single message.
+func (c *packetHandler) ReadBatch(ms []Message, flags int) (int, error) {
+ if !c.ok() {
+ return 0, syscall.EINVAL
+ }
+ switch runtime.GOOS {
+ case "linux":
+ n, err := c.RecvMsgs([]socket.Message(ms), flags)
+ if err != nil {
+ err = &net.OpError{Op: "read", Net: c.IPConn.LocalAddr().Network(), Source: c.IPConn.LocalAddr(), Err: err}
+ }
+ return n, err
+ default:
+ n := 1
+ err := c.RecvMsg(&ms[0], flags)
+ if err != nil {
+ n = 0
+ err = &net.OpError{Op: "read", Net: c.IPConn.LocalAddr().Network(), Source: c.IPConn.LocalAddr(), Err: err}
+ }
+ return n, err
+ }
+}
+
+// WriteBatch writes a batch of messages.
+//
+// The provided flags is a set of platform-dependent flags, such as
+// syscall.MSG_DONTROUTE.
+//
+// It returns the number of messages written on a successful write.
+//
+// On Linux, a batch write will be optimized.
+// On other platforms, this method will write only a single message.
+func (c *packetHandler) WriteBatch(ms []Message, flags int) (int, error) {
+ if !c.ok() {
+ return 0, syscall.EINVAL
+ }
+ switch runtime.GOOS {
+ case "linux":
+ n, err := c.SendMsgs([]socket.Message(ms), flags)
+ if err != nil {
+ err = &net.OpError{Op: "write", Net: c.IPConn.LocalAddr().Network(), Source: c.IPConn.LocalAddr(), Err: err}
+ }
+ return n, err
+ default:
+ n := 1
+ err := c.SendMsg(&ms[0], flags)
+ if err != nil {
+ n = 0
+ err = &net.OpError{Op: "write", Net: c.IPConn.LocalAddr().Network(), Source: c.IPConn.LocalAddr(), Err: err}
+ }
+ return n, err
+ }
+}
