feat(application): inital commit

vendor/golang.org/x/net/ipv4/control.go

@@ -0,0 +1,144 @@
+// Copyright 2012 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.
+
+package ipv4
+
+import (
+	"fmt"
+	"net"
+	"sync"
+
+	"golang.org/x/net/internal/iana"
+	"golang.org/x/net/internal/socket"
+)
+
+type rawOpt struct {
+	sync.RWMutex
+	cflags ControlFlags
+}
+
+func (c *rawOpt) set(f ControlFlags)        { c.cflags |= f }
+func (c *rawOpt) clear(f ControlFlags)      { c.cflags &^= f }
+func (c *rawOpt) isset(f ControlFlags) bool { return c.cflags&f != 0 }
+
+type ControlFlags uint
+
+const (
+	FlagTTL       ControlFlags = 1 << iota // pass the TTL on the received packet
+	FlagSrc                                // pass the source address on the received packet
+	FlagDst                                // pass the destination address on the received packet
+	FlagInterface                          // pass the interface index on the received packet
+)
+
+// A ControlMessage represents per packet basis IP-level socket options.
+type ControlMessage struct {
+	// Receiving socket options: SetControlMessage allows to
+	// receive the options from the protocol stack using ReadFrom
+	// method of PacketConn or RawConn.
+	//
+	// Specifying socket options: ControlMessage for WriteTo
+	// method of PacketConn or RawConn allows to send the options
+	// to the protocol stack.
+	//
+	TTL     int    // time-to-live, receiving only
+	Src     net.IP // source address, specifying only
+	Dst     net.IP // destination address, receiving only
+	IfIndex int    // interface index, must be 1 <= value when specifying
+}
+
+func (cm *ControlMessage) String() string {
+	if cm == nil {
+		return "<nil>"
+	}
+	return fmt.Sprintf("ttl=%d src=%v dst=%v ifindex=%d", cm.TTL, cm.Src, cm.Dst, cm.IfIndex)
+}
+
+// Marshal returns the binary encoding of cm.
+func (cm *ControlMessage) Marshal() []byte {
+	if cm == nil {
+		return nil
+	}
+	var m socket.ControlMessage
+	if ctlOpts[ctlPacketInfo].name > 0 && (cm.Src.To4() != nil || cm.IfIndex > 0) {
+		m = socket.NewControlMessage([]int{ctlOpts[ctlPacketInfo].length})
+	}
+	if len(m) > 0 {
+		ctlOpts[ctlPacketInfo].marshal(m, cm)
+	}
+	return m
+}
+
+// Parse parses b as a control message and stores the result in cm.
+func (cm *ControlMessage) Parse(b []byte) error {
+	ms, err := socket.ControlMessage(b).Parse()
+	if err != nil {
+		return err
+	}
+	for _, m := range ms {
+		lvl, typ, l, err := m.ParseHeader()
+		if err != nil {
+			return err
+		}
+		if lvl != iana.ProtocolIP {
+			continue
+		}
+		switch {
+		case typ == ctlOpts[ctlTTL].name && l >= ctlOpts[ctlTTL].length:
+			ctlOpts[ctlTTL].parse(cm, m.Data(l))
+		case typ == ctlOpts[ctlDst].name && l >= ctlOpts[ctlDst].length:
+			ctlOpts[ctlDst].parse(cm, m.Data(l))
+		case typ == ctlOpts[ctlInterface].name && l >= ctlOpts[ctlInterface].length:
+			ctlOpts[ctlInterface].parse(cm, m.Data(l))
+		case typ == ctlOpts[ctlPacketInfo].name && l >= ctlOpts[ctlPacketInfo].length:
+			ctlOpts[ctlPacketInfo].parse(cm, m.Data(l))
+		}
+	}
+	return nil
+}
+
+// NewControlMessage returns a new control message.
+//
+// The returned message is large enough for options specified by cf.
+func NewControlMessage(cf ControlFlags) []byte {
+	opt := rawOpt{cflags: cf}
+	var l int
+	if opt.isset(FlagTTL) && ctlOpts[ctlTTL].name > 0 {
+		l += socket.ControlMessageSpace(ctlOpts[ctlTTL].length)
+	}
+	if ctlOpts[ctlPacketInfo].name > 0 {
+		if opt.isset(FlagSrc | FlagDst | FlagInterface) {
+			l += socket.ControlMessageSpace(ctlOpts[ctlPacketInfo].length)
+		}
+	} else {
+		if opt.isset(FlagDst) && ctlOpts[ctlDst].name > 0 {
+			l += socket.ControlMessageSpace(ctlOpts[ctlDst].length)
+		}
+		if opt.isset(FlagInterface) && ctlOpts[ctlInterface].name > 0 {
+			l += socket.ControlMessageSpace(ctlOpts[ctlInterface].length)
+		}
+	}
+	var b []byte
+	if l > 0 {
+		b = make([]byte, l)
+	}
+	return b
+}
+
+// Ancillary data socket options
+const (
+	ctlTTL        = iota // header field
+	ctlSrc               // header field
+	ctlDst               // header field
+	ctlInterface         // inbound or outbound interface
+	ctlPacketInfo        // inbound or outbound packet path
+	ctlMax
+)
+
+// A ctlOpt represents a binding for ancillary data socket option.
+type ctlOpt struct {
+	name    int // option name, must be equal or greater than 1
+	length  int // option length
+	marshal func([]byte, *ControlMessage) []byte
+	parse   func(*ControlMessage, []byte)
+}