1 files changed, 79 insertions, 0 deletions
diff --git a/internal/encoding/ssh/filexfer/openssh/hardlink.go b/internal/encoding/ssh/filexfer/openssh/hardlink.go
new file mode 100644
index 0000000..17c3499
--- /dev/null
+++ b/internal/encoding/ssh/filexfer/openssh/hardlink.go
@@ -0,0 +1,79 @@
+package openssh
+
+import (
+	sshfx "github.com/pkg/sftp/internal/encoding/ssh/filexfer"
+)
+
+const extensionHardlink = "hardlink@openssh.com"
+
+// RegisterExtensionHardlink registers the "hardlink@openssh.com" extended packet with the encoding/ssh/filexfer package.
+func RegisterExtensionHardlink() {
+	sshfx.RegisterExtendedPacketType(extensionHardlink, func() sshfx.ExtendedData {
+		return new(HardlinkExtendedPacket)
+	})
+}
+
+// ExtensionHardlink returns an ExtensionPair suitable to append into an sshfx.InitPacket or sshfx.VersionPacket.
+func ExtensionHardlink() *sshfx.ExtensionPair {
+	return &sshfx.ExtensionPair{
+		Name: extensionHardlink,
+		Data: "1",
+	}
+}
+
+// HardlinkExtendedPacket defines the hardlink@openssh.com extend packet.
+type HardlinkExtendedPacket struct {
+	OldPath string
+	NewPath string
+}
+
+// Type returns the SSH_FXP_EXTENDED packet type.
+func (ep *HardlinkExtendedPacket) Type() sshfx.PacketType {
+	return sshfx.PacketTypeExtended
+}
+
+// MarshalPacket returns ep as a two-part binary encoding of the full extended packet.
+func (ep *HardlinkExtendedPacket) MarshalPacket(reqid uint32, b []byte) (header, payload []byte, err error) {
+	p := &sshfx.ExtendedPacket{
+		ExtendedRequest: extensionHardlink,
+
+		Data: ep,
+	}
+	return p.MarshalPacket(reqid, b)
+}
+
+// MarshalInto encodes ep into the binary encoding of the hardlink@openssh.com extended packet-specific data.
+func (ep *HardlinkExtendedPacket) MarshalInto(buf *sshfx.Buffer) {
+	buf.AppendString(ep.OldPath)
+	buf.AppendString(ep.NewPath)
+}
+
+// MarshalBinary encodes ep into the binary encoding of the hardlink@openssh.com extended packet-specific data.
+//
+// NOTE: This _only_ encodes the packet-specific data, it does not encode the full extended packet.
+func (ep *HardlinkExtendedPacket) MarshalBinary() ([]byte, error) {
+	// string(oldpath) + string(newpath)
+	size := 4 + len(ep.OldPath) + 4 + len(ep.NewPath)
+
+	buf := sshfx.NewBuffer(make([]byte, 0, size))
+	ep.MarshalInto(buf)
+	return buf.Bytes(), nil
+}
+
+// UnmarshalFrom decodes the hardlink@openssh.com extended packet-specific data from buf.
+func (ep *HardlinkExtendedPacket) UnmarshalFrom(buf *sshfx.Buffer) (err error) {
+	if ep.OldPath, err = buf.ConsumeString(); err != nil {
+		return err
+	}
+
+	if ep.NewPath, err = buf.ConsumeString(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// UnmarshalBinary decodes the hardlink@openssh.com extended packet-specific data into ep.
+func (ep *HardlinkExtendedPacket) UnmarshalBinary(data []byte) (err error) {
+	return ep.UnmarshalFrom(sshfx.NewBuffer(data))
+}