Added tftp datasource for cloud config.

config/cloudinit/datasource/tftp/tftp.go

@@ -0,0 +1,83 @@
+package tftp
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"regexp"
+	"strings"
+
+	"github.com/rancher/os/config/cloudinit/datasource"
+
+	"github.com/pin/tftp"
+)
+
+type Client interface {
+	Receive(filename string, mode string) (io.WriterTo, error)
+}
+
+type RemoteFile struct {
+	host      string
+	path      string
+	client    Client
+	stream    io.WriterTo
+	lastError error
+}
+
+func NewDatasource(hostAndPath string) *RemoteFile {
+	parts := strings.SplitN(hostAndPath, "/", 2)
+
+	if len(parts) < 2 {
+		return &RemoteFile{hostAndPath, "", nil, nil, nil}
+	}
+
+	host := parts[0]
+	if match, _ := regexp.MatchString(":[0-9]{2,5}$", host); !match {
+		// No port, using default port 69
+		host += ":69"
+	}
+
+	path := parts[1]
+	if client, lastError := tftp.NewClient(host); lastError == nil {
+		return &RemoteFile{host, path, client, nil, nil}
+	}
+
+	return &RemoteFile{host, path, nil, nil, nil}
+}
+
+func (f *RemoteFile) IsAvailable() bool {
+	f.stream, f.lastError = f.client.Receive(f.path, "octet")
+	return f.lastError == nil
+}
+
+func (f *RemoteFile) Finish() error {
+	return nil
+}
+
+func (f *RemoteFile) String() string {
+	return fmt.Sprintf("%s: %s%s (lastError: %v)", f.Type(), f.host, f.path, f.lastError)
+}
+
+func (f *RemoteFile) AvailabilityChanges() bool {
+	return false
+}
+
+func (f *RemoteFile) ConfigRoot() string {
+	return ""
+}
+
+func (f *RemoteFile) FetchMetadata() (datasource.Metadata, error) {
+	return datasource.Metadata{}, nil
+}
+
+func (f *RemoteFile) FetchUserdata() ([]byte, error) {
+	var b bytes.Buffer
+
+	_, err := f.stream.WriteTo(&b)
+
+	return b.Bytes(), err
+}
+
+func (f *RemoteFile) Type() string {
+	return "tftp"
+}