2 * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
8 package org.opendaylight.controller.netconf.nettyutil.handler;
10 import io.netty.buffer.ByteBuf;
11 import io.netty.buffer.ByteBufInputStream;
12 import io.netty.buffer.ByteBufUtil;
13 import io.netty.buffer.Unpooled;
14 import io.netty.channel.ChannelHandlerContext;
15 import io.netty.handler.codec.ByteToMessageDecoder;
16 import java.io.IOException;
17 import java.util.List;
18 import org.opendaylight.controller.config.util.xml.XmlUtil;
19 import org.opendaylight.controller.netconf.api.NetconfMessage;
20 import org.slf4j.Logger;
21 import org.slf4j.LoggerFactory;
22 import org.xml.sax.SAXException;
24 public final class NetconfXMLToMessageDecoder extends ByteToMessageDecoder {
25 private static final Logger LOG = LoggerFactory.getLogger(NetconfXMLToMessageDecoder.class);
28 public void decode(final ChannelHandlerContext ctx, final ByteBuf in, final List<Object> out) throws IOException, SAXException {
29 if (in.isReadable()) {
30 if (LOG.isTraceEnabled()) {
31 LOG.trace("Received to decode: {}", ByteBufUtil.hexDump(in));
34 /* According to the XML 1.0 specifications, when there is an XML declaration
35 * at the beginning of an XML document, it is invalid to have
36 * white spaces before that declaration (reminder: a XML declaration looks like:
37 * <?xml version="1.0" encoding="UTF-8"?>). In contrast, when there is no XML declaration,
38 * it is valid to have white spaces at the beginning of the document.
40 * When they send a NETCONF message, several NETCONF servers start with a new line (either
41 * LF or CRLF), presumably to improve readability in interactive sessions with a human being.
42 * Some NETCONF servers send an XML declaration, some others do not.
44 * If a server starts a NETCONF message with white spaces and follows with an XML
45 * declaration, XmlUtil.readXmlToDocument() will fail because this is invalid XML.
46 * But in the spirit of the "NETCONF over SSH" RFC 4742 and to improve interoperability, we want
47 * to accept those messages.
49 * To do this, the following code strips the leading bytes before the start of the XML messages.
52 // Skip all leading whitespaces by moving the reader index to the first non whitespace character
53 while (in.isReadable()) {
54 if (!isWhitespace(in.readByte())) {
55 // return reader index to the first non whitespace character
56 in.readerIndex(in.readerIndex() - 1);
61 // Warn about leading whitespaces
62 if (in.readerIndex() != 0 && LOG.isWarnEnabled()) {
63 final byte[] strippedBytes = new byte[in.readerIndex()];
64 in.getBytes(0, strippedBytes, 0, in.readerIndex());
65 LOG.warn("XML message with unwanted leading bytes detected. Discarded the {} leading byte(s): '{}'",
66 in.readerIndex(), ByteBufUtil.hexDump(Unpooled.wrappedBuffer(strippedBytes)));
69 if (in.isReadable()) {
70 out.add(new NetconfMessage(XmlUtil.readXmlToDocument(new ByteBufInputStream(in))));
72 LOG.debug("No more content in incoming buffer.");
77 * Check whether a byte is whitespace/control character. Considered whitespace characters: <br/>
78 * SPACE, \t, \n, \v, \r, \f
80 * @param b byte to check
81 * @return true if the byte is a whitespace/control character
83 private static boolean isWhitespace(final byte b) {
84 return b <= 0x0d && b >= 0x09 || b == 0x20;