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.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.netconf.api.messages.NetconfMessage;
19 import org.opendaylight.netconf.api.xml.XmlUtil;
20 import org.slf4j.Logger;
21 import org.slf4j.LoggerFactory;
22 import org.xml.sax.SAXException;
23 import org.xml.sax.SAXParseException;
25 public final class NetconfXMLToMessageDecoder extends ByteToMessageDecoder {
26 private static final Logger LOG = LoggerFactory.getLogger(NetconfXMLToMessageDecoder.class);
29 public void decode(final ChannelHandlerContext ctx, final ByteBuf in,
30 final List<Object> out) throws IOException, SAXException {
31 if (in.isReadable()) {
32 if (LOG.isTraceEnabled()) {
33 LOG.trace("Received to decode: {}", ByteBufUtil.hexDump(in));
36 /* According to the XML 1.0 specifications, when there is an XML declaration
37 * at the beginning of an XML document, it is invalid to have
38 * white spaces before that declaration (reminder: a XML declaration looks like:
39 * <?xml version="1.0" encoding="UTF-8"?>). In contrast, when there is no XML declaration,
40 * it is valid to have white spaces at the beginning of the document.
42 * When they send a NETCONF message, several NETCONF servers start with a new line (either
43 * LF or CRLF), presumably to improve readability in interactive sessions with a human being.
44 * Some NETCONF servers send an XML declaration, some others do not.
46 * If a server starts a NETCONF message with white spaces and follows with an XML
47 * declaration, XmlUtil.readXmlToDocument() will fail because this is invalid XML.
48 * But in the spirit of the "NETCONF over SSH" RFC 4742 and to improve interoperability, we want
49 * to accept those messages.
51 * To do this, the following code strips the leading bytes before the start of the XML messages.
54 // Skip all leading whitespaces by moving the reader index to the first non whitespace character
55 while (in.isReadable()) {
56 if (!isWhitespace(in.readByte())) {
57 // return reader index to the first non whitespace character
58 in.readerIndex(in.readerIndex() - 1);
63 // Warn about leading whitespaces
64 if (in.readerIndex() != 0 && LOG.isWarnEnabled()) {
65 final byte[] strippedBytes = new byte[in.readerIndex()];
66 in.getBytes(0, strippedBytes, 0, in.readerIndex());
67 LOG.warn("XML message with unwanted leading bytes detected. Discarded the {} leading byte(s): '{}'",
68 in.readerIndex(), ByteBufUtil.hexDump(Unpooled.wrappedBuffer(strippedBytes)));
71 if (in.isReadable()) {
73 out.add(new NetconfMessage(XmlUtil.readXmlToDocument(new ByteBufInputStream(in))));
74 } catch (SAXParseException e) {
75 LOG.error("Failed to parse received message", e);
77 in.skipBytes(in.readableBytes());
80 LOG.debug("No more content in incoming buffer.");
85 * Check whether a byte is whitespace/control character. Considered whitespace characters: <br/>
86 * SPACE, \t, \n, \v, \r, \f
88 * @param byteToCheck byte to check
89 * @return true if the byte is a whitespace/control character
91 private static boolean isWhitespace(final byte byteToCheck) {
92 return byteToCheck <= 0x0d && byteToCheck >= 0x09 || byteToCheck == 0x20;