Correct ReachTlvParser to handle IPv6 prefix

ReachTlvParser class supports Ipv6 prefix only in serialization
methods. ParseTlvBody handles only IPv4 prefix. Thus, if a peer
BGP Link State router sends an Update Message with an IPv6
prefix in IP Reachability Information NLRI, ParseTlvBody
method fails to parse the IPv6 prefix and assert a
BGPDocumentedException.

This patch looks to the length of the buffer to be parsed to
determine if the prefix is an IPv4 or an IPv6 one. SerializeModel
method has been also updated to avoid exception to determine
if the prefix is an IPv4 or an IPv6 one.

JIRA: BGPCEP-1009
Change-Id: Ia5bac0fb2a6087e5c5cfbca0e3eee7d8fd7b822c
Signed-off-by: Olivier Dugeon <olivier.dugeon@orange.com>
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>

diff --git a/bgp/extensions/linkstate/src/main/java/org/opendaylight/protocol/bgp/linkstate/impl/tlvs/ReachTlvParser.java b/bgp/extensions/linkstate/src/main/java/org/opendaylight/protocol/bgp/linkstate/impl/tlvs/ReachTlvParser.java
index e4e90d89999882b46f107bdaa8b911c47d5737ff..f203fd29dc8402cffab322bc7eb4307b28c70148 100644 (file)
--- a/bgp/extensions/linkstate/src/main/java/org/opendaylight/protocol/bgp/linkstate/impl/tlvs/ReachTlvParser.java
+++ b/bgp/extensions/linkstate/src/main/java/org/opendaylight/protocol/bgp/linkstate/impl/tlvs/ReachTlvParser.java
@@ -9,7 +9,6 @@ package org.opendaylight.protocol.bgp.linkstate.impl.tlvs;
 
 import com.google.common.annotations.VisibleForTesting;
 import io.netty.buffer.ByteBuf;
-import io.netty.buffer.Unpooled;
 import org.opendaylight.protocol.bgp.linkstate.spi.LinkstateTlvParser;
 import org.opendaylight.protocol.util.Ipv4Util;
 import org.opendaylight.protocol.util.Ipv6Util;
@@ -20,8 +19,6 @@ import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.link
 import org.opendaylight.yangtools.yang.common.QName;
 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.NodeIdentifier;
 import org.opendaylight.yangtools.yang.data.api.schema.ContainerNode;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 public final class ReachTlvParser implements LinkstateTlvParser.LinkstateTlvSerializer<IpPrefix>,
         LinkstateTlvParser<IpPrefix> {
@@ -29,12 +26,30 @@ public final class ReachTlvParser implements LinkstateTlvParser.LinkstateTlvSeri
         "ip-reachability-information").intern();
     @VisibleForTesting
     public static final NodeIdentifier IP_REACH_NID = NodeIdentifier.create(IP_REACHABILITY_QNAME);
-    private static final Logger LOG = LoggerFactory.getLogger(ReachTlvParser.class);
     private static final int IP_REACHABILITY = 265;
 
+    /**
+     * {@inheritDoc}
+     *
+     * <p>
+     * IP Reachability TLV serves to convey both an IPV4 or an IPV6 prefix as per
+     * <a href="https://datatracker.ietf.org/doc/html/rfc7752#section-3.2.3.2">RFC7752 Section 3.2.3.2</a>. However, the
+     * Length of the IP Reachability TLV could not be used to distinguish the two types of prefixes as it will be the
+     * same: for example {@code byteBuffer == [24][192][168][01]} could be parsed as IPv4 prefix {@code 192.168.1.0/24}
+     * or as IPv6 prefix {@code c0a8:100::/24}.
+     *
+     * <p>
+     * Thus, we could just verify if the length is greater than 4 bytes. In this case, it is certain that the prefix is
+     * IPv6. For a length less than or equal to 4 bytes, the parser assumes that the prefix is IPv4. In addition, the
+     * probability that an IS-IS domain advertises an IPv6 prefix with a length lower than /32 is very low.
+     */
+    // FIXME: perhaps we need a dedicated type, or just always use IPv6?
     @Override
     public IpPrefix parseTlvBody(final ByteBuf value) {
-        return new IpPrefix(Ipv4Util.prefixForByteBuf(value));
+        // Get address length to determine if it is an IPv4 or an IPv6 prefix
+        final int length = value.readableBytes() - 1;
+        return length <= Ipv4Util.IP4_LENGTH ? new IpPrefix(Ipv4Util.prefixForByteBuf(value))
+            : new IpPrefix(Ipv6Util.prefixForByteBuf(value));
     }
 
     @Override
@@ -60,14 +75,10 @@ public final class ReachTlvParser implements LinkstateTlvParser.LinkstateTlvSeri
         return prefixDesc.findChildByArg(IP_REACH_NID)
                 .map(child -> {
                     final String prefix = (String) child.body();
-                    try {
-                        final ByteBuf buffer = Unpooled.buffer(5);
-                        Ipv4Util.writeMinimalPrefix(new Ipv4Prefix(prefix), buffer);
-                        return new IpPrefix(new Ipv4Prefix(prefix));
-                    } catch (final IllegalArgumentException e) {
-                        LOG.debug("Creating Ipv6 prefix because", e);
-                        return new IpPrefix(new Ipv6Prefix(prefix));
-                    }
+                    // Get the prefix length from the string to determine if it is an IPv4 or an IPv6 prefix
+                    final int length = Ipv4Util.getPrefixLengthBytes(prefix);
+                    return length <= Ipv4Util.IP4_LENGTH ? new IpPrefix(new Ipv4Prefix(prefix))
+                        : new IpPrefix(new Ipv6Prefix(prefix));
                 })
                 .orElse(null);
     }