icmpv6: send no address-resolution NS from a tentative address

WHATSNEW

@@ -471,6 +471,10 @@ Notable bug fixes are the following:
 
    The HT mode factory now includes band and preamble format in its cache key. A 5 GHz request after an equivalent 2.4 GHz request therefore receives the requested band and timing. Previously, that request could receive the earlier mode. Identical complete requests still reuse one object.
 
+2. Address resolution sends no Neighbor Solicitation from a tentative address
+
+   Address resolution sent its Neighbor Solicitation from a tentative address, for example under Optimistic Duplicate Address Detection, although RFC 4861 Section 7.2.2 takes the source from the assigned addresses, RFC 4862 does not count a tentative address as assigned, and RFC 4429 forbids an Optimistic address as the source of a Neighbor Solicitation. The solicitation now uses an address that is not tentative, keeping the previous choice when that address is assigned; if the interface has none yet, address resolution starts when Duplicate Address Detection of an address completes. If Duplicate Address Detection finds the link-local address duplicate before any other address is assigned, datagrams to unresolved neighbours now stay queued instead of being returned with an ICMPv6 error. Simulations in which a node sends IPv6 traffic to an unresolved neighbour while every address of the interface is tentative produce different results, for example examples/ipv6/mipv6, examples/ipv6/mipv6roaming and examples/inet/hierarchical99.
+
 
 INET-4.7 (July 2026) — feature release
 --------------------------------------

src/inet/networklayer/icmpv6/Ipv6NeighbourDiscovery.cc

@@ -44,6 +44,27 @@ simsignal_t Ipv6NeighbourDiscovery::startDadSignal = registerSignal("startDad");
 simsignal_t Ipv6NeighbourDiscovery::dadCompletedSignal = registerSignal("dadCompleted");
 simsignal_t Ipv6NeighbourDiscovery::dadFailedSignal = registerSignal("dadFailed");
 
+// RFC 4861 Section 7.2.2: the source of an address-resolution NS is the source of the
+// prompting packet if it is assigned to the interface, otherwise any assigned address.
+// A tentative address is not assigned (RFC 4862 Section 5.4), and an Optimistic address
+// MUST NOT be the source of an NS (RFC 4429 Section 3.2). Returns the unspecified
+// address if the interface has no assigned address.
+static Ipv6Address chooseNsSourceAddress(const Ipv6InterfaceData *ipv6Data, const Ipv6Address& dgSrcAddr)
+{
+    if (ipv6Data->hasAddress(dgSrcAddr) && !ipv6Data->isTentativeAddress(dgSrcAddr))
+        return dgSrcAddr;
+    const Ipv6Address& preferredAddr = ipv6Data->getPreferredAddress();
+    if (!preferredAddr.isUnspecified() && !ipv6Data->isTentativeAddress(preferredAddr))
+        return preferredAddr;
+    const Ipv6Address& linkLocalAddr = ipv6Data->getLinkLocalAddress();
+    if (!linkLocalAddr.isUnspecified() && !ipv6Data->isTentativeAddress(linkLocalAddr))
+        return linkLocalAddr;
+    for (int i = 0; i < ipv6Data->getNumAddresses(); i++)
+        if (!ipv6Data->isTentativeAddress(i) && ipv6Data->getAddress(i).isUnicast())
+            return ipv6Data->getAddress(i);
+    return Ipv6Address::UNSPECIFIED_ADDRESS;
+}
+
 Ipv6NeighbourDiscovery::Ipv6NeighbourDiscovery()
     : neighbourCache(*this)
 {
@@ -670,15 +691,16 @@ void Ipv6NeighbourDiscovery::initiateAddressResolution(const Ipv6Address& dgSrcA
     Ipv6Address nsSrcAddr;
 
     /*If the source address of the packet prompting the solicitation is the
-       same as one of the addresses assigned to the outgoing interface,*/
-    if (ie->getProtocolData<Ipv6InterfaceData>()->hasAddress(dgSrcAddr))
-        /*that address SHOULD be placed in the IP Source Address of the outgoing
-           solicitation.*/
-        nsSrcAddr = dgSrcAddr;
-    else
-        /*Otherwise, any one of the addresses assigned to the interface
-           should be used.*/
-        nsSrcAddr = ie->getProtocolData<Ipv6InterfaceData>()->getPreferredAddress();
+       same as one of the addresses assigned to the outgoing interface, that
+       address SHOULD be placed in the IP Source Address of the outgoing
+       solicitation. Otherwise, any one of the addresses assigned to the
+       interface should be used.*/
+    nsSrcAddr = chooseNsSourceAddress(ie->getProtocolData<Ipv6InterfaceData>(), dgSrcAddr);
+    if (nsSrcAddr.isUnspecified()) {
+        // makeTentativeAddressPermanent() starts address resolution when an address is assigned
+        EV_INFO << "No address assigned to the interface yet, address resolution waits for DAD\n";
+        return;
+    }
     ASSERT(ifID != -1);
     // Sending NS on specified interface.
     createAndSendNsPacket(nsTargetAddr, nsDestAddr, nsSrcAddr, ie);
@@ -706,6 +728,19 @@ void Ipv6NeighbourDiscovery::processArTimeout(cMessage *arTimeoutMsg)
     EV_INFO << "Max Multicast Solicitation:" << ie->getProtocolData<Ipv6InterfaceData>()->_getMaxMulticastSolicit() << endl;
 
     if (nce->numOfARNSSent < ie->getProtocolData<Ipv6InterfaceData>()->_getMaxMulticastSolicit()) {
+        // the source chosen for the first NS may have become tentative or been removed since
+        const auto *ipv6Data = ie->getProtocolData<Ipv6InterfaceData>();
+        if (!ipv6Data->hasAddress(nce->nsSrcAddr) || ipv6Data->isTentativeAddress(nce->nsSrcAddr)) {
+            Ipv6Address dgSrcAddr = nce->pendingPackets.empty() ? Ipv6Address::UNSPECIFIED_ADDRESS : nce->pendingPackets.front()->peekAtFront<Ipv6Header>()->getSrcAddress();
+            nce->nsSrcAddr = chooseNsSourceAddress(ipv6Data, dgSrcAddr);
+            if (nce->nsSrcAddr.isUnspecified()) {
+                // makeTentativeAddressPermanent() restarts address resolution
+                EV_INFO << "No address assigned to the interface any more, address resolution waits for DAD\n";
+                nce->arTimer = nullptr;
+                delete arTimeoutMsg;
+                return;
+            }
+        }
         EV_INFO << "Sending another Address Resolution NS message" << endl;
         Ipv6Address nsDestAddr = nsTargetAddr.formSolicitedNodeMulticastAddress();
         createAndSendNsPacket(nsTargetAddr, nsDestAddr, nce->nsSrcAddr, ie);
@@ -896,6 +931,14 @@ void Ipv6NeighbourDiscovery::makeTentativeAddressPermanent(const Ipv6Address& te
 
     ie->getProtocolDataForUpdate<Ipv6InterfaceData>()->setDadInProgress(false);
 
+    // start the address resolution that waited for an assigned address (see initiateAddressResolution())
+    for (auto& elem : neighbourCache) {
+        Neighbour& nce = elem.second;
+        if (elem.first.interfaceID == ie->getInterfaceId() && nce.reachabilityState == Ipv6NeighbourCache::INCOMPLETE
+                && nce.arTimer == nullptr && !nce.pendingPackets.empty())
+            initiateAddressResolution(nce.pendingPackets.front()->peekAtFront<Ipv6Header>()->getSrcAddress(), &nce);
+    }
+
     if (!tentativeAddr.isLinkLocal()) {
         // DAD completed for a global address -- nothing else to do
         return;

tests/fingerprint/examples.csv

@@ -165,7 +165,7 @@
 
 # /examples/inet/hierarchical99/,      -f .qtenv.ini -c General -r 0
 /examples/inet/hierarchical99/,      -f networklayer.ini -c IPv4 -r 0,              10000s,          a94d-edae/tplx;1f32-e325/~tNl;b138-ee8b/~tND;66c9-cd73/tyf, PASS, EthernetMac Ipv4
-/examples/inet/hierarchical99/,      -f networklayer.ini -c IPv6 -r 0,              10000s,          0001-0108/tplx;3960-479e/~tNl;add1-e848/~tND;2c03-abef/tyf, PASS, EthernetMac
+/examples/inet/hierarchical99/,      -f networklayer.ini -c IPv6 -r 0,              10000s,          acf6-4224/tplx;af7d-b669/~tNl;710c-34d1/~tND;d96c-23d2/tyf, PASS, EthernetMac
 /examples/inet/hierarchical99/,      -f networklayer.ini -c Generic -r 0,           10000s,          6ae4-6e75/tplx;2209-80ac/~tNl;93bf-6657/tyf, PASS, EthernetMac
 /examples/inet/hierarchical99/,      -f networklayer.ini -c Flooding -r 0,          10000s,          7ba7-5b91/tplx;b0f0-411e/~tNl;2b94-8906/tyf, PASS, EthernetMac
 /examples/inet/hierarchical99/,      -f networklayer.ini -c ProbabilisticBroadcast -r 0,              10000s,          5a54-9779/tplx;1165-a70b/~tNl;760b-abfc/tyf, PASS, EthernetMac
@@ -380,9 +380,9 @@
 /examples/manetrouting/multiradio/,  -f omnetpp.ini -c MultiRadio -r 0,             20s,             55c4-44c4/tplx;92b9-416a/~tNl, PASS,  wireless adhoc Ipv4
 /examples/manetrouting/multiradio/,  -f omnetpp.ini -c SingleRadio -r 0,            20s,             5ed8-cf6b/tplx;b9f1-61b0/~tNl;3aa0-49ed/tyf, PASS,  wireless adhoc Ipv4
 
-/examples/ipv6/mipv6/,               -f omnetpp.ini -c Handover -r 0,                70s,             68ea-9693/tplx;a44c-17bf/~tNl;96ff-ed7c/~tND;44ef-1a45/tyf, PASS, wireless EthernetMac
+/examples/ipv6/mipv6/,               -f omnetpp.ini -c Handover -r 0,                70s,             c073-8d42/tplx;a457-16df/~tNl;3d28-8302/~tND;7491-bcad/tyf, PASS, wireless EthernetMac
 /examples/ipv6/mipv6/,               -f omnetpp.ini -c RouteOptimizationTwoCNs -r 0,  60s,             bacf-986a/tplx;e6db-28c0/~tNl;805b-8a25/~tND;ed3e-17fa/tyf, PASS, wireless EthernetMac
-/examples/ipv6/mipv6roaming/,        -f omnetpp.ini -c Roaming -r 0,                 70s,             b275-b584/tplx;28ce-974e/~tNl;dcec-ae59/~tND;afae-2b3c/tyf, PASS, wireless EthernetMac
+/examples/ipv6/mipv6roaming/,        -f omnetpp.ini -c Roaming -r 0,                 70s,             8ea9-9430/tplx;9273-d4eb/~tNl;6c79-6458/~tND;f3a3-116d/tyf, PASS, wireless EthernetMac
 /examples/ipv6/pmipv6/,              -f omnetpp.ini -c General -r 0,                 60s,             e801-4d1a/tplx;1064-9bd4/~tNl;bd46-d85c/~tND;0277-d784/tyf, PASS, wireless EthernetMac
 
 /examples/mobility/,                 -f omnetpp.ini -c AnsimMobility -r 0,          10000s,          72f8-5c0b/tplx;0000-0000/~tNl;0000-0000/~tND;7dd1-18eb/tyf, PASS,

tests/fingerprint/mipv6-refactoring.csv

@@ -23,7 +23,7 @@
 /examples/ipv6/nclients/,            -f omnetpp.ini -c PPP_SCTP -r 0,               100s,            3a7c-924c/~tNlb, PASS,
 
 # IPv6 networking examples
-/examples/inet/hierarchical99/,      -f networklayer.ini -c IPv6 -r 0,              10000s,          f206-a0e2/~tNlb, PASS, EthernetMac
+/examples/inet/hierarchical99/,      -f networklayer.ini -c IPv6 -r 0,              10000s,          082b-e145/~tNlb, PASS, EthernetMac
 /examples/inet/udpclientserver/,     -f omnetpp.ini -c udp_OK_ipv6 -r 0,            10s,             8feb-3936/~tNlb, PASS,
 /examples/inet/udpclientserver/,     -f omnetpp.ini -c udp_Port_Unav_ipv6 -r 0,     10s,             9661-c1f5/~tNlb, PASS,
 /examples/inet/udpclientserver/,     -f omnetpp.ini -c udp_Host_Unav_ipv6 -r 0,     10s,             6360-9ed1/~tNlb, PASS,

tests/module/IPv6_ND_no_solicitation_from_tentative_address.test

@@ -0,0 +1,71 @@
+%description:
+A host sends no address-resolution Neighbor Solicitation from a tentative address: RFC 4861
+Section 7.2.2 takes the source from the addresses assigned to the interface, RFC 4862
+Section 5.4 does not count a tentative address as assigned, and RFC 4429 Section 3.2 forbids
+an Optimistic address as the source of a Neighbor Solicitation. With no address assigned
+yet, address resolution waits for Duplicate Address Detection (DAD) to complete.
+
+Topology: router -- host
+
+The host uses Optimistic DAD and pings the router's link-local address from t=0, so its only
+address, the link-local one, is tentative when the first ping needs address resolution. Only
+the host's Neighbour Discovery and network-layer dispatcher log. No Neighbor Solicitation
+from the host's link-local address to the router's solicited-node address may come before
+the host's "DAD completed" line, and one must come after it. The packet printer colours the
+fields, so the patterns allow other characters between them.
+
+%#--------------------------------------------------------------------------------------------------------------
+%file: test.ned
+
+import inet.networklayer.configurator.ipv6.Ipv6FlatNetworkConfigurator;
+import inet.node.ipv6.Router6;
+import inet.node.ipv6.StandardHost6;
+import ned.DatarateChannel;
+
+network TentativeSolicitationTest
+{
+    types:
+        channel ethline extends DatarateChannel
+        {
+            delay = 0.1us;
+            datarate = 10Mbps;
+        }
+    submodules:
+        configurator: Ipv6FlatNetworkConfigurator;
+        router: Router6;
+        host: StandardHost6;
+    connections:
+        router.ethg++ <--> ethline <--> host.ethg++;
+}
+
+%#--------------------------------------------------------------------------------------------------------------
+%inifile: omnetpp.ini
+
+[General]
+network = TentativeSolicitationTest
+ned-path = .;../../../../src
+sim-time-limit = 3s
+record-vector-results = false
+cmdenv-express-mode = false
+
+**.neighbourDiscovery.optimisticDad = true
+**.host.numApps = 1
+**.host.app[0].typename = "PingApp"
+**.host.app[0].destAddr = "fe80::8aa:ff:fe00:1"
+**.host.app[0].startTime = 0s
+**.host.app[0].sendInterval = 0.2s
+
+**.host.ipv6.neighbourDiscovery.cmdenv-log-level = info
+**.host.nl.cmdenv-log-level = trace
+**.cmdenv-log-level = off
+
+%#--------------------------------------------------------------------------------------------------------------
+%contains-regex: stdout
+DAD completed for address fe80::8aa:ff:fe00:2 on eth0, address is unique[\s\S]*NeighbourSolicitation[^,]*, [^,]*sourceAddress[^,]*= fe80::8aa:ff:fe00:2, [^,]*destinationAddress[^,]*= ff02::1:ff00:1,
+%#--------------------------------------------------------------------------------------------------------------
+%not-contains-regex: stdout
+NeighbourSolicitation[^,]*, [^,]*sourceAddress[^,]*= fe80::8aa:ff:fe00:2, [^,]*destinationAddress[^,]*= ff02::1:ff00:1,[\s\S]*DAD completed for address fe80::8aa:ff:fe00:2
+%#--------------------------------------------------------------------------------------------------------------
+%not-contains: stdout
+<!> Error
+%#--------------------------------------------------------------------------------------------------------------