[fuzz] add fuzzer for otIp6Send (#11790)

tests/fuzz/CMakeLists.txt

@@ -80,5 +80,6 @@ endmacro()
 #----------------------------------------------------------------------------------------------------------------------
 
 ot_nexus_test(icmp6)
+ot_nexus_test(ip6)
 ot_nexus_test(mdns)
 ot_nexus_test(radio-one-node)

tests/fuzz/ip6.cpp

@@ -0,0 +1,151 @@
+/*
+ *  Copyright (c) 2025, The OpenThread Authors.
+ *  All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions are met:
+ *  1. Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *  3. Neither the name of the copyright holder nor the
+ *     names of its contributors may be used to endorse or promote products
+ *     derived from this software without specific prior written permission.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *  POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "platform/nexus_core.hpp"
+#include "platform/nexus_node.hpp"
+
+namespace ot {
+namespace Nexus {
+
+class FuzzDataProvider
+{
+public:
+    FuzzDataProvider(const uint8_t *aData, size_t aSize)
+        : mData(aData)
+        , mSize(aSize)
+    {
+    }
+
+    void ConsumeData(void *aBuf, size_t aLength)
+    {
+        assert(aLength <= mSize);
+        memcpy(aBuf, mData, aLength);
+        mData += aLength;
+        mSize -= aLength;
+    }
+
+    otError ConsumeRemainingBytes(otMessage *aMessage)
+    {
+        otError error;
+
+        SuccessOrExit(error = otMessageAppend(aMessage, mData, static_cast<uint16_t>(mSize)));
+        mSize = 0;
+
+    exit:
+        return error;
+    }
+
+    bool ConsumeBool(void)
+    {
+        assert(mSize > 0);
+
+        uint8_t result;
+
+        ConsumeData(&result, sizeof(result));
+
+        return result & 1;
+    }
+
+    size_t RemainingBytes(void) { return mSize; }
+
+private:
+    const uint8_t *mData;
+    size_t         mSize;
+};
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
+{
+    const uint16_t kMaxMessageSize = 2048;
+
+    FuzzDataProvider fdp(data, size);
+
+    unsigned int      seed;
+    otMessage        *message;
+    otMessageSettings settings;
+
+    if (size < sizeof(seed) + sizeof(settings.mLinkSecurityEnabled) + sizeof(settings.mPriority))
+    {
+        return 0;
+    }
+
+    if (size > sizeof(seed) + sizeof(settings.mLinkSecurityEnabled) + sizeof(settings.mPriority) + kMaxMessageSize)
+    {
+        return 0;
+    }
+
+    fdp.ConsumeData(&seed, sizeof(seed));
+    srand(seed);
+
+    Core nexus;
+
+    Node &node = nexus.CreateNode();
+
+    node.GetInstance().SetLogLevel(kLogLevelInfo);
+
+    node.GetInstance().Get<BorderRouter::RoutingManager>().Init(/* aInfraIfIndex */ 1, /* aInfraIfIsRunning */ true);
+    node.GetInstance().Get<BorderRouter::RoutingManager>().SetEnabled(true);
+    node.GetInstance().Get<Srp::Server>().SetAutoEnableMode(true);
+    node.GetInstance().Get<BorderRouter::RoutingManager>().SetDhcp6PdEnabled(true);
+    node.GetInstance().Get<BorderRouter::RoutingManager>().SetNat64PrefixManagerEnabled(true);
+    node.GetInstance().Get<Nat64::Translator>().SetEnabled(true);
+
+    Log("---------------------------------------------------------------------------------------");
+    Log("Form network");
+
+    node.Form();
+    nexus.AdvanceTime(60 * 1000);
+    VerifyOrQuit(node.Get<Mle::Mle>().IsLeader());
+    VerifyOrQuit(node.Get<Srp::Server>().GetState() == Srp::Server::kStateRunning);
+
+    Log("---------------------------------------------------------------------------------------");
+    Log("Fuzz");
+
+    memset(&settings, 0, sizeof(settings));
+    settings.mLinkSecurityEnabled = fdp.ConsumeBool();
+    fdp.ConsumeData(&settings.mPriority, sizeof(settings.mPriority));
+
+    message = otIp6NewMessage(&node.GetInstance(), &settings);
+    VerifyOrExit(message != nullptr);
+
+    SuccessOrQuit(fdp.ConsumeRemainingBytes(message));
+
+    otIp6Send(&node.GetInstance(), message);
+
+    nexus.AdvanceTime(10 * 1000);
+
+exit:
+    return 0;
+}
+
+} // namespace Nexus
+} // namespace ot