fix uninitialized read when stringifying an addrLocal

backport of bitcoin/bitcoin#14728 to
Komodo-Qt codebase. ipv4_peer_with_ipv6_addrMe_test bit
improved, check proper init of scopeId via child class and GetScopeId()
method.

src/Makefile.ktest.include

@@ -18,7 +18,8 @@ komodo_test_SOURCES = \
     test-komodo/test_addrman.cpp \
     test-komodo/test_netbase_tests.cpp \
     test-komodo/test_events.cpp \
-    test-komodo/test_hex.cpp
+    test-komodo/test_hex.cpp \
+    test-komodo/test_net_tests.cpp
 
 komodo_test_CPPFLAGS = $(komodod_CPPFLAGS)
 

src/netbase.cpp

@@ -662,7 +662,6 @@ bool ConnectSocketByName(CService &addr, SOCKET& hSocketRet, const char *pszDest
 void CNetAddr::Init()
 {
     memset(ip, 0, sizeof(ip));
-    scopeId = 0;
 }
 
 void CNetAddr::SetIP(const CNetAddr& ipIn)

src/netbase.h

@@ -59,7 +59,7 @@ class CNetAddr
 {
     protected:
         unsigned char ip[16]; // in network byte order
-        uint32_t scopeId; // for scoped/link-local ipv6 addresses
+        uint32_t scopeId{0}; // for scoped/link-local ipv6 addresses
 
     public:
         CNetAddr();

src/test-komodo/test_net_tests.cpp

@@ -0,0 +1,83 @@
+#include <gtest/gtest.h>
+#include "sync.h"
+#include "net.h"
+
+#include <memory>
+#include <utility>
+
+namespace TestNetTests {
+
+    //! Substitute for C++14 std::make_unique.
+    template <typename T, typename... Args>
+    std::unique_ptr<T> MakeUnique(Args&&... args)
+    {
+        return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
+    }
+
+    class CChildCService : public CService {
+        public:
+            explicit CChildCService(const CService &ipIn) : CService(ipIn) {};
+            uint32_t GetScopeId() { return scopeId; }
+    };
+
+    // https://github.com/bitcoin/bitcoin/pull/14728 - fix uninitialized read when stringifying an addrLocal
+    // prior to commit containing this test, it triggers an undefined behavior
+    TEST(TestNetTests, ipv4_peer_with_ipv6_addrMe_test) {
+        // set up local addresses; all that's necessary to reproduce the bug is
+        // that a normal IPv4 address is among the entries, but if this address is
+        // !IsRoutable the undefined behavior is easier to trigger deterministically
+        {
+            LOCK(cs_mapLocalHost);
+            in_addr ipv4AddrLocal;
+            ipv4AddrLocal.s_addr = 0x0100007f;
+            CNetAddr addr = CNetAddr(ipv4AddrLocal);
+            LocalServiceInfo lsi;
+            lsi.nScore = 23;
+            lsi.nPort = 42;
+            mapLocalHost[addr] = lsi;
+        }
+
+        // create a peer with an IPv4 address
+        in_addr ipv4AddrPeer;
+        ipv4AddrPeer.s_addr = 0xa0b0c001;
+        CAddress addr = CAddress(CService(ipv4AddrPeer, 7777), NODE_NETWORK);
+        // std::unique_ptr<CNode> pnode = MakeUnique<CNode>(0, NODE_NETWORK, 0, INVALID_SOCKET, addr, 0, 0, CAddress{}, std::string{}, false);
+        std::unique_ptr<CNode> pnode = MakeUnique<CNode>(INVALID_SOCKET, addr, std::string{}, false);
+
+        // pnode->fSuccessfullyConnected.store(true); // std::atomic_bool
+        pnode->fSuccessfullyConnected = true;
+
+        // the peer claims to be reaching us via IPv6
+        in6_addr ipv6AddrLocal;
+        memset(ipv6AddrLocal.s6_addr, 0, 16);
+        ipv6AddrLocal.s6_addr[0] = 0xcc;
+
+        CNetAddr cna_with_scope_set(ipv6AddrLocal, 0); // set scope to 0
+        CAddress addrLocal = CAddress(CService(cna_with_scope_set, 7777), NODE_NETWORK);
+
+        // pnode->SetAddrLocal(addrLocal);
+        pnode->addrLocal = addrLocal;
+
+        ASSERT_TRUE(pnode->vAddrToSend.size() == 0);
+
+        // before patch, this causes undefined behavior detectable with clang's -fsanitize=memory
+        AdvertizeLocal(&*pnode);
+
+        /* AdvertizeLocal calls SetIP without setting the scopeId:
+
+           AdvertizeLocal(CNode * pnode) -> GetLocalAddress(const CNetAddr * paddrPeer) -> GetLocal(CService & addr, const CNetAddr * paddrPeer),
+           last proc took value from mapLocalHost which contains only IPv4 address we put earlier (127.0.0.1:42), constructed without
+           set any scope (!) - CNetAddr(ipv4AddrLocal).
+        */
+
+        ASSERT_TRUE(pnode->vAddrToSend.size() == 1);
+
+        CChildCService ccs(pnode->vAddrToSend.back());
+        // scopeId should be initialized to 0, when fix applied
+        ASSERT_TRUE(ccs.GetScopeId() == 0);
+
+        // suppress no-checks-run warning; if this test fails, it's by triggering a sanitizer
+        ASSERT_TRUE(1);
+
+    }
+}