net: resolve outside of storage structures

Rather than allowing CNetAddr/CService/CSubNet to launch DNS queries, require
that addresses are already resolved.

This greatly simplifies async resolve logic, and makes it harder to
accidentally leak DNS queries.

src/init.cpp

@@ -1156,10 +1156,11 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
 
     if (mapArgs.count("-externalip")) {
         BOOST_FOREACH(const std::string& strAddr, mapMultiArgs["-externalip"]) {
-            CService addrLocal(strAddr, GetListenPort(), fNameLookup);
+            CService addrLocal;
-            if (!addrLocal.IsValid())
+            if (Lookup(strAddr.c_str(), addrLocal, GetListenPort(), fNameLookup) && addrLocal.IsValid())
+                AddLocal(addrLocal, LOCAL_MANUAL);
+            else
                 return InitError(ResolveErrMsg("externalip", strAddr));
-            AddLocal(CService(strAddr, GetListenPort(), fNameLookup), LOCAL_MANUAL);
         }
     }
 

src/netbase.cpp

@@ -614,11 +614,13 @@ bool ConnectSocketByName(CService &addr, SOCKET& hSocketRet, const char *pszDest
     proxyType nameProxy;
     GetNameProxy(nameProxy);
 
-    CService addrResolved(CNetAddr(strDest, fNameLookup && !HaveNameProxy()), port);
+    CService addrResolved;
+    if (Lookup(strDest.c_str(), addrResolved, port, fNameLookup && !HaveNameProxy())) {
         if (addrResolved.IsValid()) {
             addr = addrResolved;
             return ConnectSocket(addr, hSocketRet, nTimeout);
         }
+    }
 
     addr = CService("0.0.0.0:0");