Prevent deferred link race conditions

(cherry picked from commit e512dd0c68)

Sources/Plasma/PubUtilLib/plNetClient/plNetLinkingMgr.cpp

@@ -504,24 +504,55 @@ bool plNetLinkingMgr::IProcessVaultNotifyMsg(plVaultNotifyMsg* msg)
 			return false;
 	}
 
-	if (cVaultLink != nil)
-	{
-		// This is something that Cyan does... >.<
-		// It's very useful though...
+	if (cVaultLink != nil) {
+		// Verify that if the Age vault already exists that it matches the requested
+		// deferred link. If it doesn't exist, well, I hope you're happy with the result.
 		VaultAgeLinkNode accLink(cVaultLink);
-		accLink.CopyTo(cur);
-		if (RelVaultNode* rvnInfo = cVaultLink->GetChildNodeIncRef(plVault::kNodeType_AgeInfo, 1))
-		{
+		if (RelVaultNode* rvnInfo = cVaultLink->GetChildNodeIncRef(plVault::kNodeType_AgeInfo, 1)) {
+			plAgeInfoStruct dest;
+
 			VaultAgeInfoNode accInfo(rvnInfo);
-			accInfo.CopyTo(cur->GetAgeInfo());
+			accInfo.CopyTo(&dest);
+			if (!dest.IsEqualTo(fDeferredLink->GetAgeLink()->GetAgeInfo())) {
+				hsLogEntry(
+					plNetClientMgr::GetInstance()->DebugMsg(
+						"Waiting for a deferred link to '%s' but got AgeInfo for '%s' instead.",
+						fDeferredLink->GetAgeLink()->AsStdString().c_str(),
+						dest.AsStdString().c_str()
+					);
+				);
+
 				rvnInfo->DecRef();
+				return false;
 			}
 
+			rvnInfo->DecRef();
+		}
+
+		// If we're still here, that means the links match. Set the vault copy as our current
+		// AgeLink and AgeInfo. Note this mainly copies the AgeInfo.
+		accLink.CopyTo(cur);
+		hsLogEntry(
+			plNetClientMgr::GetInstance()->DebugMsg(
+				"Performing deferred link to '%s'",
+				cur->AsStdString().c_str()
+			);
+		);
+
+		// Steals fDeferredLink
 		IDoLink(fDeferredLink);
 		fDeferredLink = nil;
-		return true;
 
 		cVaultLink->DecRef();
+
+		return true;
+	} else {
+        hsLogEntry(
+            plNetClientMgr::GetInstance()->ErrorMsg(
+                "Waiting for a deferred link to '%s' but got a garbage link?",
+                fDeferredLink->GetAgeLink()->AsStdString().c_str()
+            )
+        );
     }
 
 	return false;