dnsdist: Prevent the use of "any" addresses for downstream server

Otherwise the corresponding `DownstreamState`'s FD is -1 (needed
for 'client' mode) and we loop endlessly on `recvfrom()` returning -1.
Reported by Sander Smeenk.

diff --git a/pdns/dnsdist-lua.cc b/pdns/dnsdist-lua.cc
index ebd6e41889d6afbadc2d94e9aa07e9041b82d65c..0fc8c57e7e24f48c13bd7c33a862f654fb692297 100644 (file)
--- a/pdns/dnsdist-lua.cc
+++ b/pdns/dnsdist-lua.cc
@@ -194,14 +194,20 @@ vector<std::function<void(void)>> setupLua(bool client, const std::string& confi
                        }
                        ComboAddress sourceAddr;
                        unsigned int sourceItf = 0;
-                       if(auto address = boost::get<string>(&pvars)) {
+                       if(auto addressStr = boost::get<string>(&pvars)) {
+                         ComboAddress address(*addressStr, 53);
                          std::shared_ptr<DownstreamState> ret;
+                         if(IsAnyAddress(address)) {
+                           g_outputBuffer="Error creating new server: invalid address for a downstream server.";
+                           errlog("Error creating new server: %s is not a valid address for a downstream server", *addressStr);
+                           return ret;
+                         }
                          try {
-                           ret=std::make_shared<DownstreamState>(ComboAddress(*address, 53));
+                           ret=std::make_shared<DownstreamState>(address);
                          }
                          catch(std::exception& e) {
                            g_outputBuffer="Error creating new server: "+string(e.what());
-                           errlog("Error creating new server with address %s: %s", *address, e.what());
+                           errlog("Error creating new server with address %s: %s", addressStr, e.what());
                            return ret;
                          }
 
@@ -280,8 +286,14 @@ vector<std::function<void(void)>> setupLua(bool client, const std::string& confi
                        }
 
                        std::shared_ptr<DownstreamState> ret;
+                       ComboAddress address(boost::get<string>(vars["address"]), 53);
+                       if(IsAnyAddress(address)) {
+                         g_outputBuffer="Error creating new server: invalid address for a downstream server.";
+                         errlog("Error creating new server: %s is not a valid address for a downstream server", boost::get<string>(vars["address"]));
+                         return ret;
+                       }
                        try {
-                         ret=std::make_shared<DownstreamState>(ComboAddress(boost::get<string>(vars["address"]), 53), sourceAddr, sourceItf);
+                         ret=std::make_shared<DownstreamState>(address, sourceAddr, sourceItf);
                        }
                        catch(std::exception& e) {
                          g_outputBuffer="Error creating new server: "+string(e.what());