* add convotags to ensure path to snode

* add service::Endpoint::EnsurePathTo which gives you a std::optional<Convotag>

llarp/handlers/tun.cpp

@@ -325,9 +325,11 @@ namespace llarp
     {
       auto ReplyToSNodeDNSWhenReady = [self = this, reply = reply](
                                           RouterID snode, auto msg, bool isV6) -> bool {
-        return self->EnsurePathToSNode(snode, [=](const RouterID&, exit::BaseSession_ptr s) {
-          self->SendDNSReply(snode, s, msg, reply, isV6);
-        });
+        return self->EnsurePathToSNode(
+            snode,
+            [=](const RouterID&, exit::BaseSession_ptr s, [[maybe_unused]] service::ConvoTag tag) {
+              self->SendDNSReply(snode, s, msg, reply, isV6);
+            });
       };
       auto ReplyToLokiDNSWhenReady = [self = this, reply = reply](
                                          service::Address addr, auto msg, bool isV6) -> bool {

llarp/service/endpoint.cpp

@@ -39,6 +39,7 @@
 #include <llarp/quic/tunnel.hpp>
 #include <llarp/ev/ev_libuv.hpp>
 #include <uvw.hpp>
+#include <variant>
 
 namespace llarp
 {
@@ -1367,10 +1368,10 @@ namespace llarp
       while (itr != range.second)
       {
         if (itr->second.first->IsReady())
-          h(snode, itr->second.first);
+          h(snode, itr->second.first, itr->second.second);
         else
         {
-          itr->second.first->AddReadyHook(std::bind(h, snode, _1));
+          itr->second.first->AddReadyHook(std::bind(h, snode, _1, itr->second.second));
           itr->second.first->BuildOne();
         }
         ++itr;
@@ -1402,10 +1403,11 @@ namespace llarp
       auto pkt = std::make_shared<net::IPPacket>();
       if (!pkt->Load(buf))
         return false;
-      EnsurePathToSNode(addr, [pkt, t](RouterID, exit::BaseSession_ptr s) {
-        if (s)
-          s->SendPacketToRemote(pkt->ConstBuffer(), t);
-      });
+      EnsurePathToSNode(
+          addr, [pkt, t](RouterID, exit::BaseSession_ptr s, [[maybe_unused]] ConvoTag tag) {
+            if (s)
+              s->SendPacketToRemote(pkt->ConstBuffer(), t);
+          });
       return true;
     }
 
@@ -1472,6 +1474,44 @@ namespace llarp
       return std::nullopt;
     }
 
+    bool
+    Endpoint::EnsurePathTo(
+        std::variant<Address, RouterID> addr,
+        std::function<void(std::optional<ConvoTag>)> hook,
+        llarp_time_t timeout)
+    {
+      if (auto ptr = std::get_if<Address>(&addr))
+      {
+        return EnsurePathToService(
+            *ptr,
+            [hook](auto, auto* ctx) {
+              if (ctx)
+              {
+                hook(ctx->currentConvoTag);
+              }
+              else
+              {
+                hook(std::nullopt);
+              }
+            },
+            timeout);
+      }
+      if (auto ptr = std::get_if<RouterID>(&addr))
+      {
+        return EnsurePathToSNode(*ptr, [hook](auto, auto session, auto tag) {
+          if (session)
+          {
+            hook(tag);
+          }
+          else
+          {
+            hook(std::nullopt);
+          }
+        });
+      }
+      return false;
+    }
+
     bool
     Endpoint::SendToServiceOrQueue(
         const service::Address& remote, const llarp_buffer_t& data, ProtocolType t)

llarp/service/endpoint.hpp

@@ -266,6 +266,12 @@ namespace llarp
       bool
       ShouldBuildMore(llarp_time_t now) const override;
 
+      bool
+      EnsurePathTo(
+          std::variant<Address, RouterID> addr,
+          std::function<void(std::optional<ConvoTag>)> hook,
+          llarp_time_t timeout);
+
       // passed a sendto context when we have a path established otherwise
       // nullptr if the path was not made before the timeout
       using PathEnsureHook = std::function<void(Address, OutboundContext*)>;
@@ -275,7 +281,7 @@ namespace llarp
       bool
       EnsurePathToService(const Address remote, PathEnsureHook h, llarp_time_t timeoutMS);
 
-      using SNodeEnsureHook = std::function<void(const RouterID, exit::BaseSession_ptr)>;
+      using SNodeEnsureHook = std::function<void(const RouterID, exit::BaseSession_ptr, ConvoTag)>;
 
       /// ensure a path to a service node by public key
       bool