Merge branch 'master-fix-stall' into elements-22-fix-ci

Author: psgreco

src/net.cpp

@@ -1361,6 +1361,9 @@ bool CConnman::GenerateSelectSet(std::set<SOCKET> &recv_set, std::set<SOCKET> &s
             //   write buffer in this case before receiving more. This avoids
             //   needlessly queueing received data, if the remote peer is not themselves
             //   receiving data. This means properly utilizing TCP flow control signalling.
+            //   This logic can put both nodes in deadlock if they are both "not receiving",
+            //   so there is a special case where we only stop receiving new messages, but
+            //   keep processing the in-progress ones.
             // * Otherwise, if there is space left in the receive buffer, select() for
             //   receiving data.
             // * Hand off all complete messages to the processor, to be handled without
@@ -1380,7 +1383,9 @@ bool CConnman::GenerateSelectSet(std::set<SOCKET> &recv_set, std::set<SOCKET> &s
             error_set.insert(pnode->hSocket);
             if (select_send) {
                 send_set.insert(pnode->hSocket);
-                continue;
+                // Only stop receiving new messages, but keep processing incomplete ones
+                if (!pnode->m_deserializer->IsEmpty())
+                    continue;
             }
             if (select_recv) {
                 recv_set.insert(pnode->hSocket);

src/net.h

@@ -302,6 +302,8 @@ class CNetMessage {
  */
 class TransportDeserializer {
 public:
+    // returns true if the current deserialization is empty
+    virtual bool IsEmpty() const = 0;
     // returns true if the current deserialization is complete
     virtual bool Complete() const = 0;
     // set the serialization context version
@@ -352,6 +354,10 @@ class V1TransportDeserializer final : public TransportDeserializer
         Reset();
     }
 
+    bool IsEmpty() const override
+    {
+        return (nHdrPos == 0);
+    }
     bool Complete() const override
     {
         if (!in_data)