refactor: new helpers in net_processing for external handlers

That's a prior work for removing circular dependencies over net_processing

Author: knst

src/net_processing.cpp

@@ -249,6 +249,9 @@ class PeerManagerImpl final : public PeerManager
     bool IsBanned(NodeId pnode) override EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
 private:
+    /** Helper to process result of external handlers of message */
+    void ProcessPeerMsgRet(const PeerMsgRet& ret, CNode& pfrom);
+
     /** Consider evicting an outbound peer based on the amount of time they've been behind our tip */
     void ConsiderEviction(CNode& pto, int64_t time_in_seconds) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
@@ -2800,6 +2803,11 @@ void PeerManagerImpl::ProcessBlock(CNode& pfrom, const std::shared_ptr<const CBl
     }
 }
 
+void PeerManagerImpl::ProcessPeerMsgRet(const PeerMsgRet& ret, CNode& pfrom)
+{
+    if (!ret) Misbehaving(pfrom.GetId(), ret.error().score, ret.error().message);
+}
+
 void PeerManagerImpl::ProcessMessage(
     CNode& pfrom,
     const std::string& msg_type,

src/net_types.h

@@ -5,11 +5,31 @@
 #ifndef BITCOIN_NET_TYPES_H
 #define BITCOIN_NET_TYPES_H
 
+#include <util/expected.h>
+
 #include <map>
+#include <string>
 
 class CBanEntry;
 class CSubNet;
 
 using banmap_t = std::map<CSubNet, CBanEntry>;
 
+struct MisbehavingError
+{
+    int score;
+    std::string message;
+
+    MisbehavingError(int s) : score{s} {}
+
+     // Constructor does a perfect forwarding reference
+    template <typename T>
+    MisbehavingError(int s, T&& msg) :
+        score{s},
+        message{std::forward<T>(msg)}
+    {}
+};
+
+using PeerMsgRet = tl::expected<void, MisbehavingError>;
+
 #endif // BITCOIN_NET_TYPES_H