net: Quiet down logging when router doesn't support natpmp/pcp

When the router doesn't support natpmp and PCP, one'd normally expect
the UDP packet to be ignored, and hit a time out. This logs a warning
that is already in the debug category. However, there's also the case in
which sending an UDP packet causes a ICMP response. This is returned to
user space as "connection refused" (despite UDP having no concept of
connections).

Move the warnings from `Send` and `Recv` to debug level too, to reduce
log spam in that case.

Closes #33301.

Author: laanwj

src/common/pcp.cpp

@@ -230,7 +230,7 @@ std::optional<std::vector<uint8_t>> PCPSendRecv(Sock &sock, const std::string &p
         }
         // Dispatch packet to gateway.
         if (sock.Send(request.data(), request.size(), 0) != static_cast<ssize_t>(request.size())) {
-            LogPrintLevel(BCLog::NET, BCLog::Level::Warning, "%s: Could not send request: %s\n", protocol, NetworkErrorString(WSAGetLastError()));
+            LogPrintLevel(BCLog::NET, BCLog::Level::Debug, "%s: Could not send request: %s\n", protocol, NetworkErrorString(WSAGetLastError()));
             return std::nullopt; // Network-level error, probably no use retrying.
         }
 
@@ -251,7 +251,7 @@ std::optional<std::vector<uint8_t>> PCPSendRecv(Sock &sock, const std::string &p
             // Receive response.
             recvsz = sock.Recv(response, sizeof(response), MSG_DONTWAIT);
             if (recvsz < 0) {
-                LogPrintLevel(BCLog::NET, BCLog::Level::Warning, "%s: Could not receive response: %s\n", protocol, NetworkErrorString(WSAGetLastError()));
+                LogPrintLevel(BCLog::NET, BCLog::Level::Debug, "%s: Could not receive response: %s\n", protocol, NetworkErrorString(WSAGetLastError()));
                 return std::nullopt; // Network-level error, probably no use retrying.
             }
             LogPrintLevel(BCLog::NET, BCLog::Level::Debug, "%s: Received response of %d bytes: %s\n", protocol, recvsz, HexStr(std::span(response, recvsz)));