Merge #17131: rpc: fix -rpcclienttimeout 0 option

b3b26e149c rpc: fix -rpcclienttimeout 0 option (Fabian Jahr)

Pull request description:

  fixes #17117

  I understood the bug as the help string being wrong, rather than that this feature is missing and should be added. Let me know if it should be the other way around.

  It is notable that if 0 is given as an argument, the fallback that is being used is the libevent default of 50 seconds, rather than `DEFAULT_HTTP_CLIENT_TIMEOUT` (900 seconds). This is not intuitive for the user. I could handle this in this PR but I am unsure which would be the better solution then: Actually adding the feature as described in the help string or falling back to `DEFAULT_HTTP_CLIENT_TIMEOUT`? Happy to hear opinions.

ACKs for top commit:
  MarcoFalke:
    unsigned ACK b3b26e149c

Tree-SHA512: 65e526a652c0adcdb4f895e8d78d60c7caa5904c9915b165a3ae95725c87d13af1f916359f80302452a2fcac1a80f4c58cd805ec8c28720fa4b91b3c8baa4155

src/bitcoin-cli.cpp

@@ -316,7 +316,20 @@ static UniValue CallRPC(BaseRequestHandler *rh, const std::string& strMethod, co
 
     // Synchronously look up hostname
     raii_evhttp_connection evcon = obtain_evhttp_connection_base(base.get(), host, port);
-    evhttp_connection_set_timeout(evcon.get(), gArgs.GetArg("-rpcclienttimeout", DEFAULT_HTTP_CLIENT_TIMEOUT));
+
+    // Set connection timeout
+    {
+        const int timeout = gArgs.GetArg("-rpcclienttimeout", DEFAULT_HTTP_CLIENT_TIMEOUT);
+        if (timeout > 0) {
+            evhttp_connection_set_timeout(evcon.get(), timeout);
+        } else {
+            // Indefinite request timeouts are not possible in libevent-http, so we
+            // set the timeout to a very long time period instead.
+
+            constexpr int YEAR_IN_SECONDS = 31556952; // Average length of year in Gregorian calendar
+            evhttp_connection_set_timeout(evcon.get(), 5 * YEAR_IN_SECONDS);
+        }
+    }
 
     HTTPReply response;
     raii_evhttp_request req = obtain_evhttp_request(http_request_done, (void*)&response);