doc: clarify -i2pacceptincoming help documentation

and also hoist the default setting to a constexpr and
remove unused f-string operators in a related functional test.

doc/i2p.md

@@ -33,12 +33,10 @@ Core configuration options:
      none)
 
 -i2pacceptincoming
-     If set and -i2psam is also set then incoming I2P connections are
-     accepted via the SAM proxy. If this is not set but -i2psam is set
-     then only outgoing connections will be made to the I2P network.
-     Ignored if -i2psam is not set. Listening for incoming I2P
-     connections is done through the SAM proxy, not by binding to a
-     local address and port (default: 1)
+     Whether to accept inbound I2P connections (default: 1). Ignored if
+     -i2psam is not set. Listening for inbound I2P connections is
+     done through the SAM proxy, not by binding to a local address and
+     port.
 ```
 
 In a typical situation, this suffices:

src/init.cpp

@@ -126,8 +126,9 @@ using node::fPruneMode;
 using node::fReindex;
 using node::nPruneTarget;
 
-static const bool DEFAULT_PROXYRANDOMIZE = true;
-static const bool DEFAULT_REST_ENABLE = false;
+static constexpr bool DEFAULT_PROXYRANDOMIZE{true};
+static constexpr bool DEFAULT_REST_ENABLE{false};
+static constexpr bool DEFAULT_I2P_ACCEPT_INCOMING{true};
 
 #ifdef WIN32
 // Win32 LevelDB doesn't use filedescriptors, and the ones used for
@@ -473,7 +474,7 @@ void SetupServerArgs(ArgsManager& argsman)
     argsman.AddArg("-maxuploadtarget=<n>", strprintf("Tries to keep outbound traffic under the given target per 24h. Limit does not apply to peers with 'download' permission or blocks created within past week. 0 = no limit (default: %s). Optional suffix units [k|K|m|M|g|G|t|T] (default: M). Lowercase is 1000 base while uppercase is 1024 base", DEFAULT_MAX_UPLOAD_TARGET), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-onion=<ip:port>", "Use separate SOCKS5 proxy to reach peers via Tor onion services, set -noonion to disable (default: -proxy)", ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-i2psam=<ip:port>", "I2P SAM proxy to reach I2P peers and accept I2P connections (default: none)", ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
-    argsman.AddArg("-i2pacceptincoming", "If set and -i2psam is also set then incoming I2P connections are accepted via the SAM proxy. If this is not set but -i2psam is set then only outgoing connections will be made to the I2P network. Ignored if -i2psam is not set. Listening for incoming I2P connections is done through the SAM proxy, not by binding to a local address and port (default: 1)", ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
+    argsman.AddArg("-i2pacceptincoming", strprintf("Whether to accept inbound I2P connections (default: %i). Ignored if -i2psam is not set. Listening for inbound I2P connections is done through the SAM proxy, not by binding to a local address and port.", DEFAULT_I2P_ACCEPT_INCOMING), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-onlynet=<net>", "Make automatic outbound connections only to network <net> (" + Join(GetNetworkNames(), ", ") + "). Inbound and manual connections are not affected by this option. It can be specified multiple times to allow multiple networks.", ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-peerbloomfilters", strprintf("Support filtering of blocks and transaction with bloom filters (default: %u)", DEFAULT_PEERBLOOMFILTERS), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-peerblockfilters", strprintf("Serve compact block filters to peers per BIP 157 (default: %u)", DEFAULT_PEERBLOCKFILTERS), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
@@ -1829,7 +1830,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         SetReachable(NET_I2P, false);
     }
 
-    connOptions.m_i2p_accept_incoming = args.GetBoolArg("-i2pacceptincoming", true);
+    connOptions.m_i2p_accept_incoming = args.GetBoolArg("-i2pacceptincoming", DEFAULT_I2P_ACCEPT_INCOMING);
 
     if (!node.connman->Start(*node.scheduler, connOptions)) {
         return false;

test/functional/p2p_i2p_sessions.py

@@ -23,12 +23,12 @@ def run_test(self):
 
         self.log.info("Ensure we create a persistent session when -i2pacceptincoming=1")
         node0 = self.nodes[0]
-        with node0.assert_debug_log(expected_msgs=[f"Creating persistent SAM session"]):
+        with node0.assert_debug_log(expected_msgs=["Creating persistent SAM session"]):
             node0.addnode(node=addr, command="onetry")
 
         self.log.info("Ensure we create a transient session when -i2pacceptincoming=0")
         node1 = self.nodes[1]
-        with node1.assert_debug_log(expected_msgs=[f"Creating transient SAM session"]):
+        with node1.assert_debug_log(expected_msgs=["Creating transient SAM session"]):
             node1.addnode(node=addr, command="onetry")