init: make inbound tx relay percentage configurable

Permit users to change the amount of inbounds that are permitted to relay
transactions. This is particularly relevant to ensure that superusers that are
not concerned with resource usage are not artificially restricted from offering
many transaction relay slots to the network.

Co-authored-by: Martin Zumsande <mzumsande@gmail.com>

test/functional/p2p_connection_limits.py

@@ -58,6 +58,16 @@ class P2PConnectionLimits(BitcoinTestFramework):
             self.nodes[0].add_p2p_connection(P2PInterface(), send_version=False, wait_for_verack=False, expect_success=False)
         self.wait_until(lambda: len(node.getpeerinfo()) == 2)
 
+        self.log.info('Test different values of inboundrelaypercent')
+        self.restart_node(0, ['-maxconnections=13', '-inboundrelaypercent=0'])
+        with node.assert_debug_log(['failed to find a tx-relaying eviction candidate - connection dropped'], timeout=2):
+            self.nodes[0].add_p2p_connection(P2PInterface(), expect_success=False, wait_for_verack=False)
+
+        self.restart_node(0, ['-maxconnections=13', '-inboundrelaypercent=100'])
+        node.add_p2p_connection(P2PInterface())
+        node.add_p2p_connection(P2PInterface())
+        self.wait_until(lambda: len(node.getpeerinfo()) == 2)
+
 
 if __name__ == '__main__':
     P2PConnectionLimits(__file__).main()

test/functional/p2p_opportunistic_1p1c.py

@@ -76,7 +76,7 @@ class PackageRelayTest(BitcoinTestFramework):
         self.setup_clean_chain = True
         self.num_nodes = 1
         self.extra_args = [[
-            "-maxmempool=5","-maxconnections=150"
+            "-maxmempool=5","-inboundrelaypercent=100"
         ]]
 
     def create_tx_below_mempoolminfee(self, wallet, utxo_to_spend=None):