Remove some useless tests in functional_tests and reject huge chans

In general we shouldn't have tests lying around that are useless as
its not genuinely testing anything and may break due to harmless
protocol changes. Here, we drop a few useless tests.

Specifically,
 * We drop a test that the channel_reserve is greater than the
   dust_limit on a random specific channel value - of *course* the
   channel reserve (1% of the channel - 1000 sats) happens to be
   greater than the dust limit (~300 sats).
 * We drop a test that we don't set any bits in `channel_flags`
   aside from 1 which is fairly useless, but more importantly its
   actually just testing that we don't change code, not that we are
   doing some specific behavior correctly.
 * We also drop a test that public keys are valid - `PublicKey`s
   are always valid per the `secp256k1` API, so should be tested by
   `secp256k1`, not us.

Further, we remove a test that channels of 2^24 (ie 26) sats fail
to open, which was intended to test pre-WUMBO channel rejection,
but actually tested too-small channels (and we have other tests for
WUMBO channels).

Author: TheBlueMatt

lightning/src/ln/functional_tests.rs

@@ -4667,27 +4667,15 @@ pub fn bolt2_open_channel_sending_node_checks_part2() {
 
 	let node_b_id = nodes[1].node.get_our_node_id();
 
-	// BOLT #2 spec: Sending node must set funding_satoshis to less than 2^24 satoshis
-	let channel_value_satoshis=2^24;
-	let push_msat=10001;
-	assert!(nodes[0].node.create_channel(node_b_id, channel_value_satoshis, push_msat, 42, None, None).is_err());
-
 	// BOLT #2 spec: Sending node must set push_msat to equal or less than 1000 * funding_satoshis
 	let channel_value_satoshis=10000;
 	// Test when push_msat is equal to 1000 * funding_satoshis.
 	let push_msat=1000*channel_value_satoshis+1;
 	assert!(nodes[0].node.create_channel(node_b_id, channel_value_satoshis, push_msat, 42, None, None).is_err());
 
-	// BOLT #2 spec: Sending node must set set channel_reserve_satoshis greater than or equal to dust_limit_satoshis
-	let channel_value_satoshis=10000;
-	let push_msat=10001;
-	assert!(nodes[0].node.create_channel(node_b_id, channel_value_satoshis, push_msat, 42, None, None).is_ok()); //Create a valid channel
-	let node0_to_1_send_open_channel = get_event_msg!(nodes[0], MessageSendEvent::SendOpenChannel, node_b_id);
-	assert!(node0_to_1_send_open_channel.channel_reserve_satoshis>=node0_to_1_send_open_channel.common_fields.dust_limit_satoshis);
+	nodes[0].node.create_channel(node_b_id, 100_000, 0, 42, None, None).unwrap();
 
-	// BOLT #2 spec: Sending node must set undefined bits in channel_flags to 0
-	// Only the least-significant bit of channel_flags is currently defined resulting in channel_flags only having one of two possible states 0 or 1
-	assert!(node0_to_1_send_open_channel.common_fields.channel_flags<=1);
+	let node0_to_1_send_open_channel = get_event_msg!(nodes[0], MessageSendEvent::SendOpenChannel, node_b_id);
 
 	// BOLT #2 spec: Sending node should set to_self_delay sufficient to ensure the sender can irreversibly spend a commitment transaction output, in case of misbehaviour by the receiver.
 	assert!(BREAKDOWN_TIMEOUT>0);
@@ -4696,13 +4684,6 @@ pub fn bolt2_open_channel_sending_node_checks_part2() {
 	// BOLT #2 spec: Sending node must ensure the chain_hash value identifies the chain it wishes to open the channel within.
 	let chain_hash = ChainHash::using_genesis_block(Network::Testnet);
 	assert_eq!(node0_to_1_send_open_channel.common_fields.chain_hash, chain_hash);
-
-	// BOLT #2 spec: Sending node must set funding_pubkey, revocation_basepoint, htlc_basepoint, payment_basepoint, and delayed_payment_basepoint to valid DER-encoded, compressed, secp256k1 pubkeys.
-	assert!(PublicKey::from_slice(&node0_to_1_send_open_channel.common_fields.funding_pubkey.serialize()).is_ok());
-	assert!(PublicKey::from_slice(&node0_to_1_send_open_channel.common_fields.revocation_basepoint.serialize()).is_ok());
-	assert!(PublicKey::from_slice(&node0_to_1_send_open_channel.common_fields.htlc_basepoint.serialize()).is_ok());
-	assert!(PublicKey::from_slice(&node0_to_1_send_open_channel.common_fields.payment_basepoint.serialize()).is_ok());
-	assert!(PublicKey::from_slice(&node0_to_1_send_open_channel.common_fields.delayed_payment_basepoint.serialize()).is_ok());
 }
 
 #[xtest(feature = "_externalize_tests")]