validator: Ensure get_rpc_addr() doesn't return a dead RPC address

[mvines]

When a validator joins gossip, there's no guarantee that its ports are truly accessible to all other network participants. This can cause trouble for a validator that is attempting to boot, and selects an advertised RPC address that is blocked.

A recent PR, #7759, improved this situation slightly be we need to do better by checking that a connection can be successfully established to the selected RPC address in

solana/validator/src/main.rs

Lines 187 to 240 in 8572b57

	fn get_rpc_addr(
	node: &Node,
	identity_keypair: &Arc<Keypair>,
	entrypoint_gossip: &SocketAddr,
	) -> (Pubkey, SocketAddr) {
	let mut cluster_info = ClusterInfo::new(node.info.clone(), identity_keypair.clone());
	cluster_info.set_entrypoint(ContactInfo::new_gossip_entry_point(entrypoint_gossip));
	let cluster_info = Arc::new(RwLock::new(cluster_info));
	let exit = Arc::new(AtomicBool::new(false));
	let gossip_service = GossipService::new(
	&cluster_info.clone(),
	None,
	None,
	node.sockets.gossip.try_clone().unwrap(),
	&exit,
	);
	let (id, rpc_addr) = loop {
	info!(
	"Searching for RPC service...\n{}",
	cluster_info.read().unwrap().contact_info_trace()
	);
	let (gossip_peers, rpc_peers) = {
	let cluster_info = cluster_info.read().unwrap();
	(cluster_info.gossip_peers(), cluster_info.rpc_peers())
	};
	let found_entrypoint = gossip_peers
	.iter()
	.any(|contact_info| contact_info.gossip == *entrypoint_gossip);
	if found_entrypoint & !rpc_peers.is_empty() {
	// Prefer the entrypoint's RPC service if present, otherwise pick a node at random
	if let Some(contact_info) = rpc_peers
	.iter()
	.find(|contact_info| contact_info.gossip == *entrypoint_gossip)
	{
	break (contact_info.id, contact_info.rpc);
	}
	let i = thread_rng().gen_range(0, rpc_peers.len());
	break (rpc_peers[i].id, rpc_peers[i].rpc);
	}
	sleep(Duration::from_secs(1));
	};
	exit.store(true, Ordering::Relaxed);
	gossip_service.join().unwrap();
	(id, rpc_addr)
	}