openethereum/util/network-devp2p/src/node_table.rs

// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.

// Parity Ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity Ethereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity Ethereum.  If not, see <http://www.gnu.org/licenses/>.

use discovery::{NodeEntry, TableUpdates};
use ethereum_types::H512;
use ip_utils::*;
use network::{AllowIP, Error, ErrorKind, IpFilter};
use rand::{self, Rng};
use rlp::{DecoderError, Rlp, RlpStream};
use serde_json;
use std::{
    collections::{HashMap, HashSet},
    fmt::{self, Display, Formatter},
    fs,
    hash::{Hash, Hasher},
    net::{Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6, ToSocketAddrs},
    path::PathBuf,
    slice,
    str::FromStr,
    time::{self, Duration, SystemTime},
};

/// Node public key
pub type NodeId = H512;

#[derive(Debug, Clone, PartialEq)]
/// Node address info
pub struct NodeEndpoint {
    /// IP(V4 or V6) address
    pub address: SocketAddr,
    /// Connection port.
    pub udp_port: u16,
}

impl NodeEndpoint {
    pub fn udp_address(&self) -> SocketAddr {
        match self.address {
            SocketAddr::V4(a) => SocketAddr::V4(SocketAddrV4::new(*a.ip(), self.udp_port)),
            SocketAddr::V6(a) => SocketAddr::V6(SocketAddrV6::new(
                *a.ip(),
                self.udp_port,
                a.flowinfo(),
                a.scope_id(),
            )),
        }
    }

    pub fn is_allowed(&self, filter: &IpFilter) -> bool {
        (self.is_allowed_by_predefined(&filter.predefined)
            || filter
                .custom_allow
                .iter()
                .any(|ipnet| self.address.ip().is_within(ipnet)))
            && !filter
                .custom_block
                .iter()
                .any(|ipnet| self.address.ip().is_within(ipnet))
    }

    pub fn is_allowed_by_predefined(&self, filter: &AllowIP) -> bool {
        match filter {
            AllowIP::All => true,
            AllowIP::Private => self.address.ip().is_usable_private(),
            AllowIP::Public => self.address.ip().is_usable_public(),
            AllowIP::None => false,
        }
    }

    pub fn from_rlp(rlp: &Rlp) -> Result<Self, DecoderError> {
        let tcp_port = rlp.val_at::<u16>(2)?;
        let udp_port = rlp.val_at::<u16>(1)?;
        let addr_bytes = rlp.at(0)?.data()?;
        let address = match addr_bytes.len() {
            4 => Ok(SocketAddr::V4(SocketAddrV4::new(
                Ipv4Addr::new(addr_bytes[0], addr_bytes[1], addr_bytes[2], addr_bytes[3]),
                tcp_port,
            ))),
            16 => unsafe {
                let o: *const u16 = addr_bytes.as_ptr() as *const u16;
                let o = slice::from_raw_parts(o, 8);
                Ok(SocketAddr::V6(SocketAddrV6::new(
                    Ipv6Addr::new(o[0], o[1], o[2], o[3], o[4], o[5], o[6], o[7]),
                    tcp_port,
                    0,
                    0,
                )))
            },
            _ => Err(DecoderError::RlpInconsistentLengthAndData),
        }?;
        Ok(NodeEndpoint { address, udp_port })
    }

    pub fn to_rlp(&self, rlp: &mut RlpStream) {
        match self.address {
            SocketAddr::V4(a) => {
                rlp.append(&(&a.ip().octets()[..]));
            }
            SocketAddr::V6(a) => unsafe {
                let o: *const u8 = a.ip().segments().as_ptr() as *const u8;
                rlp.append(&slice::from_raw_parts(o, 16));
            },
        };
        rlp.append(&self.udp_port);
        rlp.append(&self.address.port());
    }

    pub fn to_rlp_list(&self, rlp: &mut RlpStream) {
        rlp.begin_list(3);
        self.to_rlp(rlp);
    }

    /// Validates that the tcp port is not 0 and that the node is a valid discovery node (i.e. `is_valid_discovery_node()` is true).
    /// Sync happens over tcp.
    pub fn is_valid_sync_node(&self) -> bool {
        self.is_valid_discovery_node() && self.address.port() != 0
    }

    /// Validates that the udp port is not 0 and address IP is specified.
    /// Peer discovery happens over udp.
    pub fn is_valid_discovery_node(&self) -> bool {
        self.udp_port != 0
            && match self.address {
                SocketAddr::V4(a) => !a.ip().is_unspecified(),
                SocketAddr::V6(a) => !a.ip().is_unspecified(),
            }
    }
}

impl FromStr for NodeEndpoint {
    type Err = Error;

    /// Create endpoint from string. Performs name resolution if given a host name.
    fn from_str(s: &str) -> Result<NodeEndpoint, Error> {
        let address = s.to_socket_addrs().map(|mut i| i.next());
        match address {
            Ok(Some(a)) => Ok(NodeEndpoint {
                address: a,
                udp_port: a.port(),
            }),
            Ok(None) => bail!(ErrorKind::AddressResolve(None)),
            Err(_) => Err(ErrorKind::AddressParse.into()), // always an io::Error of InvalidInput kind
        }
    }
}

#[derive(Debug, PartialEq, Eq, Copy, Clone)]
pub enum PeerType {
    _Required,
    Optional,
}

/// A type for representing an interaction (contact) with a node at a given time
/// that was either a success or a failure.
#[derive(Clone, Copy, Debug)]
pub enum NodeContact {
    Success(SystemTime),
    Failure(SystemTime),
}

impl NodeContact {
    fn success() -> NodeContact {
        NodeContact::Success(SystemTime::now())
    }

    fn failure() -> NodeContact {
        NodeContact::Failure(SystemTime::now())
    }

    fn time(&self) -> SystemTime {
        match *self {
            NodeContact::Success(t) | NodeContact::Failure(t) => t,
        }
    }

    /// Filters and old contact, returning `None` if it happened longer than a
    /// week ago.
    fn recent(&self) -> Option<&NodeContact> {
        let t = self.time();
        if let Ok(d) = t.elapsed() {
            if d < Duration::from_secs(60 * 60 * 24 * 7) {
                return Some(self);
            }
        }

        None
    }
}

#[derive(Debug)]
pub struct Node {
    pub id: NodeId,
    pub endpoint: NodeEndpoint,
    pub peer_type: PeerType,
    pub last_contact: Option<NodeContact>,
}

impl Node {
    pub fn new(id: NodeId, endpoint: NodeEndpoint) -> Node {
        Node {
            id,
            endpoint,
            peer_type: PeerType::Optional,
            last_contact: None,
        }
    }
}

impl Display for Node {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        if self.endpoint.udp_port != self.endpoint.address.port() {
            write!(
                f,
                "enode://{:x}@{}+{}",
                self.id, self.endpoint.address, self.endpoint.udp_port
            )?;
        } else {
            write!(f, "enode://{:x}@{}", self.id, self.endpoint.address)?;
        }
        Ok(())
    }
}

impl FromStr for Node {
    type Err = Error;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let (id, endpoint) = if s.len() > 136 && &s[0..8] == "enode://" && &s[136..137] == "@" {
            (
                s[8..136].parse().map_err(|_| ErrorKind::InvalidNodeId)?,
                NodeEndpoint::from_str(&s[137..])?,
            )
        } else {
            (NodeId::new(), NodeEndpoint::from_str(s)?)
        };

        Ok(Node {
            id,
            endpoint,
            peer_type: PeerType::Optional,
            last_contact: None,
        })
    }
}

impl PartialEq for Node {
    fn eq(&self, other: &Self) -> bool {
        self.id == other.id
    }
}
impl Eq for Node {}

impl Hash for Node {
    fn hash<H>(&self, state: &mut H)
    where
        H: Hasher,
    {
        self.id.hash(state)
    }
}

const MAX_NODES: usize = 1024;
const NODES_FILE: &str = "nodes.json";

/// Node table backed by disk file.
pub struct NodeTable {
    nodes: HashMap<NodeId, Node>,
    useless_nodes: HashSet<NodeId>,
    path: Option<String>,
}

impl NodeTable {
    pub fn new(path: Option<String>) -> NodeTable {
        NodeTable {
            path: path.clone(),
            nodes: NodeTable::load(path),
            useless_nodes: HashSet::new(),
        }
    }

    /// Add a node to table
    pub fn add_node(&mut self, mut node: Node) {
        // preserve node last_contact
        node.last_contact = self.nodes.get(&node.id).and_then(|n| n.last_contact);
        self.nodes.insert(node.id, node);
    }

    /// Returns a list of ordered nodes according to their most recent contact
    /// and filtering useless nodes. The algorithm for creating the sorted nodes
    /// is:
    /// - Contacts that aren't recent (older than 1 week) are discarded
    /// - (1) Nodes with a successful contact are ordered (most recent success first)
    /// - (2) Nodes with unknown contact (older than 1 week or new nodes) are randomly shuffled
    /// - (3) Nodes with a failed contact are ordered (oldest failure first)
    /// - The final result is the concatenation of (1), (2) and (3)
    fn ordered_entries(&self) -> Vec<&Node> {
        let mut success = Vec::new();
        let mut failures = Vec::new();
        let mut unknown = Vec::new();

        let nodes = self
            .nodes
            .values()
            .filter(|n| !self.useless_nodes.contains(&n.id));

        for node in nodes {
            // discard contact points older that aren't recent
            match node.last_contact.as_ref().and_then(|c| c.recent()) {
                Some(&NodeContact::Success(_)) => {
                    success.push(node);
                }
                Some(&NodeContact::Failure(_)) => {
                    failures.push(node);
                }
                None => {
                    unknown.push(node);
                }
            }
        }

        success.sort_by(|a, b| {
            let a = a
                .last_contact
                .expect("vector only contains values with defined last_contact; qed");
            let b = b
                .last_contact
                .expect("vector only contains values with defined last_contact; qed");
            // inverse ordering, most recent successes come first
            b.time().cmp(&a.time())
        });

        failures.sort_by(|a, b| {
            let a = a
                .last_contact
                .expect("vector only contains values with defined last_contact; qed");
            let b = b
                .last_contact
                .expect("vector only contains values with defined last_contact; qed");
            // normal ordering, most distant failures come first
            a.time().cmp(&b.time())
        });

        rand::thread_rng().shuffle(&mut unknown);

        success.append(&mut unknown);
        success.append(&mut failures);
        success
    }

    /// Returns node ids sorted by failure percentage, for nodes with the same failure percentage the absolute number of
    /// failures is considered.
    pub fn nodes(&self, filter: &IpFilter) -> Vec<NodeId> {
        self.ordered_entries()
            .iter()
            .filter(|n| n.endpoint.is_allowed(&filter))
            .map(|n| n.id)
            .collect()
    }

    /// Ordered list of all entries by failure percentage, for nodes with the same failure percentage the absolute
    /// number of failures is considered.
    pub fn entries(&self) -> Vec<NodeEntry> {
        self.ordered_entries()
            .iter()
            .map(|n| NodeEntry {
                endpoint: n.endpoint.clone(),
                id: n.id,
            })
            .collect()
    }

    /// Get particular node
    pub fn get_mut(&mut self, id: &NodeId) -> Option<&mut Node> {
        self.nodes.get_mut(id)
    }

    /// Check if a node exists in the table.
    pub fn contains(&self, id: &NodeId) -> bool {
        self.nodes.contains_key(id)
    }

    /// Apply table changes coming from discovery
    pub fn update(&mut self, mut update: TableUpdates, reserved: &HashSet<NodeId>) {
        for (_, node) in update.added.drain() {
            let entry = self
                .nodes
                .entry(node.id)
                .or_insert_with(|| Node::new(node.id, node.endpoint.clone()));
            entry.endpoint = node.endpoint;
        }
        for r in update.removed {
            if !reserved.contains(&r) {
                self.nodes.remove(&r);
            }
        }
    }

    /// Set last contact as failure for a node
    pub fn note_failure(&mut self, id: &NodeId) {
        if let Some(node) = self.nodes.get_mut(id) {
            node.last_contact = Some(NodeContact::failure());
        }
    }

    /// Set last contact as success for a node
    pub fn note_success(&mut self, id: &NodeId) {
        if let Some(node) = self.nodes.get_mut(id) {
            node.last_contact = Some(NodeContact::success());
        }
    }

    /// Mark as useless, no further attempts to connect until next call to `clear_useless`.
    pub fn mark_as_useless(&mut self, id: &NodeId) {
        self.useless_nodes.insert(id.clone());
    }

    /// Attempt to connect to useless nodes again.
    pub fn clear_useless(&mut self) {
        self.useless_nodes.clear();
    }

    /// Save the nodes.json file.
    pub fn save(&self) {
        let mut path = match self.path {
            Some(ref path) => PathBuf::from(path),
            None => return,
        };
        if let Err(e) = fs::create_dir_all(&path) {
            warn!(target: "network", "Error creating node table directory: {:?}", e);
            return;
        }
        path.push(NODES_FILE);
        let node_ids = self.nodes(&IpFilter::default());
        let nodes = node_ids
            .into_iter()
            .map(|id| {
                self.nodes
                    .get(&id)
                    .expect("self.nodes() only returns node IDs from self.nodes")
            })
            .take(MAX_NODES)
            .map(Into::into)
            .collect();
        let table = json::NodeTable { nodes };

        match fs::File::create(&path) {
            Ok(file) => {
                if let Err(e) = serde_json::to_writer_pretty(file, &table) {
                    warn!(target: "network", "Error writing node table file: {:?}", e);
                }
            }
            Err(e) => {
                warn!(target: "network", "Error creating node table file: {:?}", e);
            }
        }
    }

    fn load(path: Option<String>) -> HashMap<NodeId, Node> {
        let path = match path {
            Some(path) => PathBuf::from(path).join(NODES_FILE),
            None => return Default::default(),
        };

        let file = match fs::File::open(&path) {
            Ok(file) => file,
            Err(e) => {
                debug!(target: "network", "Error opening node table file: {:?}", e);
                return Default::default();
            }
        };
        let res: Result<json::NodeTable, _> = serde_json::from_reader(file);
        match res {
            Ok(table) => table
                .nodes
                .into_iter()
                .filter_map(|n| n.into_node())
                .map(|n| (n.id, n))
                .collect(),
            Err(e) => {
                warn!(target: "network", "Error reading node table file: {:?}", e);
                Default::default()
            }
        }
    }
}

impl Drop for NodeTable {
    fn drop(&mut self) {
        self.save();
    }
}

/// Check if node url is valid
pub fn validate_node_url(url: &str) -> Option<Error> {
    match Node::from_str(url) {
        Ok(_) => None,
        Err(e) => Some(e),
    }
}

mod json {
    use super::*;

    #[derive(Serialize, Deserialize)]
    pub struct NodeTable {
        pub nodes: Vec<Node>,
    }

    #[derive(Serialize, Deserialize)]
    pub enum NodeContact {
        #[serde(rename = "success")]
        Success(u64),
        #[serde(rename = "failure")]
        Failure(u64),
    }

    impl NodeContact {
        pub fn into_node_contact(self) -> super::NodeContact {
            match self {
                NodeContact::Success(s) => {
                    super::NodeContact::Success(time::UNIX_EPOCH + Duration::from_secs(s))
                }
                NodeContact::Failure(s) => {
                    super::NodeContact::Failure(time::UNIX_EPOCH + Duration::from_secs(s))
                }
            }
        }
    }

    #[derive(Serialize, Deserialize)]
    pub struct Node {
        pub url: String,
        pub last_contact: Option<NodeContact>,
    }

    impl Node {
        pub fn into_node(self) -> Option<super::Node> {
            match super::Node::from_str(&self.url) {
                Ok(mut node) => {
                    node.last_contact = self.last_contact.map(|c| c.into_node_contact());
                    Some(node)
                }
                _ => None,
            }
        }
    }

    impl<'a> From<&'a super::Node> for Node {
        fn from(node: &'a super::Node) -> Self {
            let last_contact = node.last_contact.and_then(|c| match c {
                super::NodeContact::Success(t) => t
                    .duration_since(time::UNIX_EPOCH)
                    .ok()
                    .map(|d| NodeContact::Success(d.as_secs())),
                super::NodeContact::Failure(t) => t
                    .duration_since(time::UNIX_EPOCH)
                    .ok()
                    .map(|d| NodeContact::Failure(d.as_secs())),
            });

            Node {
                url: format!("{}", node),
                last_contact,
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use ethereum_types::H512;
    use ipnetwork::IpNetwork;
    use std::{
        net::{Ipv4Addr, SocketAddr, SocketAddrV4},
        str::FromStr,
    };
    use tempdir::TempDir;

    #[test]
    fn endpoint_parse() {
        let endpoint = NodeEndpoint::from_str("123.99.55.44:7770");
        assert!(endpoint.is_ok());
        let v4 = match endpoint.unwrap().address {
            SocketAddr::V4(v4address) => v4address,
            _ => panic!("should be v4 address"),
        };
        assert_eq!(SocketAddrV4::new(Ipv4Addr::new(123, 99, 55, 44), 7770), v4);
    }

    #[test]
    fn endpoint_parse_empty_ip_string_returns_error() {
        let endpoint = NodeEndpoint::from_str("");
        assert!(endpoint.is_err());
        assert_matches!(endpoint.unwrap_err().kind(), &ErrorKind::AddressParse);
    }

    #[test]
    fn endpoint_parse_invalid_ip_string_returns_error() {
        let endpoint = NodeEndpoint::from_str("beef");
        assert!(endpoint.is_err());
        assert_matches!(endpoint.unwrap_err().kind(), &ErrorKind::AddressParse);
    }

    #[test]
    fn endpoint_parse_valid_ip_without_port_returns_error() {
        let endpoint = NodeEndpoint::from_str("123.123.123.123");
        assert!(endpoint.is_err());
        assert_matches!(endpoint.unwrap_err().kind(), &ErrorKind::AddressParse);
        let endpoint = NodeEndpoint::from_str("123.123.123.123:123");
        assert!(endpoint.is_ok())
    }

    #[test]
    fn node_parse() {
        assert!(validate_node_url("enode://a979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@22.99.55.44:7770").is_none());
        let node = Node::from_str("enode://a979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@22.99.55.44:7770");
        assert!(node.is_ok());
        let node = node.unwrap();
        let v4 = match node.endpoint.address {
            SocketAddr::V4(v4address) => v4address,
            _ => panic!("should ve v4 address"),
        };
        assert_eq!(SocketAddrV4::new(Ipv4Addr::new(22, 99, 55, 44), 7770), v4);
        assert_eq!(
			H512::from_str("a979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c").unwrap(),
			node.id);
    }

    #[test]
    fn node_parse_fails_for_invalid_urls() {
        let node = Node::from_str("foo");
        assert!(node.is_err());
        assert_matches!(node.unwrap_err().kind(), &ErrorKind::AddressParse);

        let node = Node::from_str("enode://foo@bar");
        assert!(node.is_err());
        assert_matches!(node.unwrap_err().kind(), &ErrorKind::AddressParse);
    }

    #[test]
    fn table_last_contact_order() {
        let node1 = Node::from_str("enode://a979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@22.99.55.44:7770").unwrap();
        let node2 = Node::from_str("enode://b979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@22.99.55.44:7770").unwrap();
        let node3 = Node::from_str("enode://c979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@22.99.55.44:7770").unwrap();
        let node4 = Node::from_str("enode://d979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@22.99.55.44:7770").unwrap();
        let node5 = Node::from_str("enode://e979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@22.99.55.44:7770").unwrap();
        let node6 = Node::from_str("enode://f979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@22.99.55.44:7770").unwrap();
        let id1 = H512::from_str("a979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c").unwrap();
        let id2 = H512::from_str("b979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c").unwrap();
        let id3 = H512::from_str("c979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c").unwrap();
        let id4 = H512::from_str("d979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c").unwrap();
        let id5 = H512::from_str("e979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c").unwrap();
        let id6 = H512::from_str("f979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c").unwrap();
        let mut table = NodeTable::new(None);

        table.add_node(node1);
        table.add_node(node2);
        table.add_node(node3);
        table.add_node(node4);
        table.add_node(node5);
        table.add_node(node6);

        // failures - nodes 1 & 2
        table.note_failure(&id1);
        table.note_failure(&id2);

        // success - nodes 3 & 4
        table.note_success(&id3);
        table.note_success(&id4);

        // success - node 5 (old contact)
        table.get_mut(&id5).unwrap().last_contact = Some(NodeContact::Success(time::UNIX_EPOCH));

        // unknown - node 6

        // nodes are also ordered according to their addition time
        //
        // nanosecond precision lost since mac os x high sierra update so let's not compare their order
        // https://github.com/paritytech/parity-ethereum/issues/9632
        let r = table.nodes(&IpFilter::default());

        // most recent success
        assert!((r[0] == id4 && r[1] == id3) || (r[0] == id3 && r[1] == id4));

        // unknown (old contacts and new nodes), randomly shuffled
        assert!((r[2] == id5 && r[3] == id6) || (r[2] == id6 && r[3] == id5));

        // oldest failure
        assert!((r[4] == id1 && r[5] == id2) || (r[4] == id2 && r[5] == id1));
    }

    #[test]
    fn table_save_load() {
        let tempdir = TempDir::new("").unwrap();
        let node1 = Node::from_str("enode://a979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@22.99.55.44:7770").unwrap();
        let node2 = Node::from_str("enode://b979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@22.99.55.44:7770").unwrap();
        let node3 = Node::from_str("enode://c979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c@22.99.55.44:7770").unwrap();
        let id1 = H512::from_str("a979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c").unwrap();
        let id2 = H512::from_str("b979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c").unwrap();
        let id3 = H512::from_str("c979fb575495b8d6db44f750317d0f4622bf4c2aa3365d6af7c284339968eef29b69ad0dce72a4d8db5ebb4968de0e3bec910127f134779fbcb0cb6d3331163c").unwrap();

        {
            let mut table = NodeTable::new(Some(tempdir.path().to_str().unwrap().to_owned()));
            table.add_node(node1);
            table.add_node(node2);
            table.add_node(node3);

            table.note_success(&id2);
            table.note_failure(&id3);
        }

        {
            let table = NodeTable::new(Some(tempdir.path().to_str().unwrap().to_owned()));
            let r = table.nodes(&IpFilter::default());
            assert_eq!(r[0][..], id2[..]); // latest success
            assert_eq!(r[1][..], id1[..]); // unknown
            assert_eq!(r[2][..], id3[..]); // oldest failure
        }
    }

    #[test]
    fn custom_allow() {
        let filter = IpFilter {
            predefined: AllowIP::None,
            custom_allow: vec![
                IpNetwork::from_str(&"10.0.0.0/8").unwrap(),
                IpNetwork::from_str(&"1.0.0.0/8").unwrap(),
            ],
            custom_block: vec![],
        };
        assert!(!NodeEndpoint::from_str("123.99.55.44:7770")
            .unwrap()
            .is_allowed(&filter));
        assert!(NodeEndpoint::from_str("10.0.0.1:7770")
            .unwrap()
            .is_allowed(&filter));
        assert!(NodeEndpoint::from_str("1.0.0.55:5550")
            .unwrap()
            .is_allowed(&filter));
    }

    #[test]
    fn custom_block() {
        let filter = IpFilter {
            predefined: AllowIP::All,
            custom_allow: vec![],
            custom_block: vec![
                IpNetwork::from_str(&"10.0.0.0/8").unwrap(),
                IpNetwork::from_str(&"1.0.0.0/8").unwrap(),
            ],
        };
        assert!(NodeEndpoint::from_str("123.99.55.44:7770")
            .unwrap()
            .is_allowed(&filter));
        assert!(!NodeEndpoint::from_str("10.0.0.1:7770")
            .unwrap()
            .is_allowed(&filter));
        assert!(!NodeEndpoint::from_str("1.0.0.55:5550")
            .unwrap()
            .is_allowed(&filter));
    }

    #[test]
    fn custom_allow_ipv6() {
        let filter = IpFilter {
            predefined: AllowIP::None,
            custom_allow: vec![IpNetwork::from_str(&"fc00::/8").unwrap()],
            custom_block: vec![],
        };
        assert!(NodeEndpoint::from_str("[fc00::]:5550")
            .unwrap()
            .is_allowed(&filter));
        assert!(!NodeEndpoint::from_str("[fd00::]:5550")
            .unwrap()
            .is_allowed(&filter));
    }

    #[test]
    fn custom_block_ipv6() {
        let filter = IpFilter {
            predefined: AllowIP::All,
            custom_allow: vec![],
            custom_block: vec![IpNetwork::from_str(&"fc00::/8").unwrap()],
        };
        assert!(!NodeEndpoint::from_str("[fc00::]:5550")
            .unwrap()
            .is_allowed(&filter));
        assert!(NodeEndpoint::from_str("[fd00::]:5550")
            .unwrap()
            .is_allowed(&filter));
    }
}