donut 0.2.0

DNS over HTTPS server
Documentation 
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// Donut - DNS over HTTPS server
//
// Copyright 2019 Nick Pillitteri
//
// This program 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.
//
// This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
//

use clap::{crate_version, Parser};
use donut::http::{http_route, HandlerContext};
use donut::request::{RequestParserJsonGet, RequestParserWireGet, RequestParserWirePost};
use donut::resolve::UdpResolver;
use donut::response::{ResponseEncoderJson, ResponseEncoderWire};
use donut::types::DonutResult;
use hyper::service::{make_service_fn, service_fn};
use hyper::Server;
use std::net::SocketAddr;
use std::process;
use std::sync::Arc;
use std::time::{Duration, Instant};
use tokio::net::UdpSocket;
use tracing::{event, span, Instrument, Level};
use trust_dns_client::client::AsyncClient;
use trust_dns_client::udp::UdpClientStream;

const DEFAULT_UPSTREAM_UDP: ([u8; 4], u16) = ([127, 0, 0, 1], 53);
const DEFAULT_UPSTREAM_TIMEOUT_MS: u64 = 1000;
const DEFAULT_LOG_LEVEL: Level = Level::INFO;
const DEFAULT_BIND_ADDR: ([u8; 4], u16) = ([127, 0, 0, 1], 3000);

/// Donut DNS over HTTPS server
///
/// HTTP server for DNS-over-HTTPS lookups (binary and JSON)
#[derive(Debug, Parser)]
#[clap(name = "donut", version = crate_version!())]
struct DonutApplication {
    /// Send DNS queries to this upstream DNS server (via DNS over UDP)
    #[clap(long, default_value_t = DEFAULT_UPSTREAM_UDP.into())]
    upstream_udp: SocketAddr,

    /// Timeout for upstream DNS server in milliseconds.
    #[clap(long, default_value_t = DEFAULT_UPSTREAM_TIMEOUT_MS)]
    upstream_timeout: u64,

    /// Logging verbosity. Allowed values are 'trace', 'debug', 'info', 'warn', and 'error' (case insensitive).
    #[clap(long, default_value_t = DEFAULT_LOG_LEVEL)]
    log_level: Level,

    /// Address to bind to.
    #[clap(long, default_value_t = DEFAULT_BIND_ADDR.into())]
    bind: SocketAddr,
}

async fn new_udp_dns_client(addr: SocketAddr, timeout: Duration) -> DonutResult<AsyncClient> {
    let conn = UdpClientStream::<UdpSocket>::with_timeout(addr, timeout);
    let (client, bg) = AsyncClient::connect(conn).await?;
    // Trust DNS clients are really just handles for talking to a future running in the background
    // that actually does all the network activity and DNS lookups. Start the background future here
    // on whatever Tokio executor has been set up when `main()` was run.
    tokio::spawn(bg);
    Ok(client)
}

async fn new_handler_context(addr: SocketAddr, timeout: Duration) -> DonutResult<HandlerContext> {
    let client = new_udp_dns_client(addr, timeout).await?;
    let resolver = UdpResolver::new(client);
    let json_parser = RequestParserJsonGet::default();
    let get_parser = RequestParserWireGet::default();
    let post_parser = RequestParserWirePost::default();
    let json_encoder = ResponseEncoderJson::default();
    let wire_encoder = ResponseEncoderWire::default();

    Ok(HandlerContext::new(
        json_parser,
        get_parser,
        post_parser,
        resolver,
        json_encoder,
        wire_encoder,
    ))
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
    let opts = DonutApplication::parse();

    tracing::subscriber::set_global_default(
        tracing_subscriber::FmtSubscriber::builder()
            .with_max_level(opts.log_level)
            .finish(),
    )
    .expect("Failed to set tracing subscriber");

    let startup = Instant::now();
    let timeout = Duration::from_millis(opts.upstream_timeout);
    let context = Arc::new(new_handler_context(opts.upstream_udp, timeout).await.unwrap());
    let service = make_service_fn(move |_| {
        let context = context.clone();

        async move {
            Ok::<_, hyper::Error>(service_fn(move |req| {
                http_route(req, context.clone()).instrument(span!(Level::DEBUG, "donut_request"))
            }))
        }
    });

    let server = Server::try_bind(&opts.bind).unwrap_or_else(|e| {
        event!(
            Level::ERROR,
            message = "server failed to start",
            error = %e,
            upstream = %opts.upstream_udp,
            address = %opts.bind,
            timeout_ms = %timeout.as_millis(),
        );

        process::exit(1);
    });

    event!(
        Level::INFO,
        message = "server started",
        upstream = %opts.upstream_udp,
        address = %opts.bind,
        timeout_ms = %timeout.as_millis(),
    );

    server
        .serve(service)
        .with_graceful_shutdown(async {
            let _ = tokio::signal::ctrl_c().await;
        })
        .await?;

    event!(
        Level::INFO,
        message = "server shutdown",
        runtime_secs = %startup.elapsed().as_secs(),
    );

    Ok(())
}