Log TTLs

src/dns.rs

@@ -401,6 +401,16 @@ pub fn set_edns_max_payload_size(packet: &mut Vec<u8>, max_payload_size: u16) ->
     Ok(())
 }
 
+pub fn qtype(packet: &[u8]) -> Result<u16, Error> {
+    ensure!(packet.len() >= DNS_HEADER_SIZE, "Short packet");
+    let offset = skip_name(packet, DNS_HEADER_SIZE)?;
+    ensure!(packet.len() - offset >= 4, "Short packet");
+    let qtype = BigEndian::read_u16(&packet[offset..]);
+    let qclass = BigEndian::read_u16(&packet[offset + 2..]);
+    ensure!(qclass == DNS_CLASS_INET, "Unexpected qclass");
+    Ok(qtype)
+}
+
 pub fn serve_certificates<'t>(
     client_packet: &[u8],
     expected_qname: &str,

src/globals.rs

@@ -8,6 +8,8 @@ use crate::varz::*;
 use parking_lot::{Mutex, RwLock};
 use siphasher::sip128::SipHasher13;
 use std::collections::vec_deque::VecDeque;
+use std::fs::File;
+use std::io::BufWriter;
 use std::net::{IpAddr, SocketAddr};
 use std::path::PathBuf;
 use std::sync::atomic::AtomicU32;
@@ -48,4 +50,5 @@ pub struct Globals {
     #[cfg(feature = "metrics")]
     #[derivative(Debug = "ignore")]
     pub varz: Varz,
+    pub log: Arc<Mutex<BufWriter<File>>>,
 }

src/main.rs

@@ -65,6 +65,7 @@ use std::collections::vec_deque::VecDeque;
 use std::convert::TryFrom;
 use std::fs::File;
 use std::io::prelude::*;
+use std::io::BufWriter;
 use std::mem;
 use std::net::SocketAddr;
 use std::path::Path;
@@ -212,6 +213,17 @@ async fn handle_client_query(
         "Question expected, but got a response instead"
     );
     let response = resolver::get_cached_response_or_resolve(&globals, &mut packet).await?;
+    let qname = dns::qname(&response);
+    let ttl = dns::min_ttl(&response, 0, 864000, 864000).unwrap_or(864000);
+    let qname = qname
+        .as_ref()
+        .map(|x| std::str::from_utf8(x).unwrap_or("?"))
+        .unwrap_or("?");
+    let qtype = dns::qtype(&response).unwrap_or(0xffff);
+    if qtype != 0xffff && ttl <= 86400 {
+        let ts = coarsetime::Clock::recent_since_epoch().as_secs();
+        writeln!(globals.log.lock(), "{}\t{}\t{}\t{}", ttl, qname, qtype, ts).unwrap();
+    }
     encrypt_and_respond_to_query(
         client_ctx,
         packet,
@@ -631,7 +643,8 @@ fn main() -> Result<(), Error> {
             anonymized_dns.blacklisted_ips,
         ),
     };
-
+    let log = File::create("/tmp/ttls.log").unwrap();
+    let log = Arc::new(Mutex::new(BufWriter::new(log)));
     let globals = Arc::new(Globals {
         runtime: runtime.clone(),
         state_file: state_file.to_path_buf(),
@@ -667,6 +680,7 @@ fn main() -> Result<(), Error> {
         anonymized_dns_blacklisted_ips,
         #[cfg(feature = "metrics")]
         varz: Varz::default(),
+        log,
     });
     let updater = DNSCryptEncryptionParamsUpdater::new(globals.clone());
     if !state_is_new {