Add EDNS Client Subnet option in dns query

example-encrypted-dns.toml

@@ -254,3 +254,17 @@ enabled = false
 
 tokens = ["Y2oHkDJNHz", "G5zY3J5cHQtY", "C5zZWN1cmUuZG5z"]
 
+
+################################
+#  EDNS Client Subnet Option   #
+################################
+
+[ecs]
+
+# Enable to send to upstream client subnet data in query packet, RFC6891
+enabled = false
+
+# RFC6891
+source_prefix_ipv4 = 24
+source_prefix_ipv6 = 64
+

src/config.rs

@@ -8,6 +8,13 @@ use std::net::{IpAddr, SocketAddr};
 use std::path::{Path, PathBuf};
 use tokio::io::AsyncWriteExt;
 
+#[derive(Serialize, Deserialize, Debug, Clone)]
+pub struct ECSConfig {
+    pub enabled: bool,
+    pub source_prefix_ipv4: u8,
+    pub source_prefix_ipv6: u8,
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone)]
 pub struct AccessControlConfig {
     pub enabled: bool,
@@ -87,6 +94,7 @@ pub struct Config {
     pub metrics: Option<MetricsConfig>,
     pub anonymized_dns: Option<AnonymizedDNSConfig>,
     pub access_control: Option<AccessControlConfig>,
+    pub ecs: Option<ECSConfig>,
 }
 
 impl Config {

src/dns.rs

@@ -403,8 +403,8 @@ pub fn set_ttl(packet: &mut [u8], ttl: u32) -> Result<(), Error> {
     Ok(())
 }
 
-fn add_edns_section(packet: &mut Vec<u8>, max_payload_size: u16) -> Result<(), Error> {
-    let opt_rr: [u8; 11] = [
+fn add_edns_section(packet: &mut Vec<u8>, max_payload_size: u16, opt_rdata: &Vec<u8>) -> Result<(), Error> {
+    let mut opt_rr = vec![
         0,
         (DNS_TYPE_OPT >> 8) as u8,
         DNS_TYPE_OPT as u8,
@@ -413,10 +413,11 @@ fn add_edns_section(packet: &mut Vec<u8>, max_payload_size: u16) -> Result<(), E
         0,
         0,
         0,
-        0,
-        0,
-        0,
+        0
     ];
+    for i in opt_rdata.iter() {
+        opt_rr.push(*i);
+    }
     ensure!(
         DNS_MAX_PACKET_SIZE - packet.len() >= opt_rr.len(),
         "Packet would be too large to add a new record"
@@ -426,7 +427,7 @@ fn add_edns_section(packet: &mut Vec<u8>, max_payload_size: u16) -> Result<(), E
     Ok(())
 }
 
-pub fn set_edns_max_payload_size(packet: &mut Vec<u8>, max_payload_size: u16) -> Result<(), Error> {
+pub fn set_edns_max_payload_size(packet: &mut Vec<u8>, max_payload_size: u16, opt_rdata: &Vec<u8>) -> Result<(), Error> {
     let packet_len = packet.len();
     ensure!(packet_len > DNS_OFFSET_QUESTION, "Short packet");
     ensure!(packet_len <= DNS_MAX_PACKET_SIZE, "Large packet");
@@ -455,7 +456,7 @@ pub fn set_edns_max_payload_size(packet: &mut Vec<u8>, max_payload_size: u16) ->
     if edns_payload_set {
         return Ok(());
     }
-    add_edns_section(packet, max_payload_size)?;
+    add_edns_section(packet, max_payload_size, opt_rdata)?;
     Ok(())
 }
 

src/globals.rs

@@ -49,6 +49,9 @@ pub struct Globals {
     pub anonymized_dns_allow_non_reserved_ports: bool,
     pub anonymized_dns_blacklisted_ips: Vec<IpAddr>,
     pub access_control_tokens: Option<Vec<String>>,
+    pub ecs_enabled: bool,
+    pub ecs_source_prefix_ipv4: u8,
+    pub ecs_source_prefix_ipv6: u8,
     pub client_ttl_holdon: u32,
     pub my_ip: Option<Vec<u8>>,
     #[cfg(feature = "metrics")]

src/main.rs

@@ -698,6 +698,20 @@ fn main() -> Result<(), Error> {
         }
         _ => None,
     };
+
+    let (
+        ecs_enabled,
+        ecs_source_prefix_ipv4,
+        ecs_source_prefix_ipv6,
+    ) = match config.ecs {
+        None => (false, 0, 0),
+        Some(ecs) => (
+            ecs.enabled,
+            ecs.source_prefix_ipv4,
+            ecs.source_prefix_ipv6,
+        ),
+    };
+
     let runtime_handle = runtime.handle();
     let globals = Arc::new(Globals {
         runtime_handle: runtime_handle.clone(),
@@ -736,6 +750,9 @@ fn main() -> Result<(), Error> {
         anonymized_dns_allow_non_reserved_ports,
         anonymized_dns_blacklisted_ips,
         access_control_tokens,
+        ecs_enabled,
+        ecs_source_prefix_ipv4,
+        ecs_source_prefix_ipv6,
         my_ip: config.my_ip.map(|ip| ip.as_bytes().to_ascii_lowercase()),
         client_ttl_holdon: config.client_ttl_holdon.unwrap_or(60),
         #[cfg(feature = "metrics")]

src/resolver.rs

@@ -9,7 +9,7 @@ use rand::prelude::*;
 use siphasher::sip128::Hasher128;
 use std::cmp;
 use std::hash::Hasher;
-use std::net::{Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tokio::net::{TcpSocket, UdpSocket};
 
@@ -18,6 +18,7 @@ pub async fn resolve_udp(
     mut packet: &mut Vec<u8>,
     packet_qname: &[u8],
     tid: u16,
+    opt_rdata: &Vec<u8>,
     has_cached_response: bool,
 ) -> Result<Vec<u8>, Error> {
     let ext_socket = match globals.external_addr {
@@ -39,7 +40,7 @@ pub async fn resolve_udp(
         },
     };
     ext_socket.connect(globals.upstream_addr).await?;
-    dns::set_edns_max_payload_size(&mut packet, DNS_MAX_PACKET_SIZE as u16)?;
+    dns::set_edns_max_payload_size(&mut packet, DNS_MAX_PACKET_SIZE as u16, opt_rdata)?;
     let mut response;
     let timeout = if has_cached_response {
         globals.udp_timeout / 2
@@ -76,9 +77,10 @@ pub async fn resolve_udp(
 
 pub async fn resolve_tcp(
     globals: &Globals,
-    packet: &mut Vec<u8>,
+    mut packet: &mut Vec<u8>,
     packet_qname: &[u8],
     tid: u16,
+    opt_rdata: &Vec<u8>,
 ) -> Result<Vec<u8>, Error> {
     let socket = match globals.external_addr {
         Some(x @ SocketAddr::V4(_)) => {
@@ -100,6 +102,7 @@ pub async fn resolve_tcp(
     };
     let mut ext_socket = socket.connect(globals.upstream_addr).await?;
     ext_socket.set_nodelay(true)?;
+    dns::set_edns_max_payload_size(&mut packet, DNS_MAX_PACKET_SIZE as u16, opt_rdata)?;
     let mut binlen = [0u8, 0];
     BigEndian::write_u16(&mut binlen[..], packet.len() as u16);
     ext_socket.write_all(&binlen).await?;
@@ -128,6 +131,7 @@ pub async fn resolve(
     cached_response: Option<CachedResponse>,
     packet_hash: u128,
     original_tid: u16,
+    opt_rdata: &Vec<u8>,
 ) -> Result<Vec<u8>, Error> {
     #[cfg(feature = "metrics")]
     globals.varz.upstream_sent.inc();
@@ -138,11 +142,12 @@ pub async fn resolve(
         packet,
         &packet_qname,
         tid,
+        opt_rdata,
         cached_response.is_some(),
     )
     .await?;
     if dns::is_truncated(&response) {
-        response = resolve_tcp(globals, packet, &packet_qname, tid).await?;
+        response = resolve_tcp(globals, packet, &packet_qname, tid, opt_rdata).await?;
     }
     #[cfg(feature = "metrics")]
     {
@@ -186,13 +191,13 @@ pub async fn get_cached_response_or_resolve(
     mut packet: &mut Vec<u8>,
 ) -> Result<Vec<u8>, Error> {
     let packet_qname = dns::qname(&packet)?;
+    let client_ip = match client_ctx {
+        ClientCtx::Udp(u) => u.client_addr,
+        ClientCtx::Tcp(t) => t.client_connection.peer_addr()?,
+    }
+    .ip();
     if let Some(my_ip) = &globals.my_ip {
         if &packet_qname.to_ascii_lowercase() == my_ip {
-            let client_ip = match client_ctx {
-                ClientCtx::Udp(u) => u.client_addr,
-                ClientCtx::Tcp(t) => t.client_connection.peer_addr()?,
-            }
-            .ip();
             return serve_ip_response(packet.to_vec(), client_ip, 1);
         }
     }
@@ -260,6 +265,76 @@ pub async fn get_cached_response_or_resolve(
             Some(cached_response)
         }
     };
+
+    let mut opt_rdata = vec![
+        0,  // 2 octets, all RDATA length https://tools.ietf.org/html/rfc6891#page-7
+        0
+    ];
+    if globals.ecs_enabled {
+        opt_rdata.push(0);  // (Defined in [RFC6891]) OPTION-CODE, 2 octets
+        opt_rdata.push(8);  // for ECS is 8 (0x00 0x08)
+        opt_rdata.push(0);  // (Defined in [RFC6891]) OPTION-LENGTH, 2 octets
+        opt_rdata.push(8);  // contains length of the payload (everything after OPTION-LENGTH) in octets.
+        opt_rdata.push(0);  // FAMILY, 2 octets
+        opt_rdata.push(1);  // (0x00 0x01 ipv4)
+        // SOURCE PREFIX-LENGTH, an unsigned octet representing the leftmost number of significant bits of ADDRESS
+        // SCOPE PREFIX-LENGTH, an unsigned octet representing.. In queries, it MUST be set to 0
+        // ADDRESS, variable number of octets, contains either an IPv4 or
+        // IPv6 address, depending on FAMILY, which MUST be truncated to the
+        // number of bits indicated by the SOURCE PREFIX-LENGTH field,
+        // padding with 0 bits to pad to the end of the last octet needed
+        let mut iplen:usize;
+        match client_ip {
+            IpAddr::V4(ipv4) => {
+                opt_rdata.push(globals.ecs_source_prefix_ipv4);
+                opt_rdata.push(0);
+                let mut mask:u32 = 0xFFFFFFFF;
+                let mut n = 32 - globals.ecs_source_prefix_ipv4;
+                while n > 0 {
+                    mask <<= 1;
+                    n -= 1;
+                }
+                let ipnum = u32::from(ipv4) & mask;
+                let iparr: [u8; 4] = ipnum.to_be_bytes();
+                iplen = iparr.len();
+                while iplen > 1 && iparr[iplen-1] == 0 {
+                    if iparr[iplen-2] != 0 { break; }
+                    iplen -= 1;
+                }
+                let mut z = 0;
+                while z < iplen {
+                    opt_rdata.push(iparr[z]);
+                    z += 1;
+                }
+            }
+            IpAddr::V6(ipv6) => {
+                opt_rdata.push(globals.ecs_source_prefix_ipv6);
+                opt_rdata.push(0);
+                opt_rdata[7] = 2;  // family number 2 = ipv6
+                let mut mask:u128 = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF;
+                let mut n = 128 - globals.ecs_source_prefix_ipv6;
+                while n > 0 {
+                    mask <<= 1;
+                    n -= 1;
+                }
+                let ipnum = u128::from(ipv6) & mask;
+                let iparr: [u8; 16] = ipnum.to_be_bytes();
+                iplen = iparr.len();
+                while iplen > 1 && iparr[iplen-1] == 0 {
+                    if iparr[iplen-2] != 0 { break; }
+                    iplen -= 1;
+                }
+                let mut z = 0;
+                while z < iplen {
+                    opt_rdata.push(iparr[z]);
+                    z += 1;
+                }
+            }
+        }
+        opt_rdata[1] = 8 + iplen as u8;
+    }
+    //info!("ECS data {:?}", opt_rdata);
+
     resolve(
         globals,
         packet,
@@ -267,6 +342,7 @@ pub async fn get_cached_response_or_resolve(
         cached_response,
         packet_hash,
         original_tid,
+        &opt_rdata,
     )
     .await
 }