Add support for domain name and domain search to generate FQDNs

embassy-net/Cargo.toml

@@ -48,6 +48,8 @@ dns = ["smoltcp/socket-dns", "smoltcp/proto-dns"]
 dhcpv4 = ["proto-ipv4", "medium-ethernet", "smoltcp/socket-dhcpv4"]
 ## Enable DHCPv4 support with hostname
 dhcpv4-hostname = ["dhcpv4"]
+## Enable DHCP option 15 (domain-name) for use in DNS queries
+dhcpv4-domainname = ["dhcpv4"]
 ## Enable IPv4 support
 proto-ipv4 = ["smoltcp/proto-ipv4"]
 ## Enable IPv6 support

embassy-net/src/lib.rs

@@ -33,7 +33,7 @@ use embassy_net_driver::{Driver, LinkState};
 use embassy_sync::waitqueue::WakerRegistration;
 use embassy_time::{Instant, Timer};
 #[allow(unused_imports)]
-use heapless::Vec;
+use heapless::{String, Vec};
 #[cfg(feature = "dns")]
 pub use smoltcp::config::DNS_MAX_SERVER_COUNT;
 #[cfg(feature = "igmp")]
@@ -66,6 +66,10 @@ const LOCAL_PORT_MAX: u16 = 65535;
 const MAX_QUERIES: usize = 4;
 #[cfg(feature = "dhcpv4-hostname")]
 const MAX_HOSTNAME_LEN: usize = 32;
+#[cfg(feature = "dhcpv4-domainname")]
+const MAX_DOMAINNAME_LEN: usize = 64;
+#[cfg(all(feature = "dhcpv4-domainname", feature = "dns"))]
+const MAX_DNS_QUERY_LEN: usize = 128;
 
 /// Memory resources needed for a network stack.
 pub struct StackResources<const SOCK: usize> {
@@ -146,7 +150,7 @@ pub struct DhcpConfig {
  pub client_port: u16,
  /// Our hostname. This will be sent to the DHCP server as Option 12.
  #[cfg(feature = "dhcpv4-hostname")]
- pub hostname: Option<heapless::String<MAX_HOSTNAME_LEN>>,
+ pub hostname: Option<String<MAX_HOSTNAME_LEN>>,
 }
 
 #[cfg(feature = "dhcpv4")]
@@ -263,6 +267,8 @@ struct Inner<D: Driver> {
  dns_waker: WakerRegistration,
  #[cfg(feature = "dhcpv4-hostname")]
  hostname: &'static mut core::cell::UnsafeCell<HostnameResources>,
+ #[cfg(feature = "dhcpv4-domainname")]
+ domainname: String<MAX_DOMAINNAME_LEN>,
 }
 
 pub(crate) struct SocketStack {
@@ -345,6 +351,8 @@ impl<D: Driver> Stack<D> {
  dns_waker: WakerRegistration::new(),
  #[cfg(feature = "dhcpv4-hostname")]
  hostname: &mut resources.hostname,
+ #[cfg(feature = "dhcpv4-domainname")]
+ domainname: String::new(),
  };
 
  #[cfg(feature = "proto-ipv4")]
@@ -527,6 +535,20 @@ impl<D: Driver> Stack<D> {
  _ => {}
  }
 
+ // Form name together with domain name.
+ #[cfg(feature = "dhcpv4-domainname")]
+ let name = &{
+ use core::str::FromStr;
+
+ let domainname = &self.inner.borrow().domainname;
+ let mut name = String::<MAX_DNS_QUERY_LEN>::from_str(name).map_err(|_| dns::Error::NameTooLong)?;
+ if !domainname.is_empty() {
+ name.push('.').map_err(|_| dns::Error::NameTooLong)?;
+ name.push_str(domainname).map_err(|_| dns::Error::NameTooLong)?;
+ }
+ name
+ };
+
  let query = poll_fn(|cx| {
  self.with_mut(|s, i| {
  let socket = s.sockets.get_mut::<dns::Socket>(i.dns_socket);
@@ -746,6 +768,12 @@ impl<D: Driver> Inner<D> {
  socket.set_outgoing_options(core::slice::from_ref(&hostname.option));
  }
 
+ // The domain-search (119) option specifies a list of domains to use when looking up bare
+ // hostnames, and is specified in resolv.conf with the search keyword. If this option
+ // isn't provided it defaults to the single domain provided by domain-name (15).
+ #[cfg(feature = "dhcpv4-domainname")]
+ socket.set_parameter_request_list(&[1, 3, 6, 15, 119]);
+
  socket.reset();
  }
  _ => {
@@ -904,6 +932,21 @@ impl<D: Driver> Inner<D> {
  dns_servers: config.dns_servers,
  });
  apply_config = true;
+
+ #[cfg(feature = "dhcpv4-domainname")]
+ if let Some(packet) = config.packet {
+ if let Some(domainname) = packet.options().find(|o| o.kind == 15) {
+ self.domainname.clear();
+ if let Ok(name) = core::str::from_utf8(domainname.data) {
+ if self.domainname.push_str(name).is_err() {
+ warn!("Domain name is too long, skipping");
+ } else {
+ debug!("DHCP: Got domain name");
+ debug!(" Domain name: '{}'", self.domainname);
+ }
+ }
+ }
+ }
  }
  }
  } else if old_link_up {