From ae882f37d6b9e6454e19d19e7a8051ce3c3b06bf Mon Sep 17 00:00:00 2001
From: Emil Fresk <emil.fresk@gmail.com>
Date: Fri, 9 Aug 2024 16:24:11 +0200
Subject: [PATCH] Add support for domain name to generate FQDNs

---
 embassy-net/Cargo.toml    |  5 ++++-
 embassy-net/src/device.rs |  2 +-
 embassy-net/src/lib.rs    | 39 +++++++++++++++++++++++++++++++++++++--
 3 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/embassy-net/Cargo.toml b/embassy-net/Cargo.toml
index d86a30755e..89c04ea2ae 100644
--- a/embassy-net/Cargo.toml
+++ b/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
@@ -66,7 +68,7 @@ igmp = ["smoltcp/proto-igmp"]
 defmt = { version = "0.3", optional = true }
 log = { version = "0.4.14", optional = true }
 
-smoltcp = { version = "0.11.0", default-features = false, features = [
+smoltcp = { git = "https://github.com/korken89/smoltcp.git", branch = "dhcp-option-15", default-features = false, features = [
   "socket",
   "async",
 ] }
@@ -80,3 +82,4 @@ managed = { version = "0.8.0", default-features = false, features = [ "map" ] }
 heapless = { version = "0.8", default-features = false }
 embedded-nal-async = { version = "0.7.1" }
 document-features = "0.2.7"
+
diff --git a/embassy-net/src/device.rs b/embassy-net/src/device.rs
index 3b1d3c47cb..b2af1d4993 100644
--- a/embassy-net/src/device.rs
+++ b/embassy-net/src/device.rs
@@ -74,7 +74,7 @@ where
 {
     fn consume<R, F>(self, f: F) -> R
     where
-        F: FnOnce(&mut [u8]) -> R,
+        F: FnOnce(&[u8]) -> R,
     {
         self.0.consume(|buf| {
             #[cfg(feature = "packet-trace")]
diff --git a/embassy-net/src/lib.rs b/embassy-net/src/lib.rs
index 56321cec99..6699a95503 100644
--- a/embassy-net/src/lib.rs
+++ b/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 +66,8 @@ const LOCAL_PORT_MAX: u16 = 65535;
 const MAX_QUERIES: usize = 4;
 #[cfg(feature = "dhcpv4-hostname")]
 const MAX_HOSTNAME_LEN: usize = 32;
+#[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> {
@@ -110,6 +112,9 @@ pub struct StaticConfigV4 {
     pub gateway: Option<Ipv4Address>,
     /// DNS servers.
     pub dns_servers: Vec<Ipv4Address, 3>,
+    /// Domain name.
+    #[cfg(feature = "dhcpv4-domainname")]
+    pub domain_name: Option<String<{ smoltcp::config::DHCP_MAX_DOMAIN_NAME_SIZE }>>,
 }
 
 /// Static IPv6 address configuration
@@ -146,7 +151,7 @@ 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")]
@@ -527,6 +532,15 @@ impl<D: Driver> Stack<D> {
             _ => {}
         }
 
+        #[cfg(feature = "dhcpv4-domainname")]
+        let name = if name.contains(".") {
+            // Already a FQDN.
+            name
+        } else {
+            &self.create_fqdn(name)?
+        };
+        debug!("Performing DNS lookup of: {}", name);
+
         let query = poll_fn(|cx| {
             self.with_mut(|s, i| {
                 let socket = s.sockets.get_mut::<dns::Socket>(i.dns_socket);
@@ -602,6 +616,23 @@ impl<D: Driver> Stack<D> {
 
         res
     }
+
+    #[cfg(feature = "dhcpv4-domainname")]
+    fn create_fqdn(&self, name: &str) -> Result<String<MAX_DNS_QUERY_LEN>, dns::Error> {
+        use core::str::FromStr;
+
+        // Form name together with domain name.
+        let mut name = String::<MAX_DNS_QUERY_LEN>::from_str(name).map_err(|_| dns::Error::NameTooLong)?;
+
+        if let Some(Some(domain_name)) = &self.inner.borrow().static_v4.as_ref().map(|c| &c.domain_name) {
+            if !domain_name.is_empty() {
+                name.push('.').map_err(|_| dns::Error::NameTooLong)?;
+                name.push_str(&domain_name).map_err(|_| dns::Error::NameTooLong)?;
+            }
+        }
+
+        Ok(name)
+    }
 }
 
 #[cfg(feature = "igmp")]
@@ -788,6 +819,8 @@ impl<D: Driver> Inner<D> {
                 debug!("   DNS server:      {:?}", s);
                 unwrap!(dns_servers.push(s.clone().into()).ok());
             }
+            #[cfg(feature = "dhcpv4-domainname")]
+            debug!("   Domain name: {:?}", config.domain_name);
         } else {
             info!("IPv4: DOWN");
         }
@@ -902,6 +935,8 @@ impl<D: Driver> Inner<D> {
                             address: config.address,
                             gateway: config.router,
                             dns_servers: config.dns_servers,
+                            #[cfg(feature = "dhcpv4-domainname")]
+                            domain_name: config.domain_name,
                         });
                         apply_config = true;
                     }