Use libdmns on Linux

Based implementation from https://github.com/kedars/matter-rs/pull/18

matter/Cargo.toml

@@ -56,6 +56,12 @@ qrcode = { version = "0.12", default-features = false }
 [target.'cfg(target_os = "macos")'.dependencies]
 astro-dnssd = "0.3"
 
+# MDNS support
+[target.'cfg(target_os = "linux")'.dependencies]
+lazy_static = "1.4.0"
+# Patched copy of libmdns
+libmdns = { git = "https://github.com/angelybo/libmdns.git", branch = "return_all_on_query" }
+
 [[example]]
 name = "onoff_light"
 path = "../examples/onoff_light/src/main.rs"

matter/src/sys/sys_linux.rs

@@ -16,17 +16,43 @@
  */
 
 use crate::error::Error;
-use log::error;
+use lazy_static::lazy_static;
+use libmdns::{Responder, Service};
+use log::info;
+use std::sync::{Arc, Mutex};
+use std::vec::Vec;
 
 #[allow(dead_code)]
-pub struct SysMdnsService {}
-
-pub fn sys_publish_service(
-    _name: &str,
-    _regtype: &str,
-    _port: u16,
-    _txt_kvs: &[[&str; 2]],
-) -> Result<SysMdnsService, Error> {
-    error!("Linux is not yet supported for MDNS Service");
-    Ok(SysMdnsService {})
+pub struct SysMdnsService {
+    service: Service,
+}
+
+lazy_static! {
+    static ref RESPONDER: Arc<Mutex<Responder>> = Arc::new(Mutex::new(Responder::new().unwrap()));
+}
+
+/// Publish a mDNS service
+/// name - can be a service name (comma separate subtypes may follow)
+/// regtype - registration type (e.g. _matter_.tcp etc)
+/// port - the port
+pub fn sys_publish_service(
+    name: &str,
+    regtype: &str,
+    port: u16,
+    txt_kvs: &[[&str; 2]],
+) -> Result<SysMdnsService, Error> {
+    info!("mDNS Registration Type {}", regtype);
+    info!("mDNS properties {:?}", txt_kvs);
+
+    let mut properties = Vec::new();
+    for kvs in txt_kvs {
+        info!("mDNS TXT key {} val {}", kvs[0], kvs[1]);
+        properties.push(format!("{}={}", kvs[0], kvs[1]));
+    }
+    let properties: Vec<&str> = properties.iter().map(|entry| entry.as_str()).collect();
+
+    let responder = RESPONDER.lock().map_err(|_| Error::MdnsError)?;
+    let service = responder.register(regtype.to_owned(), name.to_owned(), port, &properties);
+
+    Ok(SysMdnsService { service })
 }