WIP: fw: app: Implement mDNS proof of conceptmdns

TODO: Make this work. WireShark shows that some request / response is
exchanged but it is unclear why the request is always canceled after
timeout on the Zephyr side.

2 files changed, 95 insertions, 1 deletions

diff --git a/fw/app/prj.conf b/fw/app/prj.conf
index 6589ec0..19d10c8 100644
--- a/fw/app/prj.conf
+++ b/fw/app/prj.conf
@@ -59,3 +59,18 @@ CONFIG_SETTINGS_SHELL=y
 CONFIG_GNU_C_EXTENSIONS=y
 
 CONFIG_JSON_LIBRARY=y
+
+# Enable the DNS resolver
+CONFIG_DNS_RESOLVER=y
+# Enable additional buffers
+CONFIG_DNS_RESOLVER_ADDITIONAL_BUF_CTR=5
+# Enable additional queries
+CONFIG_DNS_RESOLVER_ADDITIONAL_QUERIES=2
+# Enable mDNS support
+CONFIG_MDNS_RESOLVER=y
+# Enable LLMNR support
+CONFIG_LLMNR_RESOLVER=n
+
+CONFIG_DNS_RESOLVER_MAX_SERVERS=2
+CONFIG_DNS_SERVER_IP_ADDRESSES=y
+CONFIG_DNS_NUM_CONCUR_QUERIES=5
diff --git a/fw/app/src/heart.c b/fw/app/src/heart.c
index 6bcced6..643ec61 100644
--- a/fw/app/src/heart.c
+++ b/fw/app/src/heart.c
@@ -9,17 +9,20 @@
 
 #include <zephyr/kernel.h>
 #include <zephyr/logging/log.h>
+#include <zephyr/net/dns_resolve.h>
 
 #include "heart.h"
 
 
-LOG_MODULE_REGISTER(heart);
+LOG_MODULE_REGISTER(heart, 4);
 
 
 #define HEART_PERIOD          K_MSEC(1000)
 #define HEART_STACK_SIZE               500
 #define HEART_PRIO       K_PRIO_PREEMPT(8)
 
+#define DNS_TIMEOUT (3 * MSEC_PER_SEC)
+
 
 ZBUS_CHAN_DEFINE(
 	heartbeat_channel,
@@ -31,11 +34,87 @@ ZBUS_CHAN_DEFINE(
 );
 
 
+void mdns_result_cb(enum dns_resolve_status status,
+		    struct dns_addrinfo *info,
+		    void *user_data)
+{
+	char hr_addr[NET_IPV6_ADDR_LEN];
+	char *hr_family;
+	void *addr;
+
+	switch (status) {
+	case DNS_EAI_CANCELED:
+		LOG_INF("mDNS query was canceled");
+		return;
+	case DNS_EAI_FAIL:
+		LOG_INF("mDNS resolve failed");
+		return;
+	case DNS_EAI_NODATA:
+		LOG_INF("Cannot resolve address using mDNS");
+		return;
+	case DNS_EAI_ALLDONE:
+		LOG_INF("mDNS resolving finished");
+		return;
+	case DNS_EAI_INPROGRESS:
+		break;
+	default:
+		LOG_INF("mDNS resolving error (%d)", status);
+		return;
+	}
+
+	if (!info) {
+		return;
+	}
+
+	if (info->ai_family == AF_INET) {
+		hr_family = "IPv4";
+		addr = &net_sin(&info->ai_addr)->sin_addr;
+	} else if (info->ai_family == AF_INET6) {
+		hr_family = "IPv6";
+		addr = &net_sin6(&info->ai_addr)->sin6_addr;
+	} else {
+		LOG_ERR("Invalid IP address family %d", info->ai_family);
+		return;
+	}
+
+	LOG_INF("%s %s address: %s", user_data ? (char *)user_data : "<null>",
+		hr_family,
+		net_addr_ntop(info->ai_family, addr,
+					 hr_addr, sizeof(hr_addr)));
+}
+
+
+static void do_mdns_ipv6_lookup(void)
+{
+	static const char *query = "thinkpad.local";
+	int ret;
+
+	LOG_DBG("Doing mDNS IPv6 query");
+
+	ret = dns_get_addr_info(query,
+				DNS_QUERY_TYPE_AAAA,
+				NULL,
+				mdns_result_cb,
+				(void *)query,
+				DNS_TIMEOUT);
+	if (ret < 0) {
+		LOG_ERR("Cannot resolve mDNS IPv6 address (%d)", ret);
+		return;
+	}
+
+	LOG_DBG("mDNS v6 query sent");
+}
+
+
 static void heart_thread_function(void *ptr1, void *ptr2, void *ptr3) {
 	LOG_INF("Starting to beat");
 
 	struct heartbeat heartbeat = {.ttl_ms = 1100};
 
+	k_msleep(2000);
+	LOG_INF("Starting this thing");
+	do_mdns_ipv6_lookup();
+
 	while (true) {
 		LOG_DBG("Heart beat");
 		int ret = zbus_chan_pub(&heartbeat_channel, &heartbeat, K_FOREVER);