Switch dns_sd_browse_mode from string to integer enum

Per lo-simon's review: use a typed enum (compile-checked) rather than a
string to reduce typo risk in user configurations.

- enum dns_sd_browse_mode { dns_sd_browse_mode_both = 0, _unicast = 1,
  _mdns = 2 } defined file-local in mdns.cpp under nmos::experimental,
  mirroring how href_mode lives in settings.cpp
- field becomes field_as_integer_or with default 0
- example config.json now shows //"dns_sd_browse_mode": 0,
- doc comments updated; dns_sd_browse_mode.h header removed

Used dns_sd_browse_mode_* prefix on the enumerators (rather than the bare
both/unicast/mdns suggested in the review) to avoid polluting nmos:: with
generic identifiers, matching the href_mode_* convention.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

Author: simonbaren

Development/cmake/NmosCppLibraries.cmake

@@ -1133,7 +1133,6 @@ set(NMOS_CPP_NMOS_HEADERS
     nmos/control_protocol_ws_api.h
     nmos/device_type.h
     nmos/did_sdid.h
-    nmos/dns_sd_browse_mode.h
     nmos/event_type.h
     nmos/events_api.h
     nmos/events_resources.h

Development/nmos-cpp-node/config.json

@@ -86,9 +86,9 @@
     //"domain": "",
 
     // dns_sd_browse_mode [node]: DNS-SD browse method per TR-10-9 Section 15
-    //   "both" (default) = unicast DNS first, mDNS fallback if unsuccessful
-    //   "unicast"        = unicast DNS only
-    //   "mdns"           = mDNS only
+    //   both(0) (default) = unicast DNS first, mDNS fallback if unsuccessful
+    //   unicast(1)        = unicast DNS only
+    //   mdns(2)           = mDNS only
     // Expected resolve behaviour for each (mode, domain) combination:
     //   mode    | domain      | behaviour
     //   --------+-------------+--------------------
@@ -98,7 +98,7 @@
     //   unicast | local.      | mdns
     //   mdns    | example.com | mdns
     //   mdns    | local.      | mdns
-    //"dns_sd_browse_mode": "both",
+    //"dns_sd_browse_mode": 0,
 
     // host_address/host_addresses [registry, node]: IP addresses used to construct response headers (e.g. 'Link' or 'Location'), and host and URL fields in the data model
     //"host_address": "127.0.0.1",

Development/nmos/dns_sd_browse_mode.h

@@ -12,7 +12,6 @@
 #include "cpprest/uri_builder.h"
 #include "mdns/service_advertiser.h"
 #include "mdns/service_discovery.h"
-#include "nmos/dns_sd_browse_mode.h"
 #include "nmos/is09_versions.h"
 #include "nmos/is10_versions.h"
 #include "nmos/random.h"
@@ -302,6 +301,14 @@ namespace nmos
 
     namespace experimental
     {
+        // DNS-SD browse method per TR-10-9 Section 15; selected via the dns_sd_browse_mode setting
+        enum dns_sd_browse_mode
+        {
+            dns_sd_browse_mode_both    = 0, // unicast DNS first, mDNS fallback if unsuccessful
+            dns_sd_browse_mode_unicast = 1, // unicast DNS only
+            dns_sd_browse_mode_mdns    = 2  // mDNS only
+        };
+
         namespace details
         {
             inline int service_port(const nmos::service_type& service, const nmos::settings& settings)
@@ -744,13 +751,13 @@ namespace nmos
         // returning ((api_version, priority), uri) tuples. Highest version and highest priority first, services
         // with the same priority ordered randomly.
         // The browse method is selected by the dns_sd_browse_mode setting per TR-10-9 Section 15:
-        //  - "both" (default): unicast DNS first, mDNS fallback if unsuccessful
-        //  - "unicast"       : unicast DNS only
-        //  - "mdns"          : mDNS only
+        //  - both (default): unicast DNS first, mDNS fallback if unsuccessful
+        //  - unicast       : unicast DNS only
+        //  - mdns          : mDNS only
         pplx::task<std::list<resolved_service>> resolve_service_(mdns::service_discovery& discovery, const nmos::service_type& service, const nmos::settings& settings, const pplx::cancellation_token& token)
         {
             const auto browse_domain = utility::us2s(nmos::get_domain(settings));
-            const auto browse_mode = nmos::dns_sd_browse_mode(nmos::fields::dns_sd_browse_mode(settings));
+            const auto browse_mode = dns_sd_browse_mode(nmos::fields::dns_sd_browse_mode(settings));
             const auto versions = details::service_versions(service, settings);
             const auto priorities = details::service_priorities(service, settings);
             const auto protocols = std::set<nmos::service_protocol>{ nmos::get_service_protocol(service, settings) };
@@ -762,8 +769,8 @@ namespace nmos
             const auto timeout_dur = std::chrono::duration_cast<std::chrono::steady_clock::duration>(std::chrono::seconds(timeout));
 
             // determine primary browse domain based on mode
-            const auto primary_domain = (browse_mode == nmos::dns_sd_browse_modes::mdns) ? std::string("local.") : browse_domain;
-            const bool has_fallback = (browse_mode == nmos::dns_sd_browse_modes::both) && !is_local_domain(browse_domain);
+            const auto primary_domain = (browse_mode == dns_sd_browse_mode_mdns) ? std::string("local.") : browse_domain;
+            const bool has_fallback = (browse_mode == dns_sd_browse_mode_both) && !is_local_domain(browse_domain);
 
             auto primary_task = resolve_service_(discovery, service, primary_domain, versions, priorities, protocols, authorization, true, timeout_dur, token);
 

Development/nmos/mdns.cpp

@@ -198,9 +198,9 @@ namespace nmos
         // returning ((api_version, priority), uri) tuples. Highest version and highest priority first, services
         // with the same priority ordered randomly.
         // The browse method is selected by the dns_sd_browse_mode setting per TR-10-9 Section 15:
-        //  - "both" (default): unicast DNS first, mDNS fallback if unsuccessful
-        //  - "unicast"       : unicast DNS only
-        //  - "mdns"          : mDNS only
+        //  - both (default): unicast DNS first, mDNS fallback if unsuccessful
+        //  - unicast       : unicast DNS only
+        //  - mdns          : mDNS only
         pplx::task<std::list<resolved_service>> resolve_service_(mdns::service_discovery& discovery, const nmos::service_type& service, const nmos::settings& settings, const pplx::cancellation_token& token = pplx::cancellation_token::none());
     }
 }

Development/nmos/mdns.h

@@ -83,10 +83,9 @@ namespace nmos
         const web::json::field_as_string_or domain{ U("domain"), U("") };
 
         // dns_sd_browse_mode [node]: DNS-SD browse method per TR-10-9 Section 15
-        // (see nmos::dns_sd_browse_modes for valid values)
-        //   "both" (default) = unicast DNS first, mDNS fallback if unsuccessful
-        //   "unicast"        = unicast DNS only
-        //   "mdns"           = mDNS only
+        //   both(0) (default) = unicast DNS first, mDNS fallback if unsuccessful
+        //   unicast(1)        = unicast DNS only
+        //   mdns(2)           = mDNS only
         // Expected resolve behaviour for each (mode, domain) combination:
         //   mode    | domain      | behaviour
         //   --------+-------------+--------------------
@@ -96,7 +95,7 @@ namespace nmos
         //   unicast | local.      | mdns
         //   mdns    | example.com | mdns
         //   mdns    | local.      | mdns
-        const web::json::field_as_string_or dns_sd_browse_mode{ U("dns_sd_browse_mode"), U("both") };
+        const web::json::field_as_integer_or dns_sd_browse_mode{ U("dns_sd_browse_mode"), 0 };
 
         // host_address/host_addresses [registry, node]: IP addresses used to construct response headers (e.g. 'Link' or 'Location'), and host and URL fields in the data model
         const web::json::field_as_string_or host_address{ U("host_address"), U("127.0.0.1") };