From a0569d2d3cdca5d6ed78e0df77b08ccbbec52570 Mon Sep 17 00:00:00 2001
From: Dirk Engling <erdgeist@erdgeist.org>
Date: Mon, 2 Nov 2026 02:22:56 +0100
Subject: Report the version, event machanism and feature flags with -v

---
 man1/opentracker.1 |  4 +++
 ot_config.c        |  2 ++
 ot_stats.c         | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 ot_stats.h         |  1 +
 4 files changed, 94 insertions(+)

diff --git a/man1/opentracker.1 b/man1/opentracker.1
index 0103ebe..489a54c 100644
--- a/man1/opentracker.1
+++ b/man1/opentracker.1
@@ -15,6 +15,7 @@
 .Op Fl d Ar chdir
 .Op Fl u Ar user
 .Op Fl w| Fl b accesslist
+.Op Fl v
 .Sh DESCRIPTION
 .Nm
 is a bittorrent tracker that implements announce and scrape actions over the
@@ -85,6 +86,9 @@ has been compiled with the
 or
 .Br WANT_ACCESSLIST_WHITE
 options, this option sets the location of the accesslist.
+.It Fl v
+Report the version, the event mechanism in use and the feature flags this
+binary was built with.
 .El
 .Sh EXAMPLES
 Start
diff --git a/ot_config.c b/ot_config.c
index 272acf1..5da6642 100644
--- a/ot_config.c
+++ b/ot_config.c
@@ -432,6 +432,7 @@ static void help(char *name) {
   HELPLINE("-d dir", "specify directory to try to chroot to (default: \".\")");
   HELPLINE("-u user", "specify user under whose privileges opentracker should run (default: \"nobody\")");
   HELPLINE("-A ip[/bits]", "bless an ip address or net as admin address (e.g. to allow syncs from this address)");
+  HELPLINE("-v", "report version, event mechanism and the feature flags opentracker was built with");
 #ifdef WANT_ACCESSLIST_BLACK
   HELPLINE("-b file", "specify blacklist file.");
 #elif defined(WANT_ACCESSLIST_WHITE)
@@ -566,6 +567,7 @@ void config_parse(int argc, char **argv) {
       char *cursor = buffer;
 
       stats_return_tracker_version(&cursor, buffer + sizeof(buffer) - 1);
+      stats_return_tracker_features(&cursor, buffer + sizeof(buffer) - 1);
       *cursor = 0;
       fputs(buffer, stderr);
       exit(0);
diff --git a/ot_stats.c b/ot_stats.c
index a9f12cc..5edbe0a 100644
--- a/ot_stats.c
+++ b/ot_stats.c
@@ -19,6 +19,7 @@
 
 /* Opentracker */
 #include "ot_accesslist.h"
+#include "ot_event.h"
 #include "ot_hex.h"
 #include "ot_iovec.h"
 #include "ot_ip.h"
@@ -546,6 +547,92 @@ static void stats_return_everything(char **reply, const char *reply_end) {
   fmt_append(reply, reply_end, "</stats>");
 }
 
+/* The names as the Makefile spells them, so that what a binary reports maps
+   straight back onto the FEATURES lines it was built from */
+static const char *const build_features[] = {
+#ifdef WANT_V4_ONLY
+    "WANT_V4_ONLY",
+#endif
+#ifdef WANT_ACCESSLIST_BLACK
+    "WANT_ACCESSLIST_BLACK",
+#endif
+#ifdef WANT_ACCESSLIST_WHITE
+    "WANT_ACCESSLIST_WHITE",
+#endif
+#ifdef WANT_DYNAMIC_ACCESSLIST
+    "WANT_DYNAMIC_ACCESSLIST",
+#endif
+#ifdef WANT_SYNC_LIVE
+    "WANT_SYNC_LIVE",
+#endif
+#ifdef WANT_IP_FROM_QUERY_STRING
+    "WANT_IP_FROM_QUERY_STRING",
+#endif
+#ifdef WANT_IP_FROM_PROXY
+    "WANT_IP_FROM_PROXY",
+#endif
+#ifdef WANT_COMPRESSION_GZIP
+    "WANT_COMPRESSION_GZIP",
+#endif
+#ifdef WANT_COMPRESSION_GZIP_ALWAYS
+    "WANT_COMPRESSION_GZIP_ALWAYS",
+#endif
+#ifdef WANT_COMPRESSION_ZSTD
+    "WANT_COMPRESSION_ZSTD",
+#endif
+#ifdef WANT_COMPRESSION_ZSTD_ALWAYS
+    "WANT_COMPRESSION_ZSTD_ALWAYS",
+#endif
+#ifdef WANT_FULLSCRAPE
+    "WANT_FULLSCRAPE",
+#endif
+#ifdef WANT_MODEST_FULLSCRAPES
+    "WANT_MODEST_FULLSCRAPES",
+#endif
+#ifdef WANT_KEEPALIVE
+    "WANT_KEEPALIVE",
+#endif
+#ifdef WANT_RESTRICT_STATS
+    "WANT_RESTRICT_STATS",
+#endif
+#ifdef WANT_LOG_NUMWANT
+    "WANT_LOG_NUMWANT",
+#endif
+#ifdef WANT_SPOT_WOODPECKER
+    "WANT_SPOT_WOODPECKER",
+#endif
+#ifdef WANT_SYSLOGS
+    "WANT_SYSLOGS",
+#endif
+#ifdef WANT_DEV_RANDOM
+    "WANT_DEV_RANDOM",
+#endif
+#ifdef WANT_INSECURE_RANDOM_FALLBACK
+    "WANT_INSECURE_RANDOM_FALLBACK",
+#endif
+#ifdef _DEBUG
+    "_DEBUG",
+#endif
+#ifdef _DEBUG_HTTPERROR
+    "_DEBUG_HTTPERROR",
+#endif
+#ifdef _DEBUG_RANDOMTORRENTS
+    "_DEBUG_RANDOMTORRENTS",
+#endif
+    NULL};
+
+void stats_return_tracker_features(char **reply, const char *reply_end) {
+  size_t i;
+
+  fmt_append(reply, reply_end, "events: %s\n", event_mechanism());
+  fmt_append(reply, reply_end, "features:");
+  for (i = 0; build_features[i]; ++i)
+    fmt_append(reply, reply_end, " %s", build_features[i]);
+  if (!build_features[0])
+    fmt_append(reply, reply_end, " none");
+  fmt_append(reply, reply_end, "\n");
+}
+
 void stats_return_tracker_version(char **reply, const char *reply_end) {
   fmt_append(reply, reply_end, "opentracker %s", OT_VERSION);
   /* Empty when the build had no git to ask, which is what a release tarball
diff --git a/ot_stats.h b/ot_stats.h
index f484765..f9a9d87 100644
--- a/ot_stats.h
+++ b/ot_stats.h
@@ -35,6 +35,7 @@ void               stats_deliver(int64_t sock, int tasktype);
 void               stats_cleanup(void);
 void               return_stats_for_tracker(char **reply, const char *reply_end, int mode, int format);
 void               stats_return_tracker_version(char **reply, const char *reply_end);
+void               stats_return_tracker_features(char **reply, const char *reply_end);
 void               stats_init(void);
 void               stats_deinit(void);
 
-- 
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