From e0ced3d04e3356d5158473c80e5e5039b63e6702 Mon Sep 17 00:00:00 2001
From: Jan Willamowius <jan@willamowius.de>
Date: Tue, 26 Dec 2023 23:42:33 +0100
Subject: [PATCH] auto-detect public IP with ExternalIP=STUN and
 STUNServer=stun.example.com

---
 Toolkit.cxx                 | 18 ++++++++++++++++++
 changes.txt                 |  1 +
 docs/manual/mainconfig.sgml |  9 +++++++++
 gk.cxx                      |  1 +
 4 files changed, 29 insertions(+)

diff --git a/Toolkit.cxx b/Toolkit.cxx
index 5778d52a..457f5b08 100644
--- a/Toolkit.cxx
+++ b/Toolkit.cxx
@@ -16,6 +16,7 @@
 #include <ptclib/pdns.h>
 #include <ptclib/cypher.h>
 #include <ptclib/http.h>
+#include <ptclib/pstun.h>
 #include <h323pdu.h>
 #include <map>
 #include <vector>
@@ -3909,6 +3910,23 @@ PString Toolkit::GetExternalIP() const
         m_Config->SetString("ExternalIP", ext);
     }
 #endif // P_HTTP
+    if (ext == "STUN") {
+    	PString m_stunConfig = m_Config->GetString("STUNServer", "stun.ekiga.net");
+		PStringArray ip_parts = SplitIPAndPort(m_stunConfig, 3478);
+		PIPSocket::Address m_stunIP;
+		PIPSocket::GetHostAddress(ip_parts[0], m_stunIP);
+		WORD m_stunPort = (WORD)(ip_parts[1].AsUnsigned());
+		PSTUNClient m_stunServer(m_stunIP, m_stunPort);
+		PIPSocket::Address extIP;
+		if (m_stunServer.GetExternalAddress(extIP)) {
+			ext = ::AsString(extIP);
+		} else {
+            ext = "";
+			PTRACE(1, "STUN\tExternal IP can't be detected. Did you set STUNServer= correctly ?");
+		}
+        PTRACE(2, "STUN\tSetting ExternalIP to " << ext);
+        m_Config->SetString("ExternalIP", ext);
+	}
     return ext;
 }
 
diff --git a/changes.txt b/changes.txt
index abafa3a7..cd63677c 100644
--- a/changes.txt
+++ b/changes.txt
@@ -1,5 +1,6 @@
 Changes from 5.11 to 5.12
 =========================
+- auto-detect public IP with ExternalIP=STUN and STUNServer=stun.example.com
 - compiler support for VS2022
 - new database driver for Oracle and new timestamp format 'Oracle'
 - new switch [EP::xxx] ForceDirectMode=1 to handle all calls from this endpoint in direct mode
diff --git a/docs/manual/mainconfig.sgml b/docs/manual/mainconfig.sgml
index d9de61ee..aa32be2e 100644
--- a/docs/manual/mainconfig.sgml
+++ b/docs/manual/mainconfig.sgml
@@ -551,6 +551,10 @@ resolved when needed.
 If you set this switch to "AWSPublicIP", GnuGk will fetch the public / elastic IP from AWS meta data.
 Same with "GooglePublicIP", "AzurePublicIP" and "AlibabaPublicIP" for Google Cloud, Azure and Alibaba Cloud.
 
+If you set this switch to "STUN", GnuGk will try to detect the public IP using a STUN server.
+Use this for deployments in the Oracle Cloud or other cloud environments that don't provice
+the external IP in the metadata. use the STUNServer= switch to set the STUN server to use.
+
 <item><tt/ExternalIsDynamic=1/<newline>
 Default: <tt/0/<newline>
 <p>
@@ -560,6 +564,11 @@ messages to maintain your DDNS name lease.  You must also configure the
 <tt>ExternalIP</tt> setting with a DNS address maintained by a DDNS service
 such as www.dyndns.com or www.no-ip.com.
 
+<item><tt/STUNServer=stun.example.com/<newline>
+Default: <tt>stun.ekiga.net</tt><newline>
+<p>
+Configures the STUN server to be used when setting ExternalIP=STUN.
+
 <item><tt/DefaultDomain=gnugk.org,gnugk.de/<newline>
 Default: <tt>N/A</tt><newline>
 <p>
diff --git a/gk.cxx b/gk.cxx
index 487bd3ac..56b5d50d 100644
--- a/gk.cxx
+++ b/gk.cxx
@@ -283,6 +283,7 @@ const char * KnownConfigEntries[][2] = {
 	{ "Gatekeeper::Main", "StatusEventBacklogRegex" },
 	{ "Gatekeeper::Main", "StatusPort" },
 	{ "Gatekeeper::Main", "StatusTraceLevel" },
+	{ "Gatekeeper::Main", "STUNServer" },
 	{ "Gatekeeper::Main", "TimeToLive" },
 	{ "Gatekeeper::Main", "TimestampFormat" },
 	{ "Gatekeeper::Main", "TotalBandwidth" },