From 4566297817b3fc2b9d088d37b037b975a74926f3 Mon Sep 17 00:00:00 2001
From: Bohdan Horbeshko <bodqhrohro@gmail.com>
Date: Fri, 21 Aug 2026 21:05:51 -0400
Subject: [PATCH] Ping (XEP-0199/XEP-0410)

---
 xmpp/extensions/extensions.go | 21 ++++++++++++++++
 xmpp/gateway/gateway.go       |  1 +
 xmpp/handlers.go              | 47 +++++++++++++++++++++++++++++++++++
 3 files changed, 69 insertions(+)

diff --git a/xmpp/extensions/extensions.go b/xmpp/extensions/extensions.go
index 4d777f9..c17ccd5 100644
--- a/xmpp/extensions/extensions.go
+++ b/xmpp/extensions/extensions.go
@@ -493,6 +493,21 @@ type EntityTime struct {
 	ResultSet *stanza.ResultSet `xml:"set,omitempty"`
 }
 
+// Ping is from XEP-0199, also used for XEP-0410 MUC self-ping
+type Ping struct {
+	XMLName xml.Name `xml:"urn:xmpp:ping ping"`
+}
+
+// Namespace is a namespace!
+func (c Ping) Namespace() string {
+	return c.XMLName.Space
+}
+
+// GetSet getsets!
+func (c Ping) GetSet() *stanza.ResultSet {
+	return nil
+}
+
 // AttachTo is from XEP-0367
 type AttachTo struct {
 	XMLName xml.Name `xml:"urn:xmpp:message-attaching:1 attach-to"`
@@ -952,6 +967,12 @@ func init() {
 		"time",
 	}, EntityTime{})
 
+	// ping
+	stanza.TypeRegistry.MapExtension(stanza.PKTIQ, xml.Name{
+		"urn:xmpp:ping",
+		"ping",
+	}, Ping{})
+
 	// attach-to
 	stanza.TypeRegistry.MapExtension(stanza.PKTMessage, xml.Name{
 		"urn:xmpp:message-attaching:1",
diff --git a/xmpp/gateway/gateway.go b/xmpp/gateway/gateway.go
index 0c4cc15..b192555 100644
--- a/xmpp/gateway/gateway.go
+++ b/xmpp/gateway/gateway.go
@@ -1172,6 +1172,7 @@ func AddCommonDiscoFeatures(disco *stanza.DiscoInfo) {
 		NSCommand,
 		"jabber:iq:version",
 		"urn:xmpp:time",
+		"urn:xmpp:ping",
 		stanza.NSDiscoInfo,
 		NSCaps,
 	)
diff --git a/xmpp/handlers.go b/xmpp/handlers.go
index b078573..511f853 100644
--- a/xmpp/handlers.go
+++ b/xmpp/handlers.go
@@ -149,6 +149,11 @@ func HandleIq(s xmpp.Sender, p stanza.Packet) {
 			go handleGetEntityTime(s, iq)
 			return
 		}
+		_, ok = iq.Payload.(*extensions.Ping)
+		if ok {
+			go handleGetPing(s, iq)
+			return
+		}
 	} else if iq.Type == stanza.IQTypeSet {
 		queryRegister, ok := iq.Payload.(*extensions.QueryRegister)
 		if ok {
@@ -1459,6 +1464,48 @@ func handleGetEntityTime(s xmpp.Sender, iq *stanza.IQ) {
 	log.Debugf("%#v", entityTime)
 }
 
+// handleGetPing answers XEP-0199 ping. When addressed to a MUC occupant JID
+// (room@service/nick), it implements the XEP-0410 self-ping optimization:
+// answer directly from in-memory occupant state instead of routing the ping
+// to a (nonexistent) full JID for that occupant.
+func handleGetPing(s xmpp.Sender, iq *stanza.IQ) {
+	component, answer, ok := iqResultStub(s, iq)
+	if !ok {
+		return
+	}
+	defer gateway.ResumableSend(component, answer)
+
+	toJid, err := stanza.NewJid(iq.To)
+	if err != nil || toJid.Resource == "" {
+		// plain service/entity ping, not addressed to a MUC occupant
+		return
+	}
+
+	toID, toOk, toIsGroup := toToID(iq.To)
+	if !toOk || !toIsGroup {
+		// not a MUC room JID either, treat as a plain entity ping
+		return
+	}
+
+	bare, resource, fromOk := gateway.SplitJID(iq.From)
+	if !fromOk {
+		iqAnswerSetError(answer, 400)
+		return
+	}
+
+	session, sessionOk := sessions[bare]
+	if !sessionOk || !session.Session.MUC {
+		iqAnswerSetError(answer, 403)
+		return
+	}
+
+	nick, hasNick := session.GetMyMUCNickname(toID)
+	if !hasNick || nick != toJid.Resource || !session.MUCHasResource(toID, resource) {
+		iqAnswerSetError(answer, 404)
+		return
+	}
+}
+
 func handleGetQueryMucAdmin(s xmpp.Sender, iq *stanza.IQ, query *extensions.QueryMucAdmin) {
 	component, answer, ok := iqResultStub(s, iq)
 	if !ok {