From 764b7abe827f9a40b40c03fe192cce00c05c20be Mon Sep 17 00:00:00 2001
From: Fabio Alessandrelli <fabio.alessandrelli@gmail.com>
Date: Fri, 2 Aug 2024 12:10:19 +0200
Subject: [PATCH] [ENet] Better handle disconnected peers in DTLS server

The ENetDTLSServer socket implementation should avoid reporting errors
during send and receive operations, unless the socket is effectively no
longer usable (and thus ENet should close it).
---
 thirdparty/enet/godot.cpp | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/thirdparty/enet/godot.cpp b/thirdparty/enet/godot.cpp
index ecf0a7e6dd7e..9e766e52c3ea 100644
--- a/thirdparty/enet/godot.cpp
+++ b/thirdparty/enet/godot.cpp
@@ -299,7 +299,12 @@ class ENetDTLSServer : public ENetGodotSocket {
 
 	Error sendto(const uint8_t *p_buffer, int p_len, int &r_sent, IPAddress p_ip, uint16_t p_port) {
 		String key = String(p_ip) + ":" + itos(p_port);
-		ERR_FAIL_COND_V(!peers.has(key), ERR_UNAVAILABLE);
+		if (unlikely(!peers.has(key))) {
+			// The peer might have been disconnected due to a DTLS error.
+			// We need to wait for it to time out, just mark the packet as sent.
+			r_sent = p_len;
+			return OK;
+		}
 		Ref<PacketPeerDTLS> peer = peers[key];
 		Error err = peer->put_packet(p_buffer, p_len);
 		if (err == OK) {
@@ -307,7 +312,10 @@ class ENetDTLSServer : public ENetGodotSocket {
 		} else if (err == ERR_BUSY) {
 			r_sent = 0;
 		} else {
-			r_sent = -1;
+			// The peer might have been disconnected due to a DTLS error.
+			// We need to wait for it to time out, just mark the packet as sent.
+			r_sent = p_len;
+			return OK;
 		}
 		return err;
 	}
@@ -331,7 +339,7 @@ class ENetDTLSServer : public ENetGodotSocket {
 		Error err = ERR_BUSY;
 		// TODO this needs to be fair!
 
-		for (KeyValue<String, Ref<PacketPeerDTLS>> & E : peers) {
+		for (KeyValue<String, Ref<PacketPeerDTLS>> &E : peers) {
 			Ref<PacketPeerDTLS> peer = E.value;
 			peer->poll();
 
@@ -349,7 +357,8 @@ class ENetDTLSServer : public ENetGodotSocket {
 				if (err != OK || p_len < r_read) {
 					// Something wrong with this peer, removing it.
 					remove.push_back(E.key);
-					err = FAILED;
+					err = ERR_BUSY;
+					r_read = 0;
 					continue;
 				}
 
@@ -549,7 +558,7 @@ int enet_socket_receive(ENetSocket socket, ENetAddress *address, ENetBuffer *buf
 	return read;
 }
 
-int enet_socket_get_address (ENetSocket socket, ENetAddress * address) {
+int enet_socket_get_address(ENetSocket socket, ENetAddress *address) {
 	IPAddress ip;
 	uint16_t port;
 	ENetGodotSocket *sock = (ENetGodotSocket *)socket;