From 89a7ebd63d48a237daa06aca97f88b70fe28da8c Mon Sep 17 00:00:00 2001
From: zoeyjodon <76182954+zoeyjodon@users.noreply.github.com>
Date: Fri, 22 Dec 2023 13:48:34 -0500
Subject: [PATCH 1/3] Reduce 3DS MTU (#14)

---
 include/enet/protocol.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/enet/protocol.h b/include/enet/protocol.h
index b3c8b03e..444919a8 100644
--- a/include/enet/protocol.h
+++ b/include/enet/protocol.h
@@ -1,4 +1,4 @@
-/** 
+/**
  @file  protocol.h
  @brief ENet protocol
 */
@@ -10,7 +10,7 @@
 enum
 {
    ENET_PROTOCOL_MINIMUM_MTU             = 576,
-#ifdef __WIIU__
+#if defined(__WIIU__) || defined(__3DS__)
    ENET_PROTOCOL_MAXIMUM_MTU             = 1400,
 #else
    ENET_PROTOCOL_MAXIMUM_MTU             = 4096,

From 43218d4de23b46d7da54e32f7a5645eb4ca68e92 Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Thu, 28 Dec 2023 00:35:46 -0600
Subject: [PATCH 2/3] Add warning when IPv6 options are not defined on Apple
 platforms

---
 unix.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/unix.c b/unix.c
index 5f9b6584..6ee5ddd1 100644
--- a/unix.c
+++ b/unix.c
@@ -29,6 +29,9 @@
 #include "enet/enet.h"
 
 #if defined(__APPLE__)
+#if !defined(IPV6_RECVPKTINFO) || !defined(IPV6_PKTINFO)
+#warning Missing IPv6 socket option definitions. Is __APPLE_USE_RFC_3542 defined?
+#endif
 #ifndef HAS_POLL
 #define HAS_POLL 1
 #endif

From c6bb0e50118d08252eee308de8412751218442d6 Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Thu, 28 Dec 2023 16:07:39 -0600
Subject: [PATCH 3/3] Add workaround for Apple kernel bug

---
 unix.c | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/unix.c b/unix.c
index 6ee5ddd1..0903dadc 100644
--- a/unix.c
+++ b/unix.c
@@ -219,6 +219,27 @@ enet_time_set (enet_uint32 newTimeBase)
     timeBase = timeVal.tv_sec * 1000 + timeVal.tv_usec / 1000 - newTimeBase;
 }
 
+#ifdef __APPLE__
+void
+enet_address_make_v4mapped (ENetAddress * address)
+{
+    ENetAddress oldAddress = *address;
+    struct sockaddr_in *sin = ((struct sockaddr_in *)&oldAddress.address);
+    struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&address->address;
+    
+    memset(sin6, 0, sizeof(*sin6));
+    sin6->sin6_family = AF_INET6;
+    sin6->sin6_len = sizeof(*sin6);
+    sin6->sin6_port = sin->sin_port;
+    
+    sin6->sin6_addr.s6_addr[10] = 0xFF;
+    sin6->sin6_addr.s6_addr[11] = 0xFF;
+    memcpy(&sin6->sin6_addr.s6_addr[12], &sin->sin_addr, 4);
+    
+    address->addressLength = sizeof(*sin6);
+}
+#endif
+
 int
 enet_address_equal (ENetAddress * address1, ENetAddress * address2)
 {
@@ -729,8 +750,19 @@ enet_socket_receive (ENetSocket socket,
         }
     }
 
-    if (peerAddress != NULL)
-      peerAddress -> addressLength = msgHdr.msg_namelen;
+    if (peerAddress != NULL) {
+        peerAddress -> addressLength = msgHdr.msg_namelen;
+        
+#ifdef __APPLE__
+        // HACK: Apple platforms return AF_INET addresses in msg_name from recvmsg() on dual-stack sockets
+        // instead of AF_INET6 addresses then rejects those same addresses when they are passed to sendmsg().
+        // Strangely, this only happens when the socket is bound, and IPV6_PKTINFO properly returns v4-mapped
+        // addresses in the same call. This is probably a kernel bug, so we fix it up here.
+        if (peerAddress -> address.ss_family == AF_INET && localAddress -> address.ss_family == AF_INET6) {
+            enet_address_make_v4mapped(peerAddress);
+        }
+#endif
+    }
 
     return recvLength;
 #endif