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NOTICE.md

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+# Attribution
+
+reximemoDNS is based on the open-source sudomemoDNS project by Austin Burk / Team Sudomemo.
+The original project is distributed under the MIT License; see `LICENSE`.
+
+RexiMemo-specific changes include the project branding, default DNS targets, RexiMemo host interception, upstream DNS forwarding, and configuration options.
+
+RexiMemo is not affiliated with or endorsed by Team Sudomemo, Hatena Co., Ltd., or Nintendo.

README.md

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-![sudomemoDNS Logo](/sudomemoDNS_banner.png)
-### This server will allow you to connect to Sudomemo when your Internet Service Provider does not work with custom DNS.
+# reximemoDNS
+
+A small local DNS helper for connecting Flipnote Studio to **RexiMemo** when a network or ISP does not reliably allow the console to use RexiMemo's public DNS directly.
+
+It runs on a computer on the same local network as the Nintendo DSi. Flipnote Studio's Nintendo/Hatena hostnames are redirected to RexiMemo, while unrelated DNS lookups are forwarded to a normal upstream resolver.
+
+## Default RexiMemo routing
+
+reximemoDNS redirects these hostnames to RexiMemo's legacy service address:
+
+- `nas.nintendowifi.net`
+- `flipnote.hatena.com`
+- `ugomemo.hatena.ne.jp`
+
+The default RexiMemo server IP is **141.147.76.115**. All other DNS queries are forwarded to **8.8.8.8** by default.
+
+`conntest.nintendowifi.net` is deliberately not intercepted, matching RexiMemo's server-side DNS configuration.
 
 ## Setup
 
-The setup process does not differ from what is shown at https://flipnot.es/setup except for the values to enter in your custom DNS settings.
+1. Put the computer running reximemoDNS and the DSi on the same local network.
+2. Install the requirements.
+3. Run reximemoDNS as Administrator/root because DNS uses port 53.
+4. Enter the **Primary DNS** address printed by the program into the DSi connection settings.
+5. Use `008.008.008.008` as Secondary DNS.
+6. Save the connection and open Flipnote Studio → Flipnote Hatena.
 
-First, make sure that your console is connected to the same network as this computer.
-
-Please submit any issues to Sudomemo Support.
-
-## Running on Windows:
-
-Run the .exe provided in this release. You may have to click past a warning from Windows SmartScreen (as it sometimes turns its nose up at applications bundled by PyInstaller) or your firewall (as it needs to listen for DNS requests).
-
-## Running on anything else:
-
-Required packages are installable with the following command:
-
-    sudo python3 -m pip install -r requirements.txt
-
-Required Python version: 3.6+, tested with 3.9.9
-
-    sudo python3 sudomemoDNS.py
-
-Note: `python3` is assumed to be the name of your python binary, if it is not then it will need to be substituted with the name and/or path of your binary.
-
-## What you'll see when it starts up
-
-    +===============================+
-    |      Sudomemo DNS Server      |
-    |         Version 1.2.1         |
-    +===============================+
-
-    == Welcome to sudomemoDNS! ==
-    This server will allow you to connect to Sudomemo when your Internet Service Provider does
-    not work with custom DNS.
-
-    == How To Use ==
-    First, make sure that your console is connected to the same network as this computer.
-
-    Then, put these settings in for DNS on your console:
-    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-    Primary DNS:   XXX.XXX.XXX.XXX (NOTE: This value will be unique when you run the program)
-    Secondary DNS: 008.008.008.008
-    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-    == Getting Help ==
-    Need help? Visit our Discord server or check out https://support.sudomemo.net
-
-## Building on Windows
-
-- Install Python 3.6+ (preferably 3.9). Make sure to install the x86 version for 32 bit targets. 
-
-- Install all requirements via the following command as an administrator
+### Install requirements
 
+```bash
+python -m pip install -r requirements.txt
 ```
+
+### Run
+
+Windows, from an Administrator terminal:
+
+```powershell
+python reximemoDNS.py
+```
+
+Linux/macOS:
+
+```bash
+sudo python3 reximemoDNS.py
+```
+
+When it starts, it prints the LAN address to enter on the DSi.
+
+## Configuration
+
+The defaults are already set for the current RexiMemo server, but they can be changed with environment variables:
+
+- `REXIMEMODNS_SERVER_IP` — RexiMemo legacy-service IPv4 address. Default: `141.147.76.115`
+- `REXIMEMODNS_UPSTREAM_DNS` — resolver used for all non-RexiMemo names. Default: `8.8.8.8`
+- `REXIMEMODNS_BIND_IP` — local interface/address on which to listen. By default, reximemoDNS detects the computer's LAN IPv4 address.
+- `REXIMEMODNS_PORT` — DNS listening port. Default: `53`
+
+Example:
+
+```bash
+REXIMEMODNS_SERVER_IP=141.147.76.115 REXIMEMODNS_UPSTREAM_DNS=1.1.1.1 sudo python3 reximemoDNS.py
+```
+
+On Windows PowerShell:
+
+```powershell
+$env:REXIMEMODNS_SERVER_IP="141.147.76.115"
+$env:REXIMEMODNS_UPSTREAM_DNS="1.1.1.1"
+python reximemoDNS.py
+```
+
+## Troubleshooting
+
+If the program cannot bind to port 53, run it as Administrator/root and make sure another DNS server is not already using that port.
+
+If no console requests appear in the log, check the computer firewall and confirm the DSi's Primary DNS exactly matches the address printed by reximemoDNS.
+
+If ordinary websites or the DSi connection test stop resolving while reximemoDNS is running, verify that `REXIMEMODNS_UPSTREAM_DNS` points to a reachable DNS resolver.
+
+For RexiMemo support, join the Discord server: **https://discord.gg/K5mKWvaruF**
+
+## Building a Windows executable
+
+Install Nuitka and its build dependencies:
+
+```powershell
 python -m pip install -r requirements.txt nuitka zstandard
 ```
 
-- Run the following (answer yes to any prompts):
+Then build:
 
-```shell
-python -m nuitka --standalone --onefile --windows-icon-from-ico=sudomemoDNS_icon.ico -o sudomemoDNS.exe sudomemoDNS.py
+```powershell
+python -m nuitka --standalone --onefile -o reximemoDNS.exe reximemoDNS.py
 ```
 
-- Run `sudomemoDNS.exe`
+No RexiMemo-specific icon is bundled in this source tree, so the executable uses the default application icon unless you supply one when building.
+
+## License and attribution
+
+reximemoDNS is derived from the open-source `sudomemoDNS` project by Austin Burk / Team Sudomemo. The original MIT copyright and license are preserved in `LICENSE`.
+
+See `NOTICE.md` for attribution and RexiMemo-specific changes.

requirements.txt

@@ -1,2 +1 @@
-requests
-dnslib
+dnslib>=0.9.24

reximemoDNS.py

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+# reximemoDNS
+#
+# RexiMemo adaptation of the MIT-licensed sudomemoDNS project.
+# See LICENSE and NOTICE.md for attribution.
+
+from datetime import datetime
+from ipaddress import IPv4Address, ip_address
+import os
+from socket import AF_INET, SOCK_DGRAM, socket
+from sys import platform
+from time import sleep
+
+from dnslib import A, DNSLabel, DNSRecord, QTYPE, RCODE, RR
+from dnslib.server import DNSServer
+
+
+REXIMEMODNS_VERSION = "1.0.0"
+DEFAULT_REXIMEMO_SERVER_IP = "141.147.76.115"
+DEFAULT_UPSTREAM_DNS = "8.8.8.8"
+
+# Keep this list aligned with RexiMemo's LOCAL_DNS_HOSTS in network_services.py.
+# conntest.nintendowifi.net is intentionally not intercepted.
+REXIMEMO_HOSTS = (
+    "nas.nintendowifi.net",
+    "flipnote.hatena.com",
+    "ugomemo.hatena.ne.jp",
+)
+
+
+def get_platform():
+    platforms = {
+        "linux": "Linux",
+        "linux1": "Linux",
+        "linux2": "Linux",
+        "darwin": "macOS",
+        "win32": "Windows",
+    }
+    return platforms.get(platform, platform)
+
+
+def format_ip(address):
+    """Format an IPv4 address the way Nintendo connection screens display it."""
+    octets = str(address).split(".")
+    return ".".join(f"{int(octet):03d}" for octet in octets)
+
+
+def _ipv4_env(name, default):
+    value = (os.environ.get(name) or default).strip()
+    try:
+        parsed = ip_address(value)
+    except ValueError as exc:
+        raise SystemExit(f"[ERROR] {name} must be a valid IPv4 address; got {value!r}") from exc
+    if not isinstance(parsed, IPv4Address):
+        raise SystemExit(f"[ERROR] {name} must be an IPv4 address; got {value!r}")
+    return str(parsed)
+
+
+def get_ip():
+    configured = (os.environ.get("REXIMEMODNS_BIND_IP") or "").strip()
+    if configured:
+        return _ipv4_env("REXIMEMODNS_BIND_IP", configured)
+
+    probe = socket(AF_INET, SOCK_DGRAM)
+    try:
+        # The destination does not need to be reachable. Connecting a UDP socket
+        # is only used to discover which local IPv4 address the OS would route.
+        probe.connect(("10.255.255.255", 1))
+        return probe.getsockname()[0]
+    except OSError:
+        return "127.0.0.1"
+    finally:
+        probe.close()
+
+
+def _port_env():
+    raw = (os.environ.get("REXIMEMODNS_PORT") or "53").strip()
+    try:
+        value = int(raw)
+    except ValueError as exc:
+        raise SystemExit(f"[ERROR] REXIMEMODNS_PORT must be a number; got {raw!r}") from exc
+    if not 1 <= value <= 65535:
+        raise SystemExit("[ERROR] REXIMEMODNS_PORT must be between 1 and 65535")
+    return value
+
+
+MY_IP = get_ip()
+REXIMEMO_SERVER_IP = _ipv4_env("REXIMEMODNS_SERVER_IP", DEFAULT_REXIMEMO_SERVER_IP)
+UPSTREAM_DNS = _ipv4_env("REXIMEMODNS_UPSTREAM_DNS", DEFAULT_UPSTREAM_DNS)
+DNS_PORT = _port_env()
+SERIAL = int((datetime.utcnow() - datetime(1970, 1, 1)).total_seconds())
+
+
+def _print_banner():
+    print("+===============================+")
+    print("|      RexiMemo DNS Server      |")
+    print(f"|         Version {REXIMEMODNS_VERSION:<13}|")
+    print("+===============================+\n")
+
+    print("== Welcome to reximemoDNS! ==")
+    print(
+        "This local DNS helper routes Flipnote Studio's Nintendo/Hatena service names "
+        "to RexiMemo while forwarding unrelated DNS normally.\n"
+    )
+
+    print("== How To Use ==")
+    print("First, make sure that your console is connected to the same network as this computer.\n")
+    print("Then, put these settings in for DNS on your console:")
+    print("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~")
+    print(f"Primary DNS:   {format_ip(MY_IP)}")
+    print(f"Secondary DNS: {format_ip(DEFAULT_UPSTREAM_DNS)}")
+    print("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n")
+
+    print("== RexiMemo Routing ==")
+    print(f"RexiMemo server: {REXIMEMO_SERVER_IP}")
+    for hostname in REXIMEMO_HOSTS:
+        print(f"  {hostname} -> {REXIMEMO_SERVER_IP}")
+    print(f"Other DNS queries -> {UPSTREAM_DNS}\n")
+
+    print("== Getting Help ==")
+    print("Join the RexiMemo Discord server: https://discord.gg/K5mKWvaruF\n")
+
+
+class RexiMemoDNSLogger(object):
+    def log_recv(self, handler, data):
+        pass
+
+    def log_send(self, handler, data):
+        pass
+
+    def log_request(self, handler, request):
+        qname = str(request.q.qname).rstrip(".")
+        qtype = QTYPE.get(request.q.qtype, str(request.q.qtype))
+        print(
+            "[INFO] DNS request from %s: %s %s"
+            % (handler.client_address[0], qtype, qname)
+        )
+
+    def log_reply(self, handler, reply):
+        answer_count = len(reply.rr)
+        print(
+            "[INFO] DNS response to %s: %d answer%s"
+            % (handler.client_address[0], answer_count, "" if answer_count == 1 else "s")
+        )
+
+    def log_error(self, handler, error):
+        print("[ERROR] Invalid DNS request from %s: %s" % (handler.client_address[0], error))
+
+    def log_truncated(self, handler, reply):
+        pass
+
+    def log_data(self, dnsobj):
+        pass
+
+
+class Resolver:
+    def __init__(self):
+        self.reximemo_names = {DNSLabel(name) for name in REXIMEMO_HOSTS}
+
+    def _reximemo_reply(self, request):
+        reply = request.reply()
+        # Mirror RexiMemo's own DNS behavior: A/ANY gets the legacy-service IPv4
+        # address. Other query types get an authoritative empty NOERROR response.
+        if request.q.qtype in (QTYPE.A, QTYPE.ANY):
+            reply.add_answer(
+                RR(
+                    rname=request.q.qname,
+                    rtype=QTYPE.A,
+                    rclass=1,
+                    ttl=0,
+                    rdata=A(REXIMEMO_SERVER_IP),
+                )
+            )
+        return reply
+
+    def _forward(self, request, handler):
+        try:
+            raw = request.send(
+                UPSTREAM_DNS,
+                53,
+                tcp=(getattr(handler, "protocol", "udp") == "tcp"),
+                timeout=3,
+            )
+            reply = DNSRecord.parse(raw)
+            # Never relay a mismatched DNS transaction as if it answered this query.
+            if reply.header.id != request.header.id:
+                raise ValueError("upstream DNS transaction ID mismatch")
+            return reply
+        except Exception as exc:
+            print(f"[ERROR] Upstream DNS lookup via {UPSTREAM_DNS} failed: {exc}")
+            reply = request.reply()
+            reply.header.rcode = RCODE.SERVFAIL
+            return reply
+
+    def resolve(self, request, handler):
+        if request.q.qname in self.reximemo_names:
+            return self._reximemo_reply(request)
+        return self._forward(request, handler)
+
+
+def main():
+    _print_banner()
+    print("[INFO] Starting reximemoDNS...")
+    print("[INFO] Detected operating system:", get_platform())
+
+    current_platform = get_platform()
+    if current_platform in {"Linux", "macOS"}:
+        print("[INFO] DNS uses UDP/TCP port 53, so this normally must run as root.")
+        print("[INFO] If no requests appear, also check whether another service is already using port 53.")
+    elif current_platform == "Windows":
+        print("[INFO] Windows may ask you to allow reximemoDNS through the firewall.")
+
+    resolver = Resolver()
+    logger = RexiMemoDNSLogger()
+
+    try:
+        servers = [
+            DNSServer(resolver=resolver, port=DNS_PORT, address=MY_IP, tcp=True, logger=logger),
+            DNSServer(resolver=resolver, port=DNS_PORT, address=MY_IP, tcp=False, logger=logger),
+        ]
+    except PermissionError:
+        print("[ERROR] Permission denied while opening DNS port. Run as Administrator/root.")
+        raise SystemExit(1)
+    except OSError as exc:
+        print(f"[ERROR] Could not bind DNS server to {MY_IP}:{DNS_PORT}: {exc}")
+        raise SystemExit(1)
+
+    print(f"[INFO] reximemoDNS is ready on {MY_IP}:{DNS_PORT} (UDP/TCP).")
+    print("[INFO] Waiting for DNS requests from your console...")
+
+    for server in servers:
+        server.start_thread()
+
+    try:
+        while True:
+            sleep(0.1)
+    except KeyboardInterrupt:
+        print("\n[INFO] Stopping reximemoDNS...")
+    finally:
+        for server in servers:
+            server.stop()
+
+
+if __name__ == "__main__":
+    main()