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Add an LLMNR responder implementation (#2880)

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This is a simple implementation of an LLMNR responder for the ESP8266
Arduino package. Only support for advertizing a single hostname is
currently implemented.

LLMNR is a very similar protocol to MDNS. The primary practical
difference is that Windows systems (at least Windows 7 and later;
perhaps earlier) support the protocol out-of-the-box, whereas additional
software is required to support MDNS. However, Linux support is
currently more complex, and MacOS X support appears non-existent.
This commit is contained in:
Stephen Warren 2017-02-20 20:18:49 -07:00 committed by Ivan Grokhotkov
parent d2b370b22d
commit 04df3adb54
5 changed files with 568 additions and 0 deletions
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281
libraries/ESP8266LLMNR/ESP8266LLMNR.cpp Normal file
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/*
* ESP8266 LLMNR responder
* Copyright (C) 2017 Stephen Warren <swarren@wwwdotorg.org>
*
* Based on:
* ESP8266 Multicast DNS (port of CC3000 Multicast DNS library)
* Version 1.1
* Copyright (c) 2013 Tony DiCola (tony@tonydicola.com)
* ESP8266 port (c) 2015 Ivan Grokhotkov (ivan@esp8266.com)
* MDNS-SD Suport 2015 Hristo Gochkov
* Extended MDNS-SD support 2016 Lars Englund (lars.englund@gmail.com)
*
* License (MIT license):
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*
* Reference:
* https://tools.ietf.org/html/rfc4795 (LLMNR)
* https://tools.ietf.org/html/rfc1035 (DNS)
*/
#include <debug.h>
#include <functional>
#include <ESP8266LLMNR.h>
#include <WiFiUdp.h>
extern "C" {
#include <user_interface.h>
}
#include <lwip/udp.h>
#include <lwip/igmp.h>
#include <include/UdpContext.h>
//#define LLMNR_DEBUG
#define BIT(x) (1 << (x))
#define FLAGS_QR BIT(15)
#define FLAGS_OP_SHIFT 11
#define FLAGS_OP_MASK 0xf
#define FLAGS_C BIT(10)
#define FLAGS_TC BIT(9)
#define FLAGS_T BIT(8)
#define FLAGS_RCODE_SHIFT 0
#define FLAGS_RCODE_MASK 0xf
#define _conn_read16() (((uint16_t)_conn->read() << 8) | _conn->read())
#define _conn_read8() _conn->read()
#define _conn_readS(b, l) _conn->read((b), (l));
static const IPAddress LLMNR_MULTICAST_ADDR(224, 0, 0, 252);
static const int LLMNR_MULTICAST_TTL = 1;
static const int LLMNR_PORT = 5355;
LLMNRResponder::LLMNRResponder() :
_conn(0) {
}
LLMNRResponder::~LLMNRResponder() {
if (_conn)
_conn->unref();
}
bool LLMNRResponder::begin(const char* hostname) {
// Max length for a single label in DNS
if (strlen(hostname) > 63)
return false;
_hostname = hostname;
_hostname.toLowerCase();
_sta_got_ip_handler = WiFi.onStationModeGotIP([this](const WiFiEventStationModeGotIP& event){
_restart();
});
_sta_disconnected_handler = WiFi.onStationModeDisconnected([this](const WiFiEventStationModeDisconnected& event) {
_restart();
});
return _restart();
}
void LLMNRResponder::notify_ap_change() {
_restart();
}
bool LLMNRResponder::_restart() {
if (_conn) {
_conn->unref();
_conn = 0;
}
ip_addr_t multicast_addr;
multicast_addr.addr = (uint32_t)LLMNR_MULTICAST_ADDR;
if (igmp_joingroup(IP_ADDR_ANY, &multicast_addr) != ERR_OK)
return false;
_conn = new UdpContext;
_conn->ref();
if (!_conn->listen(*IP_ADDR_ANY, LLMNR_PORT))
return false;
_conn->setMulticastTTL(LLMNR_MULTICAST_TTL);
_conn->onRx(std::bind(&LLMNRResponder::_process_packet, this));
_conn->connect(multicast_addr, LLMNR_PORT);
}
void LLMNRResponder::_process_packet() {
if (!_conn || !_conn->next())
return;
#ifdef LLMNR_DEBUG
Serial.println("LLMNR: RX'd packet");
#endif
uint16_t id = _conn_read16();
uint16_t flags = _conn_read16();
uint16_t qdcount = _conn_read16();
uint16_t ancount = _conn_read16();
uint16_t nscount = _conn_read16();
uint16_t arcount = _conn_read16();
#ifdef LLMNR_DEBUG
Serial.print("LLMNR: ID=");
Serial.println(id, HEX);
Serial.print("LLMNR: FLAGS=");
Serial.println(flags, HEX);
Serial.print("LLMNR: QDCOUNT=");
Serial.println(qdcount);
Serial.print("LLMNR: ANCOUNT=");
Serial.println(ancount);
Serial.print("LLMNR: NSCOUNT=");
Serial.println(nscount);
Serial.print("LLMNR: ARCOUNT=");
Serial.println(arcount);
#endif
#define BAD_FLAGS (FLAGS_QR | (FLAGS_OP_MASK << FLAGS_OP_SHIFT) | FLAGS_C)
if (flags & BAD_FLAGS) {
#ifdef LLMNR_DEBUG
Serial.println("Bad flags");
#endif
return;
}
if (qdcount != 1) {
#ifdef LLMNR_DEBUG
Serial.println("QDCOUNT != 1");
#endif
return;
}
if (ancount || nscount || arcount) {
#ifdef LLMNR_DEBUG
Serial.println("AN/NS/AR-COUNT != 0");
#endif
return;
}
uint8_t namelen = _conn_read8();
#ifdef LLMNR_DEBUG
Serial.print("QNAME len ");
Serial.println(namelen);
#endif
if (namelen != _hostname.length()) {
#ifdef LLMNR_DEBUG
Serial.println("QNAME len mismatch");
#endif
return;
}
char qname[64];
_conn_readS(qname, namelen);
_conn_read8();
qname[namelen] = '\0';
#ifdef LLMNR_DEBUG
Serial.print("QNAME ");
Serial.println(qname);
#endif
if (strcmp(_hostname.c_str(), qname)) {
#ifdef LLMNR_DEBUG
Serial.println("QNAME mismatch");
#endif
return;
}
uint16_t qtype = _conn_read16();
uint16_t qclass = _conn_read16();
#ifdef LLMNR_DEBUG
Serial.print("QTYPE ");
Serial.print(qtype);
Serial.print(" QCLASS ");
Serial.println(qclass);
#endif
bool have_rr =
(qtype == 1) && /* A */
(qclass == 1); /* IN */
_conn->flush();
#ifdef LLMNR_DEBUG
Serial.println("Match; responding");
if (!have_rr)
Serial.println("(no matching RRs)");
#endif
struct ip_info remote_ip_info;
remote_ip_info.ip.addr = _conn->getRemoteAddress();
struct ip_info ip_info;
bool match_ap = false;
if (wifi_get_opmode() & SOFTAP_MODE) {
wifi_get_ip_info(SOFTAP_IF, &ip_info);
if (ip_info.ip.addr && ip_addr_netcmp(&remote_ip_info.ip, &ip_info.ip, &ip_info.netmask))
match_ap = true;
}
if (!match_ap)
wifi_get_ip_info(STATION_IF, &ip_info);
uint32_t ip = ip_info.ip.addr;
// Header
uint8_t header[] = {
id >> 8, id & 0xff, // ID
FLAGS_QR >> 8, 0, // FLAGS
0, 1, // QDCOUNT
0, !!have_rr, // ANCOUNT
0, 0, // NSCOUNT
0, 0, // ARCOUNT
};
_conn->append(reinterpret_cast<const char*>(header), sizeof(header));
// Question
_conn->append(reinterpret_cast<const char*>(&namelen), 1);
_conn->append(qname, namelen);
uint8_t q[] = {
0, // Name terminator
0, 1, // TYPE (A)
0, 1, // CLASS (IN)
};
_conn->append(reinterpret_cast<const char*>(q), sizeof(q));
// Answer, if we have one
if (have_rr) {
_conn->append(reinterpret_cast<const char*>(&namelen), 1);
_conn->append(qname, namelen);
uint8_t rr[] = {
0, // Name terminator
0, 1, // TYPE (A)
0, 1, // CLASS (IN)
0, 0, 0, 30, // TTL (30 seconds)
0, 4, // RDLENGTH
ip & 0xff, (ip >> 8) & 0xff, (ip >> 16) & 0xff, (ip >> 24) & 0xff, // RDATA
};
_conn->append(reinterpret_cast<const char*>(rr), sizeof(rr));
}
_conn->setMulticastInterface(remote_ip_info.ip);
_conn->send(&remote_ip_info.ip, _conn->getRemotePort());
}
#if !defined(NO_GLOBAL_INSTANCES) && !defined(NO_GLOBAL_LLMNR)
LLMNRResponder LLMNR;
#endif

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libraries/ESP8266LLMNR/ESP8266LLMNR.h Normal file
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/*
* ESP8266 LLMNR responder
* Copyright (C) 2017 Stephen Warren <swarren@wwwdotorg.org>
*
* Based on:
* ESP8266 Multicast DNS (port of CC3000 Multicast DNS library)
* Version 1.1
* Copyright (c) 2013 Tony DiCola (tony@tonydicola.com)
* ESP8266 port (c) 2015 Ivan Grokhotkov (ivan@esp8266.com)
* MDNS-SD Suport 2015 Hristo Gochkov
* Extended MDNS-SD support 2016 Lars Englund (lars.englund@gmail.com)
*
* License (MIT license):
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#ifndef ESP8266LLMNR_H
#define ESP8266LLMNR_H
#include <ESP8266WiFi.h>
class UdpContext;
class LLMNRResponder {
public:
LLMNRResponder();
~LLMNRResponder();
/* Initialize and start responding to LLMNR requests on all interfaces */
bool begin(const char* hostname);
/* Application should call this whenever AP is configured/disabled */
void notify_ap_change();
private:
String _hostname;
UdpContext *_conn;
WiFiEventHandler _sta_got_ip_handler;
WiFiEventHandler _sta_disconnected_handler;
bool _restart();
void _process_packet();
};
#if !defined(NO_GLOBAL_INSTANCES) && !defined(NO_GLOBAL_LLMNR)
extern LLMNRResponder LLMNR;
#endif
#endif

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ESP8266 LLMNR (Link-Local Multicast Name Resolution)
====================================================
This is a simple implementation of an LLMNR responder the ESP8266 Arduino
package. Only support for advertizing a single hostname is currently
implemented.
LLMNR is a very similar protocol to MDNS. The primary practical difference is
that Windows systems (at least Windows 7 and later; perhaps earlier) support
the protocol out-of-the-box, whereas additional software is required to support
MDNS. However, Linux support is currently more complex, and MacOS X support
appears non-existent.
Requirements
------------
- ESP8266WiFi library
- LLMNR support in your operating system/client machines:
- For Windows, support is already built in (in Windows 7 at least).
- For Linux, the systemd-resolve application supports LLMNR.
- For Mac OSX: Unknown; likely not supported.
Usage
-----
1. Install this repository using the instructions in the top-levle README.md
file.
2. Include the ESP8266LLMNR library in the sketch.
3. Call the LLMNR.begin() method in the sketch's setup() function, and provide
the hostname to advertize. This should not include any ".local" prefix.
4. If ESP8266 AP mode is enabled, disabled, or the WiFi or AP configuration is
changed, call LLMNR.notify_ap_change() after the change is made.
See the included LLMNR + HTTP server sketch for a full example.
References
----------
1. https://tools.ietf.org/html/rfc4795 (LLMNR)
2. https://tools.ietf.org/html/rfc1035 (DNS)
Caveats
-------
1. LLMNR implementations MUST support EDNS0 [RFC2671] and extended RCODE
values. It is likely that this implementation does not; I have not read
that RFC.
2. LLMNR responders MUST support listening for TCP queries. This implementation
does not.
3. On receiving an LLMNR query, the responder MUST check whether it was sent to
an LLMNR multicast addresses defined in Section 2. If it was sent to another
multicast address, then the query MUST be silently discarded. This
implementation makes no such check; it is hoped that the ESP8266 network
stack filters out such packets since the code only joins the relevant
multicast group and does not listen for unicast packets. This assumption may
be invalid.
4. Prior to sending an LLMNR response with the 'T' bit clear, a responder
configured with a UNIQUE name MUST verify that there is no other host within
the scope of LLMNR query propagation that is authoritative for the same name
on that interface. This implementation performs no such verification.
5. Prior to verifying that its name is UNIQUE, a responder MUST set the 'T' bit
in responses. This implementation does not; it assumes that name is unique
and responds with the 'T' bit clear in all cases.
6. To verify uniqueness, a responder MUST send an LLMNR query with the 'C' bit
clear, over all protocols on which it responds to LLMNR queries (IPv4 and/or
IPv6). This implementation does not.
License
-------
Copyright (C) 2017 Stephen Warren <swarren@wwwdotorg.org>
Based on:
ESP8266 Multicast DNS (port of CC3000 Multicast DNS library)
Version 1.1
Copyright (c) 2013 Tony DiCola (tony@tonydicola.com)
ESP8266 port (c) 2015 Ivan Grokhotkov (ivan@esp8266.com)
MDNS-SD Suport 2015 Hristo Gochkov
Extended MDNS-SD support 2016 Lars Englund (lars.englund@gmail.com)
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

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libraries/ESP8266LLMNR/examples/LLMNR_Web_Server/LLMNR_Web_Server.ino Normal file
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/*
* ESP8266 LLMNR responder sample
* Copyright (C) 2017 Stephen Warren <swarren@wwwdotorg.org>
*
* Based on:
* ESP8266 Multicast DNS (port of CC3000 Multicast DNS library)
* Version 1.1
* Copyright (c) 2013 Tony DiCola (tony@tonydicola.com)
* ESP8266 port (c) 2015 Ivan Grokhotkov (ivan@esp8266.com)
* MDNS-SD Suport 2015 Hristo Gochkov
* Extended MDNS-SD support 2016 Lars Englund (lars.englund@gmail.com)
*
* License (MIT license):
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*
*/
/*
* This is an example of an HTTP server that is accessible via http://esp8266/
* (or perhaps http://esp8266.local/) thanks to the LLMNR responder.
*
* Instructions:
* - Update WiFi SSID and password as necessary.
* - Flash the sketch to the ESP8266 board.
* - Windows:
* - No additional software is necessary.
* - Point your browser to http://esp8266/, you should see a response. In most
* cases, it is important that you manually type the "http://" to force the
* browser to search for a hostname to connect to, rather than perform a web
* search.
* - Alternatively, run the following command from the command prompt:
* ping esp8266
* - Linux:
* - To validate LLMNR, install the systemd-resolve utility.
* - Execute the following command:
* systemd-resolve -4 -p llmnr esp8266
* - It may be possible to configure your system to use LLMNR for all name
* lookups. However, that is beyond the scope of this description.
*
*/
#include <ESP8266WiFi.h>
#include <ESP8266LLMNR.h>
#include <ESP8266WebServer.h>
#include <WiFiClient.h>
const char* ssid = "replace_me";
const char* password = "replace_me";
ESP8266WebServer web_server(80);
void handle_http_not_found() {
web_server.send(404, "text/plain", "Not Found");
}
void handle_http_root() {
web_server.send(200, "text/plain", "It works!");
}
void setup(void) {
Serial.begin(115200);
// Connect to WiFi network
WiFi.begin(ssid, password);
Serial.println("");
// Wait for connection
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.print("Connected to ");
Serial.println(ssid);
Serial.print("IP address: ");
Serial.println(WiFi.localIP());
// Start LLMNR responder
LLMNR.begin("esp8266");
Serial.println("LLMNR responder started");
// Start HTTP server
web_server.onNotFound(handle_http_not_found);
web_server.on("/", handle_http_root);
web_server.begin();
Serial.println("HTTP server started");
}
void loop(void) {
web_server.handleClient();
}

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#######################################
# Syntax Coloring Map For Ultrasound
#######################################
#######################################
# Datatypes (KEYWORD1)
#######################################
ESP8266LLMNR KEYWORD1
LLMNRResponder KEYWORD1
LLMNR KEYWORD1
#######################################
# Methods and Functions (KEYWORD2)
#######################################
begin KEYWORD2
notify_ap_change KEYWORD2
#######################################
# Constants (LITERAL1)
#######################################