Add an LLMNR responder implementation

libraries/ESP8266LLMNR/ESP8266LLMNR.cpp

@@ -0,0 +1,281 @@
+/*
+ * ESP8266 LLMNR responder
+ * Copyright (C) 2017 Stephen Warren <[email protected]>
+ *
+ * Based on:
+ * ESP8266 Multicast DNS (port of CC3000 Multicast DNS library)
+ * Version 1.1
+ * Copyright (c) 2013 Tony DiCola ([email protected])
+ * ESP8266 port (c) 2015 Ivan Grokhotkov ([email protected])
+ * MDNS-SD Suport 2015 Hristo Gochkov
+ * Extended MDNS-SD support 2016 Lars Englund ([email protected])
+ *
+ * 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

libraries/ESP8266LLMNR/ESP8266LLMNR.h

@@ -0,0 +1,66 @@
+/*
+ * ESP8266 LLMNR responder
+ * Copyright (C) 2017 Stephen Warren <[email protected]>
+ *
+ * Based on:
+ * ESP8266 Multicast DNS (port of CC3000 Multicast DNS library)
+ * Version 1.1
+ * Copyright (c) 2013 Tony DiCola ([email protected])
+ * ESP8266 port (c) 2015 Ivan Grokhotkov ([email protected])
+ * MDNS-SD Suport 2015 Hristo Gochkov
+ * Extended MDNS-SD support 2016 Lars Englund ([email protected])
+ *
+ * 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