/*
* © 2024 Harald Barth
* © 2024 Paul M. Antoine
* All rights reserved.
*
* This file is part of CommandStation-EX
*
* This is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* It is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with CommandStation. If not, see <https://www.gnu.org/licenses/>.
*/
#include <Arduino.h>
#include "EthernetInterface.h"
#ifdef DO_MDNS
#include "EXmDNS.h"
// fixed values for mDNS
static IPAddress mdnsMulticastIPAddr = IPAddress(224, 0, 0, 251);
#define MDNS_SERVER_PORT 5353
// dotToLen()
// converts stings of form ".foo.barbar.x" to a string with the
// dots replaced with lenght. So string above would result in
// "\x03foo\x06barbar\x01x" in C notation. If not NULL, *substr
// will point to the beginning of the last component, in this
// example that would be "\x01x".
//
static void dotToLen(char *str, char **substr) {
char *dotplace = NULL;
char *s;
byte charcount = 0;
for (s = str;/*see break*/ ; s++) {
if (*s == '.' || *s == '\0') {
// take care of accumulated
if (dotplace != NULL && charcount != 0) {
*dotplace = charcount;
}
if (*s == '\0')
break;
if (substr && *s == '.')
*substr = s;
// set new values
dotplace = s;
charcount = 0;
} else {
charcount++;
}
}
}
MDNS::MDNS(EthernetUDP& udp) {
_udp = &udp;
}
MDNS::~MDNS() {
_udp->stop();
if (_name) free(_name);
if (_serviceName) free(_serviceName);
if (_serviceProto) free(_serviceProto);
}
int MDNS::begin(const IPAddress& ip, char* name) {
// if we were called very soon after the board was booted, we need to give the
// EthernetShield (WIZnet) some time to come up. Hence, we delay until millis() is at
// least 3000. This is necessary, so that if we need to add a service record directly
// after begin, the announce packet does not get lost in the bowels of the WIZnet chip.
//while (millis() < 3000)
// delay(100);
_ipAddress = ip;
_name = (char *)malloc(strlen(name)+2);
byte n;
for(n = 0; n<strlen(name); n++)
_name[n+1] = name[n];
_name[n+1] = '\0';
_name[0] = '.';
dotToLen(_name, NULL);
return _udp->beginMulticast(mdnsMulticastIPAddr, MDNS_SERVER_PORT);
}
int MDNS::addServiceRecord(const char* name, uint16_t port, MDNSServiceProtocol_t proto) {
// we ignore proto, assume TCP
(void)proto;
_serviceName = (char *)malloc(strlen(name) + 2);
byte n;
for(n = 0; n<strlen(name); n++)
_serviceName[n+1] = name[n];
_serviceName[n+1] = '\0';
_serviceName[0] = '.';
_serviceProto = NULL; //to be filled in
dotToLen(_serviceName, &_serviceProto);
_servicePort = port;
return 1;
}
static char dns_rr_services[] = "\x09_services\x07_dns-sd\x04_udp\x05local";
static char dns_rr_tcplocal[] = "\x04_tcp\x05local";
static char *dns_rr_local = dns_rr_tcplocal + dns_rr_tcplocal[0] + 1;
typedef struct _DNSHeader_t
{
uint16_t xid;
uint16_t flags; // flags condensed
uint16_t queryCount;
uint16_t answerCount;
uint16_t authorityCount;
uint16_t additionalCount;
} __attribute__((__packed__)) DNSHeader_t;
//
// MDNS::run()
// This broadcasts whatever we got evey BROADCASTTIME seconds.
// Why? Too much brokenness i all mDNS implementations available
//
void MDNS::run() {
static long int lastrun = BROADCASTTIME * 1000UL;
unsigned long int now = millis();
if (!(now - lastrun > BROADCASTTIME * 1000UL)) {
return;
}
lastrun = now;
DNSHeader_t dnsHeader = {0, 0, 0, 0, 0, 0};
// DNSHeader_t dnsHeader = { 0 };
_udp->beginPacket(mdnsMulticastIPAddr, MDNS_SERVER_PORT);
// dns header
dnsHeader.flags = HTONS((uint16_t)0x8400); // Response, authorative
dnsHeader.answerCount = HTONS(4 /*5 if TXT but we do not do that */);
_udp->write((uint8_t*)&dnsHeader, sizeof(DNSHeader_t));
// rr #1, the PTR record from generic _services.x.local to service.x.local
_udp->write((uint8_t*)dns_rr_services, sizeof(dns_rr_services));
byte buf[10];
buf[0] = 0x00;
buf[1] = 0x0c; //PTR
buf[2] = 0x00;
buf[3] = 0x01; //IN
*((uint32_t*)(buf+4)) = HTONL(120); //TTL in sec
*((uint16_t*)(buf+8)) = HTONS( _serviceProto[0] + 1 + strlen(dns_rr_tcplocal) + 1);
_udp->write(buf, 10);
_udp->write(_serviceProto,_serviceProto[0]+1);
_udp->write(dns_rr_tcplocal, strlen(dns_rr_tcplocal)+1);
// rr #2, the PTR record from proto.x to name.proto.x
_udp->write(_serviceProto,_serviceProto[0]+1);
_udp->write(dns_rr_tcplocal, strlen(dns_rr_tcplocal)+1);
*((uint16_t*)(buf+8)) = HTONS(strlen(_serviceName) + strlen(dns_rr_tcplocal) + 1); // recycle most of buf
_udp->write(buf, 10);
_udp->write(_serviceName, strlen(_serviceName));
_udp->write(dns_rr_tcplocal, strlen(dns_rr_tcplocal)+1);
// rr #3, the SRV record for the service that points to local name
_udp->write(_serviceName, strlen(_serviceName));
_udp->write(dns_rr_tcplocal, strlen(dns_rr_tcplocal)+1);
buf[1] = 0x21; // recycle most of buf but here SRV
buf[2] = 0x80; // cache flush
*((uint16_t*)(buf+8)) = HTONS(strlen(_name) + strlen(dns_rr_local) + 1 + 6);
_udp->write(buf, 10);
byte srv[6];
// priority and weight
srv[0] = srv[1] = srv[2] = srv[3] = 0;
// port
*((uint16_t*)(srv+4)) = HTONS(_servicePort);
_udp->write(srv, 6);
// target
_udp->write(_name, _name[0]+1);
_udp->write(dns_rr_local, strlen(dns_rr_local)+1);
// rr #4, the A record for the name.local
_udp->write(_name, _name[0]+1);
_udp->write(dns_rr_local, strlen(dns_rr_local)+1);
buf[1] = 0x01; // recycle most of buf but here A
*((uint16_t*)(buf+8)) = HTONS(4);
_udp->write(buf, 10);
byte ip[4];
ip[0] = _ipAddress[0];
ip[1] = _ipAddress[1];
ip[2] = _ipAddress[2];
ip[3] = _ipAddress[3];
_udp->write(ip, 4);
_udp->endPacket();
_udp->flush();
//
}
#endif //DO_MDNS