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Feature/mdnsresponder (#348)

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Basic multicast-DNS service discovery responder
This commit is contained in:
Michael Hamel 2017-04-26 02:00:09 +12:00 committed by Ruslan V. Uss
parent c90362621a
commit 4b0acbe8bf
3 changed files with 858 additions and 0 deletions
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extras/mdnsresponder/component.mk Normal file
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# Component makefile for extras/mdnsresponder
INC_DIRS += $(mdnsresponder_ROOT)
# args for passing into compile rule generation
mdnsresponder_INC_DIR = $(mdnsresponder_ROOT)
mdnsresponder_SRC_DIR = $(mdnsresponder_ROOT)
$(eval $(call component_compile_rules,mdnsresponder))

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extras/mdnsresponder/mdnsresponder.c Normal file
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/*
* Basic multicast DNS responder
*
* Advertises the IP address, port, and characteristics of a service to other devices using multicast DNS on the same LAN,
* so they can find devices with addresses dynamically allocated by DHCP. See avahi, Bonjour, etc
* See RFC6762, RFC6763
*
* This sample code is in the public domain.
*
* by M J A Hamel 2016
*/
#include <espressif/esp_common.h>
#include <espressif/esp_wifi.h>
#include <string.h>
#include <stdio.h>
#include <FreeRTOS.h>
#include <task.h>
#include <lwip/err.h>
#include <lwip/sockets.h>
#include <lwip/sys.h>
#include <lwip/netdb.h>
#include <lwip/dns.h>
#include <lwip/udp.h>
#include <lwip/igmp.h>
#include <lwip/netif.h>
#include "mdnsresponder.h"
#define qDebugLog // Log activity generally
#define qLogIncoming // Log all arriving multicast packets
#define qLogAllTraffic // Log and decode all mDNS packets
#define kMDNSStackSize 800
#define DNS_MULTICAST_ADDRESS "224.0.0.251" // RFC 6762
#define DNS_MDNS_PORT 5353 // RFC 6762
//-------------------------------------------------------------------
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
/** DNS message header */
struct mdns_hdr {
PACK_STRUCT_FIELD(u16_t id);
PACK_STRUCT_FIELD(u8_t flags1);
PACK_STRUCT_FIELD(u8_t flags2);
PACK_STRUCT_FIELD(u16_t numquestions);
PACK_STRUCT_FIELD(u16_t numanswers);
PACK_STRUCT_FIELD(u16_t numauthrr);
PACK_STRUCT_FIELD(u16_t numextrarr);
}PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#define SIZEOF_DNS_HDR 12
PACK_STRUCT_BEGIN
/** MDNS query message structure */
struct mdns_query {
/* MDNS query record starts with either a domain name or a pointer
to a name already present somewhere in the packet. */
PACK_STRUCT_FIELD(u16_t type);
PACK_STRUCT_FIELD(u16_t class);
}PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#define SIZEOF_DNS_QUERY 4
PACK_STRUCT_BEGIN
/** MDNS answer message structure */
struct mdns_answer {
/* MDNS answer record starts with either a domain name or a pointer
to a name already present somewhere in the packet. */
PACK_STRUCT_FIELD(u16_t type);
PACK_STRUCT_FIELD(u16_t class);
PACK_STRUCT_FIELD(u32_t ttl);
PACK_STRUCT_FIELD(u16_t len);
}PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#define SIZEOF_DNS_ANSWER 10
PACK_STRUCT_BEGIN
struct mdns_rr_srv {
/* RR SRV */
PACK_STRUCT_FIELD(u16_t prio);
PACK_STRUCT_FIELD(u16_t weight);
PACK_STRUCT_FIELD(u16_t port);
}PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#define SIZEOF_DNS_RR_SRV 6
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/epstruct.h"
#endif
#define vTaskDelayMs(ms) vTaskDelay((ms)/portTICK_PERIOD_MS)
#define UNUSED_ARG(x) (void)x
#define kDummyDataSize 8 // arbitrary, dynamically resized
#define kMaxNameSize 64
#define kMaxQStr 128 // max incoming question key handled
typedef struct mdns_rsrc {
struct mdns_rsrc* rNext;
u16_t rType;
u32_t rTTL;
u16_t rKeySize;
u16_t rDataSize;
char rData[kDummyDataSize]; // Key, as C str with . seperators, followed by data in network-ready form
// at rData[rKeySize]
} mdns_rsrc;
static struct udp_pcb* gMDNS_pcb = NULL;
static ip_addr_t gMulticastAddr; // == DNS_MULTICAST_ADDRESS
static mdns_rsrc* gDictP = NULL; // RR database, linked list
//---------------------- Debug/logging utilities -------------------------
#ifdef qDebugLog
// DNS field TYPE used for "Resource Records", some additions
#define DNS_RRTYPE_AAAA 28 /* IPv6 host address */
#define DNS_RRTYPE_SRV 33 /* Service record */
#define DNS_RRTYPE_OPT 41 /* EDNS0 OPT record */
#define DNS_RRTYPE_NSEC 47 /* NSEC record */
#define DNS_RRTYPE_TSIG 250 /* Transaction Signature */
#define DNS_RRTYPE_ANY 255 /* Not a DNS type, but a DNS query type, meaning "all types"*/
// DNS field CLASS used for "Resource Records"
#define DNS_RRCLASS_ANY 255 /* Any class (q) */
#define DNS_FLAG1_RESP 0x80
#define DNS_FLAG1_OPMASK 0x78
#define DNS_FLAG1_AUTH 0x04
#define DNS_FLAG1_TRUNC 0x02
#define DNS_FLAG1_RD 0x01
#define DNS_FLAG2_RA 0x80
#define DNS_FLAG2_RESMASK 0x0F
static char qstr[12];
static char* mdns_qrtype(uint16_t typ)
{
switch(typ) {
case DNS_RRTYPE_A : return ("A");
case DNS_RRTYPE_NS : return ("NS");
case DNS_RRTYPE_PTR : return ("PTR");
case DNS_RRTYPE_TXT : return ("TXT ");
case DNS_RRTYPE_AAAA : return ("AAAA");
case DNS_RRTYPE_SRV : return ("SRV ");
case DNS_RRTYPE_NSEC : return ("NSEC ");
case DNS_RRTYPE_ANY : return ("ANY");
}
sprintf(qstr,"type %d",typ);
return qstr;
}
#ifdef qLogAllTraffic
static void mdns_printhex(u8_t* p, int n)
{
int i;
for (i=0; i<n; i++) {
printf("%02X ",*p++);
if ((i % 32) == 31) printf("\n");
}
printf("\n");
}
static void mdns_print_pstr(u8_t* p)
{
int i, n;
char* cp;
n = *p++;
cp = (char*)p;
for (i=0; i<n; i++) putchar(*cp++);
}
static char cstr[16];
static char* mdns_qclass(uint16_t cls)
{
switch(cls) {
case DNS_RRCLASS_IN : return ("In");
case DNS_RRCLASS_ANY : return ("ANY");
}
sprintf(cstr,"class %d",cls);
return cstr;
}
static u8_t* mdns_print_name(u8_t* p, struct mdns_hdr* hp)
// Sequence of Pascal strings, terminated by zero-length string
// Handles compression, returns ptr to next item
{
char* cp = (char*)p;
int i, n;
do {
n = *cp++;
if ((n & 0xC0) == 0xC0) {
n = (n & 0x3F) << 8;
n |= (u8_t)*cp++;
mdns_print_name( (u8_t*)hp + n ,hp );
n = 0;
} else if (n & 0xC0) {
printf("<label $%X?>",n);
n = 0;
} else {
for (i=0; i<n; i++)
putchar(*cp++);
if (n!=0) putchar('.');
}
} while (n>0);
return (u8_t*)cp;
}
static u8_t* mdns_print_header(struct mdns_hdr* hdr)
{
if (hdr->flags1 & DNS_FLAG1_RESP) {
printf("Response, ID $%X %s ", htons(hdr->id), (hdr->flags1 & DNS_FLAG1_AUTH) ? "Auth " : "Non-auth ");
if (hdr->flags2 & DNS_FLAG2_RA) printf("RA ");
if ((hdr->flags2 & DNS_FLAG2_RESMASK)==0) printf("noerr");
else printf("err %d", hdr->flags2 & DNS_FLAG2_RESMASK);
} else {
printf("Query, ID $%X op %d", htons(hdr->id), (hdr->flags1>>4) & 0x7 );
}
if (hdr->flags1 & DNS_FLAG1_RD) printf("RD ");
if (hdr->flags1 & DNS_FLAG1_TRUNC) printf("[TRUNC] ");
printf(": %d questions", htons(hdr->numquestions) );
if (hdr->numanswers != 0)
printf(", %d answers",htons(hdr->numanswers));
if (hdr->numauthrr != 0)
printf(", %d auth RR",htons(hdr->numauthrr));
if (hdr->numextrarr != 0)
printf(", %d extra RR",htons(hdr->numextrarr));
putchar('\n');
return (u8_t*)hdr + SIZEOF_DNS_HDR;
}
static u8_t* mdns_print_query(u8_t* p)
// Copy needed because it may be misaligned
{
struct mdns_query q;
uint16_t c;
memcpy(&q,p,SIZEOF_DNS_QUERY);
c = htons(q.class);
printf(" %s %s", mdns_qrtype(htons(q.type)), mdns_qclass(c & 0x7FFF) );
if (c & 0x8000) printf(" unicast-req");
printf("\n");
return p + SIZEOF_DNS_QUERY;
}
static u8_t* mdns_print_answer(u8_t* p, struct mdns_hdr* hp)
// Copy needed because it may be misaligned
{
struct mdns_answer ans;
u16_t rrlen, atype, rrClass;;
memcpy(&ans,p,SIZEOF_DNS_ANSWER);
atype = htons(ans.type);
rrlen = htons(ans.len);
rrClass = htons(ans.class);
printf(" %s %s TTL %d ", mdns_qrtype(atype), mdns_qclass(rrClass & 0x7FFF), htonl(ans.ttl));
if (rrClass & 0x8000)
printf("cache-flush ");
if (rrlen > 0) {
u8_t* rp = p + SIZEOF_DNS_ANSWER;
if (atype==DNS_RRTYPE_A && rrlen==4) {
printf("%d.%d.%d.%d\n",rp[0],rp[1],rp[2],rp[3]);
} else if (atype==DNS_RRTYPE_PTR) {
mdns_print_name(rp, hp);
printf("\n");
} else if (atype==DNS_RRTYPE_TXT) {
mdns_print_pstr(rp);
printf("\n");
} else if (atype==DNS_RRTYPE_SRV && rrlen > SIZEOF_DNS_RR_SRV) {
struct mdns_rr_srv srvRR;
memcpy(&srvRR,rp,SIZEOF_DNS_RR_SRV);
printf("prio %d, weight %d, port %d, target ", srvRR.prio, srvRR.weight, srvRR.port);
mdns_print_name(rp + SIZEOF_DNS_RR_SRV, hp);
printf("\n");
} else {
printf("%db:",rrlen);
mdns_printhex(rp,rrlen);
}
} else
printf("\n");
return p + SIZEOF_DNS_ANSWER + rrlen;
}
static int mdns_print_msg(u8_t* msgP, int msgLen)
{
int i;
u8_t* tp;
u8_t* limP = msgP + msgLen;
struct mdns_hdr* hdr;
hdr = (struct mdns_hdr*) msgP;
tp = mdns_print_header(hdr);
for (i=0; i<htons(hdr->numquestions); i++) {
printf(" Q%d: ",i+1);
tp = mdns_print_name(tp,hdr);
tp = mdns_print_query(tp);
if (tp > limP) return 0;
}
for (i=0; i<htons(hdr->numanswers); i++) {
printf(" A%d: ",i+1);
tp = mdns_print_name(tp,hdr);
tp = mdns_print_answer(tp,hdr);
if (tp > limP) return 0;
}
for (i=0; i<htons(hdr->numauthrr); i++) {
printf(" AuRR%d: ",i+1);
tp = mdns_print_name(tp,hdr);
tp = mdns_print_answer(tp,hdr);
if (tp > limP) return 0;
}
for (i=0; i<htons(hdr->numextrarr); i++) {
printf(" ExRR%d: ",i+1);
tp = mdns_print_name(tp,hdr);
tp = mdns_print_answer(tp,hdr);
if (tp > limP) return 0;
}
return 1;
}
#endif
#endif // qDebugLog
//---------------------------------------------------------------------------
static u8_t* mdns_labels2str(u8_t* hdrP, u8_t* p, char* qStr)
// Convert a DNS domain name label sequence into C string with . seperators
// Handles compression
{
int i, n;
do {
n = *p++;
if ((n & 0xC0) == 0xC0) {
n = (n & 0x3F) << 8;
n |= (u8_t)*p++;
mdns_labels2str( hdrP, hdrP + n, qStr);
return p;
} else if (n & 0xC0) {
printf(">>> mdns_labels2str,label $%X?",n);
return p;
} else {
for (i=0; i<n; i++)
*qStr++ = *p++;
if (n==0) *qStr++ = 0;
else *qStr++ = '.';
}
} while (n>0);
return p;
}
static int mdns_str2labels(const char* name, u8_t* lseq, int max)
// Encode a <string>.<string>.<string> as a sequence of labels, return length
{
int i,n,sdx,idx = 0;
int lc = 0;
do {
sdx = idx;
while (name[idx] != '.' && name[idx] != 0) idx++;
n = idx-sdx;
*lseq++ = n;
lc++;
if (lc+n > max) {
printf(">>> mdns_str2labels: oversize (%d)\n",lc+n);
return 0;
}
for (i=0; i<n; i++)
*lseq++ = name[sdx+i];
lc += n;
if (name[idx]=='.')
idx++;
} while (n>0);
return lc;
}
static u8_t* mdns_get_question(u8_t* hdrP, u8_t* qp, char* qStr, uint16_t* qClass, uint16_t* qType, u8_t* qUnicast)
// Unpack a DNS question RR at qp, return pointer to next RR
{
struct mdns_query qr;
uint16_t cls;
qp = mdns_labels2str(hdrP, qp, qStr);
memcpy(&qr,qp,SIZEOF_DNS_QUERY);
*qType = htons(qr.type);
cls = htons(qr.class);
*qUnicast = cls>>15;
*qClass = cls & 0x7FFF;
return qp + SIZEOF_DNS_QUERY;
}
//---------------------------------------------------------------------------
static void mdns_add_response(const char* vKey, u16_t vType, u32_t ttl, const void* dataP, u16_t vDataSize)
// Add a record to the RR database list
{
mdns_rsrc* rsrcP;
int keyLen, recSize;
keyLen = strlen(vKey) + 1;
recSize = sizeof(mdns_rsrc) - kDummyDataSize + keyLen + vDataSize;
rsrcP = (mdns_rsrc*)malloc(recSize);
if (rsrcP==NULL)
printf(">>> mdns_add_response: couldn't alloc %d\n",recSize);
else {
rsrcP->rType = vType;
rsrcP->rTTL = ttl;
rsrcP->rKeySize = keyLen;
rsrcP->rDataSize = vDataSize;
memcpy(rsrcP->rData, vKey, keyLen);
memcpy(&rsrcP->rData[keyLen], dataP, vDataSize);
rsrcP->rNext = gDictP;
gDictP = rsrcP;
#ifdef qDebugLog
printf("mDNS added RR '%s' %s, %d bytes\n", vKey, mdns_qrtype(vType), vDataSize);
#endif
}
}
void mdns_add_PTR(const char* rKey, u32_t ttl, const char* nmStr)
{
int nl;
u8_t lBuff[kMaxNameSize];
nl = mdns_str2labels(nmStr,lBuff,sizeof(lBuff));
if (nl>0)
mdns_add_response(rKey, DNS_RRTYPE_PTR, ttl, lBuff, nl);
}
void mdns_add_SRV(const char* rKey, u32_t ttl, u16_t rPort, const char* targName)
{
typedef struct SrvRec {
struct mdns_rr_srv srvRR;
u8_t lBuff[kMaxNameSize];
} __attribute__((packed)) SrvRec;
int nl;
SrvRec temp;
temp.srvRR.prio = 0;
temp.srvRR.weight = 0;
temp.srvRR.port = htons(rPort);
nl = mdns_str2labels(targName,temp.lBuff,sizeof(temp.lBuff));
if (nl>0)
mdns_add_response(rKey, DNS_RRTYPE_SRV, ttl, &temp, SIZEOF_DNS_RR_SRV + nl);
}
void mdns_add_TXT(const char* rKey, u32_t ttl, const char* txStr)
// Single TXT str, can be concatenated
{
char pstr[256];
u16_t n = strlen(txStr);
if (n > 255)
printf(">>> mdns_add_TXT oversize (%d)\n",n);
else {
pstr[0] = n;
memcpy(&pstr[1],txStr,n);
mdns_add_response(rKey, DNS_RRTYPE_TXT, ttl, txStr, n+1);
}
}
void mdns_add_A(const char* rKey, u32_t ttl, struct ip_addr addr)
{
mdns_add_response(rKey, DNS_RRTYPE_A, ttl, &addr, sizeof(addr));
}
void mdns_add_facility( const char* instanceName, // Friendly name, need not be unique
const char* serviceName, // Must be _name
const char* addText, // Must be <key>=<value>
mdns_flags flags, // TCP or UDP
u16_t onPort, // port number
u32_t ttl // seconds
)
{
char key[64];
char fullName[128];
char devName[96];
struct ip_info ipInfo;
#ifdef qDebugLog
printf("\nmDNS advertising instance %s protocol %s text %s on port %d %s TTL %d secs\n",
instanceName,serviceName,addText,onPort,(flags & mdns_UDP) ? "UDP" : "TCP", ttl);
#endif
snprintf(key,sizeof(key),"%s.%s.local.",serviceName,(flags & mdns_UDP) ? "_udp" :"_tcp");
snprintf(fullName,sizeof(fullName),"%s.%s",instanceName,key);
snprintf(devName,sizeof(devName),"%s.local.",instanceName);
if (!sdk_wifi_get_ip_info(STATION_IF,&ipInfo))
ipInfo.ip.addr = IPADDR_NONE;
// Order has significance for extraRR feature
mdns_add_TXT(fullName,ttl,addText);
mdns_add_A(devName,ttl,ipInfo.ip);
mdns_add_SRV(fullName,ttl,onPort,devName);
mdns_add_PTR(key,ttl,fullName);
// Optional, makes us browsable
if (flags & mdns_Browsable)
mdns_add_PTR("_services._dns-sd._udp.local.",ttl,key);
}
static void mdns_update_ipaddr(struct ip_info* ipInfo)
// IP address has been defined/changed: update any A records with the new IP
{
mdns_rsrc* rp = gDictP;
while (rp != NULL) {
if (rp->rType==DNS_RRTYPE_A) {
#ifdef qDebugLog
printf("Updating A record for '%s' to %d.%d.%d.%d\n", rp->rData,
ip4_addr1(&ipInfo->ip), ip4_addr2(&ipInfo->ip), ip4_addr3(&ipInfo->ip), ip4_addr4(&ipInfo->ip));
#endif
memcpy(&rp->rData[rp->rKeySize], &ipInfo->ip, sizeof(ip_addr_t));
}
rp = rp->rNext;
}
}
static mdns_rsrc* mdns_match(const char* qstr, u16_t qType)
{
mdns_rsrc* rp = gDictP;
while (rp != NULL) {
if (rp->rType==qType || qType==DNS_RRTYPE_ANY) {
if (strcasecmp(rp->rData,qstr)==0) {
#ifdef qDebugLog
printf(" - matched '%s' %s\n",qstr,mdns_qrtype(rp->rType));
#endif
break;
}
}
rp = rp->rNext;
}
return rp;
}
static int mdns_add_to_answer(mdns_rsrc* rsrcP, u8_t* resp, int respLen)
// Create answer RR and append to resp[respLen], return new length
{
// Key is stored as C str, convert to labels
respLen += mdns_str2labels(rsrcP->rData, &resp[respLen], DNS_MSG_SIZE-respLen);
// Answer fields: may be misaligned, so build and memcpy
struct mdns_answer ans;
ans.type = htons(rsrcP->rType);
ans.class = htons(DNS_RRCLASS_IN);
ans.ttl = htonl(rsrcP->rTTL);
ans.len = htons(rsrcP->rDataSize);
memcpy(&resp[respLen], &ans, SIZEOF_DNS_ANSWER);
respLen += SIZEOF_DNS_ANSWER;
// Data for this key
memcpy(&resp[respLen], &rsrcP->rData[rsrcP->rKeySize], rsrcP->rDataSize);
respLen += rsrcP->rDataSize;
return respLen;
}
//---------------------------------------------------------------------------
static void mdns_send_mcast(u8_t* msgP, int nBytes)
// Send UDP to multicast address
{
struct pbuf* p;
err_t err;
p = pbuf_alloc(PBUF_TRANSPORT, nBytes, PBUF_RAM);
if (p) {
memcpy(p->payload, msgP, nBytes);
err = udp_sendto(gMDNS_pcb, p, &gMulticastAddr, DNS_MDNS_PORT);
if (err==ERR_OK) {
#ifdef qDebugLog
printf(" - responded with %d bytes err %d\n",nBytes,err);
#endif
} else
printf(">>> mdns_send failed %d\n",err);
pbuf_free(p);
} else
printf(">>> mdns_send: alloc failed[%d]\n",nBytes);
}
static void mdns_reply(struct mdns_hdr* hdrP)
// Message has passed tests, may want to send an answer
{
int i, nquestions, respLen;
struct mdns_hdr* rHdr;
mdns_rsrc* extra;
u8_t* qBase = (u8_t*)hdrP;
u8_t* qp;
u8_t* mdns_response;
mdns_response = malloc(DNS_MSG_SIZE);
if (mdns_response==NULL) {
printf(">>> mdns_reply could not alloc %d\n",DNS_MSG_SIZE);
return;
}
// Build response header
rHdr = (struct mdns_hdr*) mdns_response;
rHdr->id = hdrP->id;
rHdr->flags1 = DNS_FLAG1_RESP + DNS_FLAG1_AUTH;
rHdr->flags2 = 0;
rHdr->numquestions = 0;
rHdr->numanswers = 0;
rHdr->numauthrr = 0;
rHdr->numextrarr = 0;
respLen = SIZEOF_DNS_HDR;
extra = NULL;
qp = qBase + SIZEOF_DNS_HDR;
nquestions = htons(hdrP->numquestions);
for (i=0; i<nquestions; i++) {
char qStr[kMaxQStr];
u16_t qClass, qType;
u8_t qUnicast;
mdns_rsrc* rsrcP;
qp = mdns_get_question(qBase, qp, qStr, &qClass, &qType, &qUnicast);
if (qClass==DNS_RRCLASS_IN || qClass==DNS_RRCLASS_ANY) {
rsrcP = mdns_match(qStr,qType);
if (rsrcP) {
respLen = mdns_add_to_answer(rsrcP, mdns_response, respLen);
rHdr->numanswers = htons( htons(rHdr->numanswers) + 1 );
// Extra RR logic: if SRV follows PTR, or A follows SRV, volunteer it in extraRR
// Not required, but could do more here, see RFC6763 s12
if (qType==DNS_RRTYPE_PTR) {
if (rsrcP->rNext && rsrcP->rNext->rType==DNS_RRTYPE_SRV)
extra = rsrcP->rNext;
} else if (qType==DNS_RRTYPE_SRV) {
if (rsrcP->rNext && rsrcP->rNext->rType==DNS_RRTYPE_A)
extra = rsrcP->rNext;
}
}
}
} // for nQuestions
if (respLen > SIZEOF_DNS_HDR) {
if (extra) {
respLen = mdns_add_to_answer(extra, mdns_response, respLen);
rHdr->numextrarr = htons( htons(rHdr->numextrarr) + 1 );
}
mdns_send_mcast(mdns_response,respLen);
}
free(mdns_response);
}
static void mdns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port)
// Callback from udp_recv
{
UNUSED_ARG(pcb);
UNUSED_ARG(port);
u8_t* mdns_payload;
int plen;
// Sanity checks on size
plen = p->tot_len;
if (plen > DNS_MSG_SIZE) {
printf(">>> mdns_recv: pbuf too big\n");
} else if (plen < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY + 1 + SIZEOF_DNS_ANSWER + 1)) {
printf(">>> mdns_recv: pbuf too small\n");
} else {
#ifdef qLogIncoming
printf("\n\nmDNS got %d bytes from %d.%d.%d.%d\n",plen, ip4_addr1(addr), ip4_addr2(addr), ip4_addr3(addr), ip4_addr4(addr));
#endif
mdns_payload = malloc(plen);
if (!mdns_payload)
printf(">>> mdns_recv, could not alloc %d\n",plen);
else {
if (pbuf_copy_partial(p, mdns_payload, plen, 0) == plen) {
struct mdns_hdr* hdrP = (struct mdns_hdr*) mdns_payload;
#ifdef qLogAllTraffic
mdns_print_msg(mdns_payload, plen);
#endif
if ( (hdrP->flags1 & (DNS_FLAG1_RESP + DNS_FLAG1_OPMASK + DNS_FLAG1_TRUNC) ) == 0
&& hdrP->numquestions > 0 )
mdns_reply(hdrP);
}
free(mdns_payload);
}
}
pbuf_free(p);
}
static void mdns_start()
// If we are in station mode and have an IP address, start a multicast UDP receive
{
struct ip_info ipInfo;
err_t err;
if (sdk_wifi_get_opmode() != STATION_MODE) {
printf(">>> mDNS_start: wifi opmode not station\n");
return;
}
if (!sdk_wifi_get_ip_info(STATION_IF,&ipInfo)) {
printf(">>> mDNS_start: no IP addr\n");
return;
}
mdns_update_ipaddr(&ipInfo);
// Start IGMP on the netif for our interface: this isn't done for us
struct netif* nfp = netif_list;
while (nfp!=NULL) {
if ( ip_addr_cmp(&ipInfo.ip, &(nfp->ip_addr)) ) {
if (!(nfp->flags & NETIF_FLAG_IGMP)) {
nfp->flags |= NETIF_FLAG_IGMP;
err = igmp_start(nfp);
if (err != ERR_OK) {
printf(">>> mDNS_start: igmp_start on %c%c failed %d\n",nfp->name[0], nfp->name[1],err);
return;
}
}
}
nfp = nfp->next;
}
gMDNS_pcb = udp_new();
if (!gMDNS_pcb) {
printf(">>> mDNS_start: udp_new failed\n");
return;
}
if ((err=igmp_joingroup(&ipInfo.ip, &gMulticastAddr)) != ERR_OK) {
printf(">>> mDNS_start: igmp_join failed %d\n",err);
return;
}
if ((err=udp_bind(gMDNS_pcb, IP_ADDR_ANY, DNS_MDNS_PORT)) != ERR_OK) {
printf(">>> mDNS_start: udp_bind failed %d\n",err);
return;
}
udp_recv(gMDNS_pcb, mdns_recv, NULL);
}
static void mdns_close()
{
udp_remove(gMDNS_pcb);
gMDNS_pcb = NULL;
#ifdef qDebugLog
printf("Closing mDNS\n");
#endif
}
static void mdns_task(void *pvParameters)
{
uint8_t hasIP = 0;
uint8_t status;
UNUSED_ARG(pvParameters);
ipaddr_aton(DNS_MULTICAST_ADDRESS, &gMulticastAddr);
// Wait until we have joined AP and are assigned an IP
while (1) {
status = (sdk_wifi_station_get_connect_status() == STATION_GOT_IP);
if (status != hasIP) {
if (status) mdns_start();
else mdns_close();
hasIP = status;
}
vTaskDelayMs(status ? 1000 : 100);
}
}
void mdns_init()
{
#if LWIP_IGMP
xTaskCreate(mdns_task, "MDNS", kMDNSStackSize, NULL, 1, NULL);
#else
#error "LWIP_IGMP needs to be defined in lwipopts.h"
#endif
}

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#ifndef __MDNSRESPONDER_H__
#define __MDNSRESPONDER_H__
/*
* Basic multicast DNS responder
*
* Advertises the IP address, port, and characteristics of a service to other devices using multicast DNS on the same LAN,
* so they can find devices with addresses dynamically allocated by DHCP. See avahi, Bonjour, etc
* See RFC6762, RFC6763
*
* This sample code is in the public domain.
*
* by M J A Hamel 2016
*/
// Starts the mDNS responder task, call first
void mdns_init();
// Build and advertise an appropriate linked set of PTR/TXT/SRV/A records for the parameters provided
// This is a simple canned way to build a set of records for a single service that will
// be advertised whenever the device is given an IP address by WiFi
typedef enum {
mdns_TCP,
mdns_UDP,
mdns_Browsable // see RFC6763:11 - adds a standard record that lets browsers find the service without needing to know its name
} mdns_flags;
void mdns_add_facility( const char* instanceName, // Short user-friendly instance name, should NOT include serial number/MAC/etc
const char* serviceName, // Must be registered, _name, (see RFC6335 5.1 & 5.2)
const char* addText, // Should be <key>=<value>, or "" if unused (see RFC6763 6.3)
mdns_flags flags, // TCP or UDP plus browsable
u16_t onPort, // port number
u32_t ttl // time-to-live, seconds
);
// Low-level RR builders for rolling your own
void mdns_add_PTR(const char* rKey, u32_t ttl, const char* nameStr);
void mdns_add_SRV(const char* rKey, u32_t ttl, u16_t rPort, const char* targname);
void mdns_add_TXT(const char* rKey, u32_t ttl, const char* txtStr);
void mdns_add_A (const char* rKey, u32_t ttl, struct ip_addr addr);
/* Sample usage, advertising a secure web service
mdns_init();
mdns_add_facility("Fluffy", "_https", "Zoom=1", mdns_TCP+mdns_Browsable, 443, 600);
*/
#endif