BadVPN – Rev 1
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/**
* @file
* MDNS responder implementation
*
* @defgroup mdns MDNS
* @ingroup apps
*
* RFC 6762 - Multicast DNS\n
* RFC 6763 - DNS-Based Service Discovery\n
*
* @verbinclude mdns.txt
*
* Things left to implement:
* -------------------------
*
* - Probing/conflict resolution
* - Sending goodbye messages (zero ttl) - shutdown, DHCP lease about to expire, DHCP turned off...
* - Checking that source address of unicast requests are on the same network
* - Limiting multicast responses to 1 per second per resource record
* - Fragmenting replies if required
* - Handling multi-packet known answers
* - Individual known answer detection for all local IPv6 addresses
* - Dynamic size of outgoing packet
*/
/*
* Copyright (c) 2015 Verisure Innovation AB
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
* SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
* OF SUCH DAMAGE.
*
* This file is part of the lwIP TCP/IP stack.
*
* Author: Erik Ekman <erik@kryo.se>
*
*/
#include "lwip/apps/mdns.h"
#include "lwip/apps/mdns_priv.h"
#include "lwip/netif.h"
#include "lwip/udp.h"
#include "lwip/ip_addr.h"
#include "lwip/mem.h"
#include "lwip/prot/dns.h"
#include "lwip/prot/iana.h"
#include <string.h>
#if LWIP_MDNS_RESPONDER
#if (LWIP_IPV4 && !LWIP_IGMP)
#error "If you want to use MDNS with IPv4, you have to define LWIP_IGMP=1 in your lwipopts.h"
#endif
#if (LWIP_IPV6 && !LWIP_IPV6_MLD)
#error "If you want to use MDNS with IPv6, you have to define LWIP_IPV6_MLD=1 in your lwipopts.h"
#endif
#if (!LWIP_UDP)
#error "If you want to use MDNS, you have to define LWIP_UDP=1 in your lwipopts.h"
#endif
#if LWIP_IPV4
#include "lwip/igmp.h"
/* IPv4 multicast group 224.0.0.251 */
static const ip_addr_t v4group = DNS_MQUERY_IPV4_GROUP_INIT;
#endif
#if LWIP_IPV6
#include "lwip/mld6.h"
/* IPv6 multicast group FF02::FB */
static const ip_addr_t v6group = DNS_MQUERY_IPV6_GROUP_INIT;
#endif
#define MDNS_TTL 255
/* Stored offsets to beginning of domain names
* Used for compression.
*/
#define NUM_DOMAIN_OFFSETS 10
#define DOMAIN_JUMP_SIZE 2
#define DOMAIN_JUMP 0xc000
static u8_t mdns_netif_client_id;
static struct udp_pcb *mdns_pcb;
NETIF_DECLARE_EXT_CALLBACK(netif_callback)
#define NETIF_TO_HOST(netif) (struct mdns_host*)(netif_get_client_data(netif, mdns_netif_client_id))
#define TOPDOMAIN_LOCAL "local"
#define REVERSE_PTR_TOPDOMAIN "arpa"
#define REVERSE_PTR_V4_DOMAIN "in-addr"
#define REVERSE_PTR_V6_DOMAIN "ip6"
#define SRV_PRIORITY 0
#define SRV_WEIGHT 0
/* Payload size allocated for each outgoing UDP packet */
#define OUTPACKET_SIZE 500
/* Lookup from hostname -> IPv4 */
#define REPLY_HOST_A 0x01
/* Lookup from IPv4/v6 -> hostname */
#define REPLY_HOST_PTR_V4 0x02
/* Lookup from hostname -> IPv6 */
#define REPLY_HOST_AAAA 0x04
/* Lookup from hostname -> IPv6 */
#define REPLY_HOST_PTR_V6 0x08
/* Lookup for service types */
#define REPLY_SERVICE_TYPE_PTR 0x10
/* Lookup for instances of service */
#define REPLY_SERVICE_NAME_PTR 0x20
/* Lookup for location of service instance */
#define REPLY_SERVICE_SRV 0x40
/* Lookup for text info on service instance */
#define REPLY_SERVICE_TXT 0x80
static const char *dnssd_protos[] = {
"_udp", /* DNSSD_PROTO_UDP */
"_tcp", /* DNSSD_PROTO_TCP */
};
/** Description of a service */
struct mdns_service {
/** TXT record to answer with */
struct mdns_domain txtdata;
/** Name of service, like 'myweb' */
char name[MDNS_LABEL_MAXLEN + 1];
/** Type of service, like '_http' */
char service[MDNS_LABEL_MAXLEN + 1];
/** Callback function and userdata
* to update txtdata buffer */
service_get_txt_fn_t txt_fn;
void *txt_userdata;
/** TTL in seconds of SRV/TXT replies */
u32_t dns_ttl;
/** Protocol, TCP or UDP */
u16_t proto;
/** Port of the service */
u16_t port;
};
/** Description of a host/netif */
struct mdns_host {
/** Hostname */
char name[MDNS_LABEL_MAXLEN + 1];
/** Pointer to services */
struct mdns_service *services[MDNS_MAX_SERVICES];
/** TTL in seconds of A/AAAA/PTR replies */
u32_t dns_ttl;
};
/** Information about received packet */
struct mdns_packet {
/** Sender IP/port */
ip_addr_t source_addr;
u16_t source_port;
/** If packet was received unicast */
u16_t recv_unicast;
/** Netif that received the packet */
struct netif *netif;
/** Packet data */
struct pbuf *pbuf;
/** Current parsing offset in packet */
u16_t parse_offset;
/** Identifier. Used in legacy queries */
u16_t tx_id;
/** Number of questions in packet,
* read from packet header */
u16_t questions;
/** Number of unparsed questions */
u16_t questions_left;
/** Number of answers in packet,
* (sum of normal, authorative and additional answers)
* read from packet header */
u16_t answers;
/** Number of unparsed answers */
u16_t answers_left;
};
/** Information about outgoing packet */
struct mdns_outpacket {
/** Netif to send the packet on */
struct netif *netif;
/** Packet data */
struct pbuf *pbuf;
/** Current write offset in packet */
u16_t write_offset;
/** Identifier. Used in legacy queries */
u16_t tx_id;
/** Destination IP/port if sent unicast */
ip_addr_t dest_addr;
u16_t dest_port;
/** Number of questions written */
u16_t questions;
/** Number of normal answers written */
u16_t answers;
/** Number of additional answers written */
u16_t additional;
/** Offsets for written domain names in packet.
* Used for compression */
u16_t domain_offsets[NUM_DOMAIN_OFFSETS];
/** If all answers in packet should set cache_flush bit */
u8_t cache_flush;
/** If reply should be sent unicast */
u8_t unicast_reply;
/** If legacy query. (tx_id needed, and write
* question again in reply before answer) */
u8_t legacy_query;
/* Reply bitmask for host information */
u8_t host_replies;
/* Bitmask for which reverse IPv6 hosts to answer */
u8_t host_reverse_v6_replies;
/* Reply bitmask per service */
u8_t serv_replies[MDNS_MAX_SERVICES];
};
/** Domain, type and class.
* Shared between questions and answers */
struct mdns_rr_info {
struct mdns_domain domain;
u16_t type;
u16_t klass;
};
struct mdns_question {
struct mdns_rr_info info;
/** unicast reply requested */
u16_t unicast;
};
struct mdns_answer {
struct mdns_rr_info info;
/** cache flush command bit */
u16_t cache_flush;
/* Validity time in seconds */
u32_t ttl;
/** Length of variable answer */
u16_t rd_length;
/** Offset of start of variable answer in packet */
u16_t rd_offset;
};
static err_t
mdns_domain_add_label_base(struct mdns_domain *domain, u8_t len)
{
if (len > MDNS_LABEL_MAXLEN) {
return ERR_VAL;
}
if (len > 0 && (1 + len + domain->length >= MDNS_DOMAIN_MAXLEN)) {
return ERR_VAL;
}
/* Allow only zero marker on last byte */
if (len == 0 && (1 + domain->length > MDNS_DOMAIN_MAXLEN)) {
return ERR_VAL;
}
domain->name[domain->length] = len;
domain->length++;
return ERR_OK;
}
/**
* Add a label part to a domain
* @param domain The domain to add a label to
* @param label The label to add, like <hostname>, 'local', 'com' or ''
* @param len The length of the label
* @return ERR_OK on success, an err_t otherwise if label too long
*/
err_t
mdns_domain_add_label(struct mdns_domain *domain, const char *label, u8_t len)
{
err_t err = mdns_domain_add_label_base(domain, len);
if (err != ERR_OK) {
return err;
}
if (len) {
MEMCPY(&domain->name[domain->length], label, len);
domain->length += len;
}
return ERR_OK;
}
/**
* Add a label part to a domain (@see mdns_domain_add_label but copy directly from pbuf)
*/
static err_t
mdns_domain_add_label_pbuf(struct mdns_domain *domain, const struct pbuf *p, u16_t offset, u8_t len)
{
err_t err = mdns_domain_add_label_base(domain, len);
if (err != ERR_OK) {
return err;
}
if (len) {
if (pbuf_copy_partial(p, &domain->name[domain->length], len, offset) != len) {
/* take back the ++ done before */
domain->length--;
return ERR_ARG;
}
domain->length += len;
}
return ERR_OK;
}
/**
* Internal readname function with max 6 levels of recursion following jumps
* while decompressing name
*/
static u16_t
mdns_readname_loop(struct pbuf *p, u16_t offset, struct mdns_domain *domain, unsigned depth)
{
u8_t c;
do {
if (depth > 5) {
/* Too many jumps */
return MDNS_READNAME_ERROR;
}
c = pbuf_get_at(p, offset);
offset++;
/* is this a compressed label? */
if ((c & 0xc0) == 0xc0) {
u16_t jumpaddr;
if (offset >= p->tot_len) {
/* Make sure both jump bytes fit in the packet */
return MDNS_READNAME_ERROR;
}
jumpaddr = (((c & 0x3f) << 8) | (pbuf_get_at(p, offset) & 0xff));
offset++;
if (jumpaddr >= SIZEOF_DNS_HDR && jumpaddr < p->tot_len) {
u16_t res;
/* Recursive call, maximum depth will be checked */
res = mdns_readname_loop(p, jumpaddr, domain, depth + 1);
/* Dont return offset since new bytes were not read (jumped to somewhere in packet) */
if (res == MDNS_READNAME_ERROR) {
return res;
}
} else {
return MDNS_READNAME_ERROR;
}
break;
}
/* normal label */
if (c <= MDNS_LABEL_MAXLEN) {
err_t res;
if (c + domain->length >= MDNS_DOMAIN_MAXLEN) {
return MDNS_READNAME_ERROR;
}
res = mdns_domain_add_label_pbuf(domain, p, offset, c);
if (res != ERR_OK) {
return MDNS_READNAME_ERROR;
}
offset += c;
} else {
/* bad length byte */
return MDNS_READNAME_ERROR;
}
} while (c != 0);
return offset;
}
/**
* Read possibly compressed domain name from packet buffer
* @param p The packet
* @param offset start position of domain name in packet
* @param domain The domain name destination
* @return The new offset after the domain, or MDNS_READNAME_ERROR
* if reading failed
*/
u16_t
mdns_readname(struct pbuf *p, u16_t offset, struct mdns_domain *domain)
{
memset(domain, 0, sizeof(struct mdns_domain));
return mdns_readname_loop(p, offset, domain, 0);
}
/**
* Print domain name to debug output
* @param domain The domain name
*/
static void
mdns_domain_debug_print(struct mdns_domain *domain)
{
u8_t *src = domain->name;
u8_t i;
while (*src) {
u8_t label_len = *src;
src++;
for (i = 0; i < label_len; i++) {
LWIP_DEBUGF(MDNS_DEBUG, ("%c", src[i]));
}
src += label_len;
LWIP_DEBUGF(MDNS_DEBUG, ("."));
}
}
/**
* Return 1 if contents of domains match (case-insensitive)
* @param a Domain name to compare 1
* @param b Domain name to compare 2
* @return 1 if domains are equal ignoring case, 0 otherwise
*/
int
mdns_domain_eq(struct mdns_domain *a, struct mdns_domain *b)
{
u8_t *ptra, *ptrb;
u8_t len;
int res;
if (a->length != b->length) {
return 0;
}
ptra = a->name;
ptrb = b->name;
while (*ptra && *ptrb && ptra < &a->name[a->length]) {
if (*ptra != *ptrb) {
return 0;
}
len = *ptra;
ptra++;
ptrb++;
res = lwip_strnicmp((char *) ptra, (char *) ptrb, len);
if (res != 0) {
return 0;
}
ptra += len;
ptrb += len;
}
if (*ptra != *ptrb && ptra < &a->name[a->length]) {
return 0;
}
return 1;
}
/**
* Call user supplied function to setup TXT data
* @param service The service to build TXT record for
*/
static void
mdns_prepare_txtdata(struct mdns_service *service)
{
memset(&service->txtdata, 0, sizeof(struct mdns_domain));
if (service->txt_fn) {
service->txt_fn(service, service->txt_userdata);
}
}
#if LWIP_IPV4
/**
* Build domain for reverse lookup of IPv4 address
* like 12.0.168.192.in-addr.arpa. for 192.168.0.12
* @param domain Where to write the domain name
* @param addr Pointer to an IPv4 address to encode
* @return ERR_OK if domain was written, an err_t otherwise
*/
static err_t
mdns_build_reverse_v4_domain(struct mdns_domain *domain, const ip4_addr_t *addr)
{
int i;
err_t res;
const u8_t *ptr;
if (!domain || !addr) {
return ERR_ARG;
}
memset(domain, 0, sizeof(struct mdns_domain));
ptr = (const u8_t *) addr;
for (i = sizeof(ip4_addr_t) - 1; i >= 0; i--) {
char buf[4];
u8_t val = ptr[i];
lwip_itoa(buf, sizeof(buf), val);
res = mdns_domain_add_label(domain, buf, (u8_t)strlen(buf));
LWIP_ERROR("mdns_build_reverse_v4_domain: Failed to add label", (res == ERR_OK), return res);
}
res = mdns_domain_add_label(domain, REVERSE_PTR_V4_DOMAIN, (u8_t)(sizeof(REVERSE_PTR_V4_DOMAIN) - 1));
LWIP_ERROR("mdns_build_reverse_v4_domain: Failed to add label", (res == ERR_OK), return res);
res = mdns_domain_add_label(domain, REVERSE_PTR_TOPDOMAIN, (u8_t)(sizeof(REVERSE_PTR_TOPDOMAIN) - 1));
LWIP_ERROR("mdns_build_reverse_v4_domain: Failed to add label", (res == ERR_OK), return res);
res = mdns_domain_add_label(domain, NULL, 0);
LWIP_ERROR("mdns_build_reverse_v4_domain: Failed to add label", (res == ERR_OK), return res);
return ERR_OK;
}
#endif
#if LWIP_IPV6
/**
* Build domain for reverse lookup of IP address
* like b.a.9.8.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa. for 2001:db8::567:89ab
* @param domain Where to write the domain name
* @param addr Pointer to an IPv6 address to encode
* @return ERR_OK if domain was written, an err_t otherwise
*/
static err_t
mdns_build_reverse_v6_domain(struct mdns_domain *domain, const ip6_addr_t *addr)
{
int i;
err_t res;
const u8_t *ptr;
if (!domain || !addr) {
return ERR_ARG;
}
memset(domain, 0, sizeof(struct mdns_domain));
ptr = (const u8_t *) addr;
for (i = sizeof(ip6_addr_p_t) - 1; i >= 0; i--) {
char buf;
u8_t byte = ptr[i];
int j;
for (j = 0; j < 2; j++) {
if ((byte & 0x0F) < 0xA) {
buf = '0' + (byte & 0x0F);
} else {
buf = 'a' + (byte & 0x0F) - 0xA;
}
res = mdns_domain_add_label(domain, &buf, sizeof(buf));
LWIP_ERROR("mdns_build_reverse_v6_domain: Failed to add label", (res == ERR_OK), return res);
byte >>= 4;
}
}
res = mdns_domain_add_label(domain, REVERSE_PTR_V6_DOMAIN, (u8_t)(sizeof(REVERSE_PTR_V6_DOMAIN) - 1));
LWIP_ERROR("mdns_build_reverse_v6_domain: Failed to add label", (res == ERR_OK), return res);
res = mdns_domain_add_label(domain, REVERSE_PTR_TOPDOMAIN, (u8_t)(sizeof(REVERSE_PTR_TOPDOMAIN) - 1));
LWIP_ERROR("mdns_build_reverse_v6_domain: Failed to add label", (res == ERR_OK), return res);
res = mdns_domain_add_label(domain, NULL, 0);
LWIP_ERROR("mdns_build_reverse_v6_domain: Failed to add label", (res == ERR_OK), return res);
return ERR_OK;
}
#endif
/* Add .local. to domain */
static err_t
mdns_add_dotlocal(struct mdns_domain *domain)
{
err_t res = mdns_domain_add_label(domain, TOPDOMAIN_LOCAL, (u8_t)(sizeof(TOPDOMAIN_LOCAL) - 1));
LWIP_ERROR("mdns_add_dotlocal: Failed to add label", (res == ERR_OK), return res);
return mdns_domain_add_label(domain, NULL, 0);
}
/**
* Build the <hostname>.local. domain name
* @param domain Where to write the domain name
* @param mdns TMDNS netif descriptor.
* @return ERR_OK if domain <hostname>.local. was written, an err_t otherwise
*/
static err_t
mdns_build_host_domain(struct mdns_domain *domain, struct mdns_host *mdns)
{
err_t res;
memset(domain, 0, sizeof(struct mdns_domain));
LWIP_ERROR("mdns_build_host_domain: mdns != NULL", (mdns != NULL), return ERR_VAL);
res = mdns_domain_add_label(domain, mdns->name, (u8_t)strlen(mdns->name));
LWIP_ERROR("mdns_build_host_domain: Failed to add label", (res == ERR_OK), return res);
return mdns_add_dotlocal(domain);
}
/**
* Build the lookup-all-services special DNS-SD domain name
* @param domain Where to write the domain name
* @return ERR_OK if domain _services._dns-sd._udp.local. was written, an err_t otherwise
*/
static err_t
mdns_build_dnssd_domain(struct mdns_domain *domain)
{
err_t res;
memset(domain, 0, sizeof(struct mdns_domain));
res = mdns_domain_add_label(domain, "_services", (u8_t)(sizeof("_services") - 1));
LWIP_ERROR("mdns_build_dnssd_domain: Failed to add label", (res == ERR_OK), return res);
res = mdns_domain_add_label(domain, "_dns-sd", (u8_t)(sizeof("_dns-sd") - 1));
LWIP_ERROR("mdns_build_dnssd_domain: Failed to add label", (res == ERR_OK), return res);
res = mdns_domain_add_label(domain, dnssd_protos[DNSSD_PROTO_UDP], (u8_t)strlen(dnssd_protos[DNSSD_PROTO_UDP]));
LWIP_ERROR("mdns_build_dnssd_domain: Failed to add label", (res == ERR_OK), return res);
return mdns_add_dotlocal(domain);
}
/**
* Build domain name for a service
* @param domain Where to write the domain name
* @param service The service struct, containing service name, type and protocol
* @param include_name Whether to include the service name in the domain
* @return ERR_OK if domain was written. If service name is included,
* <name>.<type>.<proto>.local. will be written, otherwise <type>.<proto>.local.
* An err_t is returned on error.
*/
static err_t
mdns_build_service_domain(struct mdns_domain *domain, struct mdns_service *service, int include_name)
{
err_t res;
memset(domain, 0, sizeof(struct mdns_domain));
if (include_name) {
res = mdns_domain_add_label(domain, service->name, (u8_t)strlen(service->name));
LWIP_ERROR("mdns_build_service_domain: Failed to add label", (res == ERR_OK), return res);
}
res = mdns_domain_add_label(domain, service->service, (u8_t)strlen(service->service));
LWIP_ERROR("mdns_build_service_domain: Failed to add label", (res == ERR_OK), return res);
res = mdns_domain_add_label(domain, dnssd_protos[service->proto], (u8_t)strlen(dnssd_protos[service->proto]));
LWIP_ERROR("mdns_build_service_domain: Failed to add label", (res == ERR_OK), return res);
return mdns_add_dotlocal(domain);
}
/**
* Check which replies we should send for a host/netif based on question
* @param netif The network interface that received the question
* @param rr Domain/type/class from a question
* @param reverse_v6_reply Bitmask of which IPv6 addresses to send reverse PTRs for
* if reply bit has REPLY_HOST_PTR_V6 set
* @return Bitmask of which replies to send
*/
static int
check_host(struct netif *netif, struct mdns_rr_info *rr, u8_t *reverse_v6_reply)
{
err_t res;
int replies = 0;
struct mdns_domain mydomain;
LWIP_UNUSED_ARG(reverse_v6_reply); /* if ipv6 is disabled */
if (rr->klass != DNS_RRCLASS_IN && rr->klass != DNS_RRCLASS_ANY) {
/* Invalid class */
return replies;
}
/* Handle PTR for our addresses */
if (rr->type == DNS_RRTYPE_PTR || rr->type == DNS_RRTYPE_ANY) {
#if LWIP_IPV6
int i;
for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i))) {
res = mdns_build_reverse_v6_domain(&mydomain, netif_ip6_addr(netif, i));
if (res == ERR_OK && mdns_domain_eq(&rr->domain, &mydomain)) {
replies |= REPLY_HOST_PTR_V6;
/* Mark which addresses where requested */
if (reverse_v6_reply) {
*reverse_v6_reply |= (1 << i);
}
}
}
}
#endif
#if LWIP_IPV4
if (!ip4_addr_isany_val(*netif_ip4_addr(netif))) {
res = mdns_build_reverse_v4_domain(&mydomain, netif_ip4_addr(netif));
if (res == ERR_OK && mdns_domain_eq(&rr->domain, &mydomain)) {
replies |= REPLY_HOST_PTR_V4;
}
}
#endif
}
res = mdns_build_host_domain(&mydomain, NETIF_TO_HOST(netif));
/* Handle requests for our hostname */
if (res == ERR_OK && mdns_domain_eq(&rr->domain, &mydomain)) {
/* TODO return NSEC if unsupported protocol requested */
#if LWIP_IPV4
if (!ip4_addr_isany_val(*netif_ip4_addr(netif))
&& (rr->type == DNS_RRTYPE_A || rr->type == DNS_RRTYPE_ANY)) {
replies |= REPLY_HOST_A;
}
#endif
#if LWIP_IPV6
if (rr->type == DNS_RRTYPE_AAAA || rr->type == DNS_RRTYPE_ANY) {
replies |= REPLY_HOST_AAAA;
}
#endif
}
return replies;
}
/**
* Check which replies we should send for a service based on question
* @param service A registered MDNS service
* @param rr Domain/type/class from a question
* @return Bitmask of which replies to send
*/
static int
check_service(struct mdns_service *service, struct mdns_rr_info *rr)
{
err_t res;
int replies = 0;
struct mdns_domain mydomain;
if (rr->klass != DNS_RRCLASS_IN && rr->klass != DNS_RRCLASS_ANY) {
/* Invalid class */
return 0;
}
res = mdns_build_dnssd_domain(&mydomain);
if (res == ERR_OK && mdns_domain_eq(&rr->domain, &mydomain) &&
(rr->type == DNS_RRTYPE_PTR || rr->type == DNS_RRTYPE_ANY)) {
/* Request for all service types */
replies |= REPLY_SERVICE_TYPE_PTR;
}
res = mdns_build_service_domain(&mydomain, service, 0);
if (res == ERR_OK && mdns_domain_eq(&rr->domain, &mydomain) &&
(rr->type == DNS_RRTYPE_PTR || rr->type == DNS_RRTYPE_ANY)) {
/* Request for the instance of my service */
replies |= REPLY_SERVICE_NAME_PTR;
}
res = mdns_build_service_domain(&mydomain, service, 1);
if (res == ERR_OK && mdns_domain_eq(&rr->domain, &mydomain)) {
/* Request for info about my service */
if (rr->type == DNS_RRTYPE_SRV || rr->type == DNS_RRTYPE_ANY) {
replies |= REPLY_SERVICE_SRV;
}
if (rr->type == DNS_RRTYPE_TXT || rr->type == DNS_RRTYPE_ANY) {
replies |= REPLY_SERVICE_TXT;
}
}
return replies;
}
/**
* Return bytes needed to write before jump for best result of compressing supplied domain
* against domain in outpacket starting at specified offset.
* If a match is found, offset is updated to where to jump to
* @param pbuf Pointer to pbuf with the partially constructed DNS packet
* @param offset Start position of a domain written earlier. If this location is suitable
* for compression, the pointer is updated to where in the domain to jump to.
* @param domain The domain to write
* @return Number of bytes to write of the new domain before writing a jump to the offset.
* If compression can not be done against this previous domain name, the full new
* domain length is returned.
*/
u16_t
mdns_compress_domain(struct pbuf *pbuf, u16_t *offset, struct mdns_domain *domain)
{
struct mdns_domain target;
u16_t target_end;
u8_t target_len;
u8_t writelen = 0;
u8_t *ptr;
if (pbuf == NULL) {
return domain->length;
}
target_end = mdns_readname(pbuf, *offset, &target);
if (target_end == MDNS_READNAME_ERROR) {
return domain->length;
}
target_len = (u8_t)(target_end - *offset);
ptr = domain->name;
while (writelen < domain->length) {
u8_t domainlen = (u8_t)(domain->length - writelen);
u8_t labellen;
if (domainlen <= target.length && domainlen > DOMAIN_JUMP_SIZE) {
/* Compare domains if target is long enough, and we have enough left of the domain */
u8_t targetpos = (u8_t)(target.length - domainlen);
if ((targetpos + DOMAIN_JUMP_SIZE) >= target_len) {
/* We are checking at or beyond a jump in the original, stop looking */
break;
}
if (target.length >= domainlen &&
memcmp(&domain->name[writelen], &target.name[targetpos], domainlen) == 0) {
*offset += targetpos;
return writelen;
}
}
/* Skip to next label in domain */
labellen = *ptr;
writelen += 1 + labellen;
ptr += 1 + labellen;
}
/* Nothing found */
return domain->length;
}
/**
* Write domain to outpacket. Compression will be attempted,
* unless domain->skip_compression is set.
* @param outpkt The outpacket to write to
* @param domain The domain name to write
* @return ERR_OK on success, an err_t otherwise
*/
static err_t
mdns_write_domain(struct mdns_outpacket *outpkt, struct mdns_domain *domain)
{
int i;
err_t res;
u16_t writelen = domain->length;
u16_t jump_offset = 0;
u16_t jump;
if (!domain->skip_compression) {
for (i = 0; i < NUM_DOMAIN_OFFSETS; ++i) {
u16_t offset = outpkt->domain_offsets[i];
if (offset) {
u16_t len = mdns_compress_domain(outpkt->pbuf, &offset, domain);
if (len < writelen) {
writelen = len;
jump_offset = offset;
}
}
}
}
if (writelen) {
/* Write uncompressed part of name */
res = pbuf_take_at(outpkt->pbuf, domain->name, writelen, outpkt->write_offset);
if (res != ERR_OK) {
return res;
}
/* Store offset of this new domain */
for (i = 0; i < NUM_DOMAIN_OFFSETS; ++i) {
if (outpkt->domain_offsets[i] == 0) {
outpkt->domain_offsets[i] = outpkt->write_offset;
break;
}
}
outpkt->write_offset += writelen;
}
if (jump_offset) {
/* Write jump */
jump = lwip_htons(DOMAIN_JUMP | jump_offset);
res = pbuf_take_at(outpkt->pbuf, &jump, DOMAIN_JUMP_SIZE, outpkt->write_offset);
if (res != ERR_OK) {
return res;
}
outpkt->write_offset += DOMAIN_JUMP_SIZE;
}
return ERR_OK;
}
/**
* Write a question to an outpacket
* A question contains domain, type and class. Since an answer also starts with these fields this function is also
* called from mdns_add_answer().
* @param outpkt The outpacket to write to
* @param domain The domain name the answer is for
* @param type The DNS type of the answer (like 'AAAA', 'SRV')
* @param klass The DNS type of the answer (like 'IN')
* @param unicast If highest bit in class should be set, to instruct the responder to
* reply with a unicast packet
* @return ERR_OK on success, an err_t otherwise
*/
static err_t
mdns_add_question(struct mdns_outpacket *outpkt, struct mdns_domain *domain, u16_t type, u16_t klass, u16_t unicast)
{
u16_t question_len;
u16_t field16;
err_t res;
if (!outpkt->pbuf) {
/* If no pbuf is active, allocate one */
outpkt->pbuf = pbuf_alloc(PBUF_TRANSPORT, OUTPACKET_SIZE, PBUF_RAM);
if (!outpkt->pbuf) {
return ERR_MEM;
}
outpkt->write_offset = SIZEOF_DNS_HDR;
}
/* Worst case calculation. Domain string might be compressed */
question_len = domain->length + sizeof(type) + sizeof(klass);
if (outpkt->write_offset + question_len > outpkt->pbuf->tot_len) {
/* No space */
return ERR_MEM;
}
/* Write name */
res = mdns_write_domain(outpkt, domain);
if (res != ERR_OK) {
return res;
}
/* Write type */
field16 = lwip_htons(type);
res = pbuf_take_at(outpkt->pbuf, &field16, sizeof(field16), outpkt->write_offset);
if (res != ERR_OK) {
return res;
}
outpkt->write_offset += sizeof(field16);
/* Write class */
if (unicast) {
klass |= 0x8000;
}
field16 = lwip_htons(klass);
res = pbuf_take_at(outpkt->pbuf, &field16, sizeof(field16), outpkt->write_offset);
if (res != ERR_OK) {
return res;
}
outpkt->write_offset += sizeof(field16);
return ERR_OK;
}
/**
* Write answer to reply packet.
* buf or answer_domain can be null. The rd_length written will be buf_length +
* size of (compressed) domain. Most uses will need either buf or answer_domain,
* special case is SRV that starts with 3 u16 and then a domain name.
* @param reply The outpacket to write to
* @param domain The domain name the answer is for
* @param type The DNS type of the answer (like 'AAAA', 'SRV')
* @param klass The DNS type of the answer (like 'IN')
* @param cache_flush If highest bit in class should be set, to instruct receiver that
* this reply replaces any earlier answer for this domain/type/class
* @param ttl Validity time in seconds to send out for IP address data in DNS replies
* @param buf Pointer to buffer of answer data
* @param buf_length Length of variable data
* @param answer_domain A domain to write after any buffer data as answer
* @return ERR_OK on success, an err_t otherwise
*/
static err_t
mdns_add_answer(struct mdns_outpacket *reply, struct mdns_domain *domain, u16_t type, u16_t klass, u16_t cache_flush,
u32_t ttl, const u8_t *buf, size_t buf_length, struct mdns_domain *answer_domain)
{
u16_t answer_len;
u16_t field16;
u16_t rdlen_offset;
u16_t answer_offset;
u32_t field32;
err_t res;
if (!reply->pbuf) {
/* If no pbuf is active, allocate one */
reply->pbuf = pbuf_alloc(PBUF_TRANSPORT, OUTPACKET_SIZE, PBUF_RAM);
if (!reply->pbuf) {
return ERR_MEM;
}
reply->write_offset = SIZEOF_DNS_HDR;
}
/* Worst case calculation. Domain strings might be compressed */
answer_len = domain->length + sizeof(type) + sizeof(klass) + sizeof(ttl) + sizeof(field16)/*rd_length*/;
if (buf) {
answer_len += (u16_t)buf_length;
}
if (answer_domain) {
answer_len += answer_domain->length;
}
if (reply->write_offset + answer_len > reply->pbuf->tot_len) {
/* No space */
return ERR_MEM;
}
/* Answer starts with same data as question, then more fields */
mdns_add_question(reply, domain, type, klass, cache_flush);
/* Write TTL */
field32 = lwip_htonl(ttl);
res = pbuf_take_at(reply->pbuf, &field32, sizeof(field32), reply->write_offset);
if (res != ERR_OK) {
return res;
}
reply->write_offset += sizeof(field32);
/* Store offsets and skip forward to the data */
rdlen_offset = reply->write_offset;
reply->write_offset += sizeof(field16);
answer_offset = reply->write_offset;
if (buf) {
/* Write static data */
res = pbuf_take_at(reply->pbuf, buf, (u16_t)buf_length, reply->write_offset);
if (res != ERR_OK) {
return res;
}
reply->write_offset += (u16_t)buf_length;
}
if (answer_domain) {
/* Write name answer (compressed if possible) */
res = mdns_write_domain(reply, answer_domain);
if (res != ERR_OK) {
return res;
}
}
/* Write rd_length after when we know the answer size */
field16 = lwip_htons(reply->write_offset - answer_offset);
res = pbuf_take_at(reply->pbuf, &field16, sizeof(field16), rdlen_offset);
return res;
}
/**
* Helper function for mdns_read_question/mdns_read_answer
* Reads a domain, type and class from the packet
* @param pkt The MDNS packet to read from. The parse_offset field will be
* incremented to point to the next unparsed byte.
* @param info The struct to fill with domain, type and class
* @return ERR_OK on success, an err_t otherwise
*/
static err_t
mdns_read_rr_info(struct mdns_packet *pkt, struct mdns_rr_info *info)
{
u16_t field16, copied;
pkt->parse_offset = mdns_readname(pkt->pbuf, pkt->parse_offset, &info->domain);
if (pkt->parse_offset == MDNS_READNAME_ERROR) {
return ERR_VAL;
}
copied = pbuf_copy_partial(pkt->pbuf, &field16, sizeof(field16), pkt->parse_offset);
if (copied != sizeof(field16)) {
return ERR_VAL;
}
pkt->parse_offset += copied;
info->type = lwip_ntohs(field16);
copied = pbuf_copy_partial(pkt->pbuf, &field16, sizeof(field16), pkt->parse_offset);
if (copied != sizeof(field16)) {
return ERR_VAL;
}
pkt->parse_offset += copied;
info->klass = lwip_ntohs(field16);
return ERR_OK;
}
/**
* Read a question from the packet.
* All questions have to be read before the answers.
* @param pkt The MDNS packet to read from. The questions_left field will be decremented
* and the parse_offset will be updated.
* @param question The struct to fill with question data
* @return ERR_OK on success, an err_t otherwise
*/
static err_t
mdns_read_question(struct mdns_packet *pkt, struct mdns_question *question)
{
/* Safety check */
if (pkt->pbuf->tot_len < pkt->parse_offset) {
return ERR_VAL;
}
if (pkt->questions_left) {
err_t res;
pkt->questions_left--;
memset(question, 0, sizeof(struct mdns_question));
res = mdns_read_rr_info(pkt, &question->info);
if (res != ERR_OK) {
return res;
}
/* Extract unicast flag from class field */
question->unicast = question->info.klass & 0x8000;
question->info.klass &= 0x7FFF;
return ERR_OK;
}
return ERR_VAL;
}
/**
* Read an answer from the packet
* The variable length reply is not copied, its pbuf offset and length is stored instead.
* @param pkt The MDNS packet to read. The answers_left field will be decremented and
* the parse_offset will be updated.
* @param answer The struct to fill with answer data
* @return ERR_OK on success, an err_t otherwise
*/
static err_t
mdns_read_answer(struct mdns_packet *pkt, struct mdns_answer *answer)
{
/* Read questions first */
if (pkt->questions_left) {
return ERR_VAL;
}
/* Safety check */
if (pkt->pbuf->tot_len < pkt->parse_offset) {
return ERR_VAL;
}
if (pkt->answers_left) {
u16_t copied, field16;
u32_t ttl;
err_t res;
pkt->answers_left--;
memset(answer, 0, sizeof(struct mdns_answer));
res = mdns_read_rr_info(pkt, &answer->info);
if (res != ERR_OK) {
return res;
}
/* Extract cache_flush flag from class field */
answer->cache_flush = answer->info.klass & 0x8000;
answer->info.klass &= 0x7FFF;
copied = pbuf_copy_partial(pkt->pbuf, &ttl, sizeof(ttl), pkt->parse_offset);
if (copied != sizeof(ttl)) {
return ERR_VAL;
}
pkt->parse_offset += copied;
answer->ttl = lwip_ntohl(ttl);
copied = pbuf_copy_partial(pkt->pbuf, &field16, sizeof(field16), pkt->parse_offset);
if (copied != sizeof(field16)) {
return ERR_VAL;
}
pkt->parse_offset += copied;
answer->rd_length = lwip_ntohs(field16);
answer->rd_offset = pkt->parse_offset;
pkt->parse_offset += answer->rd_length;
return ERR_OK;
}
return ERR_VAL;
}
#if LWIP_IPV4
/** Write an IPv4 address (A) RR to outpacket */
static err_t
mdns_add_a_answer(struct mdns_outpacket *reply, u16_t cache_flush, struct netif *netif)
{
struct mdns_domain host;
mdns_build_host_domain(&host, NETIF_TO_HOST(netif));
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Responding with A record\n"));
return mdns_add_answer(reply, &host, DNS_RRTYPE_A, DNS_RRCLASS_IN, cache_flush, (NETIF_TO_HOST(netif))->dns_ttl, (const u8_t *) netif_ip4_addr(netif), sizeof(ip4_addr_t), NULL);
}
/** Write a 4.3.2.1.in-addr.arpa -> hostname.local PTR RR to outpacket */
static err_t
mdns_add_hostv4_ptr_answer(struct mdns_outpacket *reply, u16_t cache_flush, struct netif *netif)
{
struct mdns_domain host, revhost;
mdns_build_host_domain(&host, NETIF_TO_HOST(netif));
mdns_build_reverse_v4_domain(&revhost, netif_ip4_addr(netif));
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Responding with v4 PTR record\n"));
return mdns_add_answer(reply, &revhost, DNS_RRTYPE_PTR, DNS_RRCLASS_IN, cache_flush, (NETIF_TO_HOST(netif))->dns_ttl, NULL, 0, &host);
}
#endif
#if LWIP_IPV6
/** Write an IPv6 address (AAAA) RR to outpacket */
static err_t
mdns_add_aaaa_answer(struct mdns_outpacket *reply, u16_t cache_flush, struct netif *netif, int addrindex)
{
struct mdns_domain host;
mdns_build_host_domain(&host, NETIF_TO_HOST(netif));
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Responding with AAAA record\n"));
return mdns_add_answer(reply, &host, DNS_RRTYPE_AAAA, DNS_RRCLASS_IN, cache_flush, (NETIF_TO_HOST(netif))->dns_ttl, (const u8_t *) netif_ip6_addr(netif, addrindex), sizeof(ip6_addr_p_t), NULL);
}
/** Write a x.y.z.ip6.arpa -> hostname.local PTR RR to outpacket */
static err_t
mdns_add_hostv6_ptr_answer(struct mdns_outpacket *reply, u16_t cache_flush, struct netif *netif, int addrindex)
{
struct mdns_domain host, revhost;
mdns_build_host_domain(&host, NETIF_TO_HOST(netif));
mdns_build_reverse_v6_domain(&revhost, netif_ip6_addr(netif, addrindex));
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Responding with v6 PTR record\n"));
return mdns_add_answer(reply, &revhost, DNS_RRTYPE_PTR, DNS_RRCLASS_IN, cache_flush, (NETIF_TO_HOST(netif))->dns_ttl, NULL, 0, &host);
}
#endif
/** Write an all-services -> servicetype PTR RR to outpacket */
static err_t
mdns_add_servicetype_ptr_answer(struct mdns_outpacket *reply, struct mdns_service *service)
{
struct mdns_domain service_type, service_dnssd;
mdns_build_service_domain(&service_type, service, 0);
mdns_build_dnssd_domain(&service_dnssd);
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Responding with service type PTR record\n"));
return mdns_add_answer(reply, &service_dnssd, DNS_RRTYPE_PTR, DNS_RRCLASS_IN, 0, service->dns_ttl, NULL, 0, &service_type);
}
/** Write a servicetype -> servicename PTR RR to outpacket */
static err_t
mdns_add_servicename_ptr_answer(struct mdns_outpacket *reply, struct mdns_service *service)
{
struct mdns_domain service_type, service_instance;
mdns_build_service_domain(&service_type, service, 0);
mdns_build_service_domain(&service_instance, service, 1);
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Responding with service name PTR record\n"));
return mdns_add_answer(reply, &service_type, DNS_RRTYPE_PTR, DNS_RRCLASS_IN, 0, service->dns_ttl, NULL, 0, &service_instance);
}
/** Write a SRV RR to outpacket */
static err_t
mdns_add_srv_answer(struct mdns_outpacket *reply, u16_t cache_flush, struct mdns_host *mdns, struct mdns_service *service)
{
struct mdns_domain service_instance, srvhost;
u16_t srvdata[3];
mdns_build_service_domain(&service_instance, service, 1);
mdns_build_host_domain(&srvhost, mdns);
if (reply->legacy_query) {
/* RFC 6762 section 18.14:
* In legacy unicast responses generated to answer legacy queries,
* name compression MUST NOT be performed on SRV records.
*/
srvhost.skip_compression = 1;
}
srvdata[0] = lwip_htons(SRV_PRIORITY);
srvdata[1] = lwip_htons(SRV_WEIGHT);
srvdata[2] = lwip_htons(service->port);
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Responding with SRV record\n"));
return mdns_add_answer(reply, &service_instance, DNS_RRTYPE_SRV, DNS_RRCLASS_IN, cache_flush, service->dns_ttl,
(const u8_t *) &srvdata, sizeof(srvdata), &srvhost);
}
/** Write a TXT RR to outpacket */
static err_t
mdns_add_txt_answer(struct mdns_outpacket *reply, u16_t cache_flush, struct mdns_service *service)
{
struct mdns_domain service_instance;
mdns_build_service_domain(&service_instance, service, 1);
mdns_prepare_txtdata(service);
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Responding with TXT record\n"));
return mdns_add_answer(reply, &service_instance, DNS_RRTYPE_TXT, DNS_RRCLASS_IN, cache_flush, service->dns_ttl,
(u8_t *) &service->txtdata.name, service->txtdata.length, NULL);
}
/**
* Setup outpacket as a reply to the incoming packet
*/
static void
mdns_init_outpacket(struct mdns_outpacket *out, struct mdns_packet *in)
{
memset(out, 0, sizeof(struct mdns_outpacket));
out->cache_flush = 1;
out->netif = in->netif;
/* Copy source IP/port to use when responding unicast, or to choose
* which pcb to use for multicast (IPv4/IPv6)
*/
SMEMCPY(&out->dest_addr, &in->source_addr, sizeof(ip_addr_t));
out->dest_port = in->source_port;
if (in->source_port != LWIP_IANA_PORT_MDNS) {
out->unicast_reply = 1;
out->cache_flush = 0;
if (in->questions == 1) {
out->legacy_query = 1;
out->tx_id = in->tx_id;
}
}
if (in->recv_unicast) {
out->unicast_reply = 1;
}
}
/**
* Send chosen answers as a reply
*
* Add all selected answers (first write will allocate pbuf)
* Add additional answers based on the selected answers
* Send the packet
*/
static void
mdns_send_outpacket(struct mdns_outpacket *outpkt)
{
struct mdns_service *service;
err_t res;
int i;
struct mdns_host *mdns = NETIF_TO_HOST(outpkt->netif);
/* Write answers to host questions */
#if LWIP_IPV4
if (outpkt->host_replies & REPLY_HOST_A) {
res = mdns_add_a_answer(outpkt, outpkt->cache_flush, outpkt->netif);
if (res != ERR_OK) {
goto cleanup;
}
outpkt->answers++;
}
if (outpkt->host_replies & REPLY_HOST_PTR_V4) {
res = mdns_add_hostv4_ptr_answer(outpkt, outpkt->cache_flush, outpkt->netif);
if (res != ERR_OK) {
goto cleanup;
}
outpkt->answers++;
}
#endif
#if LWIP_IPV6
if (outpkt->host_replies & REPLY_HOST_AAAA) {
int addrindex;
for (addrindex = 0; addrindex < LWIP_IPV6_NUM_ADDRESSES; ++addrindex) {
if (ip6_addr_isvalid(netif_ip6_addr_state(outpkt->netif, addrindex))) {
res = mdns_add_aaaa_answer(outpkt, outpkt->cache_flush, outpkt->netif, addrindex);
if (res != ERR_OK) {
goto cleanup;
}
outpkt->answers++;
}
}
}
if (outpkt->host_replies & REPLY_HOST_PTR_V6) {
u8_t rev_addrs = outpkt->host_reverse_v6_replies;
int addrindex = 0;
while (rev_addrs) {
if (rev_addrs & 1) {
res = mdns_add_hostv6_ptr_answer(outpkt, outpkt->cache_flush, outpkt->netif, addrindex);
if (res != ERR_OK) {
goto cleanup;
}
outpkt->answers++;
}
addrindex++;
rev_addrs >>= 1;
}
}
#endif
/* Write answers to service questions */
for (i = 0; i < MDNS_MAX_SERVICES; ++i) {
service = mdns->services[i];
if (!service) {
continue;
}
if (outpkt->serv_replies[i] & REPLY_SERVICE_TYPE_PTR) {
res = mdns_add_servicetype_ptr_answer(outpkt, service);
if (res != ERR_OK) {
goto cleanup;
}
outpkt->answers++;
}
if (outpkt->serv_replies[i] & REPLY_SERVICE_NAME_PTR) {
res = mdns_add_servicename_ptr_answer(outpkt, service);
if (res != ERR_OK) {
goto cleanup;
}
outpkt->answers++;
}
if (outpkt->serv_replies[i] & REPLY_SERVICE_SRV) {
res = mdns_add_srv_answer(outpkt, outpkt->cache_flush, mdns, service);
if (res != ERR_OK) {
goto cleanup;
}
outpkt->answers++;
}
if (outpkt->serv_replies[i] & REPLY_SERVICE_TXT) {
res = mdns_add_txt_answer(outpkt, outpkt->cache_flush, service);
if (res != ERR_OK) {
goto cleanup;
}
outpkt->answers++;
}
}
/* All answers written, add additional RRs */
for (i = 0; i < MDNS_MAX_SERVICES; ++i) {
service = mdns->services[i];
if (!service) {
continue;
}
if (outpkt->serv_replies[i] & REPLY_SERVICE_NAME_PTR) {
/* Our service instance requested, include SRV & TXT
* if they are already not requested. */
if (!(outpkt->serv_replies[i] & REPLY_SERVICE_SRV)) {
res = mdns_add_srv_answer(outpkt, outpkt->cache_flush, mdns, service);
if (res != ERR_OK) {
goto cleanup;
}
outpkt->additional++;
}
if (!(outpkt->serv_replies[i] & REPLY_SERVICE_TXT)) {
res = mdns_add_txt_answer(outpkt, outpkt->cache_flush, service);
if (res != ERR_OK) {
goto cleanup;
}
outpkt->additional++;
}
}
/* If service instance, SRV, record or an IP address is requested,
* supply all addresses for the host
*/
if ((outpkt->serv_replies[i] & (REPLY_SERVICE_NAME_PTR | REPLY_SERVICE_SRV)) ||
(outpkt->host_replies & (REPLY_HOST_A | REPLY_HOST_AAAA))) {
#if LWIP_IPV6
if (!(outpkt->host_replies & REPLY_HOST_AAAA)) {
int addrindex;
for (addrindex = 0; addrindex < LWIP_IPV6_NUM_ADDRESSES; ++addrindex) {
if (ip6_addr_isvalid(netif_ip6_addr_state(outpkt->netif, addrindex))) {
res = mdns_add_aaaa_answer(outpkt, outpkt->cache_flush, outpkt->netif, addrindex);
if (res != ERR_OK) {
goto cleanup;
}
outpkt->additional++;
}
}
}
#endif
#if LWIP_IPV4
if (!(outpkt->host_replies & REPLY_HOST_A)) {
res = mdns_add_a_answer(outpkt, outpkt->cache_flush, outpkt->netif);
if (res != ERR_OK) {
goto cleanup;
}
outpkt->additional++;
}
#endif
}
}
if (outpkt->pbuf) {
const ip_addr_t *mcast_destaddr;
struct dns_hdr hdr;
/* Write header */
memset(&hdr, 0, sizeof(hdr));
hdr.flags1 = DNS_FLAG1_RESPONSE | DNS_FLAG1_AUTHORATIVE;
hdr.numanswers = lwip_htons(outpkt->answers);
hdr.numextrarr = lwip_htons(outpkt->additional);
if (outpkt->legacy_query) {
hdr.numquestions = lwip_htons(1);
hdr.id = lwip_htons(outpkt->tx_id);
}
pbuf_take(outpkt->pbuf, &hdr, sizeof(hdr));
/* Shrink packet */
pbuf_realloc(outpkt->pbuf, outpkt->write_offset);
if (IP_IS_V6_VAL(outpkt->dest_addr)) {
#if LWIP_IPV6
mcast_destaddr = &v6group;
#endif
} else {
#if LWIP_IPV4
mcast_destaddr = &v4group;
#endif
}
/* Send created packet */
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Sending packet, len=%d, unicast=%d\n", outpkt->write_offset, outpkt->unicast_reply));
if (outpkt->unicast_reply) {
udp_sendto_if(mdns_pcb, outpkt->pbuf, &outpkt->dest_addr, outpkt->dest_port, outpkt->netif);
} else {
udp_sendto_if(mdns_pcb, outpkt->pbuf, mcast_destaddr, LWIP_IANA_PORT_MDNS, outpkt->netif);
}
}
cleanup:
if (outpkt->pbuf) {
pbuf_free(outpkt->pbuf);
outpkt->pbuf = NULL;
}
}
/**
* Send unsolicited answer containing all our known data
* @param netif The network interface to send on
* @param destination The target address to send to (usually multicast address)
*/
static void
mdns_announce(struct netif *netif, const ip_addr_t *destination)
{
struct mdns_outpacket announce;
int i;
struct mdns_host *mdns = NETIF_TO_HOST(netif);
memset(&announce, 0, sizeof(announce));
announce.netif = netif;
announce.cache_flush = 1;
#if LWIP_IPV4
if (!ip4_addr_isany_val(*netif_ip4_addr(netif))) {
announce.host_replies = REPLY_HOST_A | REPLY_HOST_PTR_V4;
}
#endif
#if LWIP_IPV6
for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; ++i) {
if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i))) {
announce.host_replies |= REPLY_HOST_AAAA | REPLY_HOST_PTR_V6;
announce.host_reverse_v6_replies |= (1 << i);
}
}
#endif
for (i = 0; i < MDNS_MAX_SERVICES; i++) {
struct mdns_service *serv = mdns->services[i];
if (serv) {
announce.serv_replies[i] = REPLY_SERVICE_TYPE_PTR | REPLY_SERVICE_NAME_PTR |
REPLY_SERVICE_SRV | REPLY_SERVICE_TXT;
}
}
announce.dest_port = LWIP_IANA_PORT_MDNS;
SMEMCPY(&announce.dest_addr, destination, sizeof(announce.dest_addr));
mdns_send_outpacket(&announce);
}
/**
* Handle question MDNS packet
* 1. Parse all questions and set bits what answers to send
* 2. Clear pending answers if known answers are supplied
* 3. Put chosen answers in new packet and send as reply
*/
static void
mdns_handle_question(struct mdns_packet *pkt)
{
struct mdns_service *service;
struct mdns_outpacket reply;
int replies = 0;
int i;
err_t res;
struct mdns_host *mdns = NETIF_TO_HOST(pkt->netif);
mdns_init_outpacket(&reply, pkt);
while (pkt->questions_left) {
struct mdns_question q;
res = mdns_read_question(pkt, &q);
if (res != ERR_OK) {
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Failed to parse question, skipping query packet\n"));
return;
}
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Query for domain "));
mdns_domain_debug_print(&q.info.domain);
LWIP_DEBUGF(MDNS_DEBUG, (" type %d class %d\n", q.info.type, q.info.klass));
if (q.unicast) {
/* Reply unicast if any question is unicast */
reply.unicast_reply = 1;
}
reply.host_replies |= check_host(pkt->netif, &q.info, &reply.host_reverse_v6_replies);
replies |= reply.host_replies;
for (i = 0; i < MDNS_MAX_SERVICES; ++i) {
service = mdns->services[i];
if (!service) {
continue;
}
reply.serv_replies[i] |= check_service(service, &q.info);
replies |= reply.serv_replies[i];
}
if (replies && reply.legacy_query) {
/* Add question to reply packet (legacy packet only has 1 question) */
res = mdns_add_question(&reply, &q.info.domain, q.info.type, q.info.klass, 0);
if (res != ERR_OK) {
goto cleanup;
}
}
}
/* Handle known answers */
while (pkt->answers_left) {
struct mdns_answer ans;
u8_t rev_v6;
int match;
res = mdns_read_answer(pkt, &ans);
if (res != ERR_OK) {
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Failed to parse answer, skipping query packet\n"));
goto cleanup;
}
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Known answer for domain "));
mdns_domain_debug_print(&ans.info.domain);
LWIP_DEBUGF(MDNS_DEBUG, (" type %d class %d\n", ans.info.type, ans.info.klass));
if (ans.info.type == DNS_RRTYPE_ANY || ans.info.klass == DNS_RRCLASS_ANY) {
/* Skip known answers for ANY type & class */
continue;
}
rev_v6 = 0;
match = reply.host_replies & check_host(pkt->netif, &ans.info, &rev_v6);
if (match && (ans.ttl > (mdns->dns_ttl / 2))) {
/* The RR in the known answer matches an RR we are planning to send,
* and the TTL is less than half gone.
* If the payload matches we should not send that answer.
*/
if (ans.info.type == DNS_RRTYPE_PTR) {
/* Read domain and compare */
struct mdns_domain known_ans, my_ans;
u16_t len;
len = mdns_readname(pkt->pbuf, ans.rd_offset, &known_ans);
res = mdns_build_host_domain(&my_ans, mdns);
if (len != MDNS_READNAME_ERROR && res == ERR_OK && mdns_domain_eq(&known_ans, &my_ans)) {
#if LWIP_IPV4
if (match & REPLY_HOST_PTR_V4) {
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Skipping known answer: v4 PTR\n"));
reply.host_replies &= ~REPLY_HOST_PTR_V4;
}
#endif
#if LWIP_IPV6
if (match & REPLY_HOST_PTR_V6) {
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Skipping known answer: v6 PTR\n"));
reply.host_reverse_v6_replies &= ~rev_v6;
if (reply.host_reverse_v6_replies == 0) {
reply.host_replies &= ~REPLY_HOST_PTR_V6;
}
}
#endif
}
} else if (match & REPLY_HOST_A) {
#if LWIP_IPV4
if (ans.rd_length == sizeof(ip4_addr_t) &&
pbuf_memcmp(pkt->pbuf, ans.rd_offset, netif_ip4_addr(pkt->netif), ans.rd_length) == 0) {
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Skipping known answer: A\n"));
reply.host_replies &= ~REPLY_HOST_A;
}
#endif
} else if (match & REPLY_HOST_AAAA) {
#if LWIP_IPV6
if (ans.rd_length == sizeof(ip6_addr_p_t) &&
/* TODO this clears all AAAA responses if first addr is set as known */
pbuf_memcmp(pkt->pbuf, ans.rd_offset, netif_ip6_addr(pkt->netif, 0), ans.rd_length) == 0) {
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Skipping known answer: AAAA\n"));
reply.host_replies &= ~REPLY_HOST_AAAA;
}
#endif
}
}
for (i = 0; i < MDNS_MAX_SERVICES; ++i) {
service = mdns->services[i];
if (!service) {
continue;
}
match = reply.serv_replies[i] & check_service(service, &ans.info);
if (match && (ans.ttl > (service->dns_ttl / 2))) {
/* The RR in the known answer matches an RR we are planning to send,
* and the TTL is less than half gone.
* If the payload matches we should not send that answer.
*/
if (ans.info.type == DNS_RRTYPE_PTR) {
/* Read domain and compare */
struct mdns_domain known_ans, my_ans;
u16_t len;
len = mdns_readname(pkt->pbuf, ans.rd_offset, &known_ans);
if (len != MDNS_READNAME_ERROR) {
if (match & REPLY_SERVICE_TYPE_PTR) {
res = mdns_build_service_domain(&my_ans, service, 0);
if (res == ERR_OK && mdns_domain_eq(&known_ans, &my_ans)) {
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Skipping known answer: service type PTR\n"));
reply.serv_replies[i] &= ~REPLY_SERVICE_TYPE_PTR;
}
}
if (match & REPLY_SERVICE_NAME_PTR) {
res = mdns_build_service_domain(&my_ans, service, 1);
if (res == ERR_OK && mdns_domain_eq(&known_ans, &my_ans)) {
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Skipping known answer: service name PTR\n"));
reply.serv_replies[i] &= ~REPLY_SERVICE_NAME_PTR;
}
}
}
} else if (match & REPLY_SERVICE_SRV) {
/* Read and compare to my SRV record */
u16_t field16, len, read_pos;
struct mdns_domain known_ans, my_ans;
read_pos = ans.rd_offset;
do {
/* Check priority field */
len = pbuf_copy_partial(pkt->pbuf, &field16, sizeof(field16), read_pos);
if (len != sizeof(field16) || lwip_ntohs(field16) != SRV_PRIORITY) {
break;
}
read_pos += len;
/* Check weight field */
len = pbuf_copy_partial(pkt->pbuf, &field16, sizeof(field16), read_pos);
if (len != sizeof(field16) || lwip_ntohs(field16) != SRV_WEIGHT) {
break;
}
read_pos += len;
/* Check port field */
len = pbuf_copy_partial(pkt->pbuf, &field16, sizeof(field16), read_pos);
if (len != sizeof(field16) || lwip_ntohs(field16) != service->port) {
break;
}
read_pos += len;
/* Check host field */
len = mdns_readname(pkt->pbuf, read_pos, &known_ans);
mdns_build_host_domain(&my_ans, mdns);
if (len == MDNS_READNAME_ERROR || !mdns_domain_eq(&known_ans, &my_ans)) {
break;
}
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Skipping known answer: SRV\n"));
reply.serv_replies[i] &= ~REPLY_SERVICE_SRV;
} while (0);
} else if (match & REPLY_SERVICE_TXT) {
mdns_prepare_txtdata(service);
if (service->txtdata.length == ans.rd_length &&
pbuf_memcmp(pkt->pbuf, ans.rd_offset, service->txtdata.name, ans.rd_length) == 0) {
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Skipping known answer: TXT\n"));
reply.serv_replies[i] &= ~REPLY_SERVICE_TXT;
}
}
}
}
}
mdns_send_outpacket(&reply);
cleanup:
if (reply.pbuf) {
/* This should only happen if we fail to alloc/write question for legacy query */
pbuf_free(reply.pbuf);
reply.pbuf = NULL;
}
}
/**
* Handle response MDNS packet
* Only prints debug for now. Will need more code to do conflict resolution.
*/
static void
mdns_handle_response(struct mdns_packet *pkt)
{
/* Ignore all questions */
while (pkt->questions_left) {
struct mdns_question q;
err_t res;
res = mdns_read_question(pkt, &q);
if (res != ERR_OK) {
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Failed to parse question, skipping response packet\n"));
return;
}
}
while (pkt->answers_left) {
struct mdns_answer ans;
err_t res;
res = mdns_read_answer(pkt, &ans);
if (res != ERR_OK) {
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Failed to parse answer, skipping response packet\n"));
return;
}
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Answer for domain "));
mdns_domain_debug_print(&ans.info.domain);
LWIP_DEBUGF(MDNS_DEBUG, (" type %d class %d\n", ans.info.type, ans.info.klass));
}
}
/**
* Receive input function for MDNS packets.
* Handles both IPv4 and IPv6 UDP pcbs.
*/
static void
mdns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
{
struct dns_hdr hdr;
struct mdns_packet packet;
struct netif *recv_netif = ip_current_input_netif();
u16_t offset = 0;
LWIP_UNUSED_ARG(arg);
LWIP_UNUSED_ARG(pcb);
LWIP_DEBUGF(MDNS_DEBUG, ("MDNS: Received IPv%d MDNS packet, len %d\n", IP_IS_V6(addr) ? 6 : 4, p->tot_len));
if (NETIF_TO_HOST(recv_netif) == NULL) {
/* From netif not configured for MDNS */
goto dealloc;
}
if (pbuf_copy_partial(p, &hdr, SIZEOF_DNS_HDR, offset) < SIZEOF_DNS_HDR) {
/* Too small */
goto dealloc;
}
offset += SIZEOF_DNS_HDR;
if (DNS_HDR_GET_OPCODE(&hdr)) {
/* Ignore non-standard queries in multicast packets (RFC 6762, section 18.3) */
goto dealloc;
}
memset(&packet, 0, sizeof(packet));
SMEMCPY(&packet.source_addr, addr, sizeof(packet.source_addr));
packet.source_port = port;
packet.netif = recv_netif;
packet.pbuf = p;
packet.parse_offset = offset;
packet.tx_id = lwip_ntohs(hdr.id);
packet.questions = packet.questions_left = lwip_ntohs(hdr.numquestions);
packet.answers = packet.answers_left = lwip_ntohs(hdr.numanswers) + lwip_ntohs(hdr.numauthrr) + lwip_ntohs(hdr.numextrarr);
#if LWIP_IPV6
if (IP_IS_V6(ip_current_dest_addr())) {
if (!ip_addr_cmp(ip_current_dest_addr(), &v6group)) {
packet.recv_unicast = 1;
}
}
#endif
#if LWIP_IPV4
if (!IP_IS_V6(ip_current_dest_addr())) {
if (!ip_addr_cmp(ip_current_dest_addr(), &v4group)) {
packet.recv_unicast = 1;
}
}
#endif
if (hdr.flags1 & DNS_FLAG1_RESPONSE) {
mdns_handle_response(&packet);
} else {
mdns_handle_question(&packet);
}
dealloc:
pbuf_free(p);
}
/**
* @ingroup mdns
* Announce IP settings have changed on netif.
* Call this in your callback registered by netif_set_status_callback().
* No need to call this function when LWIP_NETIF_EXT_STATUS_CALLBACK==1,
* this handled automatically for you.
* @param netif The network interface where settings have changed.
*/
void
mdns_resp_netif_settings_changed(struct netif *netif)
{
LWIP_ERROR("mdns_resp_netif_ip_changed: netif != NULL", (netif != NULL), return);
if (NETIF_TO_HOST(netif) == NULL) {
return;
}
/* Announce on IPv6 and IPv4 */
#if LWIP_IPV6
mdns_announce(netif, IP6_ADDR_ANY);
#endif
#if LWIP_IPV4
mdns_announce(netif, IP4_ADDR_ANY);
#endif
}
#if LWIP_NETIF_EXT_STATUS_CALLBACK
static void
mdns_netif_ext_status_callback(struct netif *netif, netif_nsc_reason_t reason, const netif_ext_callback_args_t *args)
{
LWIP_UNUSED_ARG(args);
/* MDNS enabled on netif? */
if (NETIF_TO_HOST(netif) == NULL) {
return;
}
switch (reason) {
case LWIP_NSC_STATUS_CHANGED:
if (args->status_changed.state != 0) {
mdns_resp_netif_settings_changed(netif);
}
/* TODO: send goodbye message */
break;
case LWIP_NSC_LINK_CHANGED:
if (args->link_changed.state != 0) {
mdns_resp_netif_settings_changed(netif);
}
break;
case LWIP_NSC_IPV4_ADDRESS_CHANGED: /* fall through */
case LWIP_NSC_IPV4_GATEWAY_CHANGED: /* fall through */
case LWIP_NSC_IPV4_NETMASK_CHANGED: /* fall through */
case LWIP_NSC_IPV4_SETTINGS_CHANGED: /* fall through */
case LWIP_NSC_IPV6_SET: /* fall through */
case LWIP_NSC_IPV6_ADDR_STATE_CHANGED:
mdns_resp_netif_settings_changed(netif);
break;
default:
break;
}
}
#endif
/**
* @ingroup mdns
* Activate MDNS responder for a network interface and send announce packets.
* @param netif The network interface to activate.
* @param hostname Name to use. Queries for <hostname>.local will be answered
* with the IP addresses of the netif. The hostname will be copied, the
* given pointer can be on the stack.
* @param dns_ttl Validity time in seconds to send out for IP address data in DNS replies
* @return ERR_OK if netif was added, an err_t otherwise
*/
err_t
mdns_resp_add_netif(struct netif *netif, const char *hostname, u32_t dns_ttl)
{
err_t res;
struct mdns_host *mdns;
LWIP_ERROR("mdns_resp_add_netif: netif != NULL", (netif != NULL), return ERR_VAL);
LWIP_ERROR("mdns_resp_add_netif: Hostname too long", (strlen(hostname) <= MDNS_LABEL_MAXLEN), return ERR_VAL);
LWIP_ASSERT("mdns_resp_add_netif: Double add", NETIF_TO_HOST(netif) == NULL);
mdns = (struct mdns_host *) mem_calloc(1, sizeof(struct mdns_host));
LWIP_ERROR("mdns_resp_add_netif: Alloc failed", (mdns != NULL), return ERR_MEM);
netif_set_client_data(netif, mdns_netif_client_id, mdns);
MEMCPY(&mdns->name, hostname, LWIP_MIN(MDNS_LABEL_MAXLEN, strlen(hostname)));
mdns->dns_ttl = dns_ttl;
/* Join multicast groups */
#if LWIP_IPV4
res = igmp_joingroup_netif(netif, ip_2_ip4(&v4group));
if (res != ERR_OK) {
goto cleanup;
}
#endif
#if LWIP_IPV6
res = mld6_joingroup_netif(netif, ip_2_ip6(&v6group));
if (res != ERR_OK) {
goto cleanup;
}
#endif
mdns_resp_netif_settings_changed(netif);
return ERR_OK;
cleanup:
mem_free(mdns);
netif_set_client_data(netif, mdns_netif_client_id, NULL);
return res;
}
/**
* @ingroup mdns
* Stop responding to MDNS queries on this interface, leave multicast groups,
* and free the helper structure and any of its services.
* @param netif The network interface to remove.
* @return ERR_OK if netif was removed, an err_t otherwise
*/
err_t
mdns_resp_remove_netif(struct netif *netif)
{
int i;
struct mdns_host *mdns;
LWIP_ASSERT("mdns_resp_remove_netif: Null pointer", netif);
mdns = NETIF_TO_HOST(netif);
LWIP_ERROR("mdns_resp_remove_netif: Not an active netif", (mdns != NULL), return ERR_VAL);
for (i = 0; i < MDNS_MAX_SERVICES; i++) {
struct mdns_service *service = mdns->services[i];
if (service) {
mem_free(service);
}
}
/* Leave multicast groups */
#if LWIP_IPV4
igmp_leavegroup_netif(netif, ip_2_ip4(&v4group));
#endif
#if LWIP_IPV6
mld6_leavegroup_netif(netif, ip_2_ip6(&v6group));
#endif
mem_free(mdns);
netif_set_client_data(netif, mdns_netif_client_id, NULL);
return ERR_OK;
}
/**
* @ingroup mdns
* Add a service to the selected network interface.
* @param netif The network interface to publish this service on
* @param name The name of the service
* @param service The service type, like "_http"
* @param proto The service protocol, DNSSD_PROTO_TCP for TCP ("_tcp") and DNSSD_PROTO_UDP
* for others ("_udp")
* @param port The port the service listens to
* @param dns_ttl Validity time in seconds to send out for service data in DNS replies
* @param txt_fn Callback to get TXT data. Will be called each time a TXT reply is created to
* allow dynamic replies.
* @param txt_data Userdata pointer for txt_fn
* @return service_id if the service was added to the netif, an err_t otherwise
*/
s8_t
mdns_resp_add_service(struct netif *netif, const char *name, const char *service, enum mdns_sd_proto proto, u16_t port, u32_t dns_ttl, service_get_txt_fn_t txt_fn, void *txt_data)
{
s8_t i;
s8_t slot = -1;
struct mdns_service *srv;
struct mdns_host *mdns;
LWIP_ASSERT("mdns_resp_add_service: netif != NULL", netif);
mdns = NETIF_TO_HOST(netif);
LWIP_ERROR("mdns_resp_add_service: Not an mdns netif", (mdns != NULL), return ERR_VAL);
LWIP_ERROR("mdns_resp_add_service: Name too long", (strlen(name) <= MDNS_LABEL_MAXLEN), return ERR_VAL);
LWIP_ERROR("mdns_resp_add_service: Service too long", (strlen(service) <= MDNS_LABEL_MAXLEN), return ERR_VAL);
LWIP_ERROR("mdns_resp_add_service: Bad proto (need TCP or UDP)", (proto == DNSSD_PROTO_TCP || proto == DNSSD_PROTO_UDP), return ERR_VAL);
for (i = 0; i < MDNS_MAX_SERVICES; i++) {
if (mdns->services[i] == NULL) {
slot = i;
break;
}
}
LWIP_ERROR("mdns_resp_add_service: Service list full (increase MDNS_MAX_SERVICES)", (slot >= 0), return ERR_MEM);
srv = (struct mdns_service *)mem_calloc(1, sizeof(struct mdns_service));
LWIP_ERROR("mdns_resp_add_service: Alloc failed", (srv != NULL), return ERR_MEM);
MEMCPY(&srv->name, name, LWIP_MIN(MDNS_LABEL_MAXLEN, strlen(name)));
MEMCPY(&srv->service, service, LWIP_MIN(MDNS_LABEL_MAXLEN, strlen(service)));
srv->txt_fn = txt_fn;
srv->txt_userdata = txt_data;
srv->proto = (u16_t)proto;
srv->port = port;
srv->dns_ttl = dns_ttl;
mdns->services[slot] = srv;
/* Announce on IPv6 and IPv4 */
#if LWIP_IPV6
mdns_announce(netif, IP6_ADDR_ANY);
#endif
#if LWIP_IPV4
mdns_announce(netif, IP4_ADDR_ANY);
#endif
return slot;
}
/**
* @ingroup mdns
* Delete a service on the selected network interface.
* @param netif The network interface on which service should be removed
* @param slot The service slot number returned by mdns_resp_add_service
* @return ERR_OK if the service was removed from the netif, an err_t otherwise
*/
err_t
mdns_resp_del_service(struct netif *netif, s8_t slot)
{
struct mdns_host *mdns;
struct mdns_service *srv;
LWIP_ASSERT("mdns_resp_del_service: netif != NULL", netif);
mdns = NETIF_TO_HOST(netif);
LWIP_ERROR("mdns_resp_del_service: Not an mdns netif", (mdns != NULL), return ERR_VAL);
LWIP_ERROR("mdns_resp_del_service: Invalid Service ID", (slot >= 0) && (slot < MDNS_MAX_SERVICES), return ERR_VAL);
LWIP_ERROR("mdns_resp_del_service: Invalid Service ID", (mdns->services[slot] != NULL), return ERR_VAL);
srv = mdns->services[slot];
mdns->services[slot] = NULL;
mem_free(srv);
return ERR_OK;
}
/**
* @ingroup mdns
* Call this function from inside the service_get_txt_fn_t callback to add text data.
* Buffer for TXT data is 256 bytes, and each field is prefixed with a length byte.
* @param service The service provided to the get_txt callback
* @param txt String to add to the TXT field.
* @param txt_len Length of string
* @return ERR_OK if the string was added to the reply, an err_t otherwise
*/
err_t
mdns_resp_add_service_txtitem(struct mdns_service *service, const char *txt, u8_t txt_len)
{
LWIP_ASSERT("mdns_resp_add_service_txtitem: service != NULL", service);
/* Use a mdns_domain struct to store txt chunks since it is the same encoding */
return mdns_domain_add_label(&service->txtdata, txt, txt_len);
}
/**
* @ingroup mdns
* Initiate MDNS responder. Will open UDP sockets on port 5353
*/
void
mdns_resp_init(void)
{
err_t res;
mdns_pcb = udp_new_ip_type(IPADDR_TYPE_ANY);
LWIP_ASSERT("Failed to allocate pcb", mdns_pcb != NULL);
#if LWIP_MULTICAST_TX_OPTIONS
udp_set_multicast_ttl(mdns_pcb, MDNS_TTL);
#else
mdns_pcb->ttl = MDNS_TTL;
#endif
res = udp_bind(mdns_pcb, IP_ANY_TYPE, LWIP_IANA_PORT_MDNS);
LWIP_UNUSED_ARG(res); /* in case of LWIP_NOASSERT */
LWIP_ASSERT("Failed to bind pcb", res == ERR_OK);
udp_recv(mdns_pcb, mdns_recv, NULL);
mdns_netif_client_id = netif_alloc_client_data_id();
/* register for netif events when started on first netif */
netif_add_ext_callback(&netif_callback, mdns_netif_ext_status_callback);
}
#endif /* LWIP_MDNS_RESPONDER */