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mdns.c
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mdns.c
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#ifdef _WIN32
#define _CRT_SECURE_NO_WARNINGS 1
#endif
#include <stdio.h>
#include <errno.h>
#include <signal.h>
#ifdef _WIN32
#include <winsock2.h>
#include <iphlpapi.h>
#define sleep(x) Sleep(x * 1000)
#else
#include <netdb.h>
#include <ifaddrs.h>
#include <net/if.h>
#include <sys/time.h>
#endif
// Alias some things to simulate recieving data to fuzz library
#if defined(MDNS_FUZZING)
#define recvfrom(sock, buffer, capacity, flags, src_addr, addrlen) ((mdns_ssize_t)capacity)
#define printf
#endif
#include "mdns.h"
#if defined(MDNS_FUZZING)
#undef recvfrom
#endif
static char addrbuffer[64];
static char entrybuffer[256];
static char namebuffer[256];
static char sendbuffer[1024];
static mdns_record_txt_t txtbuffer[128];
static struct sockaddr_in service_address_ipv4;
static struct sockaddr_in6 service_address_ipv6;
static int has_ipv4;
static int has_ipv6;
volatile sig_atomic_t running = 1;
// Data for our service including the mDNS records
typedef struct {
mdns_string_t service;
mdns_string_t hostname;
mdns_string_t service_instance;
mdns_string_t hostname_qualified;
struct sockaddr_in address_ipv4;
struct sockaddr_in6 address_ipv6;
int port;
mdns_record_t record_ptr;
mdns_record_t record_srv;
mdns_record_t record_a;
mdns_record_t record_aaaa;
mdns_record_t txt_record[2];
} service_t;
static mdns_string_t
ipv4_address_to_string(char* buffer, size_t capacity, const struct sockaddr_in* addr,
size_t addrlen) {
char host[NI_MAXHOST] = {0};
char service[NI_MAXSERV] = {0};
int ret = getnameinfo((const struct sockaddr*)addr, (socklen_t)addrlen, host, NI_MAXHOST,
service, NI_MAXSERV, NI_NUMERICSERV | NI_NUMERICHOST);
int len = 0;
if (ret == 0) {
if (addr->sin_port != 0)
len = snprintf(buffer, capacity, "%s:%s", host, service);
else
len = snprintf(buffer, capacity, "%s", host);
}
if (len >= (int)capacity)
len = (int)capacity - 1;
mdns_string_t str;
str.str = buffer;
str.length = len;
return str;
}
static mdns_string_t
ipv6_address_to_string(char* buffer, size_t capacity, const struct sockaddr_in6* addr,
size_t addrlen) {
char host[NI_MAXHOST] = {0};
char service[NI_MAXSERV] = {0};
int ret = getnameinfo((const struct sockaddr*)addr, (socklen_t)addrlen, host, NI_MAXHOST,
service, NI_MAXSERV, NI_NUMERICSERV | NI_NUMERICHOST);
int len = 0;
if (ret == 0) {
if (addr->sin6_port != 0)
len = snprintf(buffer, capacity, "[%s]:%s", host, service);
else
len = snprintf(buffer, capacity, "%s", host);
}
if (len >= (int)capacity)
len = (int)capacity - 1;
mdns_string_t str;
str.str = buffer;
str.length = len;
return str;
}
static mdns_string_t
ip_address_to_string(char* buffer, size_t capacity, const struct sockaddr* addr, size_t addrlen) {
if (addr->sa_family == AF_INET6)
return ipv6_address_to_string(buffer, capacity, (const struct sockaddr_in6*)addr, addrlen);
return ipv4_address_to_string(buffer, capacity, (const struct sockaddr_in*)addr, addrlen);
}
// Callback handling parsing answers to queries sent
static int
query_callback(int sock, const struct sockaddr* from, size_t addrlen, mdns_entry_type_t entry,
uint16_t query_id, uint16_t rtype, uint16_t rclass, uint32_t ttl, const void* data,
size_t size, size_t name_offset, size_t name_length, size_t record_offset,
size_t record_length, void* user_data) {
(void)sizeof(sock);
(void)sizeof(query_id);
(void)sizeof(name_length);
(void)sizeof(user_data);
mdns_string_t fromaddrstr = ip_address_to_string(addrbuffer, sizeof(addrbuffer), from, addrlen);
const char* entrytype = (entry == MDNS_ENTRYTYPE_ANSWER) ?
"answer" :
((entry == MDNS_ENTRYTYPE_AUTHORITY) ? "authority" : "additional");
mdns_string_t entrystr =
mdns_string_extract(data, size, &name_offset, entrybuffer, sizeof(entrybuffer));
if (rtype == MDNS_RECORDTYPE_PTR) {
mdns_string_t namestr = mdns_record_parse_ptr(data, size, record_offset, record_length,
namebuffer, sizeof(namebuffer));
printf("%.*s : %s %.*s PTR %.*s rclass 0x%x ttl %u length %d\n",
MDNS_STRING_FORMAT(fromaddrstr), entrytype, MDNS_STRING_FORMAT(entrystr),
MDNS_STRING_FORMAT(namestr), rclass, ttl, (int)record_length);
} else if (rtype == MDNS_RECORDTYPE_SRV) {
mdns_record_srv_t srv = mdns_record_parse_srv(data, size, record_offset, record_length,
namebuffer, sizeof(namebuffer));
printf("%.*s : %s %.*s SRV %.*s priority %d weight %d port %d\n",
MDNS_STRING_FORMAT(fromaddrstr), entrytype, MDNS_STRING_FORMAT(entrystr),
MDNS_STRING_FORMAT(srv.name), srv.priority, srv.weight, srv.port);
} else if (rtype == MDNS_RECORDTYPE_A) {
struct sockaddr_in addr;
mdns_record_parse_a(data, size, record_offset, record_length, &addr);
mdns_string_t addrstr =
ipv4_address_to_string(namebuffer, sizeof(namebuffer), &addr, sizeof(addr));
printf("%.*s : %s %.*s A %.*s\n", MDNS_STRING_FORMAT(fromaddrstr), entrytype,
MDNS_STRING_FORMAT(entrystr), MDNS_STRING_FORMAT(addrstr));
} else if (rtype == MDNS_RECORDTYPE_AAAA) {
struct sockaddr_in6 addr;
mdns_record_parse_aaaa(data, size, record_offset, record_length, &addr);
mdns_string_t addrstr =
ipv6_address_to_string(namebuffer, sizeof(namebuffer), &addr, sizeof(addr));
printf("%.*s : %s %.*s AAAA %.*s\n", MDNS_STRING_FORMAT(fromaddrstr), entrytype,
MDNS_STRING_FORMAT(entrystr), MDNS_STRING_FORMAT(addrstr));
} else if (rtype == MDNS_RECORDTYPE_TXT) {
size_t parsed = mdns_record_parse_txt(data, size, record_offset, record_length, txtbuffer,
sizeof(txtbuffer) / sizeof(mdns_record_txt_t));
for (size_t itxt = 0; itxt < parsed; ++itxt) {
if (txtbuffer[itxt].value.length) {
printf("%.*s : %s %.*s TXT %.*s = %.*s\n", MDNS_STRING_FORMAT(fromaddrstr),
entrytype, MDNS_STRING_FORMAT(entrystr),
MDNS_STRING_FORMAT(txtbuffer[itxt].key),
MDNS_STRING_FORMAT(txtbuffer[itxt].value));
} else {
printf("%.*s : %s %.*s TXT %.*s\n", MDNS_STRING_FORMAT(fromaddrstr), entrytype,
MDNS_STRING_FORMAT(entrystr), MDNS_STRING_FORMAT(txtbuffer[itxt].key));
}
}
} else {
printf("%.*s : %s %.*s type %u rclass 0x%x ttl %u length %d\n",
MDNS_STRING_FORMAT(fromaddrstr), entrytype, MDNS_STRING_FORMAT(entrystr), rtype,
rclass, ttl, (int)record_length);
}
return 0;
}
// Callback handling questions incoming on service sockets
static int
service_callback(int sock, const struct sockaddr* from, size_t addrlen, mdns_entry_type_t entry,
uint16_t query_id, uint16_t rtype, uint16_t rclass, uint32_t ttl, const void* data,
size_t size, size_t name_offset, size_t name_length, size_t record_offset,
size_t record_length, void* user_data) {
(void)sizeof(ttl);
if (entry != MDNS_ENTRYTYPE_QUESTION)
return 0;
const char dns_sd[] = "_services._dns-sd._udp.local.";
const service_t* service = (const service_t*)user_data;
mdns_string_t fromaddrstr = ip_address_to_string(addrbuffer, sizeof(addrbuffer), from, addrlen);
size_t offset = name_offset;
mdns_string_t name = mdns_string_extract(data, size, &offset, namebuffer, sizeof(namebuffer));
const char* record_name = 0;
if (rtype == MDNS_RECORDTYPE_PTR)
record_name = "PTR";
else if (rtype == MDNS_RECORDTYPE_SRV)
record_name = "SRV";
else if (rtype == MDNS_RECORDTYPE_A)
record_name = "A";
else if (rtype == MDNS_RECORDTYPE_AAAA)
record_name = "AAAA";
else if (rtype == MDNS_RECORDTYPE_TXT)
record_name = "TXT";
else if (rtype == MDNS_RECORDTYPE_ANY)
record_name = "ANY";
else
return 0;
printf("Query %s %.*s\n", record_name, MDNS_STRING_FORMAT(name));
if ((name.length == (sizeof(dns_sd) - 1)) &&
(strncmp(name.str, dns_sd, sizeof(dns_sd) - 1) == 0)) {
if ((rtype == MDNS_RECORDTYPE_PTR) || (rtype == MDNS_RECORDTYPE_ANY)) {
// The PTR query was for the DNS-SD domain, send answer with a PTR record for the
// service name we advertise, typically on the "<_service-name>._tcp.local." format
// Answer PTR record reverse mapping "<_service-name>._tcp.local." to
// "<hostname>.<_service-name>._tcp.local."
mdns_record_t answer = {
.name = name, .type = MDNS_RECORDTYPE_PTR, .data.ptr.name = service->service};
// Send the answer, unicast or multicast depending on flag in query
uint16_t unicast = (rclass & MDNS_UNICAST_RESPONSE);
printf(" --> answer %.*s (%s)\n", MDNS_STRING_FORMAT(answer.data.ptr.name),
(unicast ? "unicast" : "multicast"));
if (unicast) {
mdns_query_answer_unicast(sock, from, addrlen, sendbuffer, sizeof(sendbuffer),
query_id, rtype, name.str, name.length, answer, 0, 0, 0,
0);
} else {
mdns_query_answer_multicast(sock, sendbuffer, sizeof(sendbuffer), answer, 0, 0, 0,
0);
}
}
} else if ((name.length == service->service.length) &&
(strncmp(name.str, service->service.str, name.length) == 0)) {
if ((rtype == MDNS_RECORDTYPE_PTR) || (rtype == MDNS_RECORDTYPE_ANY)) {
// The PTR query was for our service (usually "<_service-name._tcp.local"), answer a PTR
// record reverse mapping the queried service name to our service instance name
// (typically on the "<hostname>.<_service-name>._tcp.local." format), and add
// additional records containing the SRV record mapping the service instance name to our
// qualified hostname (typically "<hostname>.local.") and port, as well as any IPv4/IPv6
// address for the hostname as A/AAAA records, and two test TXT records
// Answer PTR record reverse mapping "<_service-name>._tcp.local." to
// "<hostname>.<_service-name>._tcp.local."
mdns_record_t answer = service->record_ptr;
mdns_record_t additional[5] = {0};
size_t additional_count = 0;
// SRV record mapping "<hostname>.<_service-name>._tcp.local." to
// "<hostname>.local." with port. Set weight & priority to 0.
additional[additional_count++] = service->record_srv;
// A/AAAA records mapping "<hostname>.local." to IPv4/IPv6 addresses
if (service->address_ipv4.sin_family == AF_INET)
additional[additional_count++] = service->record_a;
if (service->address_ipv6.sin6_family == AF_INET6)
additional[additional_count++] = service->record_aaaa;
// Add two test TXT records for our service instance name, will be coalesced into
// one record with both key-value pair strings by the library
additional[additional_count++] = service->txt_record[0];
additional[additional_count++] = service->txt_record[1];
// Send the answer, unicast or multicast depending on flag in query
uint16_t unicast = (rclass & MDNS_UNICAST_RESPONSE);
printf(" --> answer %.*s (%s)\n",
MDNS_STRING_FORMAT(service->record_ptr.data.ptr.name),
(unicast ? "unicast" : "multicast"));
if (unicast) {
mdns_query_answer_unicast(sock, from, addrlen, sendbuffer, sizeof(sendbuffer),
query_id, rtype, name.str, name.length, answer, 0, 0,
additional, additional_count);
} else {
mdns_query_answer_multicast(sock, sendbuffer, sizeof(sendbuffer), answer, 0, 0,
additional, additional_count);
}
}
} else if ((name.length == service->service_instance.length) &&
(strncmp(name.str, service->service_instance.str, name.length) == 0)) {
if ((rtype == MDNS_RECORDTYPE_SRV) || (rtype == MDNS_RECORDTYPE_ANY)) {
// The SRV query was for our service instance (usually
// "<hostname>.<_service-name._tcp.local"), answer a SRV record mapping the service
// instance name to our qualified hostname (typically "<hostname>.local.") and port, as
// well as any IPv4/IPv6 address for the hostname as A/AAAA records, and two test TXT
// records
// Answer PTR record reverse mapping "<_service-name>._tcp.local." to
// "<hostname>.<_service-name>._tcp.local."
mdns_record_t answer = service->record_srv;
mdns_record_t additional[5] = {0};
size_t additional_count = 0;
// A/AAAA records mapping "<hostname>.local." to IPv4/IPv6 addresses
if (service->address_ipv4.sin_family == AF_INET)
additional[additional_count++] = service->record_a;
if (service->address_ipv6.sin6_family == AF_INET6)
additional[additional_count++] = service->record_aaaa;
// Add two test TXT records for our service instance name, will be coalesced into
// one record with both key-value pair strings by the library
additional[additional_count++] = service->txt_record[0];
additional[additional_count++] = service->txt_record[1];
// Send the answer, unicast or multicast depending on flag in query
uint16_t unicast = (rclass & MDNS_UNICAST_RESPONSE);
printf(" --> answer %.*s port %d (%s)\n",
MDNS_STRING_FORMAT(service->record_srv.data.srv.name), service->port,
(unicast ? "unicast" : "multicast"));
if (unicast) {
mdns_query_answer_unicast(sock, from, addrlen, sendbuffer, sizeof(sendbuffer),
query_id, rtype, name.str, name.length, answer, 0, 0,
additional, additional_count);
} else {
mdns_query_answer_multicast(sock, sendbuffer, sizeof(sendbuffer), answer, 0, 0,
additional, additional_count);
}
}
} else if ((name.length == service->hostname_qualified.length) &&
(strncmp(name.str, service->hostname_qualified.str, name.length) == 0)) {
if (((rtype == MDNS_RECORDTYPE_A) || (rtype == MDNS_RECORDTYPE_ANY)) &&
(service->address_ipv4.sin_family == AF_INET)) {
// The A query was for our qualified hostname (typically "<hostname>.local.") and we
// have an IPv4 address, answer with an A record mappiing the hostname to an IPv4
// address, as well as any IPv6 address for the hostname, and two test TXT records
// Answer A records mapping "<hostname>.local." to IPv4 address
mdns_record_t answer = service->record_a;
mdns_record_t additional[5] = {0};
size_t additional_count = 0;
// AAAA record mapping "<hostname>.local." to IPv6 addresses
if (service->address_ipv6.sin6_family == AF_INET6)
additional[additional_count++] = service->record_aaaa;
// Add two test TXT records for our service instance name, will be coalesced into
// one record with both key-value pair strings by the library
additional[additional_count++] = service->txt_record[0];
additional[additional_count++] = service->txt_record[1];
// Send the answer, unicast or multicast depending on flag in query
uint16_t unicast = (rclass & MDNS_UNICAST_RESPONSE);
mdns_string_t addrstr = ip_address_to_string(
addrbuffer, sizeof(addrbuffer), (struct sockaddr*)&service->record_a.data.a.addr,
sizeof(service->record_a.data.a.addr));
printf(" --> answer %.*s IPv4 %.*s (%s)\n", MDNS_STRING_FORMAT(service->record_a.name),
MDNS_STRING_FORMAT(addrstr), (unicast ? "unicast" : "multicast"));
if (unicast) {
mdns_query_answer_unicast(sock, from, addrlen, sendbuffer, sizeof(sendbuffer),
query_id, rtype, name.str, name.length, answer, 0, 0,
additional, additional_count);
} else {
mdns_query_answer_multicast(sock, sendbuffer, sizeof(sendbuffer), answer, 0, 0,
additional, additional_count);
}
} else if (((rtype == MDNS_RECORDTYPE_AAAA) || (rtype == MDNS_RECORDTYPE_ANY)) &&
(service->address_ipv6.sin6_family == AF_INET6)) {
// The AAAA query was for our qualified hostname (typically "<hostname>.local.") and we
// have an IPv6 address, answer with an AAAA record mappiing the hostname to an IPv6
// address, as well as any IPv4 address for the hostname, and two test TXT records
// Answer AAAA records mapping "<hostname>.local." to IPv6 address
mdns_record_t answer = service->record_aaaa;
mdns_record_t additional[5] = {0};
size_t additional_count = 0;
// A record mapping "<hostname>.local." to IPv4 addresses
if (service->address_ipv4.sin_family == AF_INET)
additional[additional_count++] = service->record_a;
// Add two test TXT records for our service instance name, will be coalesced into
// one record with both key-value pair strings by the library
additional[additional_count++] = service->txt_record[0];
additional[additional_count++] = service->txt_record[1];
// Send the answer, unicast or multicast depending on flag in query
uint16_t unicast = (rclass & MDNS_UNICAST_RESPONSE);
mdns_string_t addrstr =
ip_address_to_string(addrbuffer, sizeof(addrbuffer),
(struct sockaddr*)&service->record_aaaa.data.aaaa.addr,
sizeof(service->record_aaaa.data.aaaa.addr));
printf(" --> answer %.*s IPv6 %.*s (%s)\n",
MDNS_STRING_FORMAT(service->record_aaaa.name), MDNS_STRING_FORMAT(addrstr),
(unicast ? "unicast" : "multicast"));
if (unicast) {
mdns_query_answer_unicast(sock, from, addrlen, sendbuffer, sizeof(sendbuffer),
query_id, rtype, name.str, name.length, answer, 0, 0,
additional, additional_count);
} else {
mdns_query_answer_multicast(sock, sendbuffer, sizeof(sendbuffer), answer, 0, 0,
additional, additional_count);
}
}
}
return 0;
}
// Callback handling questions and answers dump
static int
dump_callback(int sock, const struct sockaddr* from, size_t addrlen, mdns_entry_type_t entry,
uint16_t query_id, uint16_t rtype, uint16_t rclass, uint32_t ttl, const void* data,
size_t size, size_t name_offset, size_t name_length, size_t record_offset,
size_t record_length, void* user_data) {
mdns_string_t fromaddrstr = ip_address_to_string(addrbuffer, sizeof(addrbuffer), from, addrlen);
size_t offset = name_offset;
mdns_string_t name = mdns_string_extract(data, size, &offset, namebuffer, sizeof(namebuffer));
const char* record_name = 0;
if (rtype == MDNS_RECORDTYPE_PTR)
record_name = "PTR";
else if (rtype == MDNS_RECORDTYPE_SRV)
record_name = "SRV";
else if (rtype == MDNS_RECORDTYPE_A)
record_name = "A";
else if (rtype == MDNS_RECORDTYPE_AAAA)
record_name = "AAAA";
else if (rtype == MDNS_RECORDTYPE_TXT)
record_name = "TXT";
else if (rtype == MDNS_RECORDTYPE_ANY)
record_name = "ANY";
else
record_name = "<UNKNOWN>";
const char* entry_type = "Question";
if (entry == MDNS_ENTRYTYPE_ANSWER)
entry_type = "Answer";
else if (entry == MDNS_ENTRYTYPE_AUTHORITY)
entry_type = "Authority";
else if (entry == MDNS_ENTRYTYPE_ADDITIONAL)
entry_type = "Additional";
printf("%.*s: %s %s %.*s rclass 0x%x ttl %u\n", MDNS_STRING_FORMAT(fromaddrstr), entry_type,
record_name, MDNS_STRING_FORMAT(name), (unsigned int)rclass, ttl);
return 0;
}
// Open sockets for sending one-shot multicast queries from an ephemeral port
static int
open_client_sockets(int* sockets, int max_sockets, int port) {
// When sending, each socket can only send to one network interface
// Thus we need to open one socket for each interface and address family
int num_sockets = 0;
#ifdef _WIN32
IP_ADAPTER_ADDRESSES* adapter_address = 0;
ULONG address_size = 8000;
unsigned int ret;
unsigned int num_retries = 4;
do {
adapter_address = (IP_ADAPTER_ADDRESSES*)malloc(address_size);
ret = GetAdaptersAddresses(AF_UNSPEC, GAA_FLAG_SKIP_MULTICAST | GAA_FLAG_SKIP_ANYCAST, 0,
adapter_address, &address_size);
if (ret == ERROR_BUFFER_OVERFLOW) {
free(adapter_address);
adapter_address = 0;
address_size *= 2;
} else {
break;
}
} while (num_retries-- > 0);
if (!adapter_address || (ret != NO_ERROR)) {
free(adapter_address);
printf("Failed to get network adapter addresses\n");
return num_sockets;
}
int first_ipv4 = 1;
int first_ipv6 = 1;
for (PIP_ADAPTER_ADDRESSES adapter = adapter_address; adapter; adapter = adapter->Next) {
if (adapter->TunnelType == TUNNEL_TYPE_TEREDO)
continue;
if (adapter->OperStatus != IfOperStatusUp)
continue;
for (IP_ADAPTER_UNICAST_ADDRESS* unicast = adapter->FirstUnicastAddress; unicast;
unicast = unicast->Next) {
if (unicast->Address.lpSockaddr->sa_family == AF_INET) {
struct sockaddr_in* saddr = (struct sockaddr_in*)unicast->Address.lpSockaddr;
if ((saddr->sin_addr.S_un.S_un_b.s_b1 != 127) ||
(saddr->sin_addr.S_un.S_un_b.s_b2 != 0) ||
(saddr->sin_addr.S_un.S_un_b.s_b3 != 0) ||
(saddr->sin_addr.S_un.S_un_b.s_b4 != 1)) {
int log_addr = 0;
if (first_ipv4) {
service_address_ipv4 = *saddr;
first_ipv4 = 0;
log_addr = 1;
}
has_ipv4 = 1;
if (num_sockets < max_sockets) {
saddr->sin_port = htons((unsigned short)port);
int sock = mdns_socket_open_ipv4(saddr);
if (sock >= 0) {
sockets[num_sockets++] = sock;
log_addr = 1;
} else {
log_addr = 0;
}
}
if (log_addr) {
char buffer[128];
mdns_string_t addr = ipv4_address_to_string(buffer, sizeof(buffer), saddr,
sizeof(struct sockaddr_in));
printf("Local IPv4 address: %.*s\n", MDNS_STRING_FORMAT(addr));
}
}
} else if (unicast->Address.lpSockaddr->sa_family == AF_INET6) {
struct sockaddr_in6* saddr = (struct sockaddr_in6*)unicast->Address.lpSockaddr;
// Ignore link-local addresses
if (saddr->sin6_scope_id)
continue;
static const unsigned char localhost[] = {0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1};
static const unsigned char localhost_mapped[] = {0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0xff, 0xff, 0x7f, 0, 0, 1};
if ((unicast->DadState == NldsPreferred) &&
memcmp(saddr->sin6_addr.s6_addr, localhost, 16) &&
memcmp(saddr->sin6_addr.s6_addr, localhost_mapped, 16)) {
int log_addr = 0;
if (first_ipv6) {
service_address_ipv6 = *saddr;
first_ipv6 = 0;
log_addr = 1;
}
has_ipv6 = 1;
if (num_sockets < max_sockets) {
saddr->sin6_port = htons((unsigned short)port);
int sock = mdns_socket_open_ipv6(saddr);
if (sock >= 0) {
sockets[num_sockets++] = sock;
log_addr = 1;
} else {
log_addr = 0;
}
}
if (log_addr) {
char buffer[128];
mdns_string_t addr = ipv6_address_to_string(buffer, sizeof(buffer), saddr,
sizeof(struct sockaddr_in6));
printf("Local IPv6 address: %.*s\n", MDNS_STRING_FORMAT(addr));
}
}
}
}
}
free(adapter_address);
#else
struct ifaddrs* ifaddr = 0;
struct ifaddrs* ifa = 0;
if (getifaddrs(&ifaddr) < 0)
printf("Unable to get interface addresses\n");
int first_ipv4 = 1;
int first_ipv6 = 1;
for (ifa = ifaddr; ifa; ifa = ifa->ifa_next) {
if (!ifa->ifa_addr)
continue;
if (!(ifa->ifa_flags & IFF_UP) || !(ifa->ifa_flags & IFF_MULTICAST))
continue;
if ((ifa->ifa_flags & IFF_LOOPBACK) || (ifa->ifa_flags & IFF_POINTOPOINT))
continue;
if (ifa->ifa_addr->sa_family == AF_INET) {
struct sockaddr_in* saddr = (struct sockaddr_in*)ifa->ifa_addr;
if (saddr->sin_addr.s_addr != htonl(INADDR_LOOPBACK)) {
int log_addr = 0;
if (first_ipv4) {
service_address_ipv4 = *saddr;
first_ipv4 = 0;
log_addr = 1;
}
has_ipv4 = 1;
if (num_sockets < max_sockets) {
saddr->sin_port = htons(port);
int sock = mdns_socket_open_ipv4(saddr);
if (sock >= 0) {
sockets[num_sockets++] = sock;
log_addr = 1;
} else {
log_addr = 0;
}
}
if (log_addr) {
char buffer[128];
mdns_string_t addr = ipv4_address_to_string(buffer, sizeof(buffer), saddr,
sizeof(struct sockaddr_in));
printf("Local IPv4 address: %.*s\n", MDNS_STRING_FORMAT(addr));
}
}
} else if (ifa->ifa_addr->sa_family == AF_INET6) {
struct sockaddr_in6* saddr = (struct sockaddr_in6*)ifa->ifa_addr;
// Ignore link-local addresses
if (saddr->sin6_scope_id)
continue;
static const unsigned char localhost[] = {0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 1};
static const unsigned char localhost_mapped[] = {0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0xff, 0xff, 0x7f, 0, 0, 1};
if (memcmp(saddr->sin6_addr.s6_addr, localhost, 16) &&
memcmp(saddr->sin6_addr.s6_addr, localhost_mapped, 16)) {
int log_addr = 0;
if (first_ipv6) {
service_address_ipv6 = *saddr;
first_ipv6 = 0;
log_addr = 1;
}
has_ipv6 = 1;
if (num_sockets < max_sockets) {
saddr->sin6_port = htons(port);
int sock = mdns_socket_open_ipv6(saddr);
if (sock >= 0) {
sockets[num_sockets++] = sock;
log_addr = 1;
} else {
log_addr = 0;
}
}
if (log_addr) {
char buffer[128];
mdns_string_t addr = ipv6_address_to_string(buffer, sizeof(buffer), saddr,
sizeof(struct sockaddr_in6));
printf("Local IPv6 address: %.*s\n", MDNS_STRING_FORMAT(addr));
}
}
}
}
freeifaddrs(ifaddr);
#endif
return num_sockets;
}
// Open sockets to listen to incoming mDNS queries on port 5353
static int
open_service_sockets(int* sockets, int max_sockets) {
// When recieving, each socket can recieve data from all network interfaces
// Thus we only need to open one socket for each address family
int num_sockets = 0;
// Call the client socket function to enumerate and get local addresses,
// but not open the actual sockets
open_client_sockets(0, 0, 0);
if (num_sockets < max_sockets) {
struct sockaddr_in sock_addr;
memset(&sock_addr, 0, sizeof(struct sockaddr_in));
sock_addr.sin_family = AF_INET;
#ifdef _WIN32
sock_addr.sin_addr = in4addr_any;
#else
sock_addr.sin_addr.s_addr = INADDR_ANY;
#endif
sock_addr.sin_port = htons(MDNS_PORT);
#ifdef __APPLE__
sock_addr.sin_len = sizeof(struct sockaddr_in);
#endif
int sock = mdns_socket_open_ipv4(&sock_addr);
if (sock >= 0)
sockets[num_sockets++] = sock;
}
if (num_sockets < max_sockets) {
struct sockaddr_in6 sock_addr;
memset(&sock_addr, 0, sizeof(struct sockaddr_in6));
sock_addr.sin6_family = AF_INET6;
sock_addr.sin6_addr = in6addr_any;
sock_addr.sin6_port = htons(MDNS_PORT);
#ifdef __APPLE__
sock_addr.sin6_len = sizeof(struct sockaddr_in6);
#endif
int sock = mdns_socket_open_ipv6(&sock_addr);
if (sock >= 0)
sockets[num_sockets++] = sock;
}
return num_sockets;
}
// Send a DNS-SD query
static int
send_dns_sd(void) {
int sockets[32];
int num_sockets = open_client_sockets(sockets, sizeof(sockets) / sizeof(sockets[0]), 0);
if (num_sockets <= 0) {
printf("Failed to open any client sockets\n");
return -1;
}
printf("Opened %d socket%s for DNS-SD\n", num_sockets, num_sockets > 1 ? "s" : "");
printf("Sending DNS-SD discovery\n");
for (int isock = 0; isock < num_sockets; ++isock) {
if (mdns_discovery_send(sockets[isock]))
printf("Failed to send DNS-DS discovery: %s\n", strerror(errno));
}
size_t capacity = 2048;
void* buffer = malloc(capacity);
void* user_data = 0;
size_t records;
// This is a simple implementation that loops for 5 seconds or as long as we get replies
int res;
printf("Reading DNS-SD replies\n");
do {
struct timeval timeout;
timeout.tv_sec = 5;
timeout.tv_usec = 0;
int nfds = 0;
fd_set readfs;
FD_ZERO(&readfs);
for (int isock = 0; isock < num_sockets; ++isock) {
if (sockets[isock] >= nfds)
nfds = sockets[isock] + 1;
FD_SET(sockets[isock], &readfs);
}
records = 0;
res = select(nfds, &readfs, 0, 0, &timeout);
if (res > 0) {
for (int isock = 0; isock < num_sockets; ++isock) {
if (FD_ISSET(sockets[isock], &readfs)) {
records += mdns_discovery_recv(sockets[isock], buffer, capacity, query_callback,
user_data);
}
}
}
} while (res > 0);
free(buffer);
for (int isock = 0; isock < num_sockets; ++isock)
mdns_socket_close(sockets[isock]);
printf("Closed socket%s\n", num_sockets ? "s" : "");
return 0;
}
// Send a mDNS query
static int
send_mdns_query(mdns_query_t* query, size_t count) {
int sockets[32];
int query_id[32];
int num_sockets = open_client_sockets(sockets, sizeof(sockets) / sizeof(sockets[0]), 0);
if (num_sockets <= 0) {
printf("Failed to open any client sockets\n");
return -1;
}
printf("Opened %d socket%s for mDNS query\n", num_sockets, num_sockets ? "s" : "");
size_t capacity = 2048;
void* buffer = malloc(capacity);
void* user_data = 0;
printf("Sending mDNS query");
for (size_t iq = 0; iq < count; ++iq) {
const char* record_name = "PTR";
if (query[iq].type == MDNS_RECORDTYPE_SRV)
record_name = "SRV";
else if (query[iq].type == MDNS_RECORDTYPE_A)
record_name = "A";
else if (query[iq].type == MDNS_RECORDTYPE_AAAA)
record_name = "AAAA";
else
query[iq].type = MDNS_RECORDTYPE_PTR;
printf(" : %s %s", query[iq].name, record_name);
}
printf("\n");
for (int isock = 0; isock < num_sockets; ++isock) {
query_id[isock] = mdns_multiquery_send(sockets[isock], query, count, buffer, capacity, 0);
if (query_id[isock] < 0)
printf("Failed to send mDNS query: %s\n", strerror(errno));
}
// This is a simple implementation that loops for 5 seconds or as long as we get replies
int res;
printf("Reading mDNS query replies\n");
int records = 0;
do {
struct timeval timeout;
timeout.tv_sec = 10;
timeout.tv_usec = 0;
int nfds = 0;
fd_set readfs;
FD_ZERO(&readfs);
for (int isock = 0; isock < num_sockets; ++isock) {
if (sockets[isock] >= nfds)
nfds = sockets[isock] + 1;
FD_SET(sockets[isock], &readfs);
}
res = select(nfds, &readfs, 0, 0, &timeout);
if (res > 0) {
for (int isock = 0; isock < num_sockets; ++isock) {
if (FD_ISSET(sockets[isock], &readfs)) {
size_t rec = mdns_query_recv(sockets[isock], buffer, capacity, query_callback,
user_data, query_id[isock]);
if (rec > 0)
records += rec;
}
FD_SET(sockets[isock], &readfs);
}
}
} while (res > 0);
printf("Read %d records\n", records);
free(buffer);
for (int isock = 0; isock < num_sockets; ++isock)
mdns_socket_close(sockets[isock]);
printf("Closed socket%s\n", num_sockets ? "s" : "");
return 0;
}
// Provide a mDNS service, answering incoming DNS-SD and mDNS queries
static int
service_mdns(const char* hostname, const char* service_name, int service_port) {
int sockets[32];
int num_sockets = open_service_sockets(sockets, sizeof(sockets) / sizeof(sockets[0]));
if (num_sockets <= 0) {
printf("Failed to open any client sockets\n");
return -1;
}
printf("Opened %d socket%s for mDNS service\n", num_sockets, num_sockets ? "s" : "");
size_t service_name_length = strlen(service_name);
if (!service_name_length) {
printf("Invalid service name\n");
return -1;
}
char* service_name_buffer = malloc(service_name_length + 2);
memcpy(service_name_buffer, service_name, service_name_length);
if (service_name_buffer[service_name_length - 1] != '.')
service_name_buffer[service_name_length++] = '.';
service_name_buffer[service_name_length] = 0;
service_name = service_name_buffer;
printf("Service mDNS: %s:%d\n", service_name, service_port);
printf("Hostname: %s\n", hostname);
size_t capacity = 2048;
void* buffer = malloc(capacity);
mdns_string_t service_string = (mdns_string_t){service_name, strlen(service_name)};
mdns_string_t hostname_string = (mdns_string_t){hostname, strlen(hostname)};
// Build the service instance "<hostname>.<_service-name>._tcp.local." string
char service_instance_buffer[256] = {0};
snprintf(service_instance_buffer, sizeof(service_instance_buffer) - 1, "%.*s.%.*s",
MDNS_STRING_FORMAT(hostname_string), MDNS_STRING_FORMAT(service_string));
mdns_string_t service_instance_string =
(mdns_string_t){service_instance_buffer, strlen(service_instance_buffer)};
// Build the "<hostname>.local." string
char qualified_hostname_buffer[256] = {0};
snprintf(qualified_hostname_buffer, sizeof(qualified_hostname_buffer) - 1, "%.*s.local.",
MDNS_STRING_FORMAT(hostname_string));
mdns_string_t hostname_qualified_string =
(mdns_string_t){qualified_hostname_buffer, strlen(qualified_hostname_buffer)};
service_t service = {0};
service.service = service_string;
service.hostname = hostname_string;
service.service_instance = service_instance_string;
service.hostname_qualified = hostname_qualified_string;
service.address_ipv4 = service_address_ipv4;
service.address_ipv6 = service_address_ipv6;
service.port = service_port;
// Setup our mDNS records
// PTR record reverse mapping "<_service-name>._tcp.local." to
// "<hostname>.<_service-name>._tcp.local."
service.record_ptr = (mdns_record_t){.name = service.service,
.type = MDNS_RECORDTYPE_PTR,
.data.ptr.name = service.service_instance,
.rclass = 0,
.ttl = 0};
// SRV record mapping "<hostname>.<_service-name>._tcp.local." to
// "<hostname>.local." with port. Set weight & priority to 0.
service.record_srv = (mdns_record_t){.name = service.service_instance,
.type = MDNS_RECORDTYPE_SRV,
.data.srv.name = service.hostname_qualified,
.data.srv.port = service.port,
.data.srv.priority = 0,
.data.srv.weight = 0,
.rclass = 0,
.ttl = 0};
// A/AAAA records mapping "<hostname>.local." to IPv4/IPv6 addresses
service.record_a = (mdns_record_t){.name = service.hostname_qualified,
.type = MDNS_RECORDTYPE_A,
.data.a.addr = service.address_ipv4,
.rclass = 0,
.ttl = 0};
service.record_aaaa = (mdns_record_t){.name = service.hostname_qualified,
.type = MDNS_RECORDTYPE_AAAA,
.data.aaaa.addr = service.address_ipv6,
.rclass = 0,
.ttl = 0};
// Add two test TXT records for our service instance name, will be coalesced into
// one record with both key-value pair strings by the library
service.txt_record[0] = (mdns_record_t){.name = service.service_instance,
.type = MDNS_RECORDTYPE_TXT,
.data.txt.key = {MDNS_STRING_CONST("test")},
.data.txt.value = {MDNS_STRING_CONST("1")},
.rclass = 0,
.ttl = 0};
service.txt_record[1] = (mdns_record_t){.name = service.service_instance,
.type = MDNS_RECORDTYPE_TXT,
.data.txt.key = {MDNS_STRING_CONST("other")},
.data.txt.value = {MDNS_STRING_CONST("value")},
.rclass = 0,
.ttl = 0};
// Send an announcement on startup of service
{
printf("Sending announce\n");
mdns_record_t additional[5] = {0};
size_t additional_count = 0;
additional[additional_count++] = service.record_srv;
if (service.address_ipv4.sin_family == AF_INET)
additional[additional_count++] = service.record_a;
if (service.address_ipv6.sin6_family == AF_INET6)
additional[additional_count++] = service.record_aaaa;
additional[additional_count++] = service.txt_record[0];
additional[additional_count++] = service.txt_record[1];
for (int isock = 0; isock < num_sockets; ++isock)
mdns_announce_multicast(sockets[isock], buffer, capacity, service.record_ptr, 0, 0,
additional, additional_count);
}
// This is a crude implementation that checks for incoming queries
while (running) {
int nfds = 0;
fd_set readfs;
FD_ZERO(&readfs);
for (int isock = 0; isock < num_sockets; ++isock) {
if (sockets[isock] >= nfds)
nfds = sockets[isock] + 1;
FD_SET(sockets[isock], &readfs);
}
struct timeval timeout;
timeout.tv_sec = 0;
timeout.tv_usec = 100000;
if (select(nfds, &readfs, 0, 0, &timeout) >= 0) {
for (int isock = 0; isock < num_sockets; ++isock) {
if (FD_ISSET(sockets[isock], &readfs)) {
mdns_socket_listen(sockets[isock], buffer, capacity, service_callback,
&service);
}
FD_SET(sockets[isock], &readfs);
}
} else {
break;
}
}
// Send a goodbye on end of service
{
printf("Sending goodbye\n");
mdns_record_t additional[5] = {0};
size_t additional_count = 0;
additional[additional_count++] = service.record_srv;
if (service.address_ipv4.sin_family == AF_INET)
additional[additional_count++] = service.record_a;
if (service.address_ipv6.sin6_family == AF_INET6)