xref: /aosp_15_r20/external/mdnsresponder/mDNSPosix/Identify.c (revision 48a54d368dc4fa860885eef7b70b6c53499e7c25)

/* -*- Mode: C; tab-width: 4 -*-
 *
 * Copyright (c) 2002-2004 Apple Computer, Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Formatting notes:
 * This code follows the "Whitesmiths style" C indentation rules. Plenty of discussion
 * on C indentation can be found on the web, such as <http://www.kafejo.com/komp/1tbs.htm>,
 * but for the sake of brevity here I will say just this: Curly braces are not syntactially
 * part of an "if" statement; they are the beginning and ending markers of a compound statement;
 * therefore common sense dictates that if they are part of a compound statement then they
 * should be indented to the same level as everything else in that compound statement.
 * Indenting curly braces at the same level as the "if" implies that curly braces are
 * part of the "if", which is false. (This is as misleading as people who write "char* x,y;"
 * thinking that variables x and y are both of type "char*" -- and anyone who doesn't
 * understand why variable y is not of type "char*" just proves the point that poor code
 * layout leads people to unfortunate misunderstandings about how the C language really works.)
 */

//*************************************************************************************************************
// Incorporate mDNS.c functionality

// We want to use the functionality provided by "mDNS.c",
// except we'll sneak a peek at the packets before forwarding them to the normal mDNSCoreReceive() routine
#define mDNSCoreReceive __MDNS__mDNSCoreReceive
#include "mDNS.c"
#undef mDNSCoreReceive

//*************************************************************************************************************
// Headers

#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>		// For n_long, required by <netinet/ip.h> below
#include <netinet/ip.h>				// For IPTOS_LOWDELAY etc.
#include <arpa/inet.h>
#include <signal.h>

#include "mDNSEmbeddedAPI.h"// Defines the interface to the mDNS core code
#include "mDNSPosix.h"    // Defines the specific types needed to run mDNS on this platform
#include "ExampleClientApp.h"

//*************************************************************************************************************
// Globals

static mDNS mDNSStorage;       // mDNS core uses this to store its globals
static mDNS_PlatformSupport PlatformStorage;  // Stores this platform's globals
#define RR_CACHE_SIZE 500
static CacheEntity gRRCache[RR_CACHE_SIZE];
mDNSexport const char ProgramName[] = "mDNSIdentify";

static volatile int StopNow;	// 0 means running, 1 means stop because we got an answer, 2 means stop because of Ctrl-C
static volatile int NumAnswers, NumAddr, NumAAAA, NumHINFO;
static char hostname[MAX_ESCAPED_DOMAIN_NAME], hardware[256], software[256];
static mDNSAddr lastsrc, hostaddr, target;
static mDNSOpaque16 lastid, id;

//*************************************************************************************************************
// Utilities

// Special version of printf that knows how to print IP addresses, DNS-format name strings, etc.
mDNSlocal mDNSu32 mprintf(const char *format, ...) IS_A_PRINTF_STYLE_FUNCTION(1,2);
mDNSlocal mDNSu32 mprintf(const char *format, ...)
	{
	mDNSu32 length;
	unsigned char buffer[512];
	va_list ptr;
	va_start(ptr,format);
	length = mDNS_vsnprintf((char *)buffer, sizeof(buffer), format, ptr);
	va_end(ptr);
	printf("%s", buffer);
	return(length);
	}

//*************************************************************************************************************
// Main code

mDNSexport void mDNSCoreReceive(mDNS *const m, DNSMessage *const msg, const mDNSu8 *const end,
	const mDNSAddr *const srcaddr, const mDNSIPPort srcport, const mDNSAddr *const dstaddr, const mDNSIPPort dstport,
	const mDNSInterfaceID InterfaceID)
	{
	(void)dstaddr; // Unused
	// Snag copy of header ID, then call through
	lastid = msg->h.id;
	lastsrc = *srcaddr;

	// We *want* to allow off-net unicast responses here.
	// For now, the simplest way to allow that is to pretend it was received via multicast so that mDNSCore doesn't reject the packet
	__MDNS__mDNSCoreReceive(m, msg, end, srcaddr, srcport, &AllDNSLinkGroup_v4, dstport, InterfaceID);
	}

mDNSlocal void NameCallback(mDNS *const m, DNSQuestion *question, const ResourceRecord *const answer, QC_result AddRecord)
	{
	(void)m;		// Unused
	(void)question;	// Unused
	(void)AddRecord;// Unused
	if (!id.NotAnInteger) id = lastid;
	if (answer->rrtype == kDNSType_PTR || answer->rrtype == kDNSType_CNAME)
		{
		ConvertDomainNameToCString(&answer->rdata->u.name, hostname);
		StopNow = 1;
		mprintf("%##s %s %##s\n", answer->name->c, DNSTypeName(answer->rrtype), answer->rdata->u.name.c);
		}
	}

mDNSlocal void InfoCallback(mDNS *const m, DNSQuestion *question, const ResourceRecord *const answer, QC_result AddRecord)
	{
	(void)m;		// Unused
	(void)question;	// Unused
	(void)AddRecord;// Unused
	if (answer->rrtype == kDNSType_A)
		{
		if (!id.NotAnInteger) id = lastid;
		NumAnswers++;
		NumAddr++;
		mprintf("%##s %s %.4a\n", answer->name->c, DNSTypeName(answer->rrtype), &answer->rdata->u.ipv4);
		hostaddr.type = mDNSAddrType_IPv4;	// Prefer v4 target to v6 target, for now
		hostaddr.ip.v4 = answer->rdata->u.ipv4;
		}
	else if (answer->rrtype == kDNSType_AAAA)
		{
		if (!id.NotAnInteger) id = lastid;
		NumAnswers++;
		NumAAAA++;
		mprintf("%##s %s %.16a\n", answer->name->c, DNSTypeName(answer->rrtype), &answer->rdata->u.ipv6);
		if (!hostaddr.type)	// Prefer v4 target to v6 target, for now
			{
			hostaddr.type = mDNSAddrType_IPv6;
			hostaddr.ip.v6 = answer->rdata->u.ipv6;
			}
		}
	else if (answer->rrtype == kDNSType_HINFO)
		{
		mDNSu8 *p = answer->rdata->u.data;
		strncpy(hardware, (char*)(p+1), p[0]);
		hardware[p[0]] = 0;
		p += 1 + p[0];
		strncpy(software, (char*)(p+1), p[0]);
		software[p[0]] = 0;
		NumAnswers++;
		NumHINFO++;
		}

	// If we've got everything we're looking for, don't need to wait any more
	if (/*NumHINFO && */ (NumAddr || NumAAAA)) StopNow = 1;
	}

mDNSlocal void ServicesCallback(mDNS *const m, DNSQuestion *question, const ResourceRecord *const answer, QC_result AddRecord)
	{
	(void)m;		// Unused
	(void)question;	// Unused
	(void)AddRecord;// Unused
	// Right now the mDNSCore targeted-query code is incomplete --
	// it issues targeted queries, but accepts answers from anywhere
	// For now, we'll just filter responses here so we don't get confused by responses from someone else
	if (answer->rrtype == kDNSType_PTR && mDNSSameAddress(&lastsrc, &target))
		{
		NumAnswers++;
		mprintf("%##s %s %##s\n", answer->name->c, DNSTypeName(answer->rrtype), answer->rdata->u.name.c);
		}
	}

mDNSlocal void WaitForAnswer(mDNS *const m, int seconds)
	{
	struct timeval end;
	gettimeofday(&end, NULL);
	end.tv_sec += seconds;
	StopNow = 0;
	NumAnswers = 0;
	while (!StopNow)
		{
		int nfds = 0;
		fd_set readfds;
		struct timeval now, remain = end;
		int result;

		FD_ZERO(&readfds);
		gettimeofday(&now, NULL);
		if (remain.tv_usec < now.tv_usec) { remain.tv_usec += 1000000; remain.tv_sec--; }
		if (remain.tv_sec < now.tv_sec)
			{
			if (!NumAnswers) printf("No response after %d seconds\n", seconds);
			return;
			}
		remain.tv_usec -= now.tv_usec;
		remain.tv_sec  -= now.tv_sec;
		mDNSPosixGetFDSet(m, &nfds, &readfds, &remain);
		result = select(nfds, &readfds, NULL, NULL, &remain);
		if (result >= 0) mDNSPosixProcessFDSet(m, &readfds);
		else if (errno != EINTR) StopNow = 2;
		}
	}

mDNSlocal mStatus StartQuery(DNSQuestion *q, char *qname, mDNSu16 qtype, const mDNSAddr *target, mDNSQuestionCallback callback)
	{
	lastsrc = zeroAddr;
	if (qname) MakeDomainNameFromDNSNameString(&q->qname, qname);
	q->InterfaceID      = mDNSInterface_Any;
	q->Target           = target ? *target : zeroAddr;
	q->TargetPort       = MulticastDNSPort;
	q->TargetQID        = zeroID;
	q->qtype            = qtype;
	q->qclass           = kDNSClass_IN;
	q->LongLived        = mDNSfalse;
	q->ExpectUnique     = mDNSfalse;	// Don't want to stop after the first response packet
	q->ForceMCast       = mDNStrue;		// Query via multicast, even for apparently uDNS names like 1.1.1.17.in-addr.arpa.
	q->ReturnIntermed   = mDNStrue;
	q->SuppressUnusable = mDNSfalse;
	q->SearchListIndex  = 0;
	q->AppendSearchDomains = 0;
	q->RetryWithSearchDomains = mDNSfalse;
	q->TimeoutQuestion  = 0;
	q->WakeOnResolve    = 0;
	q->qnameOrig        = mDNSNULL;
	q->QuestionCallback = callback;
	q->QuestionContext  = NULL;

	//mprintf("%##s %s ?\n", q->qname.c, DNSTypeName(qtype));
	return(mDNS_StartQuery(&mDNSStorage, q));
	}

mDNSlocal void DoOneQuery(DNSQuestion *q, char *qname, mDNSu16 qtype, const mDNSAddr *target, mDNSQuestionCallback callback)
	{
	mStatus status = StartQuery(q, qname, qtype, target, callback);
	if (status != mStatus_NoError)
		StopNow = 2;
	else
		{
		WaitForAnswer(&mDNSStorage, 4);
		mDNS_StopQuery(&mDNSStorage, q);
		}
	}

mDNSlocal int DoQuery(DNSQuestion *q, char *qname, mDNSu16 qtype, const mDNSAddr *target, mDNSQuestionCallback callback)
	{
	DoOneQuery(q, qname, qtype, target, callback);
	if (StopNow == 0 && NumAnswers == 0 && target && target->type)
		{
		mprintf("%##s %s Trying multicast\n", q->qname.c, DNSTypeName(q->qtype));
		DoOneQuery(q, qname, qtype, NULL, callback);
		}
	if (StopNow == 0 && NumAnswers == 0)
		mprintf("%##s %s *** No Answer ***\n", q->qname.c, DNSTypeName(q->qtype));
	return(StopNow);
	}

mDNSlocal void HandleSIG(int signal)
	{
	(void)signal;	// Unused
	debugf("%s","");
	debugf("HandleSIG");
	StopNow = 2;
	}

mDNSexport int main(int argc, char **argv)
	{
	const char *progname = strrchr(argv[0], '/') ? strrchr(argv[0], '/') + 1 : argv[0];
	int this_arg = 1;
	mStatus status;
	struct in_addr s4;
#if HAVE_IPV6
	struct in6_addr s6;
#endif
	char buffer[256];
	DNSQuestion q;

	if (argc < 2) goto usage;

	// Since this is a special command-line tool, we want LogMsg() errors to go to stderr, not syslog
	mDNS_DebugMode = mDNStrue;

    // Initialise the mDNS core.
	status = mDNS_Init(&mDNSStorage, &PlatformStorage,
    	gRRCache, RR_CACHE_SIZE,
    	mDNS_Init_DontAdvertiseLocalAddresses,
    	mDNS_Init_NoInitCallback, mDNS_Init_NoInitCallbackContext);
	if (status) { fprintf(stderr, "Daemon start: mDNS_Init failed %d\n", (int)status); return(status); }

	signal(SIGINT, HandleSIG);	// SIGINT is what you get for a Ctrl-C
	signal(SIGTERM, HandleSIG);

	while (this_arg < argc)
		{
		char *arg = argv[this_arg++];
		if (this_arg > 2) printf("\n");

		lastid = id = zeroID;
		hostaddr = target = zeroAddr;
		hostname[0] = hardware[0] = software[0] = 0;
		NumAddr = NumAAAA = NumHINFO = 0;

		if (inet_pton(AF_INET, arg, &s4) == 1)
			{
			mDNSu8 *p = (mDNSu8 *)&s4;
			// Note: This is reverse order compared to a normal dotted-decimal IP address, so we can't use our customary "%.4a" format code
			mDNS_snprintf(buffer, sizeof(buffer), "%d.%d.%d.%d.in-addr.arpa.", p[3], p[2], p[1], p[0]);
			printf("%s\n", buffer);
			target.type = mDNSAddrType_IPv4;
			target.ip.v4.NotAnInteger = s4.s_addr;
			DoQuery(&q, buffer, kDNSType_PTR, &target, NameCallback);
			if (StopNow == 2) break;
			}
#if HAVE_IPV6
		else if (inet_pton(AF_INET6, arg, &s6) == 1)
			{
			int i;
			mDNSu8 *p = (mDNSu8 *)&s6;
			for (i = 0; i < 16; i++)
				{
				static const char hexValues[] = "0123456789ABCDEF";
				buffer[i * 4    ] = hexValues[p[15-i] & 0x0F];
				buffer[i * 4 + 1] = '.';
				buffer[i * 4 + 2] = hexValues[p[15-i] >> 4];
				buffer[i * 4 + 3] = '.';
				}
			mDNS_snprintf(&buffer[64], sizeof(buffer)-64, "ip6.arpa.");
			target.type = mDNSAddrType_IPv6;
			mDNSPlatformMemCopy(&target.ip.v6, &s6, sizeof(target.ip.v6));
			DoQuery(&q, buffer, kDNSType_PTR, &target, NameCallback);
			if (StopNow == 2) break;
			}
#endif
		else {
			if (strlen(arg) >= sizeof(hostname)) {
				fprintf(stderr, "hostname must be < %d characters\n", (int)sizeof(hostname));
				goto usage;
			}
			strcpy(hostname, arg);
		}

		// Now we have the host name; get its A, AAAA, and HINFO
		if (hostname[0]) DoQuery(&q, hostname, kDNSQType_ANY, &target, InfoCallback);
		if (StopNow == 2) break;

		if (hardware[0] || software[0])
			{
			printf("HINFO Hardware: %s\n", hardware);
			printf("HINFO Software: %s\n", software);
			}
		else if (NumAnswers) printf("%s has no HINFO record\n", hostname);
		else printf("Incorrect dot-local hostname, address, or no mDNSResponder running on that machine\n");

		if (NumAnswers)
			{
			// Because of the way we use lastsrc in ServicesCallback, we need to clear the cache to make sure we're getting fresh answers
			mDNS *const m = &mDNSStorage;
			mDNSu32 slot;
			CacheGroup *cg;
			CacheRecord *rr;
			FORALL_CACHERECORDS(slot, cg, rr) mDNS_PurgeCacheResourceRecord(m, rr);
			if (target.type == 0) target = hostaddr;		// Make sure the services query is targeted
			DoQuery(&q, "_services._dns-sd._udp.local.", kDNSType_PTR, &target, ServicesCallback);
			if (StopNow == 2) break;
			}
		}

	mDNS_Close(&mDNSStorage);
	return(0);

usage:
	fprintf(stderr, "Usage: %s <dot-local hostname> or <IPv4 address> or <IPv6 address> ...\n", progname);
	return(-1);
	}