ProxyResponder.c

/* -*- 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.
 */

#include <stdio.h>              // For printf()
#include <stdlib.h>             // For exit() etc.
#include <string.h>             // For strlen() etc.
#include <unistd.h>             // For select()
#include <signal.h>             // For SIGINT, SIGTERM
#include <errno.h>              // For errno, EINTR
#include <netinet/in.h>         // For INADDR_NONE
#include <arpa/inet.h>          // For inet_addr()
#include <netdb.h>              // For gethostbyname()

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

// Compatibility workaround: Solaris 2.5 has no INADDR_NONE
#ifndef INADDR_NONE
#define INADDR_NONE (mDNSu32)0xffffffff
#endif

//*************************************************************************************************************
// Globals
mDNS mDNSStorage;       // mDNS core uses this to store its globals
static mDNS_PlatformSupport PlatformStorage;  // Stores this platform's globals
mDNSexport const char ProgramName[] = "mDNSProxyResponderPosix";

//*************************************************************************************************************
// Proxy Host Registration

typedef struct
{
    mDNSv4Addr ip;
    domainlabel hostlabel;      // Conforms to standard DNS letter-digit-hyphen host name rules
    AuthRecord RR_A;        // 'A' (address) record for our ".local" name
    AuthRecord RR_PTR;      // PTR (reverse lookup) record
} ProxyHost;

mDNSlocal void HostNameCallback(mDNS *const m, AuthRecord *const rr, mStatus result)
{
    ProxyHost *f = (ProxyHost*)rr->RecordContext;
    if (result == mStatus_NoError)
        debugf("Host name successfully registered: %##s", rr->resrec.name->c);
    else
    {
        debugf("Host name conflict for %##s", rr->resrec.name->c);
        mDNS_Deregister(m, &f->RR_A);
        mDNS_Deregister(m, &f->RR_PTR);
        exit(-1);
    }
}

mDNSlocal mStatus mDNS_RegisterProxyHost(mDNS *m, ProxyHost *p)
{
    char buffer[32];

    mDNS_SetupResourceRecord(&p->RR_A,   mDNSNULL, mDNSInterface_Any, kDNSType_A,   60, kDNSRecordTypeUnique,      AuthRecordAny, HostNameCallback, p);
    mDNS_SetupResourceRecord(&p->RR_PTR, mDNSNULL, mDNSInterface_Any, kDNSType_PTR, 60, kDNSRecordTypeKnownUnique, AuthRecordAny, HostNameCallback, p);

    p->RR_A.namestorage.c[0] = 0;
    AppendDomainLabel(&p->RR_A.namestorage, &p->hostlabel);
    AppendLiteralLabelString(&p->RR_A.namestorage, "local");

    // 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->ip.b[3], p->ip.b[2], p->ip.b[1], p->ip.b[0]);
    MakeDomainNameFromDNSNameString(&p->RR_PTR.namestorage, buffer);
    p->RR_PTR.ForceMCast = mDNStrue; // This PTR points to our dot-local name, so don't ever try to write it into a uDNS server

    p->RR_A.resrec.rdata->u.ipv4 = p->ip;
    AssignDomainName(&p->RR_PTR.resrec.rdata->u.name, p->RR_A.resrec.name);

    mDNS_Register(m, &p->RR_A);
    mDNS_Register(m, &p->RR_PTR);

    debugf("Made Proxy Host Records for %##s", p->RR_A.resrec.name->c);

    return(mStatus_NoError);
}

//*************************************************************************************************************
// Service Registration

// This sample ServiceCallback just calls mDNS_RenameAndReregisterService to automatically pick a new
// unique name for the service. For a device such as a printer, this may be appropriate.
// For a device with a user interface, and a screen, and a keyboard, the appropriate
// response may be to prompt the user and ask them to choose a new name for the service.
mDNSlocal void ServiceCallback(mDNS *const m, ServiceRecordSet *const sr, mStatus result)
{
    switch (result)
    {
    case mStatus_NoError:      debugf("Callback: %##s Name Registered",    sr->RR_SRV.resrec.name->c); break;
    case mStatus_NameConflict: debugf("Callback: %##s Name Conflict",      sr->RR_SRV.resrec.name->c); break;
    case mStatus_MemFree:      debugf("Callback: %##s Memory Free",        sr->RR_SRV.resrec.name->c); break;
    default:                   debugf("Callback: %##s Unknown Result %ld", sr->RR_SRV.resrec.name->c, result); break;
    }

    if (result == mStatus_NoError)
    {
        char buffer[MAX_ESCAPED_DOMAIN_NAME];
        ConvertDomainNameToCString(sr->RR_SRV.resrec.name, buffer);
        printf("Service %s now registered and active\n", buffer);
    }

    if (result == mStatus_NameConflict)
    {
        char buffer1[MAX_ESCAPED_DOMAIN_NAME], buffer2[MAX_ESCAPED_DOMAIN_NAME];
        ConvertDomainNameToCString(sr->RR_SRV.resrec.name, buffer1);
        mDNS_RenameAndReregisterService(m, sr, mDNSNULL);
        ConvertDomainNameToCString(sr->RR_SRV.resrec.name, buffer2);
        printf("Name Conflict! %s renamed as %s\n", buffer1, buffer2);
    }
}

// RegisterService() is a simple wrapper function which takes C string
// parameters, converts them to domainname parameters, and calls mDNS_RegisterService()
mDNSlocal void RegisterService(mDNS *m, ServiceRecordSet *recordset,
                               const char name[], const char type[], const char domain[],
                               const domainname *host, mDNSu16 PortAsNumber, int argc, char **argv)
{
    domainlabel n;
    domainname t, d;
    unsigned char txtbuffer[1024], *bptr = txtbuffer;
    char buffer[MAX_ESCAPED_DOMAIN_NAME];

    MakeDomainLabelFromLiteralString(&n, name);
    MakeDomainNameFromDNSNameString(&t, type);
    MakeDomainNameFromDNSNameString(&d, domain);
    while (argc)
    {
        int len = strlen(argv[0]);
        if (len > 255 || bptr + 1 + len >= txtbuffer + sizeof(txtbuffer)) break;
        printf("STR: %s\n", argv[0]);
        bptr[0] = len;
        strcpy((char*)(bptr+1), argv[0]);
        bptr += 1 + len;
        argc--;
        argv++;
    }

    mDNS_RegisterService(m, recordset,
                         &n, &t, &d, // Name, type, domain
                         host, mDNSOpaque16fromIntVal(PortAsNumber),
                         mDNSNULL, txtbuffer, bptr-txtbuffer, // TXT data, length
                         mDNSNULL, 0, // Subtypes
                         mDNSInterface_Any, // Interface ID
                         ServiceCallback, mDNSNULL, 0); // Callback, context, flags

    ConvertDomainNameToCString(recordset->RR_SRV.resrec.name, buffer);
    printf("Made Service Records for %s\n", buffer);
}

//*************************************************************************************************************
// Service non-existence assertion
// (claiming a service name without actually providing a service at that name, to prevent anyone else using that name)
// This is useful to avoid confusion between similar services
// e.g. A printer that implements IPP printing service using the name "My Printer", but doesn't implement LPR service,
// should also claim the LPR service name "My Printer" to stop a different printer offering LPR service under the same name,
// since it would be confusing to users to have two equivalent services with the same name.

mDNSlocal void NoSuchServiceCallback(mDNS *const m, AuthRecord *const rr, mStatus result)
{
    const domainname *proxyhostname = (const domainname *)rr->RecordContext;
    switch (result)
    {
    case mStatus_NoError:      debugf("Callback: %##s Name Registered",    rr->resrec.name->c); break;
    case mStatus_NameConflict: debugf("Callback: %##s Name Conflict",      rr->resrec.name->c); break;
    case mStatus_MemFree:      debugf("Callback: %##s Memory Free",        rr->resrec.name->c); break;
    default:                   debugf("Callback: %##s Unknown Result %ld", rr->resrec.name->c, result); break;
    }

    if (result == mStatus_NoError)
    {
        char buffer[MAX_ESCAPED_DOMAIN_NAME];
        ConvertDomainNameToCString(rr->resrec.name, buffer);
        printf("Non-existence assertion %s now registered and active\n", buffer);
    }

    if (result == mStatus_NameConflict)
    {
        domainlabel n;
        domainname t, d;
        char buffer1[MAX_ESCAPED_DOMAIN_NAME], buffer2[MAX_ESCAPED_DOMAIN_NAME];
        ConvertDomainNameToCString(rr->resrec.name, buffer1);
        DeconstructServiceName(rr->resrec.name, &n, &t, &d);
        IncrementLabelSuffix(&n, mDNStrue);
        mDNS_RegisterNoSuchService(m, rr, &n, &t, &d, proxyhostname, mDNSInterface_Any, NoSuchServiceCallback, mDNSNULL, 0);
        ConvertDomainNameToCString(rr->resrec.name, buffer2);
        printf("Name Conflict! %s renamed as %s\n", buffer1, buffer2);
    }
}

mDNSlocal void RegisterNoSuchService(mDNS *m, AuthRecord *const rr, domainname *proxyhostname,
                                     const char name[], const char type[], const char domain[])
{
    domainlabel n;
    domainname t, d;
    char buffer[MAX_ESCAPED_DOMAIN_NAME];
    MakeDomainLabelFromLiteralString(&n, name);
    MakeDomainNameFromDNSNameString(&t, type);
    MakeDomainNameFromDNSNameString(&d, domain);
    mDNS_RegisterNoSuchService(m, rr, &n, &t, &d, proxyhostname, mDNSInterface_Any, NoSuchServiceCallback, proxyhostname, 0);
    ConvertDomainNameToCString(rr->resrec.name, buffer);
    printf("Made Non-existence Record for %s\n", buffer);
}

//*************************************************************************************************************
// Main

mDNSexport int main(int argc, char **argv)
{
    mStatus status;
    sigset_t signals;

    if (argc < 3) goto usage;

    status = mDNS_Init(&mDNSStorage, &PlatformStorage,
                       mDNS_Init_NoCache, mDNS_Init_ZeroCacheSize,
                       mDNS_Init_DontAdvertiseLocalAddresses,
                       mDNS_Init_NoInitCallback, mDNS_Init_NoInitCallbackContext);
    if (status) { fprintf(stderr, "Daemon start: mDNS_Init failed %d\n", (int)status); return(status); }

    mDNSPosixListenForSignalInEventLoop(SIGINT);
    mDNSPosixListenForSignalInEventLoop(SIGTERM);

    if (!strcmp(argv[1], "-"))
    {
        domainname proxyhostname;
        AuthRecord proxyrecord;
        if (argc < 5) goto usage;
        proxyhostname.c[0] = 0;
        AppendLiteralLabelString(&proxyhostname, argv[2]);
        AppendLiteralLabelString(&proxyhostname, "local");
        RegisterNoSuchService(&mDNSStorage, &proxyrecord, &proxyhostname, argv[3], argv[4], "local.");
    }
    else
    {
        ProxyHost proxyhost;
        ServiceRecordSet proxyservice;

        proxyhost.ip.NotAnInteger = inet_addr(argv[1]);
        if (proxyhost.ip.NotAnInteger == INADDR_NONE)   // INADDR_NONE is 0xFFFFFFFF
        {
            struct hostent *h = gethostbyname(argv[1]);
            if (h) proxyhost.ip.NotAnInteger = *(long*)h->h_addr;
        }
        if (proxyhost.ip.NotAnInteger == INADDR_NONE)   // INADDR_NONE is 0xFFFFFFFF
        {
            fprintf(stderr, "%s is not valid host address\n", argv[1]);
            return(-1);
        }

        MakeDomainLabelFromLiteralString(&proxyhost.hostlabel, argv[2]);

        mDNS_RegisterProxyHost(&mDNSStorage, &proxyhost);

        if (argc >=6)
            RegisterService(&mDNSStorage, &proxyservice, argv[3], argv[4], "local.",
                            proxyhost.RR_A.resrec.name, atoi(argv[5]), argc-6, &argv[6]);
    }

    do
    {
        struct timeval timeout = { FutureTime, 0 };     // wait until SIGINT or SIGTERM
        mDNSBool gotSomething;
        mDNSPosixRunEventLoopOnce(&mDNSStorage, &timeout, &signals, &gotSomething);
    }
    while ( !( sigismember( &signals, SIGINT) || sigismember( &signals, SIGTERM)));

    mDNS_Close(&mDNSStorage);

    return(0);

usage:
    fprintf(stderr, "%s ip hostlabel [srvname srvtype port txt [txt ...]]\n", argv[0]);
    fprintf(stderr, "ip        Real IP address (or valid host name) of the host where the service actually resides\n");
    fprintf(stderr, "hostlabel First label of the dot-local host name to create for this host, e.g. \"foo\" for \"foo.local.\"\n");
    fprintf(stderr, "srvname   Descriptive name of service, e.g. \"Stuart's Ink Jet Printer\"\n");
    fprintf(stderr, "srvtype   IANA service type, e.g. \"_ipp._tcp\" or \"_ssh._tcp\", etc.\n");
    fprintf(stderr, "port      Port number where the service resides (1-65535)\n");
    fprintf(stderr, "txt       Additional name/value pairs specified in service definition, e.g. \"pdl=application/postscript\"\n");
    fprintf(stderr, "e.g. %s 169.254.12.34 thehost                                (just create a dot-local host name)\n", argv[0]);
    fprintf(stderr, "or   %s 169.254.12.34 thehost \"My Printer\" _printer._tcp. 515 rp=lpt1 pdl=application/postscript\n", argv[0]);
    fprintf(stderr, "or   %s -             thehost \"My Printer\" _printer._tcp.           (assertion of non-existence)\n", argv[0]);
    return(-1);
}