SNFMilter/SNFMilter.cpp

// SNFMilter.cpp
// Copyright (C) 2008 ARM Research Labs, LLC.
// See www.armresearch.com for the copyright terms.
//
// This file contains the "guts" of the SNFMilter interface. Specifically,
// the SNFMilter() function.

#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <unistd.h>
#include <grp.h>

#include "SNFMulti.hpp"
#include "configuration.hpp"
#include "SNFMilter.hpp"
#include "config.h"

#include <syslog.h>
#include <sstream>

#if SMFI_VERSION > 3
#define NEW_LIBMILTER
#endif

SNFMilterContextPool* MilterContexts = 0;                                       // The global contexts handle.
bool MilterDebugMode;                                                           // True if debug mode is on.

/// Get the connection context object.
//
// \param[in] Ctx is the libmilter context object.
//
// \returns the pointer to the connection context object.
//
// \throws runtime_error if the obtained pointer is 0.
//
SNFMilterContext *
getContextFromCtx(SMFICTX* Ctx) {
    SNFMilterContext* Context = (SNFMilterContext*) smfi_getpriv(Ctx);
    if(0 == Context) throw runtime_error("Got NULL from snfi_getpriv()");
    return Context;
}

// Function to output an info message.
void logInfo(const string ContextName, int Code, std::string Message) {
    cout << ContextName << " (code " << Code << "): " << Message << endl;
#if 0
    syslog(LOG_MAIL | LOG_DEBUG, "%s", Message.c_str());                        // Output to system mail log.
#endif
    MilterContexts->logThisInfo(ContextName, Code, Message);                    // Log message.
}

// Function to output an error message.
void logError(const string &ContextName, const int &Code, const std::string &Message) {
    cout << ContextName << " (code " << Code << "): " << Message << endl;
#if 0
    syslog(LOG_MAIL | LOG_DEBUG, "%s", Message.c_str());                        // Output to system mail log.
#endif
    MilterContexts->logThisError(ContextName, Code, Message);                   // Log message.
}

class ResultActionHandler : public Configurator {
private:
    SNFMilterEngine* Target;

public:
    ResultActionHandler(SNFMilterEngine* T) : Target(T) {}
    void operator()(ConfigurationElement& E, ConfigurationData& D) {
        Target->setResultAction(
                                Code,
                                (Action >= Allow && Action <= Quarantine) ?
                                static_cast<SNFMilterAction>(Action)
                                : Allow
                                );
    }
    int Code;
    int Action;
};

const int NoSuchCode = -1;                                                      // Magic number for no such code
const int NoSuchAction = -1;                                                    // Magic number for no such action

void SNFMilterEngine::readConfiguration() {                                     // Parse the configuration.
    string NewConfiguration = myRulebase->PlatformConfiguration();              // Get the latest configuration.
    if(0 != RunningConfiguration.compare(NewConfiguration)) {                   // If it does not match, read it!
        RunningConfiguration = NewConfiguration;                                // Capture the latest.
        for(int i = 1; i < ResultCodesCount; i++) ResultActions[i] = NoAction;  // Init Result/Action config.
        ResultActions[0] = Allow;
        NonZeroAction = NoAction;                                               // NoAction if no configuration for
                                                                                // non-zero result.
        ResultActionHandler ResultActionConfigurator(this);                     // Create a Result/Action handler.
        ConfigurationElement Reader("milter");                                  // Create a configuration reader.
        Reader
          .Element("connect")
            .Element("white")
              .Attribute("action", reinterpret_cast<int&>(WhiteAction), static_cast<int>(Allow))
                 .Mnemonic("Allow", AllowActionMnemonic)
                 .Mnemonic("Accept", AcceptActionMnemonic)
                 .Mnemonic("Retry", RetryActionMnemonic)
                 .Mnemonic("Reject", RejectActionMnemonic)
                 .Mnemonic("Discard", DiscardActionMnemonic)
                 .Mnemonic("Quarantine", QuarantineActionMnemonic)
            .End("white")
            .Element("caution")
              .Attribute("action", reinterpret_cast<int&>(CautionAction), static_cast<int>(Allow))
                 .Mnemonic("Allow", AllowActionMnemonic)
                 .Mnemonic("Accept", AcceptActionMnemonic)
                 .Mnemonic("Retry", RetryActionMnemonic)
                 .Mnemonic("Reject", RejectActionMnemonic)
                 .Mnemonic("Discard", DiscardActionMnemonic)
                 .Mnemonic("Quarantine", QuarantineActionMnemonic)
            .End("caution")
            .Element("black")
              .Attribute("action", reinterpret_cast<int&>(BlackAction), static_cast<int>(Allow))
                 .Mnemonic("Allow", AllowActionMnemonic)
                 .Mnemonic("Accept", AcceptActionMnemonic)
                 .Mnemonic("Retry", RetryActionMnemonic)
                 .Mnemonic("Reject", RejectActionMnemonic)
                 .Mnemonic("Discard", DiscardActionMnemonic)
                 .Mnemonic("Quarantine", QuarantineActionMnemonic)
            .End("black")
            .Element("truncate")
              .Attribute("action", reinterpret_cast<int&>(TruncateAction), static_cast<int>(Allow))
                 .Mnemonic("Allow", AllowActionMnemonic)
                 .Mnemonic("Accept", AcceptActionMnemonic)
                 .Mnemonic("Retry", RetryActionMnemonic)
                 .Mnemonic("Reject", RejectActionMnemonic)
                 .Mnemonic("Discard", DiscardActionMnemonic)
                 .Mnemonic("Quarantine", QuarantineActionMnemonic)
            .End("truncate")
          .End("connect")
          .Element("scan")
            .Element("result")
              .atEndCall(ResultActionConfigurator)
              .Attribute("code", ResultActionConfigurator.Code, NoSuchCode)
              .Attribute("action", ResultActionConfigurator.Action, NoSuchAction)
                 .Mnemonic("Allow", AllowActionMnemonic)
                 .Mnemonic("Accept", AcceptActionMnemonic)
                 .Mnemonic("Retry", RetryActionMnemonic)
                 .Mnemonic("Reject", RejectActionMnemonic)
                 .Mnemonic("Discard", DiscardActionMnemonic)
                 .Mnemonic("Quarantine", QuarantineActionMnemonic)
            .End("result")
            .Element("nonzero")
              .Attribute("action", reinterpret_cast<int&>(NonZeroAction), static_cast<int>(NoAction))
                 .Mnemonic("Allow", AllowActionMnemonic)
                 .Mnemonic("Accept", AcceptActionMnemonic)
                 .Mnemonic("Retry", RetryActionMnemonic)
                 .Mnemonic("Reject", RejectActionMnemonic)
                 .Mnemonic("Discard", DiscardActionMnemonic)
                 .Mnemonic("Quarantine", QuarantineActionMnemonic)
            .End("nonzero")
          .End("scan")
        .End("milter");
        ConfigurationData ConfigurationData(                                    // Convert our configuration string
                                            NewConfiguration.c_str(),           // to a configuration data buffer.
                                            NewConfiguration.length());

        Reader.initialize();                                                    // Initialize the defaults.
        Reader.interpret(ConfigurationData);                                    // Read the new configuration.
    }

}

void SNFMilterEngine::setResultAction(int Result, SNFMilterAction Action) {     // Set a result / action pair.
    if(
       0 <= Result &&
       ResultCodesCount > Result                                                // If the Result code is in
       ) { ResultActions[Result] = Action; }                                    // range then set the action.
}

void SNFMilterEngine::checkConfiguration() {                                    // Reload the config if it is old.
    if(ConfigurationCheckTime.isExpired()) readConfiguration();
}

SNFMilterEngine::SNFMilterEngine(snf_RulebaseHandler* R) :                      // Construct the engine.
    myRulebase(R),                                                              // Remember our rulebase.
    myEngine(0),                                                                // We need to set this later.
    WhiteAction(Allow),                                                         // Initialize our default actions.
    CautionAction(Allow),
    BlackAction(Allow),
    TruncateAction(Allow),
    ConfigurationCheckTime(ConfigurationLifetime)
{
    myEngine = new snf_EngineHandler();                                         // Create an engine handler.
    myEngine->open(myRulebase);                                                 // Connect it to the rulebase.
    readConfiguration();                                                        // Read our configuration.
}

SNFMilterEngine::~SNFMilterEngine() {                                           // Destroy the engine.
    try {
        ScopeMutex EngineLock(ConfigMutex);                                     // Don't die while scanning.
        if(myEngine) {                                                          // If we're not dead then die.
            myEngine->close();                                                  // Close the engine.
            delete myEngine;                                                    // Delete it.
            myEngine = 0;                                                       // Forget it.
            myRulebase = 0;                                                     // Forget (don't delete) this too.
        }
    }
    catch(...) {}                                                               // Silently capture exceptions.
}

SNFMilterAction SNFMilterEngine::scanIP(unsigned long int IP) {                 // Scans an IP.
    IPTestRecord Tester(IP);                                                    // Make up a test record for this IP.
    ScopeMutex ConfigurationLock(ConfigMutex);                                  // Lock our configuration.
    if(0 == myEngine) throw runtime_error("Null engine when scanning IP");      // Skip safely if we're down.
    checkConfiguration();                                                       // Re-read our config if it is old.
    myRulebase->performIPTest(Tester);                                          // Tun it past the engine.
    SNFMilterAction TestResult = Allow;                                         // Allow by default.
    switch(Tester.R) {                                                          // Convert the result to an action.
    case White: { TestResult = WhiteAction; break; }                            // If the IP scan range is recognized
    case Caution: { TestResult = CautionAction; break; }                        // in our configuration then we will
    case Black: { TestResult = BlackAction; break; }                            // return the action code that is
    case Truncate: { TestResult = TruncateAction; break; }                      // configured. Otherwise we will return
    default: break;
    }                                                                           // the default "Allow" action.
    return TestResult;                                                          // Tell them what we've got.
}

SNFMilterAction SNFMilterEngine::scanMessage(                                   // Scans a message.
                                             const unsigned char* bfr,          // Requires a pointer to the buffer.
                                             int length) {                      // Requires the buffer length.
    ScopeMutex ConfigurationLock(ConfigMutex);                                  // Lock the configuration.
    if(0 == myEngine) throw runtime_error("Null engine when scanning message"); // Skip safely if we're down.
    checkConfiguration();                                                       // Re-read our config if it is old.
    int R = myEngine->scanMessage(bfr, length, "", 0);                          // Scan the message & get the result.
    if(0 > R || ResultCodesCount <= R) return Error;                            // If R is out of range, return Error.
    if (0 == R || NoAction != ResultActions[R]) return ResultActions[R];        // Return the translated action.
    return NonZeroAction;
}

string SNFMilterEngine::XHeaders() {                                            // Return X headers from last scan.
    ScopeMutex EngineLock(ConfigMutex);                                         // Use myEngine safely.
    if(0 == myEngine) return "";                                                // Return no headers if dead.
    return myEngine->getXHDRs();                                                // Simply return them.
}

//// SNFMilterContext

SNFMilterContext::SNFMilterContext(snf_RulebaseHandler *myRulebase) :
    SkipReturn(SMFIS_CONTINUE),
    milterEngine(myRulebase),
    MessageData(MailBufferReserveSize) {}

SNFMilterContext::~SNFMilterContext() {}

/// Return the local received header.
//
// \returns the local received header.
//
string
SNFMilterContext::getLocalReceivedHeader() {

    string locHeader;

    locHeader = "Received: from <" + ConnectionData.HostName;
    locHeader += "> [" + (string) ConnectionData.HostIP;
    locHeader += "] by " PACKAGE_NAME;
    return locHeader;
}

/// Map return value from SNFMilterEngine scan to libmilter return value.
//
// \param[in] MilterAction is the return from an SNFMilterEngine scan.
//
// \returns the return value for the libmilter callback.
//
// \throws std::out_of_range if MilterAction of out of range.
//
sfsistat
SNFMilterContext::smfisReturn(SNFMilterAction MilterAction) {

    static const sfsistat ReturnValue[] = {
        SMFIS_CONTINUE,
        SMFIS_ACCEPT,
        SMFIS_TEMPFAIL,
        SMFIS_REJECT,
        SMFIS_DISCARD,
        SMFIS_CONTINUE
    };

    if ( (MilterAction < 0) || (MilterAction >= NMilterActions) ) {
        ostringstream Temp;
        Temp << "Illegal value of SNFMilterAction in SNFMilterContext::smfisReturn ("
             << MilterAction << ") while processing message from "
             << MessageData.SenderAddress
             << " (connection from " << ConnectionData.HostName << " ("
             << (string) ConnectionData.HostIP << ").";
        throw std::out_of_range(Temp.str());
    }

    return ReturnValue[MilterAction];
    
}

//// SNFMilterContextPool

SNFMilterContextPool::SNFMilterContextPool(snf_RulebaseHandler* Rulebase) :     // Ctor needs a live rulebase handler.
    myRulebase(Rulebase),                                                       // Capture the rulebase handler.
    MilterSocketPort(0) {

    string NewConfiguration = myRulebase->PlatformConfiguration();              // Get the latest configuration.
    ConfigurationElement Reader("milter");                                      // Create a configuration reader.
    Reader
      .Element("socket")
        .Attribute("type", reinterpret_cast<int&>(MilterSocketType), static_cast<int>(NOMilterSocket))
           .Mnemonic("unix", UNIXMilterSocketMnemonic)
           .Mnemonic("tcp", TCPMilterSocketMnemonic)
        .Attribute("path", MilterSocketPath, "")
        .Attribute("group", MilterSocketGroup, "")
        .Attribute("ip", MilterSocketIP, "")
        .Attribute("port", MilterSocketPort, 0)
      .End("socket")
    .End("milter");

    ConfigurationData ConfigurationData(                                        // Convert our configuration string
                                        NewConfiguration.c_str(),               // to a configuration data buffer.
                                        NewConfiguration.length());

    Reader.initialize();                                                        // Initialize the defaults.
    Reader.interpret(ConfigurationData);                                        // Read the new configuration.

    switch (MilterSocketType) {                                                 // Named pipe.
    case UNIXMilterSocket:
        if (0 == MilterSocketPath.size()) {                                     // Path specified?
            ostringstream Temp;                                                 // No.
            Temp << "Path needs to be specified for socket type \"unix\"";
            throw runtime_error(Temp.str());
        }
        if ( (0 != MilterSocketIP.size()) ||                                    // These should not be specified.
             (0 != MilterSocketPort) ) {
            ostringstream Temp;
            Temp << "IP (" << MilterSocketIP << ") and/or port (" << MilterSocketPort
                 << ") were specified for socket type \"unix\".  They should not be specified.";
            throw runtime_error(Temp.str());
        }

        break;
    case TCPMilterSocket:
        if (0 == MilterSocketIP.size()) {                                       // IP/host specified?
            ostringstream Temp;                                                 // No.
            Temp << "Host or IP address needs to be specified for socket type \"inet\"";
            throw runtime_error(Temp.str());
        }
        if (0 == MilterSocketPort) {                                            // Port specified?
            ostringstream Temp;                                                 // No.
            Temp << "Port needs to be specified for socket type \"inet\"";
            throw runtime_error(Temp.str());
        }
        if ( (0 != MilterSocketPath.size()) ||                                  // These should not be specified.
             (0 != MilterSocketGroup.size()) ) {
            ostringstream Temp;
            Temp << "Path (" << MilterSocketPath << ") and/or group (" << MilterSocketGroup
                 << ") were specified for socket type \"inet\".  They should not be specified.";
            throw runtime_error(Temp.str());
        }

        break;

    case NOMilterSocket:
        {
            ostringstream Temp;
            Temp << "The required <socket> element was not present in the configuration file.";
            throw runtime_error(Temp.str());
        }

        break;

    default:
        {
            ostringstream Temp;
            Temp << "The type of the <socket> element configuration file is invalid.  "
              "The type must by \"unix\" or \"inet\"";
            throw runtime_error(Temp.str());
        }
    }
}

SNFMilterSocketType SNFMilterContextPool::getSocketType() {
    return MilterSocketType;
}

string SNFMilterContextPool::getSocketPath() { return MilterSocketPath; }

string SNFMilterContextPool::getSocketGroup() { return MilterSocketGroup; }

string SNFMilterContextPool::getSocketIP() { return MilterSocketIP; }

int SNFMilterContextPool::getSocketPort() { return MilterSocketPort; }

SNFMilterContextPool::~SNFMilterContextPool() {                                 // Dtor gracefully discards contexts.
    ScopeMutex ContextPoolLock(ContextAllocationControl);                       // Lock the context allocation system.
    myRulebase = 0;                                                             // Forget our rulebase. We're dead.
    for(                                                                        // Loop through the context pool
        vector<SNFMilterContext*>::iterator iC = ContextPool.begin();           // and delete any contexts we have
        iC != ContextPool.end();                                                // allocated.
        iC++) { delete (*iC); }
}

SNFMilterContext* SNFMilterContextPool::grab() {                                // Get a context to use.
    ScopeMutex ContextPoolLock(ContextAllocationControl);                       // Lock the context allocation system.
    if(0 == myRulebase) return 0;                                               // No contexts left if we're dead.
    if(1 > AvailableContexts.size()) {                                          // If we need more contexts then
        SNFMilterContext* N = new SNFMilterContext(myRulebase);                 // Create a new context,
        ContextPool.push_back(N);                                               // add it to the pool,
        AvailableContexts.give(N);                                              // and make it available.
    }
    return AvailableContexts.take();                                            // Return the next avialable context.
}

void SNFMilterContextPool::drop(SNFMilterContext* E) {                          // Drop a context after use.
    // Update context state.
    E->State = SNFMilterContext::Pooled;

    AvailableContexts.give(E);                                                  // Make this context available.
}

bool SNFMilterContextPool::allUnused() {
    return (AvailableContexts.size() == ContextPool.size());
}

void SNFMilterContextPool::logThisError(string ContextName, int Code, string Text) {
    myRulebase->logThisError(ContextName, Code, Text);
}

void SNFMilterContextPool::logThisInfo(string ContextName, int Code, string Text) {
    myRulebase->logThisInfo(ContextName, Code, Text);
}

// End of configuration setup and engine and context interface components
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
// SNFMilter callback definitions, constants, and global data.

extern "C" {

    // Connection callback.
    //
    // This callback is invoked when a new connection is made to the
    // MTA.  It obtains an available connection context object if one
    // hasn't already been assigned, and saves the IP address and name
    // of the connecting MTA.  Next, it performs an IP scan, and
    // returns the appropriate response.
    //
    // Returns: SMFIS_CONTINUE, SMFIS_ACCEPT, SMFIS_TEMPFAIL, or
    // SMFIS_REJECT according to the following mapping:
    //
    //   IPScanResult return                      mlfi_connect return
    //
    //   Quarantine, Discard, Error               FailSafeMilterResponse
    //
    //   Anything else                            SNFMilterContext::smfisReturn(IPScanResult)
    //
    sfsistat
    mlfi_connect(SMFICTX *Ctx, char *HostName, _SOCK_ADDR *HostAddr)
    {
        const string ContextName = PACKAGE_NAME "::mlfi_connect";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = FailSafeMilterResponse;
 
        try {
#ifdef NEW_SNFMILTER
            SNFMilterContext *Context = getContextFromCtx(Ctx);                 // Get the existing context object.
#else
            SNFMilterContext *Context = (SNFMilterContext *) smfi_getpriv(Ctx); // Get the context object.
            if (0 == Context) {
                Context = MilterContexts->grab();                               // Get a context object.
                if(0 == Context)                                                // Check address.
                    throw runtime_error("Got NULL from MilterContexts->grab()");
                smfi_setpriv(Ctx, Context);                                     // Save the context object.
                Context->ConnectionData.clear();                                // Clear the connection context object.
            }
#endif

            Context->State = SNFMilterContext::Connect;                         // Update context state.

            sockaddr_in *SaIn = (sockaddr_in *) HostAddr;                       // Fetch the IP address.

            Context->ConnectionData.HostName = HostName;                        // Load the info.
            Context->ConnectionData.HostIP = ntohl(SaIn->sin_addr.s_addr);

            if (MilterDebugMode) {
                ostringstream Temp;
                Temp << "Connect from " << Context->ConnectionData.HostName << " ("
                     << (string) Context->ConnectionData.HostIP << ").";
                logInfo(ContextName, InfoCode, Temp.str());
            }

            SNFMilterAction IpScanResult;                                       // Perform IP scan.

            IpScanResult = Context->milterEngine.scanIP(Context->ConnectionData.HostIP);

            if (MilterDebugMode) {
                ostringstream Temp;
                Temp << "IP scan result for connection from "
                     << Context->ConnectionData.HostName << " ("
                     << (string) Context->ConnectionData.HostIP << "):  " << IpScanResult << ".";
                logInfo(ContextName, InfoCode, Temp.str());
            }

            if ( (Error == IpScanResult) ||                                     // Check for error
                 (Quarantine == IpScanResult) ||
                 (Discard == IpScanResult) ) {
                std::ostringstream Temp;                                        // Illegal result.
                Temp << "Illegal result from IP scan for "
                     << (string) Context->ConnectionData.HostIP
                     << ":  " << IpScanResult;
                throw std::runtime_error(Temp.str());
            }

            CallbackResult = Context->smfisReturn(IpScanResult);                // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;
    }

    //
    // HELO callback.
    //
    // This callback is invoked when the connecting MTA sends a HELO
    // message.  It saves the argument of the HELO command in the
    // connection context object.
    //
    // Returns: SMFIS_CONTINUE if no error, FailSafeMilterResponse
    // otherwise.
    //
    sfsistat
    mlfi_helo(SMFICTX *Ctx, char *heloHost)
    {
        const string ContextName = PACKAGE_NAME "::mlfi_helo";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = FailSafeMilterResponse;
 
        try {

            SNFMilterContext *Context = getContextFromCtx(Ctx);                 // Get the context object.

            Context->State = SNFMilterContext::Helo;                            // Update context state.

            Context->ConnectionData.HostHelo = heloHost;                        // Save the helo host name.

            if (MilterDebugMode) {
                ostringstream Temp;
                Temp << "HELO " << Context->ConnectionData.HostHelo << " from "
                     << Context->ConnectionData.HostName << " ("
                     << (string) Context->ConnectionData.HostIP << ").";
                logInfo(ContextName, InfoCode, Temp.str());
            }

            CallbackResult =  SMFIS_CONTINUE;                                   // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;
    }

    //
    // envfrom callback.
    //
    // This callback is invoked to process the envelope from line of the
    // mail message.  It clears the message buffer, and adds the local
    // received header to the message buffer to scan.  The local received
    // header is added to the email message in mlfi_eom.
    //
    // Returns: SMFIS_CONTINUE if no error, FailSafeMilterResponse
    // otherwise.
    //
    sfsistat
    mlfi_envfrom(SMFICTX *Ctx, char **argv)
    {
        const string ContextName = PACKAGE_NAME "::mlfi_envfrom";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = FailSafeMilterResponse;
 
        try {
            SNFMilterContext *Context = getContextFromCtx(Ctx);                 // Get the context object.

            Context->State = SNFMilterContext::EnvFrom;                         // Update context state.

            Context->MessageData.clear();                                       // This is the beginning of a new message.
                                                                                // Clear data from any previous message.

            if (MilterDebugMode) {
                Context->MessageData.SenderAddress = argv[0];
                ostringstream Temp;
                Temp << "Processing sender address " << Context->MessageData.SenderAddress
                     << " (connection from " << Context->ConnectionData.HostName << " ("
                     << (string) Context->ConnectionData.HostIP << ")).\n";
                logInfo(ContextName, InfoCode, Temp.str());
            }

            CallbackResult =  SMFIS_CONTINUE;                                   // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;
    }

    //
    // envrcpt callback.
    //
    // This callback is invoked to process the envelope receipt line of
    // the mail message.
    //
    // Returns: SMFIS_CONTINUE if no error, FailSafeMilterResponse
    // otherwise.
    //
    sfsistat
    mlfi_envrcpt(SMFICTX *Ctx, char **argv)
    {
        const string ContextName = PACKAGE_NAME "::mlfi_envrcpt";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = FailSafeMilterResponse;
 
        try {
            SNFMilterContext *Context = getContextFromCtx(Ctx);                 // Get the context object.

            // Update context state.
            Context->State = SNFMilterContext::EnvRcpt;

            if (MilterDebugMode) {
                ostringstream Temp;
                Temp << "Processing recipient " << argv[0] << " for message from "
                     << Context->MessageData.SenderAddress
                     << " (connection from " << Context->ConnectionData.HostName << " ("
                     << (string) Context->ConnectionData.HostIP << ")).";
                logInfo(ContextName, InfoCode, Temp.str());
            }

            CallbackResult =  SMFIS_CONTINUE;                                   // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;
    }

    //
    // header callback.
    //
    // This callback is invoked to process the a header line of the mail
    // message.  It writes the header line + SMTPENDL to the message buffer
    // that is scanned.
    //
    // Returns: SMFIS_CONTINUE if no error, FailSafeMilterResponse
    // otherwise.
    //
    sfsistat
    mlfi_header(SMFICTX *Ctx, char *headerf, char *headerv)
    {
        const string ContextName = PACKAGE_NAME "::mlfi_header";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = FailSafeMilterResponse;
 
        try {
            SNFMilterContext *Context = getContextFromCtx(Ctx);                 // Get the context object.

            Context->State = SNFMilterContext::Header;                          // Update context state.

            if (MilterDebugMode) {
                ostringstream Temp;
                Temp << "Processing header '" << headerf << ": " << headerv
                     << "' for message from "
                     << Context->MessageData.SenderAddress
                     << " (connection from " << Context->ConnectionData.HostName << " ("
                     << (string) Context->ConnectionData.HostIP << ")).";
                logInfo(ContextName, InfoCode, Temp.str());
            }


            Context->MessageData.MessageBuffer += headerf;                      // Add the header.
            Context->MessageData.MessageBuffer += ": ";
            Context->MessageData.MessageBuffer += headerv;
            Context->MessageData.MessageBuffer += SMTPENDL;

            CallbackResult =  SMFIS_CONTINUE;                                   // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;
    }

    //
    // End of header callback.
    //
    // This callback is invoked after the last header of the mail
    // message is sent.  It writes SMTPENDL SMTPENDL to the message
    // buffer that is scanned.
    //
    // Returns: SMFIS_CONTINUE if no error, FailSafeMilterResponse
    // otherwise.
    //
    sfsistat
    mlfi_eoh(SMFICTX *Ctx)
    {
        const string ContextName = PACKAGE_NAME "::mlfi_eoh";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = FailSafeMilterResponse;
 
        try {
            SNFMilterContext *Context = getContextFromCtx(Ctx);                 // Get the context object.

            Context->State = SNFMilterContext::EOH;                             // Update context state.

            Context->MessageData.MessageBuffer += SMTPENDL + SMTPENDL;          // Add the blank lines..

            if (MilterDebugMode) {
                ostringstream Temp;
                Temp << "All headers received  for message from "
                     << Context->MessageData.SenderAddress
                     << " (connection from " << Context->ConnectionData.HostName << " ("
                     << (string) Context->ConnectionData.HostIP << ")).  Message buffer--\n'"
                     << Context->MessageData.MessageBuffer << "'.";
                logInfo(ContextName, InfoCode, Temp.str());
            }

            CallbackResult =  SMFIS_CONTINUE;                                   // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;
    }

    //
    // message body callback.
    //
    // This callback is invoked zero or more times to send the body of the
    // mail message is sent. It writes the body to the message buffer that
    // is scanned.
    //
    // Returns: SMFIS_CONTINUE if more of the message body is needed,
    // Context->SkipReturn if more of the message body is not needed,
    // or FailSafeMilterResponse if an error occurs.  Context is the
    // connection context object.
    //
    sfsistat
    mlfi_body(SMFICTX *Ctx, unsigned char *Bodyp, size_t Bodylen)
    {

        const string ContextName = PACKAGE_NAME "::mlfi_body";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = FailSafeMilterResponse;
 
        try {
            SNFMilterContext *Context = getContextFromCtx(Ctx);                 // Get the context object.

            Context->State = SNFMilterContext::Body;                            // Update context state.

            if (Context->MessageData.MessageBuffer.size() >=                    // Return if there is enough in the
              MailBufferReserveSize) {                                          // message buffer.

                return Context->SkipReturn;

            }

            if (Context->MessageData.MessageBuffer.size() <                     // Do we need to copy this?
              MailBufferReserveSize) {

                string::size_type NCharToTransfer = MailBufferReserveSize -     // Yes. How much more?
                  Context->MessageData.MessageBuffer.size();

                if (NCharToTransfer > Bodylen) {                                // Don't transfer more characters
                                                                                // than are available.
                    NCharToTransfer = Bodylen;
                }
    
                Context->MessageData.MessageBuffer.append((const char *) Bodyp, // Append the message.
                                                          NCharToTransfer);

                if (MilterDebugMode) {
                    ostringstream Temp;
                    Temp << "Appended " << NCharToTransfer << " bytes to "
                         << "message from " << Context->MessageData.SenderAddress
                         << " (connection from " << Context->ConnectionData.HostName << " ("
                         << (string) Context->ConnectionData.HostIP << ")).  Message length:  "
                         << Context->MessageData.MessageBuffer.size() << ".";
                    logInfo(ContextName, InfoCode, Temp.str());
                }

            } else {
                if (MilterDebugMode) {
                    ostringstream Temp;
                    Temp << "Discarded " << Bodylen << " bytes "
                         << "message from " << Context->MessageData.SenderAddress
                         << " (connection from " << Context->ConnectionData.HostName << " ("
                         << (string) Context->ConnectionData.HostIP << ")) because "
                         << MailBufferReserveSize << " bytes have already been "
                         << "transferred.  Message length:  "
                         << Context->MessageData.MessageBuffer.size() << ".";
                    logInfo(ContextName, InfoCode, Temp.str());
                }
            }
            CallbackResult =  SMFIS_CONTINUE;                               // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;
    }

    //
    // End-Of-Message callback.
    //
    // This callback is invoked to when the entire message has been sent
    // to SNFMilter.  It adds the local received header to the email
    // message, and then scans the message body.  If the scan result
    // indicates that the message is to be quarantined, then the message
    // is set to be quarantined (using smfi_quarantine).
    //
    // Returns: SMFIS_CONTINUE, SMFIS_ACCEPT, SMFIS_TEMPFAIL, or
    // SMFIS_DISCARD, SMFIS_REJECT, or FailSafeMilterResponse
    // according to the following mapping:
    //
    //   MessageScan return                       mlfi_connect return
    //
    //   Error                                    FailSafeMilterResponse
    //
    //   Anything else                            SNFMilterContext::smfisReturn(IPScanResult)
    //
    // Side effect: If the MessageScan result is Quarantine, the
    // message is quarantined using smfi_quarantine().
    //
    sfsistat
    mlfi_eom(SMFICTX *Ctx)
    {
        const string ContextName = PACKAGE_NAME "::mlfi_eom";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = FailSafeMilterResponse;
 
        try {
            SNFMilterContext *Context = getContextFromCtx(Ctx);                 // Get the context object.

            Context->State = SNFMilterContext::EOM;                             // Update context state.

            if (MilterDebugMode) {
                ostringstream Temp;
                Temp << "End of message from " << Context->MessageData.SenderAddress
                     << " (connection from " << Context->ConnectionData.HostName << " ("
                     << (string) Context->ConnectionData.HostIP << ")).";
                logInfo(ContextName, InfoCode, Temp.str());
            }


            if (PrependLocalReceivedHeader) {
              Context->MessageData.MessageBuffer.
                insert(0, Context->getLocalReceivedHeader() + SMTPENDL);        // Prepend local received header line
                                                                                // to the message buffer.
            }

            SNFMilterAction MsgScanResult;                                     // Perform scan.

            MsgScanResult =
              Context->milterEngine.scanMessage((unsigned char *) Context->MessageData.MessageBuffer.c_str(),
                                                Context->MessageData.MessageBuffer.size());

            if (MilterDebugMode) {
                ostringstream Temp;
                Temp << "Message scan result for message from " << Context->MessageData.SenderAddress
                     << " (connection from " << Context->ConnectionData.HostName << " ("
                     << (string) Context->ConnectionData.HostIP << ")):  " << MsgScanResult << ".";
                logInfo(ContextName, InfoCode, Temp.str());
            }


            if (Error == MsgScanResult) {                                       // Check for scan error

                // Illegal result.
                std::ostringstream Temp;

                Temp << "Illegal message scan result for message from "
                     << Context->MessageData.SenderAddress
                     << " (connection from " << Context->ConnectionData.HostName << " ("
                     << (string) Context->ConnectionData.HostIP << ")):  " << MsgScanResult;
                throw std::runtime_error(Temp.str());

            }

            string XHeaders = Context->milterEngine.XHeaders();                 // Fetch X-headers to submit.
            MailHeaders MailHeadersParse;                                       // Object to parse X-headers.

            MailHeadersParse.loadHeaders(XHeaders);                             // Load the headers to be parsed.

            string HeaderName;                                                  // Name of X-header.
            string HeaderBody;                                                  // Body of X-header, formatted for libmilter.

            while (MailHeadersParse.getNameBody(&HeaderName, &HeaderBody)) {    // While there is an X-Header...

                if (MilterDebugMode) {
                    ostringstream Temp;
                    Temp << "Processed X-Header for message from " << Context->MessageData.SenderAddress
                         << " (connection from " << Context->ConnectionData.HostName << " ("
                         << (string) Context->ConnectionData.HostIP << ")).  X-Header name:  '"
                         << HeaderName << "'.  X-Header body:  '" << HeaderBody << "'.";
                    logInfo(ContextName, InfoCode, Temp.str());
                }

                if (MI_SUCCESS != smfi_addheader(Ctx,                           // Add header to the email message.
                                                 (char *) HeaderName.c_str(),
                                                 (char *) HeaderBody.c_str())) {
                    ostringstream Temp;
                    Temp << "Error adding X-header to message from " << Context->MessageData.SenderAddress
                         << " (connection from " << Context->ConnectionData.HostName << " ("
                         << (string) Context->ConnectionData.HostIP
                         << ")).\nX-Header name:  '" << HeaderName << "'.  X-Header body--\n'"
                         << HeaderBody << "'.";
                    logError(ContextName, 1, Temp.str());
                }
            }

            if (Quarantine == MsgScanResult) {                                  // Quarantine the message?

                if (MilterDebugMode) {
                    ostringstream Temp;
                    Temp << "Quarantining message from " << Context->MessageData.SenderAddress
                         << " (connection from " << Context->ConnectionData.HostName << " ("
                         << (string) Context->ConnectionData.HostIP << ")).";
                    logInfo(ContextName, InfoCode, Temp.str());
                }

                if (MI_SUCCESS != smfi_quarantine(Ctx,
                                                  (char *) "Quarantined by " PACKAGE_NAME)) {

                    ostringstream Temp;
                    Temp << "Error quarantining message from "
                         << Context->MessageData.SenderAddress
                         << " (connection from " << Context->ConnectionData.HostName << " ("
                         << (string) Context->ConnectionData.HostIP << ")).";
                    logError(ContextName, 1, Temp.str());

                }

                return SMFIS_CONTINUE;
            }

            CallbackResult = Context->smfisReturn(MsgScanResult);               // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;
    }

    //
    // Callback for aborting the message.
    //
    // This callback is invoked to when the processing of the current
    // message is to be aborted.  It logs the abort as an info event,
    // clears the email message buffer, and sets the state to
    // connected.
    //
    // Returns: SMFIS_CONTINUE if no error, FailSafeMilterResponse
    // otherwise.
    //
    sfsistat
    mlfi_abort(SMFICTX *Ctx)
    {
        const string ContextName = PACKAGE_NAME "::mlfi_abort";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = FailSafeMilterResponse;
 
        try {
            SNFMilterContext *Context = getContextFromCtx(Ctx);                 // Get the context object.

            Context->State = SNFMilterContext::Connect;                         // Update context state.

            ostringstream Temp;                                                 // Log message.
            Temp << "Aborted processing of message from " << Context->MessageData.SenderAddress
                 << " (connection from " << Context->ConnectionData.HostName << " ("
                 << (string) Context->ConnectionData.HostIP << ")).";
            logInfo(ContextName, InfoCode, Temp.str());

            Context->MessageData.clear();                                       // Clear data for this message.
            CallbackResult =  SMFIS_CONTINUE;                                   // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;

    }

    //
    // Callback for closing the connection.
    //
    // This callback is invoked to when the connection with the remote MTA is closed.
    // It returns the connection context object to the pool.
    //
    // Returns: SMFIS_CONTINUE if no error, FailSafeMilterResponse
    // otherwise.
    //
    sfsistat
    mlfi_close(SMFICTX *Ctx)
    {
        const string ContextName = PACKAGE_NAME "::mlfi_close";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = FailSafeMilterResponse;
 
        try {
            SNFMilterContext *Context = getContextFromCtx(Ctx);                 // Get the context object.

            Context->State = SNFMilterContext::Close;                           // Update context state.

            if (MilterDebugMode) {
                ostringstream Temp;
                Temp << "Closing connection from "
                     << Context->ConnectionData.HostName << " ("
                     << (string) Context->ConnectionData.HostIP << ").";
                logInfo(ContextName, InfoCode, Temp.str());
            }


            MilterContexts->drop(Context);                                      // Return the context object.

            smfi_setpriv(Ctx, 0);
            CallbackResult =  SMFIS_CONTINUE;                                   // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;

    }

#ifdef NEW_LIBMILTER
    //
    // Callback for unknown SMTP command.
    //
    // This callback is invoked to when an unknown SMTP command is
    // received by the local MTA.  The unknown command is logged.
    //
    // Returns: SMFIS_CONTINUE if no error, FailSafeMilterResponse
    // otherwise.
    //
    sfsistat
    mlfi_unknown(SMFICTX *Ctx, const char *Cmd)
    {
        const string ContextName = PACKAGE_NAME "::mlfi_unknown";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = FailSafeMilterResponse;
 
        try {
            SNFMilterContext *Context = getContextFromCtx(Ctx);                 // Get the context object.

            ostringstream Temp;                                                 // Log.
            Temp << "Unknown SMTP command from "
                 << Context->ConnectionData.HostName << " ("
                 << (string) Context->ConnectionData.HostIP << "):  '"
                 << *Cmd << "'";
            logInfo(ContextName, InfoCode, Temp.str());

            CallbackResult =  SMFIS_CONTINUE;                                   // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;

    }

    //
    // data callback.
    //
    // This callback is invoked when the connecting MTA sends a DATA
    // message.
    //
    // Returns: SMFIS_CONTINUE if no error, FailSafeMilterResponse
    // otherwise.
    //
    sfsistat
    mlfi_data(SMFICTX *Ctx)
    {
        const string ContextName = PACKAGE_NAME "::mlfi_data";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = FailSafeMilterResponse;
 
        try {
            SNFMilterContext *Context = getContextFromCtx(Ctx);                 // Get the context object.

            Context->State = SNFMilterContext::Data;                            // Update context state.

            if (MilterDebugMode) {
                ostringstream Temp;
                Temp << "DATA for message from "
                     << Context->MessageData.SenderAddress
                     << " (connection from " << Context->ConnectionData.HostName << " ("
                     << (string) Context->ConnectionData.HostIP << ")).";
                logInfo(ContextName, InfoCode, Temp.str());
            }

            CallbackResult =  SMFIS_CONTINUE;                                   // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;
    }

    //
    // Callback for negotiating the capabilities of the MTA.
    //
    // This callback is invoked at the start of each SMTP connection.
    // It obtains an available connection context object if one hasn't
    // already been assigned, checks whether the MTA can accept an
    // SMFIS_SKIP return, and configures the connection context object
    // to return an acceptable value.
    //
    // Returns: SMFIS_CONTINUE if no error, FailSafeMilterResponse
    // otherwise.
    //
    sfsistat
    mlfi_negotiate(SMFICTX *Ctx,
                   unsigned long F0,
                   unsigned long F1,
                   unsigned long F2,
                   unsigned long F3,
                   unsigned long *PF0,
                   unsigned long *PF1,
                   unsigned long *PF2,
                   unsigned long *PF3)
    {
        const string ContextName = PACKAGE_NAME "::mlfi_negotiate";
        int ErrorCode = 1;
        int InfoCode = 1;
        sfsistat CallbackResult = SMFIS_ALL_OPTS;
 
        try {
            SNFMilterContext *Context = (SNFMilterContext *) smfi_getpriv(Ctx); // Get the context object.
            if (0 == Context) {
                Context = MilterContexts->grab();                               // Get a context object.
                if(0 == Context)                                                // Check address.
                    throw runtime_error("Got NULL from MilterContexts->grab()");
                smfi_setpriv(Ctx, Context);                                     // Save the context object.
                Context->ConnectionData.clear();                                // Clear the connection context object.
            }

            bool AcceptsSkip = F1 & SMFIP_SKIP;
            if (AcceptsSkip) {                                                  // MTA accepts SMFIS_SKIP return?
                Context->SkipReturn = SMFIS_SKIP;                               // Yes.  Use SMFIS_SKIP.
            } else {
                Context->SkipReturn = SMFIS_CONTINUE;                           // No.  Use SMFIS_CONTINUE.
            }

            if (MilterDebugMode) {
                ostringstream Temp;                                             // Log message.
                Temp << "MTA does " << (AcceptsSkip ? "" : "not ") << "accept SMFIS_SKIP.";
                logInfo(ContextName, InfoCode, Temp.str());
            }
            CallbackResult =  SMFIS_ALL_OPTS;                                   // Load return value.
        } catch (exception &E) {
            logError(ContextName, ErrorCode, E.what());
        } catch (...) {
            logError(ContextName, ErrorCode, UnknownExceptionMessage);
        }

        return CallbackResult;

    }

#endif

}

// End of SNFMilter callback definitions, constants, and global data.
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
// SNFMilter setup & run function.

// The runLibMilter function establishes the appropriate libmilter call backs and
// accepts calls from the MTA via libmilter until it is told to quit. When it
// is told to quit it gracefully closes down, reclaims any memory it allocated,
// and returns.

void runLibMilter(SNFMilterContextPool* Contexts, bool DebugMode) {             // Run the milter 'til it's done.

    MilterContexts = Contexts;                                                  // Save the pool of context objects.
    MilterDebugMode = DebugMode;                                                // Save the debug mode flag.

#if 0
    if (MilterDebugMode) {
        openlog(PACKAGE_NAME, LOG_PID | LOG_PERROR, LOG_MAIL);                  // Initialize system logging to log
                                                                                // messages to mail file.
    }
#endif

    struct smfiDesc smfilter = {                                                // Load structure containing callbacks.
        (char *) PACKAGE_NAME,	                                                // Filter name.
        SMFI_VERSION,	                                                        // Version code -- do not change.
        SMFIF_ADDHDRS | SMFIF_QUARANTINE,                                       // Flags.
        mlfi_connect,                                                           // Connection info callback.
        mlfi_helo,                                                              // SMTP HELO command callback.
        mlfi_envfrom,                                                           // Envelope sender callback.
        mlfi_envrcpt,                                                           // Envelope recipient callback.
        mlfi_header,                                                            // Header callback.
        mlfi_eoh,                                                               // End of headers callback.
        mlfi_body,                                                              // Body block callback.
        mlfi_eom,                                                               // End of message callback.
        mlfi_abort,                                                             // Message abort callback.
        mlfi_close                                                              // Connection closed callback.
#ifdef NEW_LIBMILTER
        ,
        mlfi_unknown,                                                           // Unknown SMTP command callback.
        mlfi_data,                                                              // DATA ccallback.
        mlfi_negotiate                                                          // Negotiation at the start of each SMTP
#endif
                                                                                // connection callback.
    };

    string MilterConnSpec;

    switch (Contexts->getSocketType()) {                                        // Configure the connection.
    case UNIXMilterSocket:

        MilterConnSpec = "unix:" +  Contexts->getSocketPath();                  // Generate the connection spec.
              
        break;

    case TCPMilterSocket:
        {
            ostringstream Temp;

            Temp << "inet:" << Contexts->getSocketPort() << "@"                 // Generate the connection spec.
                 << Contexts->getSocketIP();
            MilterConnSpec = Temp.str();
        }

        break;

    default:
        {
            ostringstream Temp;
            Temp << PACKAGE " internal error:  Invalid socket type from SNFMilterContextPool.";
            throw logic_error(Temp.str());
        }
    }

    if (MI_FAILURE == smfi_setconn(const_cast<char *>(MilterConnSpec.c_str()))) {
        ostringstream Temp;
        Temp << "smfi_setconn failed with input \"" << MilterConnSpec << "\"";
        throw std::runtime_error(Temp.str());
    }

    if (MI_FAILURE == smfi_register(smfilter)) {                                // Register the callbacks.
        string msg = "smfi_register failed";
        throw std::runtime_error(msg);
    }

    if (UNIXMilterSocket == Contexts->getSocketType()) {
        if (MI_FAILURE == smfi_opensocket(true)) {                              // Create the named pipe.
            ostringstream Temp;
            Temp << "smfi_opensocket failed for \"" << MilterConnSpec << "\"";
            throw std::runtime_error(Temp.str());
        }

        string MilterConnPath = Contexts->getSocketPath();

        if (chmod(MilterConnPath.c_str(),                                       // Set permissions.
                  S_IRUSR | S_IWUSR |
                  S_IRGRP | S_IWGRP) != 0) {
            ostringstream Temp;
            Temp << "Error setting permissions of " << MilterConnPath << ":  "
                 << strerror(errno);
            throw runtime_error(Temp.str());
        }

        string GroupName = Contexts->getSocketGroup();
        if (0 != GroupName.size()) {                                            // Was a group specified?
            struct group *Group = getgrnam(GroupName.c_str());                  // Get the ID of the group.
            errno = 0;
            if (NULL == Group) {
                ostringstream Temp;
                if (0 != errno) {                                               // Error?
                    Temp << "Error obtaining the group ID of " << GroupName << ":  "
                         << strerror(errno);
                } else {                                                        // Group not found.
                    Temp << "Error obtaining the group ID of " << GroupName << ":  "
                         << "No such group";
                }
                throw runtime_error(Temp.str());
            }

            if (chown(MilterConnPath.c_str(),                                   // Set group.
                      -1,
                      Group->gr_gid) != 0) {
                ostringstream Temp;
                Temp << "Error setting group of " << MilterConnPath << " to "
                     << Group->gr_name << ":  " << strerror(errno);
                throw runtime_error(Temp.str());
            }
        }
    }

    if (MI_FAILURE == smfi_main()) {                                            // Hand control to libmilter
        string msg = "smfi_main failed";
        throw std::runtime_error(msg);
    }

    const string ContextName = "--EXITING--";
    int ErrorCode = 1;
    int InfoCode = 1;

    logInfo(ContextName, InfoCode, "Shutdown command received.  Waiting for message processing to complete...");

    Sleeper WaitATic;

    try {

        WaitATic.setMillisecondsToSleep(ShutdownWaitPeriod_ms);                 // Learn to wait.

    }
    catch(...) {

        ostringstream Temp;
        Temp << "Invalid value for ShutdownWaitPeriod_ms:  " << ShutdownWaitPeriod_ms << ".";
        throw out_of_range(Temp.str());

    }

    int iPeriod = 0;                                                            // Number of periods waited.

    while (!MilterContexts->allUnused() && iPeriod < ShutdownPeriods) {

        iPeriod++;
        WaitATic();                                                             // Wait a period.
        
    }

    if (!MilterContexts->allUnused()) {

        logError(ContextName, ErrorCode, "Not all messages finished processing.");

    }

    logInfo(ContextName, InfoCode, "Exiting");

    WaitATic();                                                                 // Wait for messages to be logged.

    MilterContexts = 0;                                                         // Turn off.

}