syslog.c

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/*
 * syslog-client.c - syslog client implementation for windows
 *
 * Created by Alexander Yaworsky
 *
 * THIS SOFTWARE IS NOT COPYRIGHTED
 *
 * This source code is offered for use in the public domain. You may
 * use, modify or distribute it freely.
 *
 * This code is distributed in the hope that it will be useful but
 * WITHOUT ANY WARRANTY. ALL WARRANTIES, EXPRESS OR IMPLIED ARE HEREBY
 * DISCLAIMED. This includes but is not limited to warranties of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 */

/* define SYSLOG_CONF_DIR where syslog.host should be
 */

#ifndef SYSLOG_CONF_DIR
static const char *syslog_conf_dir = ".";
#else
static const char *syslog_conf_dir = SYSLOG_CONF_DIR;
#endif

#include <stdio.h>
#include <string.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include "syslog.h"

#ifdef TEST
#    define SYSLOG_DGRAM_SIZE 80
#else
#    define SYSLOG_DGRAM_SIZE 1024
#endif

static BOOL initialized = FALSE;
static int log_mask = 0xFF;
static char *syslog_ident;
static int syslog_facility;
static char str_pid[ 40 ];
static SOCKADDR_IN sa_logger;
static SOCKET sock;
static char local_hostname[ MAX_COMPUTERNAME_LENGTH + 1 ];
static char datagramm[ SYSLOG_DGRAM_SIZE ];
static int datagramm_size;

/******************************************************************************
 * set_syslog_conf_dir
 *
 * maybe this function will be useful...
 */
const char* set_syslog_conf_dir( const char* dir )
{
    const char *ret = syslog_conf_dir;
    syslog_conf_dir = dir;
    return ret;
}

/******************************************************************************
 * init_logger_addr
 *
 * Read configuration file syslog.host. This file should contain host address
 * and, optionally, port. Initialize sa_logger. If the configuration file does
 * not exist, use localhost:514.
 * Returns: 0 - ok, -1 - error.
 */
static void init_logger_addr()
{
    char pathname[ FILENAME_MAX ];
    char *p;
    FILE *fd;
    char host[256];
    struct hostent * phe;

    memset( &sa_logger, 0, sizeof(SOCKADDR_IN) );
    sa_logger.sin_family = AF_INET;

    if( '\\' == syslog_conf_dir[0] || '/' == syslog_conf_dir[0] || ':' == syslog_conf_dir[1] )
    {
        /* absolute path */
        strcpy( pathname, syslog_conf_dir );
    }
    else
    {
        /* relative path */
        char *q;

        strcpy( pathname, __argv[0] );
        p = strrchr( pathname, '\\' ) + 1;
        q = strrchr( pathname, '/' ) + 1;
        if( p < q )
            *q = 0;
        else if( p > q )
            *p = 0;
        else
            pathname[0] = 0;
        strcat( pathname, syslog_conf_dir );
    }
    p = &pathname[ strlen( pathname ) - 1 ];
    if( '\\' != *p && '/' != *p )
    {
        p++; *p = '/';
    }
    strcpy( ++p, "syslog.host" );

    /* read destination host name */
    fd = fopen( pathname, "r" );
    if( !fd )
        goto use_default;

    if( NULL == fgets( host, sizeof(host), fd ) )
        host[0] = 0;
    else
    {
        p = strchr( host, '\n' );
        if( p )
            *p = 0;
        p = strchr( host, '\r' );
        if( p )
            *p = 0;
    }
    fclose( fd );

    p = strchr( host, ':' );
    if( p )
        *p++ = 0;

    phe = gethostbyname( host );
    if( !phe )
        goto use_default;

    memcpy( &sa_logger.sin_addr.s_addr, phe->h_addr, phe->h_length );

    if( p )
        sa_logger.sin_port = htons( (unsigned short) strtoul( p, NULL, 0 ) );
    else
        sa_logger.sin_port = htons( SYSLOG_PORT );
    return;

use_default:
    sa_logger.sin_addr.S_un.S_addr = htonl( 0x7F000001 );
    sa_logger.sin_port = htons( SYSLOG_PORT );
}

/******************************************************************************
 * closelog
 *
 * Close descriptor used to write to system logger.
 */
void closelog()
{
    if( !initialized )
        return;
    closesocket( sock );
    WSACleanup();
    initialized = FALSE;
}

/******************************************************************************
 * openlog
 *
 * Open connection to system logger.
 */
void openlog( char* ident, int option, int facility )
{
    BOOL failed = TRUE, wsa_initialized = FALSE;
    WSADATA wsd;
    SOCKADDR_IN sa_local;
    DWORD n;
    int size;

    if( initialized )
        return;

    syslog_facility = facility? facility : LOG_USER;

    /* FIXME: should we reset logmask? */

    if( option & LOG_PID )
        snprintf( str_pid, sizeof(str_pid), "[%lu]", GetCurrentProcessId() );
    else
        str_pid[0] = 0;

    /* FIXME: handle other options */

    n = sizeof(local_hostname);
    if( !GetComputerName( local_hostname, &n ) )
        goto done;

    sock = INVALID_SOCKET;
    if( WSAStartup( MAKEWORD( 2, 2 ), &wsd ) )
        goto done;
    wsa_initialized = TRUE;

    init_logger_addr();

    for( n = 0;; n++ )
    {
        sock = socket( AF_INET, SOCK_DGRAM, 0 );
        if( INVALID_SOCKET == sock )
            goto done;

        memset( &sa_local, 0, sizeof(SOCKADDR_IN) );
        sa_local.sin_family = AF_INET;
        if( bind( sock, (SOCKADDR*) &sa_local, sizeof(SOCKADDR_IN) ) == 0 )
            break;
        closesocket( sock );
        sock = INVALID_SOCKET;
        if( n == 100 )
            goto done;
        Sleep(0);
    }

    /* get size of datagramm */
    size = sizeof(datagramm_size);
    if( getsockopt( sock, SOL_SOCKET, SO_MAX_MSG_SIZE, (char*) &datagramm_size, &size ) )
        goto done;
    if( datagramm_size - strlen(local_hostname) - (ident? strlen(ident) : 0) < 64 )
        goto done;
    if( datagramm_size > sizeof(datagramm) )
        datagramm_size = sizeof(datagramm);

    if( atexit( closelog ) )
        goto done;

    syslog_ident = ident;
    syslog_facility = facility;
    failed = FALSE;

done:
    if( failed )
    {
        if( sock != INVALID_SOCKET ) closesocket( sock );
        if( wsa_initialized ) WSACleanup();
    }
    initialized = !failed;
}

/******************************************************************************
 * setlogmask
 *
 * Set the log mask level.
 */
int setlogmask( int mask )
{
    int ret = log_mask;

    if( mask )
        log_mask = mask;
    return ret;
}

/******************************************************************************
 * syslog
 *
 * Generate a log message using FMT string and option arguments.
 */
void syslog( int pri, char* fmt, ... )
{
    va_list ap;

    va_start( ap, fmt );
    vsyslog( pri, fmt, ap );
    va_end( ap );
}

/******************************************************************************
 * vsyslog
 *
 * Generate a log message using FMT and using arguments pointed to by AP.
 */
void vsyslog( int pri, char* fmt, va_list ap )
{
    static char *month[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
                            "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
    SYSTEMTIME stm;
    int len;
    char *p;

    if( !(LOG_MASK( LOG_PRI( pri )) & log_mask) )
        return;

    openlog( NULL, 0, pri & LOG_FACMASK );
    if( !initialized )
        return;

    if( !(pri & LOG_FACMASK) )
        pri |= syslog_facility;

    GetLocalTime( &stm );
    len = sprintf( datagramm, "<%d>%s %2d %02d:%02d:%02d %s %s%s: ",
                   pri,
                   month[ stm.wMonth - 1 ], stm.wDay, stm.wHour, stm.wMinute, stm.wSecond,
                   local_hostname, syslog_ident? syslog_ident : "", str_pid );
    vsnprintf( datagramm + len, datagramm_size - len, fmt, ap );
    p = strchr( datagramm, '\n' );
    if( p )
        *p = 0;
    p = strchr( datagramm, '\r' );
    if( p )
        *p = 0;

    sendto( sock, datagramm, strlen(datagramm), 0, (SOCKADDR*) &sa_logger, sizeof(SOCKADDR_IN) );
}