parser.cpp

这个是网络编程

    else if ((version == 3) && (message == IGMP_MEMBERSHIP_REPORT_V3))
    {
        USHORT      numrecs, 
                    numsources,
                    i, j;
        UCHAR       rectype, auxdatalen;

        hdr += 2;                    // skip reserved
        memcpy(&numrecs, hdr, 2);
        numrecs = htons(numrecs);
        hdr += 2;

        printf("    Number of Group Records: %d\n", numrecs);
        for(i=0; i < numrecs ;i++)
        {
            memcpy(&rectype, hdr, 1);
            hdr += 1;

            memcpy(&auxdatalen, hdr, 1);
            hdr += 1;

            memcpy(&numsources, hdr, 2);
            numsources = ntohs(numsources);
            hdr += 2;

            memcpy(&(addr.sin_addr.s_addr), hdr, 4);
            hdr += 4;

            printf("        Record Type:  %d\n", rectype);
            printf("        Aux Data Len: %d\n", auxdatalen);
            printf("        Source Count: %d\n", numsources);
            printf("        Group Addr:   %s\n", inet_ntoa(addr.sin_addr));
            for(j=0; j < numsources ;j++)
            {
                memcpy(&(addr.sin_addr.s_addr), hdr, 4);
                hdr += 4;

                printf("          Source IP: %s\n", inet_ntoa(addr.sin_addr));
            }
        }
    }

    return 0;
}

// 
// Function: DecodeUDPHeader
//
// Description:
//    This function takes a buffer which points to a UDP
//    header and prints it out in a readable form.
//
int DecodeUDPHeader(WSABUF *wsabuf, DWORD iphdrlen)
{
    BYTE          *hdr = (BYTE *)(wsabuf->buf + iphdrlen);
    unsigned short shortval,
                   udp_src_port,
                   udp_dest_port,
                   udp_len,
                   udp_chksum;
    
    memcpy(&shortval, hdr, 2);
    udp_src_port = ntohs(shortval);
    hdr += 2;

    memcpy(&shortval, hdr, 2);
    udp_dest_port = ntohs(shortval);
    hdr += 2;

    memcpy(&shortval, hdr, 2);
    udp_len = ntohs(shortval);
    hdr += 2;

    memcpy(&shortval, hdr, 2);
    udp_chksum = ntohs(shortval);

    printf("   UDP HEADER\n");
    printf("   Source Port: %-05d       | Dest Port: %-05d\n",
        udp_src_port, udp_dest_port);
    printf("       UDP Len: %-05d       |    ChkSum: 0x%08x\n",
        udp_len, udp_chksum);
    return 0;
}

//
// Function: DecodeTCPHeader
//
// Description:
//    This function takes a buffer pointing to a TCP header
//    and prints it out in a readable form.
//
int DecodeTCPHeader(WSABUF *wsabuf, DWORD iphdrlen)
{
    BYTE           *hdr = (BYTE *)(wsabuf->buf + iphdrlen);
    unsigned short shortval;
    unsigned int   longval;

    printf("   TCP HEADER\n");
    memcpy(&shortval, hdr, 2);
    shortval = ntohs(shortval);
    printf("   Src Port   : %d\n", shortval);
    hdr += 2;

    memcpy(&shortval, hdr, 2);
    shortval = ntohs(shortval);
    printf("   Dest Port  : %d\n", shortval);
    hdr += 2;

    memcpy(&longval, hdr, 4);
    longval = ntohl(longval);
    printf("   Seq Num    : %d\n", longval);
    hdr += 4;

    memcpy(&longval, hdr, 4);
    longval = ntohl(longval);
    printf("   ACK Num    : %d\n", longval);
    hdr += 4;

    printf("   Header Len : %d (bytes %d)\n", HI_WORD(*hdr), 
        (HI_WORD(*hdr) * 4));

    memcpy(&shortval, hdr, 2);
    shortval = ntohs(shortval) & 0x3F;
    printf("   Flags      : ");
    if (shortval & 0x20)
        printf("URG ");
    if (shortval & 0x10)
        printf("ACK ");
    if (shortval & 0x08)
        printf("PSH ");
    if (shortval & 0x04)
        printf("RST ");
    if (shortval & 0x02)
        printf("SYN ");
    if (shortval & 0x01)
        printf("FIN ");
    printf("\n");
    hdr += 2;

    memcpy(&shortval, hdr, 2);
    shortval = ntohs(shortval);
    printf("   Window size: %d\n", shortval);
    hdr += 2;

    memcpy(&shortval, hdr, 2);
    shortval = ntohs(shortval);
    printf("   TCP Chksum : %d\n", shortval);
    hdr += 2;

    memcpy(&shortval, hdr, 2);
    shortval = ntohs(shortval);
    printf("   Urgent ptr : %d\n", shortval);

    return 0;
}

//
// Function: DecodeIPHeader
//
// Description:
//    This function takes a pointer to an IP header and prints
//    it out in a readable form.
//
int DecodeIPHeader(WSABUF *wsabuf, unsigned int srcip, unsigned short srcport,
        unsigned int destip, unsigned short destport)
{
    BYTE          *hdr = (BYTE *)wsabuf->buf,
                  *nexthdr = NULL;
    unsigned short shortval;
    SOCKADDR_IN    srcaddr,
                   destaddr;
    
    unsigned short ip_version,
                   ip_hdr_len,
                   ip_tos,
                   ip_total_len,
                   ip_id,
                   ip_flags,
                   ip_ttl,
                   ip_frag_offset,
                   ip_proto,
                   ip_hdr_chksum,
                   ip_src_port,
                   ip_dest_port;
    unsigned int   ip_src,
                   ip_dest;
    BOOL           bPrint = TRUE;


    ip_version = HI_WORD(*hdr);
    ip_hdr_len = LO_WORD(*hdr) * 4;
    nexthdr = (BYTE *)(wsabuf->buf + ip_hdr_len);
    hdr++;

    ip_tos = *hdr;
    hdr++;

    memcpy(&shortval, hdr, 2);
    ip_total_len = ntohs(shortval);
    hdr += 2;

    memcpy(&shortval, hdr, 2);
    ip_id = ntohs(shortval);
    hdr += 2;

    ip_flags = ((*hdr) >> 5);

    memcpy(&shortval, hdr, 2);
    ip_frag_offset = ((ntohs(shortval)) & 0x1FFF);
    hdr += 2;

    ip_ttl = *hdr;
    hdr++;

    ip_proto = *hdr;
    hdr++;

    memcpy(&shortval, hdr, 2);
    ip_hdr_chksum = ntohs(shortval);
    hdr += 2;

    memcpy(&srcaddr.sin_addr.s_addr, hdr, 4);
    ip_src = ntohl(srcaddr.sin_addr.s_addr);
    hdr += 4;

    memcpy(&destaddr.sin_addr.s_addr, hdr, 4);
    ip_dest = ntohl(destaddr.sin_addr.s_addr);
    hdr += 4;
    //
    // If packet is UDP, TCP, or IGMP read ahead and
    //  get the port values.
    //
    if (((ip_proto == 2) ||
         (ip_proto == 6) ||
         (ip_proto == 17)) &&
         bFilter)
    {
        memcpy(&ip_src_port, nexthdr, 2);
        ip_src_port = ntohs(ip_src_port);
        memcpy(&ip_dest_port, nexthdr+2, 2);
        ip_dest_port = ntohs(ip_dest_port);

        if ((srcip == ip_src) ||
            (srcport == ip_src_port) ||
            (destip == ip_dest) ||
            (destport == ip_dest_port))
        {
            bPrint = TRUE;
        }
        else
        {
            bPrint = FALSE;
        }
        
    }
    else if (bFilter)
        bPrint = FALSE;

    // Print IP Hdr
    //
    if (bPrint)
    {
        printf("IP HEADER\n");
        printf("   IP Version: %-10d  |  IP Header Len: %2d bytes   |   IP TOS: %X%X (hex)\n",
            ip_version, ip_hdr_len, HI_WORD(ip_tos), LO_WORD(ip_tos));
        printf(" IP Total Len: %-05d bytes | Identification: 0x%08X | IP Flags: %X  (hex)\n",
            ip_total_len, ip_id, ip_flags);
        printf("  Frag Offset: 0x%08X  |            TTL: %-10d | Protocol: %-10s \n",
            ip_frag_offset, ip_ttl, szProto[ip_proto]);
        printf(" Hdr Checksum: 0x%08X\n", ip_hdr_chksum);
        printf("     Src Addr: %-15s\n", inet_ntoa(srcaddr.sin_addr));
        printf("    Dest Addr: %-15s\n", inet_ntoa(destaddr.sin_addr));
    }
    else
        return ip_hdr_len;

    switch (ip_proto)
    {
        case 2:        // IGMP
            DecodeIGMPHeader(wsabuf, ip_hdr_len, ip_total_len);
            break;
        case 6:        // TCP
            DecodeTCPHeader(wsabuf, ip_hdr_len);
            break;
        case 17:       // UDP
            DecodeUDPHeader(wsabuf, ip_hdr_len);
            break;
        default:
            printf("   No decoder installed for protocol\n");
            break;
    }
    printf("\n");

    return ip_hdr_len;
}