ICMPHDR | Back to Index page

| Prolog Control Block Contents ICMPHDR DSECT Storage Layout Cross Reference (Contains links to field and bit definitions) |
Programming Interface Information: This information is NOT intended to be used as Programming Interfaces of z/VM.

ICMPHDR Control Block Content | Top of page

     ICMPHDR DSECT
    Top of page

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      ICMPHDR        IP (Internet Protocol) Header
          ICMP Common Header
    0000    0 Bitstring    1 ICMPTYPE       +00 ICMP Type
              00000003       ICMDESUR       3 ICMDESUR - IPv4 PMTUD Dest
                                            Unreachable
              00000002       ICMPACBG       2 ICMPACBG - IPv6 PNTUD Packet
                                            too big
              00000008       ICM4ECRQ       8 ICM4ECRQ - IPv4 Echo Request
              00000000       ICM4ECRP       0 ICM4ECRP - IPv4 Echo Reply
              00000080       ICM6ECRQ       128 ICM6ECRQ - IPv6 Echo Request
              00000081       ICM6ECRP       129 ICM6ECRP - IPv6 Echo Reply
    0001    1 Bitstring    1 ICMPCODE       +01 ICMP Code
              00000001       ICMHSTUR       1 ICMHSTUR - Host Unreachable
              00000004       ICMDFSET       4 ICMDFSET - Fragmentation needed
                                            and Don't Fragment set
              00000000       ICM6MTUD       0 ICM6MTUD - PMTUD set by
                                            originator ignored by receiver
    0002    2 Bitstring    2 ICMPCHKS       +02 ICMP CheckSum
    0004    4 Bitstring    4 ICMPSPEC       +04 Response specific area
              00000008       ICMLENTH       *-ICMPHDR Lenght of header +
                                            specific area
    0008    8 Bitstring  500 ICMPDATA       +08 ICMP v4 and v6 Datagrams
              ...1 11..      ICMPPAYL       X'1C' ICMPPAYL ICMP Payload IP
                                            header + 8
              ICMPDATA       IPV6PLL        X'4A8' IPV6PLL ICMPv6 Sender
                                            payload limit MAX is 1240 X'4D8'
          ICMPv4 Echo Request and Echo Reply format
    0004    4 Bitstring    2 ICMPIDNO       +04 ICMPv4 Identifier
    0006    6 Bitstring    2 ICMPSQNO       +06 ICMPv4 Sequence Number
          ICMPv4 Message - Destination Unreachable
          Destination Unreachable message format includes an
          "sender's datagram" area which consists of the source's
          Internet header (IP) + leading bytes of the original
          datagram.  This data starts at ICMPDATA for a length of
          8 bytes.
    0004    4 Bitstring    1 ICMPV4NU       +02 Unused = 0
    0005    5 Bitstring    1 ICMPV4LN       +04 Length of "original datagram"
                                            field measured in 32-bit words
    0006    6 Bitstring    2 ICMP4MTU       +06 Next-Hop MTU
          ICMPv6 Messgae - Packet Too Big
          Packet Too Big message format includes the "original
          datagram" area which consists of the source's internet IP
          header (IP) + leading bytes of the original datagram. This
          datagram.  This data starts at ICMPDATA for a length of
          128 bytes.
    0004    4 Bitstring    1 ICMPV6LN       +04 Length of "original datagram"
                                            field measured in 64-bit words
    0005    5 Bitstring    1 *              MTU alignment gap
    0006    6 Bitstring    2 ICMP6MTU       +06 Next-Hop MTU
          IPv6 'pseudo-header" required for calculating ICMPv6
          header checksum.  This header prepends the ICMPv6 response
          for the checksum calculation and it contains those IPv6
          header fields as defined in RFC 2460 IPv6 Specification,
          Section 8.1 (Upper Layer Checksum).

ICMPHDR Storage Layout | Top of page

    *** ICMPHDR - IP (Internet Protocol) Header
    *
    *     +------+------+-------------+---------------------------+
    *   0 |:PTYPE|:PCODE|  ICMPCHKS   |         ICMPSPEC          |
    *     +------+------+-------------+---------------------------+
    *   8 |                                                       |
    *     =                       ICMPDATA                        =
    *     |                           +---------------------------+
    *     |                           | 1FC
    *     +---------------------------+
    *
    *** ICMPHDR - IP (Internet Protocol) Header

    *** Overlay for ICMPSPEC in ICMPHDR
    *
    *                                 +-------------+-------------+
    *   0 ...                       4 |  ICMPIDNO   |  ICMPSQNO   |
    *                                 +-------------+-------------+
    *   8
    *
    *** Overlay for ICMPSPEC in ICMPHDR

    *** Overlay for ICMPSPEC in ICMPHDR
    *
    *                                 +------+------+-------------+
    *   0 ...                       4 |:PV4NU|:PV4LN|  ICMP4MTU   |
    *                                 +------+------+-------------+
    *   8
    *
    *** Overlay for ICMPSPEC in ICMPHDR

    *** Overlay for ICMPSPEC in ICMPHDR
    *
    *                                 +------+------+-------------+
    *   0 ...                       4 |:PV6LN|//////|  ICMP6MTU   |
    *                                 +------+------+-------------+
    *   8
    *
    *** Overlay for ICMPSPEC in ICMPHDR

ICMPHDR Cross Reference | Top of page

    Symbol         Dspl Value
    -------------- ---- -----
    ICMDESUR       0000 00000003
    ICMDFSET       0001 00000004
    ICMHSTUR       0001 00000001
    ICMLENTH       0004 00000008
    ICMPACBG       0000 00000002
    ICMPCHKS       0002
    ICMPCODE       0001
    ICMPDATA       0008
    ICMPIDNO       0004
    ICMPPAYL       0008 1C
    ICMPSPEC       0004
    ICMPSQNO       0006
    ICMPTYPE       0000
    ICMPV4LN       0005
    ICMPV4NU       0004
    ICMPV6LN       0004
    ICMP4MTU       0006
    ICMP6MTU       0006
    ICM4ECRP       0000 00000000
    ICM4ECRQ       0000 00000008
    ICM6ECRP       0000 00000081
    ICM6ECRQ       0000 00000080
    ICM6MTUD       0001 00000000
    IPV6PLL        0008 ICMPDATA

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:28:39 EDT.
Copyright IBM Corporation, 1990, 2020