A fix is available
APAR status
Closed as program error.
Error description
A system is configured as a Sysplex Distributor for a DVIPA with SYSPLEXPORTS enabled. The potential exists for SYN packet to arrive at the distributing system before the NEWCONN message from the target system identifying the listener has been processed. Normally this would result in the distributor holding on to the SYN packet until after the NEWCONN arrives, and at that time forwarding it to the target to complete the connection. However if the LIF cache entry on the device over which the packet originally arrived is replaced during this period, there are two symptoms: - A RESET for that connection will be sent back to the originating client, causing a connection failure. The exact symptoms for this on that client will depend on the application being used. - If another SYN packet arrives with the same 4-tuple (client IP address and port, and server IP address and port) during the next six minutes, the processing for that packet will trigger an ABEND trying to process the old connection information (XFCRHTE). Possible ABEND symptoms seen: - UNKNOWN (??????? ??????)+?????? S4C5/77BD0402 - EZBITSTO(HIP61D0 11.090)+0027C2 S4C5/74BE2506 Other symptoms: - The ABENDing DUCB will have gone through the Remove_CRHT routine in EZBXFMS6.
Local fix
This problem is most likely to occur FTP server sessions using passive transfers and having PASSIVEDATAPORTS specified. Increasing the size of this range will reduce the likelihood of the same port numbers being used with the same client system during that six minute period.
Problem summary
**************************************************************** * USERS AFFECTED: * * All users of the IBM Communication Server for z/OS Version 2 * * Release 1 * * IP: Distributed DVIPA * **************************************************************** * PROBLEM DESCRIPTION: * * Connections using sysplexports reset * * and XFCRHTE hash table points to * * freed storage resulting in ABEND4C5 * * RC 77BD0402 * **************************************************************** * RECOMMENDATION: * * Apply fix. * **************************************************************** A scenario exists which can cause connections to a distributed DVIPA using sysplexports to be reset and potentially cause an abend. The problem is summarized as follows: 1. An application on a target stack binds and listens to DVIPA A port B. An XCF message is sent to the distributor. 2. Prior to the XCF message arriving, a SYN is received for DVIPA A port B. A XFCRHTE is created with the SYN queued to it. 3. The XCF message arrives from the target. EZBIPINB is scheduled to send the queued SYN to the target 4. EZBIPINB incorrectly sets the logical interface the SYN was received on if the DVIPA address is no longer in the physical interface cache. 5. The SYN is sent to the TCP layer on the distributor, causing a reset to be sent to the remote client. 6. If DVIPA A Port B is reused by another application, an entry will be added to the XFCRHTE hash table which points to freed storage. This can cause abends when the connection is closed by the application. +-------------------------------------------------------------+ + Please check our Communications Server for OS/390 homepages + + for common networking tips and fixes. The URL for these + + homepages can be found in Informational APAR II11334. + +-------------------------------------------------------------+
Problem conclusion
TCPIP has been modified to correctly forward the SYN to the target stack. * Cross Reference between External and Internal Names
Temporary fix
Comments
APAR Information
APAR number
PM88785
Reported component name
TCP/IP V3 MVS
Reported component ID
5655HAL00
Reported release
210
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt
Submitted date
2013-05-10
Closed date
2013-05-24
Last modified date
2013-07-03
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Modules/Macros
EZBIPINB EZBXFACI EZB2IUDR
Fix information
Fixed component name
TCP/IP V3 MVS
Fixed component ID
5655HAL00
Applicable component levels
R210 PSY UK94777
UP13/06/21 P F306
Fix is available
Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.
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Document Information
Modified date:
03 July 2013