I needed to get my ZD&T machine connected to the internet so it could download some files as part of an install. Note, while this allows my z/OS to contact the internet, externals machines cannot contact my machine.

As a follow-on to this Blog post I wrote Connecting a zPDT z/OS to the internet to using IPV6 which extends this post.

As usual there are many strands to this, so I wrote Understanding BT home hub and my IPv6 addresses to cover some of the background knowledge.

It took a while to get it working. It is based on scenario 4 of the zD&T documentation.

The configuration uses the wireless connection from my Linux server.

You need to know/configure the address of various end points. Some addresses are configured by the systems, some addresses you need to configure.

What’s my TCP configuration on Linux?

The command ip addr gave (displaying only the IP V4 entries)

1: lo: <...> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
   
2: eno1: <...> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:...
    altname enp0s31f6
    inet 10.1.0.3/24 brd 10.1.0.255 scope global eno1
       valid_lft forever preferred_lft forever 
   
3: wlxcc641aee92c5: <...> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether cc:...
    inet 192.168.1.139/24 brd 192.168.1.255 scope global dynamic noprefixroute wlxcc641aee92c5
       valid_lft 80179sec preferred_lft 80179sec
  noprefixroute 
       valid_lft 263sec preferred_lft 83sec
    inet6 fe80::7bfc:5da1:8c80:37a4/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
5: tap0: <...> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 1000
    link/ether 46:...
    inet 10.1.1.1/24 brd 10.1.1.255 scope global tap0
       valid_lft forever preferred_lft forever
   

Where

• lo is the loop back address.
• eno1 is the connection over an Ethernet cable to my laptop with the address (on this linux machine) 10.1.0.3. The address of the other end of the Ethernet, on my laptop, is 10.1.0.2
• wlxcc641aee92c5 is the wireless connection to my router and the outside world. The IP address of the Linux server end is 192.168.1.139.
• tap0 is the tunnel interface to z/OS from the base linux machine. It has address 10.1.1.1

I think these end point addresses were all generated for me.

Linux Settings

I believe that you need some Linux settings. Having repeated the scenario, it works even when the values described where set to 0, so the guidance in this section may not be relevant.

sysctl net.ipv4.ip_forward

to display the value. It needs to be 1. You can set it using

sudo sysctl -w net.ipv4.ip_forward=1
#sudo sysctl -w net.ipv6.conf.all.forwarding=1

You can do commands like

sysctl -a |grep v4
sysctl -a |grep v6

My devmap

The devmap file contains the definitions of the emulated devices. For the OSA I had

[manager]  # tap0 define network adapter (OSA) for communication with Linux
name awsosa 0009 --path=A0 --pathtype=OSD --tunnel_intf=y   # QDIO mode
device 400 osa osa --unitadd=0
device 401 osa osa --unitadd=1
device 402 osa osa --unitadd=2

name awsosa 0010 --path=F1 --pathtype=OSD  --interface=wlxcc641aee92c5 
device 404 osa osa --unitadd=0
device 405 osa osa --unitadd=1
device 406 osa osa --unitadd=2
device 407 osa osa --unitadd=3
device 408 osa osa --unitadd=4
device 409 osa osa --unitadd=5

Where the –interface is the same name as my wireless interface (see above).

When I used IPv6 as well as IPv4, there were two TCPIP Interface on the same OSA. I need address 406 and 407 for one interface, and 408 and 409 for the other interface. The TCPIP documentation does not say this.

Find_io

The find_io command gives the network configuration known by the emulation code.

FIND_IO for "colin@colin-ThinkCentre-M920s" 
                                                                                                
         Interface         Current          MAC    IPv4          IPv6           
 Path    Name              State            Addr   Address       Address        
------   ----------------  ---------------- ----   ------------- --------------   
  F0     eno1              UP, RUNNING      00:..  10.1.0.3      fe80::...%eno1  
  F1     wlxcc641aee92c5   UP, RUNNING      cc:..  192.168.1.139 2a00:... 
  A0     tap0              UP, RUNNING      46:..  10.1.1.1      fe80::...@tap0
  ...
   
 End of FIND_IO 

This is the same information as the ip addr command

The OSAs

In the devmap file the OSAs were defined as starting at 400 and 404. One for reading, one for writing, and several for data.

In the z/OS VTAM file ADCD.Z31B.VTAMLST(OSATRL2) (below) defines two OSAs.

The first is for my Ethernet. This has one TCPIP Interface, and so paths 402 and 403 for the data.

The second is for the wireless connection. This has two TCPIP interfaces one for IPV4 and one for IPv6. One uses path (406,407), the other uses(408,409). These addresses must match the devmap definitions.

OSATRL1 VBUILD TYPE=TRL                                                 
OSATRL1E TRLE LNCTL=MPC,READ=(0400),WRITE=(0401),DATAPATH=(0402),      X
               PORTNAME=PORTA,                                         X
               MPCLEVEL=QDIO                                            
OSATRL2E TRLE LNCTL=MPC,READ=(0404),WRITE=(0405),DATAPATH=(0406,407),  X
               PORTNAME=PORTB,                                         X
               MPCLEVEL=QDIO                                                                              

You refer to these definitions using PORTA and PORTB in the TCPIP interfaces

You can use the VTAM command D NET,TRL to display the status of them

          d net,trl                                         
STC05323  IST097I DISPLAY ACCEPTED                          
STC05323  IST350I DISPLAY TYPE = TRL                        
------------------------------------------------------------
TRL MAJOR NODE = ISTTRL                                     
TRLE = IUTIQDIO  STATUS = NEVAC       CONTROL = MPC         
TRLE = IUTSAMEH  STATUS = NEVAC       CONTROL = MPC         
2 TRLE(S) DISPLAYED                                         
------------------------------------------------------------
TRL MAJOR NODE = OSATRL2                                    
TRLE = OSATRL1E  STATUS = ACTIV       CONTROL = MPC         
TRLE = OSATRL2E  STATUS = ACTIV       CONTROL = MPC         

Define the TCP/IP interfaces

Current levels of TCP define interfaces with the “INTERFACE” statement. DEVICE and LINK statements are deprecated.

My definitions for IPv4 are

 INTERFACE TAP0 
     DEFINE IPAQENET 
     CHPIDTYPE OSD 
     IPADDR 10.1.1.2 
     PORTNAME PORTA 
 START TAP0 
                                                 
 INTERFACE WIRE 
     DEFINE IPAQENET 
     CHPIDTYPE OSD 
     IPADDR 192.168.1.61 
     PRIROUTER 
     PORTNAME PORTB 
 START WIRE 

This defines an interface TAP0 using the PORTA definitions above, and gives the z/OS end of the connection the address 10.1.1.2. From my laptop I can ping 10.1.1.2, it gets routed to the Linux server, and into z/OS.

The interface is started

Another interface WIRE is defined using PORTB and the z/OS end of the connection is 192.168.1.61

I chose these two addresses myself. These address show up in the NETSTAT HOME command.

After it has started

The TSO NETSTAT HOME command gave

MVS TCP/IP NETSTAT CS 3.1     
Home address list: 
LinkName:   LOOPBACK 
  Address:  127.0.0.1 
    Flags: 
IntfName:   TAP0 
  Address:  10.1.1.2 
    Flags:  Primary 
IntfName:   WIRE 
  Address:  192.168.1.61 
    Flags: 

Where we see the interfaces and their IP addresses.

Define the TCP Routes

I created COLIN.TCPPARMS(S5ROUTE) with content

BEGINRoutes 
;     Destination   SubnetMask    FirstHop       LinkName  Size 
ROUTE 10.0.0.0    255.0.0.0       10.1.1.1       TAP0 MTU 1492 
ROUTE 192.168.1.0 255.255.255.0       =          WIRE  MTU 1492 
ROUTE DEFAULT                    192.168.1.254   WIRE  MTU 1492 
ENDRoutes 

This says for the destination IP address if it is

• anything beginning with 10. (from the subnet mask 255.0.0.0) send it over interface TAP0. The command ip addr shows tap0 with inet 10.1.1.1/24 brd 10.1.1.255
• anything with address 192.168.1.something (from the subnet mask 255.255.255.0) sent it over interface WIRE (note: in this case this definition is redundant because of the default below).
• anything else, send it down the DEFAULT definition over interface WIRE. The IP address of my wireless router is 192.168.1.254. Initially I had a different address – the address in the find_io. After several pings which timed out, ping worked. It is better to specify the address of the router/hub.

I used the TCPIP console command v tcpip,,obey,COLIN.TCPPARMS(S5ROUTE) to activate the routing table. If you get it wrong, edit the member, save the changes, and issue the command again.

The TSO NETSTAT ROUTE command gave me

IPv4 Destinations 
Destination        Gateway         Flags    Refcnt     Interface 
-----------        -------         -----    ------     --------- 
Default            192.168.1.254   UGS      0000000000 WIRE 
10.0.0.0/8         0.0.0.0         US       0000000000 TAP0 
10.1.1.2/32        0.0.0.0         UH       0000000000 TAP0 
127.0.0.1/32       0.0.0.0         UH       0000000000 LOOPBACK 
192.168.1.61/32    0.0.0.0         UH       0000000000 WIRE 

And finally – test it

I could use the TSO PING command to ping a server the internet. Check you can ping the address from Linux before you try it from z/OS, because some servers do not respond to ping requests.

Useful commands

On Linux

• ip addr
• ip route

On z/OS

VTAM operator commands

• D NET,TRL
• d net,trl,trle=OSATRL2E This gives information such as which OSA data ports are being used, by with TCPIP interfaces.
• D NET,ID=…
• D NET,ID=…,E
• V NET,ACT,ID=….
• V NET,INACT,ID=….

TCPIP operator commands

• v tcpip,,obey,… for example COLIN.TCPPARMS(S5ROUTE)

TSO commands

• TSO NETSTAT HOME
• TSO NETSTAT ROUTE
• TSO PING x.x.x.x
• TSO TRACERTE x.x.x.x

Some problems I experienced

A ping did not get a response back

A wireshark trace of the wireless interface showed the ping request had an originator IP address of 10.1.1.2. This was caused by having the wrong routing table

MVS TCP/IP NETSTAT CS 3.1       TCPIP Name: TCPIP           17:10:28 
IPv4 Destinations 
Destination        Gateway         Flags    Refcnt     Interface 
-----------        -------         -----    ------     --------- 
Default            10.1.1.1        UGS      0000000000 TAP0 
10.0.0.0/8         0.0.0.0         US       0000000000 TAP0 
10.1.0.0/24        10.1.1.1        UGS      0000000000 TAP0 
10.1.1.2/32        0.0.0.0         UH       0000000000 TAP0 
127.0.0.1/32       0.0.0.0         UH       0000000000 LOOPBACK 
192.168.1.61/32    0.0.0.0         UH       0000000000 WIRE 

The default routing was via TAP0

The NETSTAT HOME gave

 MVS TCP/IP NETSTAT CS 3.1       TCPIP Name: TCPIP       
 Home address list: 
 LinkName:   LOOPBACK 
   Address:  127.0.0.1 
     Flags: 
 IntfName:   TAP0 
   Address:  10.1.1.2 
     Flags:  Primary 
 IntfName:   WIRE 
   Address:  192.168.1.61 
     Flags: 

So the IP address of the TAP0 interface was 10.1.1.2, and this was used as the originating end point.

Any nodes on the route to the destination do not know where 10.1.12 is located …. 10.*.*.* it is usually an address on the local machine, and so you get no response back.

With the address 192.168.1.xx the wireless router converts it to the router’s own address, and so the intermediate nodes on the journey can use the hub’s IP address, and the reply gets back to the wireless router.

Ping failed – nothing in wireshark

  INTERFACE WIRE 
     DEFINE IPAQENET 
     CHPIDTYPE OSD 
     IPADDR 192.168.1.60 
     PRIROUTER 
     VLANID  2 
     PORTNAME PORTB 

I had VLANID 2 … when I removed this statement it worked.

Sessions failed to start

When I started TCPIP I got the message

EZZ4336I ERROR DURING ACTIVATION OF INTERFACE WIRE – CODE 8010002A DIAGNOSTIC CODE 02

Using the command D U,,,400,8 showed

UNIT TYPE STATUS        VOLSER     VOLSTATE      SS  
0400 OSA  A-BSY                                   0  
0401 OSA  A                                       0  
0402 OSA  A-BSY                                   0  
0403 OSA  O                                       0  
0404 OSA  OFFLINE                                 0  
0405 OSA  OFFLINE                                 0  
0406 OSA  OFFLINE                                 0  
0407 OSA  OFFLINE                                 0  

This shows the second OSA was not available (it was offline). I found I had misconfigured the OSA with addresses (404, 405, and 406) in my devmap.