Hercules SDL aka 4.x aka Hyperion networking on Linux with OS/390 or z/Os as a guest

gistfile1.txt

Ok, listen up folks, the amount of old, outdated, wrong and misleading crap on this topic in the interiets if thru the roof.

The important parts aka what and how, often left out of scope.

So, to fix it and also to create a note for myself, this GIST.
Here we're talking about just making the networking work, not some fancy bigblue stuff.
Static routing, private subnet.

So, what:
- Hercules SDL compiled from sources:

vinsentru@minipc:~/src/hyperion$ git branch -v
* master f7d2360a (preparatory commits for release of 4.7)

- Deuvian Linux
vinsentru@minipc:~$ cat /etc/os-release
PRETTY_NAME="Devuan GNU/Linux 5 (daedalus)"

- And finally, OS/390 v2r10

First of all, if you compiled Hercules yourself, you'll probably need to set Setuid bit on hercifc:
chmod u+s /usr/local/bin/hercifc # or where we hell is it on your system

Next, the networking config in the hercules.cnf:

0E20.2  CTCI GUEST_IP HOST_IP

In my case:

0E20.2  CTCI 192.168.88.210 192.168.88.53

That's it, you don't need anything else here

RTFM: https://github.com/SDL-Hercules-390/hyperion/blob/master/readme/README.NETWORKING.md

Next. I run Hercules with sudo to make things easy with networking.
This is the script I use:

vinsentru@minipc:~$ cat /usr/local/bin/hercsudo.sh
sudo LD_LIBRARY_PATH=/usr/local/lib /usr/local/bin/hercules "$@"

We need to do some stuff after Hercules started but before IPL.
Enter hercules.rc:

$ cat hercules.rc
# Start the network
shcmdopt enable
sh echo "1"  > /proc/sys/net/ipv4/conf/all/proxy_arp
sh echo "1"  > /proc/sys/net/ipv4/conf/all/forwarding

If you don't run Hercules with sudo, add sudo to these commands.

I'm IPL manually, but you may add IPL command to the same .rc script

That's the whole Linux side setup.

Now to the guest setup. IPL and login as usual. 

You'll need to edit an OS/390 TCP/IP PROFILE. (This is
TCPIP.PROFILE.TCPIP for AD systems). Use 3.4, Luke!

There you'll need to do two operations: comment out old shit
and add the new one.

Find the DEVICE lines and make them look like this:

DEVICE CTCA1 CTC e20
LINK CTC1 CTC 1 CTCA1

Find HOME line and update it too:
HOME
  GUEST_ADDR CTC1
  
where GUEST_ADDR is obv. should be the address you've used in the hercules.cnf

Comment out the GATEWAY line and all related crap below.
Instead, use the new config form:

BEGINROUTES
; Destination Mask First-Hop Link MTU Options
ROUTE YOUR_NET 255.255.255.0 = CTC1 mtu 1492
ROUTE default YOUR_GW CTC1 mtu 1492
ENDROUTES

In my case it was:

000253 BEGINRoutes 
000254 ; Destimation Mask First-Hop Link MTU 
000255 ROUTE 192.168.88.0 255.255.255.0 = CTC1 mtu 1492 
000256 ROUTE DEFAULT 192.168.88.1 CTC1 MTU 1492 
000257 ENDRoutes 

Comment out defaultnet line as well.

And the last thing, at the bottom of this file, make sure you have this:

START CTCA1

That's it, save and exit this editor. 
Now in the Operator's console window run this command to stop TCPIP:
STOP TCPIP

Wait until it stops. Now you'll need to edit another file/member: 

Edit TCPIP.TCPIP.DATA. Change the HOSTNAME and DOMAINORIGIN lines as
appropriate. Comment out the NSINTERADDR line, or point it to your name server if you
know the IP address.

Save/exit as usual.

Start TCPIP again with
START TCPIP

That's it. 
Additional reading, part 6.22 in this book: https://www.redbooks.ibm.com/redbooks/pdfs/sg246204.pdf