[HECnet] Re: pydecnet on LinuxMint

As far as I am aware, the NI will not handle having multiple simultaneous MAC addresses.  I don't recall there being any production code to put the transceiver into promiscuous mode, sniffing packets and changing the MAC address on a transmit.  In theory, it would appear to be possible in that the NI would do this.

If you are not running DECnet, you can change the MAC address to whatever you want while the machine is up and you just have to wait for ARP caches to catch up.  There is some support for multi-homing, but I had thought that this required separate hardware interfaces, such as an IMP interface or CI, in addition to an NI. If you do have DECnet, and you change the MAC address after SETSPD has set the machine's DECnet address, DECnet won't work. Changing the DECnet address to correspond to the new MAC address won't work; you have to reboot.  I don't really quite remember, but I had thought that youcan't change your CI's hardware address at all as this is based on where you plug into the STAR connector.

I run a separate, dedicated Ethernet interface on a per-KLH10 instance. I did have both the host and the 20 sharing the same interface and this will work as long as you use the MAC address that the 20 wants you to. I ran into trouble with that (I don't remember what, this was 20 years ago), so I bought an additional NIC for the 20 and never looked back.

I don't know enough about tap interfaces to have an informed opinion.

On 5/16/24 4:47 PM, Johnny Billquist wrote: > DECnet addresses are AA-00-04-00-xx-yy, which I'm sure most people are > aware of. As such, as long as each machine has it's own DECnet > address, they will also have their own MAC address. The question is, > though, if KLH handles this completely transparent to you, or if you > need to do some things yourself here. For other simulators, it sortof > depends on the host system and your setup, and so on, since there is > no standardized API under Unix (or Windows, I believe) to set the MAC > address on an interface. But there sometimes do exist an API for it. > > For real hardware, the network interfaces do have a MAC from the > factory, but it's also stated in the standards that ethernet > interfaces should support software changing the MAC address of the > interface. And that is what DECnet normally does, and all DEC ethernet > interfaces certainly allows this to be changed. And that means any > emulator/simulator also gets informed about the MAC address change, > since the OS running on the emulator will poke at the controller for > it to change the MAC address to whatever DECnet needs it to be. > The question is then, what does the emulator/simulator do when this > happens? > >   Johnny > > On 2024-05-16 22:41, Thomas DeBellis wrote: >> On a KL emulation running Tops-20, if you want to run Phase IV, you >> have a choice of the CI or NI.  In order to not implement ARP for >> DECnet, they came up with the idea of a certain range of 48 bit MAC >> address having a direct mapping. >> >> For the CI, this is built off of the CI interface number and there is >> no getting around that, as I recall.  For the NI, it wants to pick >> the MAC address.  You can get around this by knowing what MAC address >> it will pick and configuring that. It's sometimes easier to just >> spend the $15 and get another USB interface and dedicate it to the >> engine. >> >> Otherwise, if you have three separate klh10's, they will insist on >> having their own separate MAC address. >> >> I wasn't sure how you could do that except maybe with virtual >> machines and some kind of hypervisor. >> >> ------------------------------------------------------------------------ >> >> >> On 5/16/24 4:17 PM, Johnny Billquist wrote: >>> Oh. One more thing - tap2 and tap3 are for KLH, right? Is there some >>> trickery you need to do in order to get the DECnet correct MAC >>> address on things here? Also applies for the PyDECnet instance >>> perhaps... >>> >>>   Johnny >>> >>> On 2024-05-16 20:30, Anders Andersson wrote: >>>> Thank you foryourfeedback Yes,the KLH10istancesall run on thsame >>>> Linux Mint >>>> host that runs the apydecanet router calledKSKAL,and I haveno >>>> additioal >>>> hardware on that internal segment which lookslike this now: >>>> >>>> oot@kaskal:/home/andersa# brctl show >>>> bridge name    bridge id       STP enabled    interfaces >>>> bridge0        8000.26d039e4c0f4    no        tap1 >>>>                              tap2 >>>>                              tap3 >>>> >>>> If that doesn't indicate that thethreetap interfaceshavbeen addedto >>>> the bridge,I don't know what does. Are there any other diagnostics you >>>> want me to check? I dont know whether the following add anything >>>> relevant: >>>> >>>> root@kaskal:/home/andersa# ifconfig bridge0 >>>> bridge0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 >>>>          inet 192.168.9.78  netmask 255.255.255.0  broadcast >>>> 192.168.9.255 >>>>          inet6 fe80::4cf6:1fff:fe01:f257  prefixlen 64 scopeid >>>> 0x20<link> >>>>          ether 26:d0:39:e4:c0:f4 txqueuelen 1000  (Ethernet) >>>>          RX packets 557072  bytes 143985475 (143.9 MB) >>>>          RX errors 0  dropped 450854  overruns 0  frame 0 >>>>          TX packets 106193  bytes 4586565 (4.5 MB) >>>>          TX errors 0  dropped 0overruns 0  carrier 0 collisions 0 >>>> >>>> root@kaskal:/home/andersa# ifconfig tap1 >>>> tap1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500 >>>>          inet6 fe80::6032:eff:fedb:7b94  prefixlen 64 scopeid >>>> 0x20<link> >>>>          ether 62:32:0e:db:7b:94 txqueuelen 1000  (Ethernet) >>>>          RX packets 176227  bytes 46414104 (46.4 MB) >>>>          RX errors 0  dropped 0  overruns 0  frame 0 >>>>          TX packets 318825  bytes 90356527 (90.3 MB) >>>>          TX errors 0  dropped 0overruns 0  carrier 0 collisions 0 >>>> >>>> root@kaskal:/home/andersa# ip tuntap show >>>> tap0: tap persist >>>> tap1: tap >>>> tap2: tap >>>> tap3: tap >>>> >>>> The threeTOPS-20 hosts arealso awareof and can communicate with each >>>> other. When I run tcpdump -i bridge0 I do see DECnet, DEC LAT and >>>> TCP/IP >>>> ARP traffic to or from the three TOPS-20 hosts pass by,according to >>>> the >>>> ethertype code as well as decoding done by tcpdump. >>>> >>>> The KLH10 instances obtain their tap interfaces as part of their >>>> startup configuration, so I have to restart them whenever I have reset >>>> the bridge which I haven't done in a few days now. This is a sample >>>> net >>>> device onfiguration line from one host: >>>> >>>> devdef ni0  564   ni20 dedic=true ifc=tap2 ifmeth=tap+bridge >>>> ipaddr=192.168.9.72 >>>>   dpdelay=3 >>>> >>>> >>>> The number of the interface specified with ifc= doesn't seem to >>>> matter the machine >>>> still gets assigned the next unassiged tap interface in order.And >>>> it did work previously. >>>> >>>> Eventually I hope to put all the bridge and pydecnet configuration >>>> intoa >>>> hecnet.service file andstart it from systemd. >>>> >>>> Now I plan to restartpydecnet while logging bridg0 traffic using >>>> tcpdmpto see >>>> what comes up. >>>> >>>>   /AndersAndersson >>>> >>>> >>>> _______________________________________________ >>>> HECnet mailing list -- hecnet(a)lists.dfupdate.se >>>> To unsubscribe send an email to hecnet-leave(a)lists.dfupdate.se >>> >> >> _______________________________________________ >> HECnet mailing list -- hecnet(a)lists.dfupdate.se >> To unsubscribe send an email to hecnet-leave(a)lists.dfupdate.se >