Hello,
While working with the qeth/qeth_l2 drivers I've noticed that once the
nic enters promiscuous mode, every received frame is duplicated. This
appears to happen at the (virtual) hardware level since the "RX Packets"
counter printed by `#cp q nic [...] det` shows this duplicated count. It
also happens when setting promiscuous mode using `#cp set nic [...]
pro`.
It can be witnessed in tcpdump output or simply by pinging the machine
from another host. As soon as promiscuous mode is enabled using the cp
command above, the machine receives the echo request in duplicate and
answers them accordingly:
64 bytes from 10.121.155.133: icmp_seq=61 ttl=64 time=0.314 ms
64 bytes from 10.121.155.133: icmp_seq=62 ttl=64 time=0.308 ms
# enable promiscuous mode on 10.121.155.133 now
64 bytes from 10.121.155.133: icmp_seq=63 ttl=64 time=0.301 ms
64 bytes from 10.121.155.133: icmp_seq=63 ttl=64 time=0.326 ms (DUP!)
64 bytes from 10.121.155.133: icmp_seq=64 ttl=64 time=0.309 ms
64 bytes from 10.121.155.133: icmp_seq=64 ttl=64 time=0.330 ms (DUP!)
This duplication happens for multicast and unicast frames, whether those
are directed to an address in the uc filter list or not.
Tested on v3.8.
Is this a known issue?
Here is the nic info, let me know if you need anything else, I'm not
familiar with s390.
CP Q NIC 0800 DET
Adapter 0800.P00 Type: QDIO Name: UNASSIGNED Devices: 3
MAC: 02-00-00-00-00-07 VSWITCH: SYSTEM VSWNL2
RX Packets: 3005625 Discarded: 1318 Errors: 0
TX Packets: 287690 Discarded: 0 Errors: 0
RX Bytes: 3777624734 TX Bytes: 32040428
Connection Name: HALLOLE State: Session Established
Device: 0800 Unit: 000 Role: CTL-READ
Device: 0801 Unit: 001 Role: CTL-WRITE
Device: 0802 Unit: 002 Role: DATA vPort: 0264 Index: 0264
VLAN: 0556
Options: Ethernet Broadcast Promiscuous
Unicast MAC Addresses:
02-00-00-00-00-07
Multicast MAC Addresses:
01-00-5E-00-00-01
33-33-00-00-00-01
33-33-00-00-02-02
33-33-FF-00-00-07
Thank you,
-Benjamin
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