[Pkg-xen-devel] Bug#1042842: network interface names wrong in domU (>10 interfaces)

[Valentin Kleibel]

Package: xen-utils-4.17
Version: 4.17.1+2-gb773c48e36-1
Severity: important

Dear Maintainers,

On one of our domUs we discovered that the network interface names were 
wrongly assigned since recreating the domU after an upgrade to bookworm.

If over 10 network interfaces are configured the mapping (dom0) vifX.10 
<-> eth10 (domU) does not apply anymore.
Instead the interfaces on dom0 are sorted primarily by the leftmost 
digit. so for 11 interfaces we will end up with:
vifX.0 <> eth0
vifX.1 <> eth1
vifX.10 <> eth2
vifX.2 <> eth3
vifX.3 <> eth4
....

This was observed with linux-kernel versions 5.10.179-3 and 6.1.38-2 
(all combinations of domU and dom0) and xen 4.17.1+2-gb773c48e36-1.
You can find a config snippet and "xl network-list" + "ip a" command 
output demonstrating the issue below.
Booting the host with Xen 4.14.5+94-ge49571868d-1 restored the expected 
behaviour.

Looking for relevant changes i found commit fce6999 [0] which changes 
the way libxl__device_list works, but i'm not sure that's the cause of 
this issue.

Thanks for your help,
Valentin

[0] http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=fce6999

Sample vif configuration (ascending MACs):
vif         = [
                 'mac=00:16:3e:fd:83:2f,bridge=lanbr',
                 'mac=00:16:3e:fd:83:30,bridge=lanbr',
                 'mac=00:16:3e:fd:83:31,bridge=lanbr',
                 'mac=00:16:3e:fd:83:32,bridge=lanbr',
                 'mac=00:16:3e:fd:83:33,bridge=lanbr',
                 'mac=00:16:3e:fd:83:34,bridge=lanbr',
                 'mac=00:16:3e:fd:83:35,bridge=lanbr',
                 'mac=00:16:3e:fd:83:36,bridge=lanbr',
                 'mac=00:16:3e:fd:83:37,bridge=lanbr',
                 'mac=00:16:3e:fd:83:38,bridge=lanbr',
                 'mac=00:16:3e:fd:83:39,bridge=lanbr',
               ]

dom0# xl network-list 3
Idx BE Mac Addr.         handle state evt-ch   tx-/rx-ring-ref BE-path 

0   0  00:16:3e:fd:83:2f     0     4     -1    -1/-1 
/local/domain/0/backend/vif/3/0
1   0  00:16:3e:fd:83:30     1     4     -1    -1/-1 
/local/domain/0/backend/vif/3/1
10  0  00:16:3e:fd:83:39    10     4     -1    -1/-1 
/local/domain/0/backend/vif/3/10
2   0  00:16:3e:fd:83:31     2     4     -1    -1/-1 
/local/domain/0/backend/vif/3/2
3   0  00:16:3e:fd:83:32     3     4     -1    -1/-1 
/local/domain/0/backend/vif/3/3
4   0  00:16:3e:fd:83:33     4     4     -1    -1/-1 
/local/domain/0/backend/vif/3/4
5   0  00:16:3e:fd:83:34     5     4     -1    -1/-1 
/local/domain/0/backend/vif/3/5
6   0  00:16:3e:fd:83:35     6     4     -1    -1/-1 
/local/domain/0/backend/vif/3/6
7   0  00:16:3e:fd:83:36     7     4     -1    -1/-1 
/local/domain/0/backend/vif/3/7
8   0  00:16:3e:fd:83:37     8     4     -1    -1/-1 
/local/domain/0/backend/vif/3/8
9   0  00:16:3e:fd:83:38     9     4     -1    -1/-1 
/local/domain/0/backend/vif/3/9

domU# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> 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
     inet6 ::1/128 scope host
        valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP 
group default qlen 1000
     link/ether 00:16:3e:fd:83:2f brd ff:ff:ff:ff:ff:ff
     inet X.X.X.X/16 brd X.X.X.X scope global eth0
        valid_lft forever preferred_lft forever
     inet6 fe80::216:3eff:fefd:832f/64 scope link
        valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group 
default qlen 1000
     link/ether 00:16:3e:fd:83:30 brd ff:ff:ff:ff:ff:ff
4: eth2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group 
default qlen 1000
     link/ether 00:16:3e:fd:83:39 brd ff:ff:ff:ff:ff:ff
5: eth3: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group 
default qlen 1000
     link/ether 00:16:3e:fd:83:31 brd ff:ff:ff:ff:ff:ff
6: eth4: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group 
default qlen 1000
     link/ether 00:16:3e:fd:83:32 brd ff:ff:ff:ff:ff:ff
7: eth5: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group 
default qlen 1000
     link/ether 00:16:3e:fd:83:33 brd ff:ff:ff:ff:ff:ff
8: eth6: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group 
default qlen 1000
     link/ether 00:16:3e:fd:83:34 brd ff:ff:ff:ff:ff:ff
9: eth7: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group 
default qlen 1000
     link/ether 00:16:3e:fd:83:35 brd ff:ff:ff:ff:ff:ff
10: eth8: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group 
default qlen 1000
     link/ether 00:16:3e:fd:83:36 brd ff:ff:ff:ff:ff:ff
11: eth9: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group 
default qlen 1000
     link/ether 00:16:3e:fd:83:37 brd ff:ff:ff:ff:ff:ff
12: eth10: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group 
default qlen 1000
     link/ether 00:16:3e:fd:83:38 brd ff:ff:ff:ff:ff:ff