Hello,

On Wednesday, January 29th, 2025 at 3:26 PM, Stefano Brivio <sbrivio(a)redhat.com>
wrote:

...
  Hi,
 
 On Wed, 29 Jan 2025 09:14:12 +0000
 Prafulla Giri prafulla.giri(a)protonmail.com wrote:
 
  Esteemed maintainer,
 
 First and foremost, thank you very much for your hard work: passt is awesome and allows
one to run more useful user-space VM-s.
 
 I have encountered 2 particular issues with the usage of passt with Debian, and wanted to
bring them to your attention as I think you are probably the best person to deal with
this. I do plan on sending a report to the Debian team afterwards.
 
 For reference, I tested these on Debian Testing Daily Image dated 28 January 2025, with
updates, and the version of passt available with it is passt 0.0~git20250121.4f2c8e7-1
 
 - Passt's default Apparmor config needs to allow writes to $XDG_RUNTIME_DIR (which
is at /run/user/$UID). Currently it doesn't. Virt-manager, at least, tries to create
the necessary sockets in the directory but apparmor prevents that from happening (and the
error message Virt-Manager gives isn't helpful either: the first time around I
falsely believed it was a segfault or similar issue). I managed to get passt working past
this flaw (pun intended) by manually disabling apparmor for the binary. Passt works just
fine in Fedora 41 as it doesn't use Apparmor but uses SELinux, and thus the configs
don't affect it. 
 
 
 Thanks for reporting this! I'm the maintainer of the Debian package, by
 the way. Cc'ing Andrea, who is a maintainer of the libvirt package for
 Debian and surely more knowledgeable about this.
  
I'm glad to have bumped into you. Because of the email domain, I thought you
weren't the Debian maintainer. Silly me.

...
  Note that virt-manager uses passt through libvirt (I
think that's only
 possibility) and this should actually be allowed in libvirt's AppArmor
 policy, in the sub-profile for passt:
 

https://gitlab.com/libvirt/libvirt/-/blob/0264a7704ada52f686cafe8f6402d5b60…
 
 the rationale is that passt itself doesn't know which directory libvirt
 will pick for its socket and PID files, so libvirt's policy has to
 specify that.
 
 So I think you should file an issue for the libvirt package in this
 case, unless Andrea has some pointers. 
I will wait for the maintainers input on this one.

...
  
  - This second issue is perhaps a bit more
Debian-specific, but I am going to mention it so that you might drop some hints for the
Debian maintainers to debug this: Once Apparmor is disabled and a VM is configured to work
with passt, DNS resolution doesn't work in the VM (IP Addresses work just fine) i.e.
ping fsf.org doesn't work but `ping 209.51.188.174` does. The hypervisor details
follow:
 $ virsh version # on Debian Testing a.k.a. 'Trixie'
 Compiled against library: libvirt 11.0.0
 Using library: libvirt 11.0.0
 Using API: QEMU 11.0.0Running hypervisor: QEMU 9.2.0
 This, again, isn't an issue with Fedora 41, where everything just works. The
hypervisor details for Fedora 41 are:
 $ virsh version # on Fedora 41
 Compiled against library: libvirt 10.6.0
 Using library: libvirt 10.6.0
 Using API: QEMU 10.6.0
 Running hypervisor: QEMU 9.1.2 
 
 
 Oops. Can you share the command line of passt as run by libvirt
 (say, 'ps aux|grep passt') for this case? passt has some basic
 DNS forwarding capabilities, which are configured depending on
 the host's resolver configuration.
  
Certainly! I'm sorry I didn't do this earlier. I'd checked on this: there
is no difference between the command that runs passt on Fedora 41 or Debian Trixie.

This is the command on Fedora 41:
passt --one-off --socket /run/user/1000/libvirt/qemu/run/passt/4-dragora-net0.socket --pid
/run/user/1000/libvirt/qemu/run/passt/4-dragora-net0-passt.pid

and this is the command on Debian Trixie:
passt --one-off --socket /run/user/1000/libvirt/qemu/run/passt/1-vm1-net0.socket --pid
/run/user/1000/libvirt/qemu/run/passt/1-vm1-net0-passt.pid

Just for the record, I'm also putting in the QEMU commands for Fedora 41 and Debian
Trixie, as well:

Fedora 41:
/usr/bin/qemu-system-x86_64 -name guest=debian-trixie,debug-threads=on -S -object
{"qom-type":"secret","id":"masterKey0","format":"raw","file":"/home/larryboy/.config/libvirt/qemu/lib/domain-5-debian-trixie/master-key.aes"}
-machine
pc-q35-9.1,usb=off,vmport=off,dump-guest-core=off,memory-backend=pc.ram,hpet=off,acpi=on
-accel kvm -cpu host,migratable=on -m size=8388608k -object
{"qom-type":"memory-backend-ram","id":"pc.ram","size":8589934592}
-overcommit mem-lock=off -smp 4,sockets=4,cores=1,threads=1 -uuid
d00ad47e-3cfe-4a1a-af01-b23417aad670 -no-user-config -nodefaults -chardev
socket,id=charmonitor,fd=31,server=on,wait=off -mon
chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew -global
kvm-pit.lost_tick_policy=delay -no-shutdown -global ICH9-LPC.disable_s3=1 -global
ICH9-LPC.disable_s4=1 -boot strict=on -device
{"driver":"pcie-root-port","port":16,"chassis":1,"id":"pci.1","bus":"pcie.0","multifunction":true,"addr":"0x2"}
-device
{"driver":"pcie-root-port","port":17,"chassis":2,"id":"pci.2","bus":"pcie.0","addr":"0x2.0x1"}
-device
{"driver":"pcie-root-port","port":18,"chassis":3,"id":"pci.3","bus":"pcie.0","addr":"0x2.0x2"}
-device
{"driver":"pcie-root-port","port":19,"chassis":4,"id":"pci.4","bus":"pcie.0","addr":"0x2.0x3"}
-device
{"driver":"pcie-root-port","port":20,"chassis":5,"id":"pci.5","bus":"pcie.0","addr":"0x2.0x4"}
-device
{"driver":"pcie-root-port","port":21,"chassis":6,"id":"pci.6","bus":"pcie.0","addr":"0x2.0x5"}
-device
{"driver":"pcie-root-port","port":22,"chassis":7,"id":"pci.7","bus":"pcie.0","addr":"0x2.0x6"}
-device
{"driver":"pcie-root-port","port":23,"chassis":8,"id":"pci.8","bus":"pcie.0","addr":"0x2.0x7"}
-device
{"driver":"pcie-root-port","port":24,"chassis":9,"id":"pci.9","bus":"pcie.0","multifunction":true,"addr":"0x3"}
-device
{"driver":"pcie-root-port","port":25,"chassis":10,"id":"pci.10","bus":"pcie.0","addr":"0x3.0x1"}
-device
{"driver":"pcie-root-port","port":26,"chassis":11,"id":"pci.11","bus":"pcie.0","addr":"0x3.0x2"}
-device
{"driver":"pcie-root-port","port":27,"chassis":12,"id":"pci.12","bus":"pcie.0","addr":"0x3.0x3"}
-device
{"driver":"pcie-root-port","port":28,"chassis":13,"id":"pci.13","bus":"pcie.0","addr":"0x3.0x4"}
-device
{"driver":"pcie-root-port","port":29,"chassis":14,"id":"pci.14","bus":"pcie.0","addr":"0x3.0x5"}
-device
{"driver":"qemu-xhci","p2":15,"p3":15,"id":"usb","bus":"pci.2","addr":"0x0"}
-device
{"driver":"virtio-serial-pci","id":"virtio-serial0","bus":"pci.3","addr":"0x0"}
-blockdev
{"driver":"file","filename":"/home/larryboy/.local/share/libvirt/images/debian-13-nocloud-amd64-daily.qcow2","node-name":"libvirt-2-storage","auto-read-only":true,"discard":"unmap"}
-blockdev
{"node-name":"libvirt-2-format","read-only":true,"discard":"unmap","driver":"qcow2","file":"libvirt-2-storage","backing":null}
-blockdev
{"driver":"file","filename":"/home/larryboy/.local/share/libvirt/images/debian-trixie.qcow2","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}
-blockdev
{"node-name":"libvirt-1-format","read-only":false,"discard":"unmap","driver":"qcow2","file":"libvirt-1-storage","backing":"libvirt-2-format"}
-device
{"driver":"virtio-blk-pci","bus":"pci.4","addr":"0x0","drive":"libvirt-1-format","id":"virtio-disk0","bootindex":1}
-netdev
{"type":"stream","addr":{"type":"unix","path":"/run/user/1000/libvirt/qemu/run/passt/5-debian-trixie-net0.socket"},"server":false,"reconnect":5,"id":"hostnet0"}
-device
{"driver":"virtio-net-pci","netdev":"hostnet0","id":"net0","mac":"52:54:00:8f:e7:c3","bus":"pci.1","addr":"0x0"}
-chardev pty,id=charserial0 -device
{"driver":"isa-serial","chardev":"charserial0","id":"serial0","index":0}
-chardev socket,id=charchannel0,fd=30,server=on,wait=off -device
{"driver":"virtserialport","bus":"virtio-serial0.0","nr":1,"chardev":"charchannel0","id":"channel0","name":"org.qemu.guest_agent.0"}
-chardev spicevmc,id=charchannel1,name=vdagent -device
{"driver":"virtserialport","bus":"virtio-serial0.0","nr":2,"chardev":"charchannel1","id":"channel1","name":"com.redhat.spice.0"}
-device
{"driver":"usb-tablet","id":"input0","bus":"usb.0","port":"1"}
-audiodev {"id":"audio1","driver":"spice"} -spice
port=5901,addr=127.0.0.1,disable-ticketing=on,image-compression=off,seamless-migration=on
-display egl-headless,rendernode=/dev/dri/renderD128 -device
{"driver":"virtio-vga-gl","id":"video0","max_outputs":1,"bus":"pcie.0","addr":"0x1"}
-device
{"driver":"ich9-intel-hda","id":"sound0","bus":"pcie.0","addr":"0x1b"}
-device
{"driver":"hda-duplex","id":"sound0-codec0","bus":"sound0.0","cad":0,"audiodev":"audio1"}
-global ICH9-LPC.noreboot=off -watchdog-action reset -chardev
spicevmc,id=charredir0,name=usbredir -device
{"driver":"usb-redir","chardev":"charredir0","id":"redir0","bus":"usb.0","port":"2"}
-chardev spicevmc,id=charredir1,name=usbredir -device
{"driver":"usb-redir","chardev":"charredir1","id":"redir1","bus":"usb.0","port":"3"}
-device
{"driver":"virtio-balloon-pci","id":"balloon0","bus":"pci.5","addr":"0x0"}
-object
{"qom-type":"rng-random","id":"objrng0","filename":"/dev/urandom"}
-device
{"driver":"virtio-rng-pci","rng":"objrng0","id":"rng0","bus":"pci.6","addr":"0x0"}
-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny -msg
timestamp=on

Debian Trixie:
/usr/bin/qemu-system-x86_64 -name guest=vm1,debug-threads=on -S -object
{"qom-type":"secret","id":"masterKey0","format":"raw","file":"/home/larryboy/.config/libvirt/qemu/lib/domain-1-vm1/master-key.aes"}
-machine
pc-i440fx-9.2,usb=off,vmport=off,dump-guest-core=off,memory-backend=pc.ram,hpet=off,acpi=on
-accel kvm -cpu
Denverton,vmx=on,fma=on,pdcm=on,pcid=on,avx=on,f16c=on,hypervisor=on,ss=on,tsc-adjust=on,bmi1=on,avx2=on,bmi2=on,invpcid=on,avx512f=on,avx512dq=on,adx=on,avx512ifma=on,clwb=on,avx512cd=on,avx512bw=on,avx512vl=on,avx512vbmi=on,umip=on,pku=on,avx512vbmi2=on,gfni=on,vaes=on,vpclmulqdq=on,avx512vnni=on,avx512bitalg=on,avx512-vpopcntdq=on,rdpid=on,movdiri=on,movdir64b=on,fsrm=on,avx512-vp2intersect=on,md-clear=on,stibp=on,flush-l1d=on,xsaves=on,abm=on,ibpb=on,ibrs=on,amd-stibp=on,amd-ssbd=on,ibrs-all=on,mds-no=on,pschange-mc-no=on,fbsdp-no=on,gds-no=on,rfds-no=on,vmx-activity-wait-sipi=on,vmx-xsaves=on,vmx-tsc-scaling=on,vmx-invvpid=on,mpx=off
-m size=1048576k -object
{"qom-type":"memory-backend-ram","id":"pc.ram","size":1073741824}
-overcommit mem-lock=off -smp 1,sockets=1,cores=1,threads=1 -uuid
aa332a62-1b7f-4a3c-b2c5-908e5e339b72 -no-user-config -nodefaults -chardev
socket,id=charmonitor,fd=27,server=on,wait=off -mon
chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew -global
kvm-pit.lost_tick_policy=delay -no-shutdown -global PIIX4_PM.disable_s3=1 -global
PIIX4_PM.disable_s4=1 -boot menu=on,strict=on -device
{"driver":"ich9-usb-ehci1","id":"usb","bus":"pci.0","addr":"0x5.0x7"}
-device
{"driver":"ich9-usb-uhci1","masterbus":"usb.0","firstport":0,"bus":"pci.0","multifunction":true,"addr":"0x5"}
-device
{"driver":"ich9-usb-uhci2","masterbus":"usb.0","firstport":2,"bus":"pci.0","addr":"0x5.0x1"}
-device
{"driver":"ich9-usb-uhci3","masterbus":"usb.0","firstport":4,"bus":"pci.0","addr":"0x5.0x2"}
-device
{"driver":"virtio-serial-pci","id":"virtio-serial0","bus":"pci.0","addr":"0x6"}
-blockdev
{"driver":"file","filename":"/home/larryboy/.local/share/libvirt/images/vm1.qcow2","node-name":"libvirt-2-storage","auto-read-only":true,"discard":"unmap"}
-blockdev
{"node-name":"libvirt-2-format","read-only":false,"driver":"qcow2","file":"libvirt-2-storage","backing":null}
-device
{"driver":"ide-hd","bus":"ide.0","unit":0,"drive":"libvirt-2-format","id":"ide0-0-0","bootindex":2}
-blockdev
{"driver":"file","filename":"/home/larryboy/.local/share/libvirt/images/dsl-2024.rc7.iso","node-name":"libvirt-1-storage","read-only":true}
-device
{"driver":"ide-cd","bus":"ide.0","unit":1,"drive":"libvirt-1-storage","id":"ide0-0-1","bootindex":1}
-netdev
{"type":"stream","addr":{"type":"unix","path":"/run/user/1000/libvirt/qemu/run/passt/1-vm1-net0.socket"},"server":false,"reconnect-ms":5000,"id":"hostnet0"}
-device
{"driver":"rtl8139","netdev":"hostnet0","id":"net0","mac":"52:54:00:a0:e1:7c","bus":"pci.0","addr":"0x3"}
-chardev pty,id=charserial0 -device
{"driver":"isa-serial","chardev":"charserial0","id":"serial0","index":0}
-chardev spicevmc,id=charchannel0,name=vdagent -device
{"driver":"virtserialport","bus":"virtio-serial0.0","nr":1,"chardev":"charchannel0","id":"channel0","name":"com.redhat.spice.0"}
-device
{"driver":"usb-tablet","id":"input0","bus":"usb.0","port":"1"}
-audiodev {"id":"audio1","driver":"spice"} -spice
port=5900,addr=127.0.0.1,disable-ticketing=on,seamless-migration=on -display
egl-headless,rendernode=/dev/dri/renderD128 -device
{"driver":"virtio-vga-gl","id":"video0","max_outputs":1,"bus":"pci.0","addr":"0x2"}
-device
{"driver":"AC97","id":"sound0","audiodev":"audio1","bus":"pci.0","addr":"0x4"}
-chardev spicevmc,id=charredir0,name=usbredir -device
{"driver":"usb-redir","chardev":"charredir0","id":"redir0","bus":"usb.0","port":"2"}
-chardev spicevmc,id=charredir1,name=usbredir -device
{"driver":"usb-redir","chardev":"charredir1","id":"redir1","bus":"usb.0","port":"3"}
-device
{"driver":"virtio-balloon-pci","id":"balloon0","bus":"pci.0","addr":"0x7"}
-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny -msg
timestamp=on

...
 
  Again, I will
be making a report to the Debian maintainers, should they wish to chime in regarding
Apparmor configs or the DNS resolution issue. 
 
 
 Please file a separate issue, in case. This one would be for
 passt.
  
I think I no longer have to, since I have the Debian maintainer right here. (:

...
 
  Thank you once
again for this awesome tool. 
 
 
 And thanks again for trying it out and reporting issues!
  
I'm happy to be of some assistance (:
...
  --
 Stefano 

On Thursday, January 30th, 2025 at 12:33 AM, Stefano Brivio <sbrivio(a)redhat.com>
wrote:

...
  On Wed, 29 Jan 2025 18:10:36 +0000
 Prafulla Giri prafulla.giri(a)protonmail.com wrote:
 
  Hello,
 
 On Wednesday, January 29th, 2025 at 3:26 PM, Stefano Brivio sbrivio(a)redhat.com wrote:
 
  Hi,
 
 On Wed, 29 Jan 2025 09:14:12 +0000
 Prafulla Giri prafulla.giri(a)protonmail.com wrote:
 
  Esteemed maintainer,
 
 First and foremost, thank you very much for your hard work: passt is awesome and allows
one to run more useful user-space VM-s.
 
 I have encountered 2 particular issues with the usage of passt with Debian, and wanted to
bring them to your attention as I think you are probably the best person to deal with
this. I do plan on sending a report to the Debian team afterwards.
 
 For reference, I tested these on Debian Testing Daily Image dated 28 January 2025, with
updates, and the version of passt available with it is passt 0.0~git20250121.4f2c8e7-1
 
 - Passt's default Apparmor config needs to allow writes to $XDG_RUNTIME_DIR (which
is at /run/user/$UID). Currently it doesn't. Virt-manager, at least, tries to create
the necessary sockets in the directory but apparmor prevents that from happening (and the
error message Virt-Manager gives isn't helpful either: the first time around I
falsely believed it was a segfault or similar issue). I managed to get passt working past
this flaw (pun intended) by manually disabling apparmor for the binary. Passt works just
fine in Fedora 41 as it doesn't use Apparmor but uses SELinux, and thus the configs
don't affect it. 
 
 Thanks for reporting this! I'm the maintainer of the Debian package, by
 the way. Cc'ing Andrea, who is a maintainer of the libvirt package for
 Debian and surely more knowledgeable about this. 
 
 I'm glad to have bumped into you. Because of the email domain, I thought you
weren't the Debian maintainer. Silly me. 
 
 
 :)
 
 
  Note that
virt-manager uses passt through libvirt (I think that's only
 possibility) and this should actually be allowed in libvirt's AppArmor
 policy, in the sub-profile for passt:
 

https://gitlab.com/libvirt/libvirt/-/blob/0264a7704ada52f686cafe8f6402d5b60…
 
 the rationale is that passt itself doesn't know which directory libvirt
 will pick for its socket and PID files, so libvirt's policy has to
 specify that.
 
 So I think you should file an issue for the libvirt package in this
 case, unless Andrea has some pointers. 
 
 I will wait for the maintainers input on this one. 
 
 
 One thing that might help meanwhile is if you have a look at
 /var/log/audit/audit.log after the failure occurs. Look for 'passt'
 there. There should be a message logging a denied access to some
 file: what does it say?
  
I didn't have auditd installed on Debian and installed it, and running
everything with the default auditd config (with my Apparmor disabled for passt, as
mentioned previously) does not result in anything. Do I have to configure auditd manually?
Any pointers on that, please?

On Fedora 41, which seems to have auditd preconfigured, there aren't any significant
reports about passt.

...
 
 
 
  - This second
issue is perhaps a bit more Debian-specific, but I am going to mention it so that you
might drop some hints for the Debian maintainers to debug this: Once Apparmor is disabled
and a VM is configured to work with passt, DNS resolution doesn't work in the VM (IP
Addresses work just fine) i.e. ping fsf.org doesn't work but `ping 209.51.188.174`
does. The hypervisor details follow:
 $ virsh version # on Debian Testing a.k.a. 'Trixie'
 Compiled against library: libvirt 11.0.0
 Using library: libvirt 11.0.0
 Using API: QEMU 11.0.0Running hypervisor: QEMU 9.2.0
 This, again, isn't an issue with Fedora 41, where everything just works. The
hypervisor details for Fedora 41 are:
 $ virsh version # on Fedora 41
 Compiled against library: libvirt 10.6.0
 Using library: libvirt 10.6.0
 Using API: QEMU 10.6.0
 Running hypervisor: QEMU 9.1.2 
 
 Oops. Can you share the command line of passt as run by libvirt
 (say, 'ps aux|grep passt') for this case? passt has some basic
 DNS forwarding capabilities, which are configured depending on
 the host's resolver configuration. 
 
 Certainly! I'm sorry I didn't do this earlier. I'd checked on this: there
is no difference between the command that runs passt on Fedora 41 or Debian Trixie.
 
 This is the command on Fedora 41:
 passt --one-off --socket /run/user/1000/libvirt/qemu/run/passt/4-dragora-net0.socket
--pid /run/user/1000/libvirt/qemu/run/passt/4-dragora-net0-passt.pid
 
 and this is the command on Debian Trixie:
 passt --one-off --socket /run/user/1000/libvirt/qemu/run/passt/1-vm1-net0.socket --pid
/run/user/1000/libvirt/qemu/run/passt/1-vm1-net0-passt.pid 
 
 
 Okay, nothing unexpected so far. Could you also please compare the
 output of 'passt -f -d' between the two cases? Just terminate it with
 ^C once you have the output. 
Here are the outputs:
$ passt -f -d # on Debian Testing/Trixie
0.0016: No interfaces with usable IPv6 routes
0.0017: Failed to detect external interface for IPv6
0.0028: UNIX domain socket bound at /tmp/passt_1.socket
0.0029: Template interface: enp1s0 (IPv4)
0.0029: MAC:
0.0029:     host: 9a:55:9a:55:9a:55
0.0029:     NAT to host 127.0.0.1: 192.168.100.1
0.0029: DHCP:
0.0029:     assign: 192.168.100.157
0.0029:     mask: 255.255.255.0
0.0029:     router: 192.168.100.1
0.0029: DNS:
0.0029:     192.168.100.1
0.0029: DNS search list:
0.0029:     .
0.0056: 
You can now start qemu (>= 7.2, with commit 13c6be96618c):
0.0056:     kvm ... -device virtio-net-pci,netdev=s -netdev
stream,id=s,server=off,addr.type=unix,addr.path=/tmp/passt_1.socket
0.0057: or qrap, for earlier qemu versions:
0.0057:     ./qrap 5 kvm ... -net socket,fd=5 -net nic,model=virtio
0.0067: SO_PEEK_OFF supported
0.0067: TCP_INFO tcpi_snd_wnd field  supported
0.0067: TCP_INFO tcpi_bytes_acked field  supported
0.0067: TCP_INFO tcpi_min_rtt field  supported

$ passt -f -d
0.0022: UNIX domain socket bound at /tmp/passt_1.socket
0.0022: Template interface: wlp0s20f3 (IPv4)
0.0022: MAC:
0.0022:     host: 9a:55:9a:55:9a:55
0.0022:     NAT to host 127.0.0.1: 192.168.100.1
0.0023: DHCP:
0.0023:     assign: 192.168.100.157
0.0023:     mask: 255.255.255.0
0.0023:     router: 192.168.100.1
0.0023: DNS:
0.0023:     192.168.100.1
0.0023: DNS search list:
0.0023:     .
0.0047: 
You can now start qemu (>= 7.2, with commit 13c6be96618c):
0.0047:     kvm ... -device virtio-net-pci,netdev=s -netdev
stream,id=s,server=off,addr.type=unix,addr.path=/tmp/passt_1.socket
0.0047: or qrap, for earlier qemu versions:
0.0047:     ./qrap 5 kvm ... -net socket,fd=5 -net nic,model=virtio
0.0055: SO_PEEK_OFF supported
0.0055: TCP_INFO tcpi_snd_wnd field  supported
0.0055: TCP_INFO tcpi_bytes_acked field  supported
0.0055: TCP_INFO tcpi_min_rtt field  supported

...
  
 How are resolvers configured on the two hosts? What does
 /etc/resolv.conf say? 
$ cat /etc/resolv.conf # On Fedora 41
# This is /run/systemd/resolve/stub-resolv.conf managed by man:systemd-resolved(8).
[...]
nameserver 127.0.0.53
options edns0 trust-ad
search .
$ cat /etc/resolv.conf # On Debian Trixie
# This is /run/systemd/resolve/resolv.conf managed by man:systemd-resolved(8).
[...]
nameserver 192.168.100.1
search .
$ cat /etc/resolv.conf # On a Debian 11 OS
# Generated by NetworkManager
nameserver 192.168.100.1

Also the output of `resolvectl status` for good measure:
# On Fedora 41
Global
         Protocols: LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
  resolv.conf mode: stub

Link 2 (wlp0s20f3)
    Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
         Protocols: +DefaultRoute LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 192.168.100.1
       DNS Servers: 192.168.100.1

# On Debian Trixie
Global
         Protocols: +LLMNR +mDNS -DNSOverTLS DNSSEC=no/unsupported
  resolv.conf mode: uplink

Link 2 (enp1s0)
    Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
         Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
       DNS Servers: 192.168.100.1
     Default Route: yes

...
  
 If nothing is visible from there, next check: 'virsh edit vm1' on
 Debian and add a log file in the XML, that is, replace this line:
 
 <backend type='passt'/>
 
 
 with:
 
 <backend type='passt' logFile='/tmp/passt.log'/>
 
 
 and then share the log.
  
The log from Debian Trixie host for VM1:
passt 0.0~git20250121.4f2c8e7-1: /usr/bin/passt.avx2 (6428)
0.0017: info:    No interfaces with usable IPv6 routes
0.0029: info:    UNIX domain socket bound at
/run/user/1000/libvirt/qemu/run/passt/2-vm1-net0.socket
0.0030: info:    Template interface: enp1s0 (IPv4)
0.0030: info:    MAC:
0.0030: info:        host: 9a:55:9a:55:9a:55
0.0030: info:        NAT to host 127.0.0.1: 192.168.100.1
0.0030: info:    DHCP:
0.0031: info:        assign: 192.168.100.157
0.0031: info:        mask: 255.255.255.0
0.0031: info:        router: 192.168.100.1
0.0031: info:    DNS:
0.0031: info:        192.168.100.1
0.0031: info:    DNS search list:
0.0031: info:        .
0.0066: info:    
You can now start qemu (>= 7.2, with commit 13c6be96618c):
0.0066: info:        kvm ... -device virtio-net-pci,netdev=s -netdev
stream,id=s,server=off,addr.type=unix,addr.path=/run/user/1000/libvirt/qemu/run/passt/2-vm1-net0.socket
0.0066: info:    or qrap, for earlier qemu versions:
0.0066: info:        ./qrap 5 kvm ... -net socket,fd=5 -net nic,model=virtio
0.0617: info:    accepted connection from PID 0
38.6257: info:    DHCP: offer to discover
38.6257: info:        from 52:54:00:a0:e1:7c
38.6471: info:    DHCP: ack to request
38.6471: info:        from 52:54:00:a0:e1:7c
451.4989: info:    Client connection closed, exiting

The log from Fedora 41:
passt 0^20250121.g4f2c8e7-2.fc41.x86_64: /usr/bin/passt.avx2 (3138)
0.0017: info:    UNIX domain socket bound at
/run/user/1000/libvirt/qemu/run/passt/3-debian-trixie-net0.socket
0.0018: info:    Template interface: wlp0s20f3 (IPv4)
0.0018: info:    MAC:
0.0018: info:        host: 9a:55:9a:55:9a:55
0.0018: info:        NAT to host 127.0.0.1: 192.168.100.1
0.0018: info:    DHCP:
0.0018: info:        assign: 192.168.100.157
0.0018: info:        mask: 255.255.255.0
0.0018: info:        router: 192.168.100.1
0.0018: info:    DNS:
0.0018: info:        192.168.100.1
0.0018: info:    DNS search list:
0.0018: info:        .
0.0043: info:    
You can now start qemu (>= 7.2, with commit 13c6be96618c):
0.0043: info:        kvm ... -device virtio-net-pci,netdev=s -netdev
stream,id=s,server=off,addr.type=unix,addr.path=/run/user/1000/libvirt/qemu/run/passt/3-debian-trixie-net0.socket
0.0043: info:    or qrap, for earlier qemu versions:
0.0043: info:        ./qrap 5 kvm ... -net socket,fd=5 -net nic,model=virtio
0.0591: info:    accepted connection from PID 0
10.7894: info:    DHCP: ack to discover (Rapid Commit)
10.7894: info:        from 52:54:00:8f:e7:c3
99.6704: info:    Client connection closed, exiting


...
  --
 Stefano 

On Saturday, February 1st, 2025 at 2:05 AM, Stefano Brivio <sbrivio(a)redhat.com>
wrote:

...
  On Thu, 30 Jan 2025 10:05:14 +0000
 Prafulla Giri prafulla.giri(a)protonmail.com wrote:
 
  I didn't have auditd installed on Debian and
installed it, and
 running everything with the default auditd config (with my Apparmor
 disabled for passt, as mentioned previously) does not result in
 anything. Do I have to configure auditd manually? Any pointers on
 that, please? 
 
 
 No, the default configuration is just fine. But you should re-enable
 AppArmor for passt so that we can see meaningful messages in the logs.
  
The following is the output of grep-ping 'passt' after re-enforcing the
apparmor config and trying to start a VM:
$ grep passt /var/log/audit/audit.log # Debian Trixie
type=AVC msg=audit(1738501259.829:124): apparmor="STATUS"
operation="profile_load" profile="unconfined" name="passt"
pid=1935 comm="apparmor_parser"
type=AVC msg=audit(1738501309.118:135): apparmor="DENIED"
operation="file_mmap" class="file" profile="passt"
name="/usr/bin/passt" pid=2030 comm="passt"
requested_mask="r" denied_mask="r" fsuid=1000 ouid=0FSUID="larryboy" OUID="root"
type=SYSCALL msg=audit(1738501309.118:135): arch=c000003e syscall=59 success=no exit=-13
a0=7faf24035fc0 a1=7faf24035210 a2=7ffc063280d0 a3=0 items=0 ppid=1964 pid=2030 auid=1000
uid=1000 gid=1000 euid=1000 suid=1000 fsuid=1000 egid=1000 sgid=1000 fsgid=1000 tty=(none)
ses=1 comm="passt" exe="/usr/bin/passt" subj=passt key=(null)ARCH=x86_64 SYSCALL=execve AUID="larryboy" UID="larryboy"
GID="larryboy" EUID="larryboy" SUID="larryboy"
FSUID="larryboy" EGID="larryboy" SGID="larryboy"
FSGID="larryboy"
type=ANOM_ABEND msg=audit(1738501309.118:136): auid=1000 uid=1000 gid=1000 ses=1
subj=passt pid=2030 comm="passt" exe="/usr/bin/passt" sig=11 res=1AUID="larryboy" UID="larryboy" GID="larryboy"
type=AVC msg=audit(1738501923.727:148): apparmor="DENIED"
operation="file_mmap" class="file" profile="passt"
name="/usr/bin/passt" pid=2088 comm="passt"
requested_mask="r" denied_mask="r" fsuid=1000 ouid=0FSUID="larryboy" OUID="root"
type=SYSCALL msg=audit(1738501923.727:148): arch=c000003e syscall=59 success=no exit=-13
a0=7ff564035d40 a1=7ff564039d00 a2=7fffe9aa1de0 a3=0 items=0 ppid=2060 pid=2088 auid=1000
uid=1000 gid=1000 euid=1000 suid=1000 fsuid=1000 egid=1000 sgid=1000 fsgid=1000 tty=(none)
ses=1 comm="passt" exe="/usr/bin/passt" subj=passt key=(null)ARCH=x86_64 SYSCALL=execve AUID="larryboy" UID="larryboy"
GID="larryboy" EUID="larryboy" SUID="larryboy"
FSUID="larryboy" EGID="larryboy" SGID="larryboy"
FSGID="larryboy"
type=ANOM_ABEND msg=audit(1738501923.727:149): auid=1000 uid=1000 gid=1000 ses=1
subj=passt pid=2088 comm="passt" exe="/usr/bin/passt" sig=11 res=1AUID="larryboy" UID="larryboy" GID="larryboy"
type=AVC msg=audit(1738502301.651:174): apparmor="DENIED"
operation="file_mmap" class="file" profile="passt"
name="/usr/bin/passt" pid=2145 comm="passt"
requested_mask="r" denied_mask="r" fsuid=1000 ouid=0FSUID="larryboy" OUID="root"
type=SYSCALL msg=audit(1738502301.651:174): arch=c000003e syscall=59 success=no exit=-13
a0=7fe208034ce0 a1=7fe208034350 a2=7fffd2e60120 a3=0 items=0 ppid=2117 pid=2145 auid=1000
uid=1000 gid=1000 euid=1000 suid=1000 fsuid=1000 egid=1000 sgid=1000 fsgid=1000 tty=(none)
ses=1 comm="passt" exe="/usr/bin/passt" subj=passt key=(null)ARCH=x86_64 SYSCALL=execve AUID="larryboy" UID="larryboy"
GID="larryboy" EUID="larryboy" SUID="larryboy"
FSUID="larryboy" EGID="larryboy" SGID="larryboy"
FSGID="larryboy"
type=ANOM_ABEND msg=audit(1738502301.651:175): auid=1000 uid=1000 gid=1000 ses=1
subj=passt pid=2145 comm="passt" exe="/usr/bin/passt" sig=11 res=1AUID="larryboy" UID="larryboy" GID="larryboy"

...
 
  $ passt -f -d
# on Debian Testing/Trixie
 0.0016: No interfaces with usable IPv6 routes
 0.0017: Failed to detect external interface for IPv6
 0.0028: UNIX domain socket bound at /tmp/passt_1.socket
 0.0029: Template interface: enp1s0 (IPv4)
 0.0029: MAC:
 0.0029: host: 9a:55:9a:55:9a:55
 0.0029: NAT to host 127.0.0.1: 192.168.100.1
 0.0029: DHCP:
 0.0029: assign: 192.168.100.157
 0.0029: mask: 255.255.255.0
 0.0029: router: 192.168.100.1
 0.0029: DNS:
 0.0029: 192.168.100.1 
 
 
 So, judging from this configuration, it looks like we advertise to
 the guest (via DHCP) 192.168.100.1 as resolver (copied from the host),
 and when we receive packets from the guest for 192.168.100.1, we'll
 re-map them to the host.
 
 Nothing strange so far, systemd-resolved is running on the host, it
 should get our queries and reply to them.
 
  $ cat /etc/resolv.conf # On Debian Trixie
 # This is /run/systemd/resolve/resolv.conf managed by
 man:systemd-resolved(8). [...]
 nameserver 192.168.100.1
 search .
 $ cat /etc/resolv.conf # On a Debian 11 OS
 # Generated by NetworkManager
 nameserver 192.168.100.1
 
 Also the output of `resolvectl status` for good measure:
 # On Fedora 41
 Global
 Protocols: LLMNR=resolve -mDNS -DNSOverTLS
 DNSSEC=no/unsupported resolv.conf mode: stub
 
 Link 2 (wlp0s20f3)
 Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
 Protocols: +DefaultRoute LLMNR=resolve -mDNS -DNSOverTLS
 DNSSEC=no/unsupported Current DNS Server: 192.168.100.1
 DNS Servers: 192.168.100.1
 
 # On Debian Trixie
 Global
 Protocols: +LLMNR +mDNS -DNSOverTLS DNSSEC=no/unsupported
 resolv.conf mode: uplink
 
 Link 2 (enp1s0)
 Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
 Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS
 DNSSEC=no/unsupported DNS Servers: 192.168.100.1
 Default Route: yes 
 
 
 Everything as expected here, I don't see any obvious reason why
 systemd-resolved should discard our queries.
 
  The log from Debian Trixie host for VM1:
 passt 0.0~git20250121.4f2c8e7-1: /usr/bin/passt.avx2 (6428)
 0.0017: info: No interfaces with usable IPv6 routes
 0.0029: info: UNIX domain socket bound at
 /run/user/1000/libvirt/qemu/run/passt/2-vm1-net0.socket 0.0030: info:
 Template interface: enp1s0 (IPv4) 0.0030: info: MAC:
 0.0030: info: host: 9a:55:9a:55:9a:55
 0.0030: info: NAT to host 127.0.0.1: 192.168.100.1
 0.0030: info: DHCP:
 0.0031: info: assign: 192.168.100.157
 0.0031: info: mask: 255.255.255.0
 0.0031: info: router: 192.168.100.1
 0.0031: info: DNS:
 0.0031: info: 192.168.100.1
 0.0031: info: DNS search list:
 0.0031: info: .
 0.0066: info:
 You can now start qemu (>= 7.2, with commit 13c6be96618c):
 0.0066: info: kvm ... -device virtio-net-pci,netdev=s -netdev

stream,id=s,server=off,addr.type=unix,addr.path=/run/user/1000/libvirt/qemu/run/passt/2-vm1-net0.socket
 0.0066: info: or qrap, for earlier qemu versions: 0.0066: info:
 ./qrap 5 kvm ... -net socket,fd=5 -net nic,model=virtio 0.0617:
 info: accepted connection from PID 0 38.6257: info: DHCP: offer
 to discover 38.6257: info: from 52:54:00:a0:e1:7c
 38.6471: info: DHCP: ack to request
 38.6471: info: from 52:54:00:a0:e1:7c
 451.4989: info: Client connection closed, exiting 
 
 
 Unfortunately libvirt doesn't let us enable more verbose logging. I
 hoped to see DNS queries there, but without --debug given to passt,
 that won't work.
 
 Another idea: pasta(1) does the same job as passt(1) (it's the same
 code and same binary) and it's intended for containers, but it has a
 stand-alone mode that can probably help us to debug this, because it's
 a network namespace that will look like your guest, and it can also
 take packet captures.
 
 What happens if you run:
 
 pasta --config-net --trace --pcap /tmp/dns.pcap -- nslookup fsf.org
 
 ? 
This one errors out. dns.pcap is attached.
$ pasta --config-net --trace --pcap /tmp/dns.pcap -- nslookup fsf.org # Debian
Trixie/Testing
0.0015: No interfaces with usable IPv6 routes
0.0015: Failed to detect external interface for IPv6
0.0073: Template interface: enp1s0 (IPv4)
0.0073: Namespace interface: enp1s0
0.0074: MAC:
0.0074:     host: 9a:55:9a:55:9a:55
0.0074:     NAT to host 127.0.0.1: 192.168.100.1
0.0074: DHCP:
0.0074:     assign: 192.168.100.157
0.0074:     mask: 255.255.255.0
0.0075:     router: 192.168.100.1
0.0075: DNS:
0.0075:     192.168.100.1
0.0076: DNS search list:
0.0076:     .
0.0146: SO_PEEK_OFF supported
0.0146: TCP_INFO tcpi_snd_wnd field  supported
0.0146: TCP_INFO tcpi_bytes_acked field  supported
0.0146: TCP_INFO tcpi_min_rtt field  supported
0.0147: Saving packet capture to /tmp/dns.pcap
0.0197: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
0.0371: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
0.0372: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
0.0372: tap: protocol 17, 192.168.100.157:41892 -> 192.168.100.1:53 (1 packet)
0.0372: Flow 0 (NEW): FREE -> NEW
0.0372: Flow 0 (INI): NEW -> INI
0.0372: Flow 0 (INI): TAP [192.168.100.157]:41892 -> [192.168.100.1]:53 => ?
0.0372: Flow 0 (TGT): INI -> TGT
0.0373: Flow 0 (TGT): TAP [192.168.100.157]:41892 -> [192.168.100.1]:53 => HOST
[0.0.0.0]:41892 -> [127.0.0.1]:53
0.0373: Flow 0 (UDP flow): TGT -> TYPED
0.0373: Flow 0 (UDP flow): TAP [192.168.100.157]:41892 -> [192.168.100.1]:53 => HOST
[0.0.0.0]:41892 -> [127.0.0.1]:53
0.0373: Flow 0 (UDP flow): Side 0 hash table insert: bucket: 31049
0.0374: Flow 0 (UDP flow): TYPED -> ACTIVE
0.0374: Flow 0 (UDP flow): TAP [192.168.100.157]:41892 -> [192.168.100.1]:53 => HOST
[0.0.0.0]:41892 -> [127.0.0.1]:53
0.0374: pasta: epoll event on UDP reply socket 95 (events: 0x00000008)
0.0374: ICMP error on UDP socket 95: Connection refused
0.5320: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
0.8201: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
1.5560: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
2.3240: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
;; communications error to 192.168.100.1#53: timed out
5.0431: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
5.0431: tap: protocol 17, 192.168.100.157:46013 -> 192.168.100.1:53 (1 packet)
5.0432: Flow 1 (NEW): FREE -> NEW
5.0432: Flow 1 (INI): NEW -> INI
5.0432: Flow 1 (INI): TAP [192.168.100.157]:46013 -> [192.168.100.1]:53 => ?
5.0432: Flow 1 (TGT): INI -> TGT
5.0432: Flow 1 (TGT): TAP [192.168.100.157]:46013 -> [192.168.100.1]:53 => HOST
[0.0.0.0]:46013 -> [127.0.0.1]:53
5.0432: Flow 1 (UDP flow): TGT -> TYPED
5.0432: Flow 1 (UDP flow): TAP [192.168.100.157]:46013 -> [192.168.100.1]:53 => HOST
[0.0.0.0]:46013 -> [127.0.0.1]:53
5.0433: Flow 1 (UDP flow): Side 0 hash table insert: bucket: 100062
5.0433: Flow 1 (UDP flow): TYPED -> ACTIVE
5.0433: Flow 1 (UDP flow): TAP [192.168.100.157]:46013 -> [192.168.100.1]:53 => HOST
[0.0.0.0]:46013 -> [127.0.0.1]:53
5.0434: pasta: epoll event on UDP reply socket 160 (events: 0x00000008)
5.0434: ICMP error on UDP socket 160: Connection refused
5.4924: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
;; communications error to 192.168.100.1#53: timed out
10.0478: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
10.0478: tap: protocol 17, 192.168.100.157:55861 -> 192.168.100.1:53 (1 packet)
10.0478: Flow 2 (NEW): FREE -> NEW
10.0478: Flow 2 (INI): NEW -> INI
10.0478: Flow 2 (INI): TAP [192.168.100.157]:55861 -> [192.168.100.1]:53 => ?
10.0478: Flow 2 (TGT): INI -> TGT
10.0479: Flow 2 (TGT): TAP [192.168.100.157]:55861 -> [192.168.100.1]:53 => HOST
[0.0.0.0]:55861 -> [127.0.0.1]:53
10.0479: Flow 2 (UDP flow): TGT -> TYPED
10.0479: Flow 2 (UDP flow): TAP [192.168.100.157]:55861 -> [192.168.100.1]:53 =>
HOST [0.0.0.0]:55861 -> [127.0.0.1]:53
10.0480: Flow 2 (UDP flow): Side 0 hash table insert: bucket: 342763
10.0481: Flow 2 (UDP flow): TYPED -> ACTIVE
10.0481: Flow 2 (UDP flow): TAP [192.168.100.157]:55861 -> [192.168.100.1]:53 =>
HOST [0.0.0.0]:55861 -> [127.0.0.1]:53
10.0482: pasta: epoll event on UDP reply socket 161 (events: 0x00000008)
10.0483: ICMP error on UDP socket 161: Connection refused
13.4282: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
;; communications error to 192.168.100.1#53: timed out
;; no servers could be reached


...
  
 If the query fails (that's what I would expect), can you please attach
 the output and the resulting packet capture?
 
 Note that the packet capture might have sensitive data, please have a
 look at it with e.g. Wireshark/tshark before sharing it.
 
 By the way, if you run this without specifying any command, for example:
 
 pasta --config-net --pcap /tmp/dns.pcap
 
 you will get a shell where you can play around in a separate network
 namespace and with a network stack that looks pretty much the same as
 passt for your guest.
  
This is rather strange: from the shell I successfully managed to `ping fsf.org`
and `ping gnu.org`.

I went back and ran
$ pasta --config-net --trace --pcap /tmp/ping.pcap -- ping -c 5 fsf.org # and the
following output followed (ping.pcap is also attached)

0.0013: No interfaces with usable IPv6 routes
0.0013: Failed to detect external interface for IPv6
0.0091: Template interface: enp1s0 (IPv4)
0.0091: Namespace interface: enp1s0
0.0092: MAC:
0.0092:     host: 9a:55:9a:55:9a:55
0.0092:     NAT to host 127.0.0.1: 192.168.100.1
0.0092: DHCP:
0.0092:     assign: 192.168.100.157
0.0093:     mask: 255.255.255.0
0.0093:     router: 192.168.100.1
0.0093: DNS:
0.0093:     192.168.100.1
0.0093: DNS search list:
0.0094:     .
0.0161: SO_PEEK_OFF supported
0.0161: TCP_INFO tcpi_snd_wnd field  supported
0.0161: TCP_INFO tcpi_bytes_acked field  supported
0.0161: TCP_INFO tcpi_min_rtt field  supported
0.0162: Saving packet capture to /tmp/ping.pcap
PING fsf.org (209.51.188.174) 56(84) bytes of data.
0.0181: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
0.0181: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
0.0182: tap: protocol 1, 192.168.100.157 -> 209.51.188.174 (1 packet)
0.0182: Flow 0 (NEW): FREE -> NEW
0.0182: Flow 0 (INI): NEW -> INI
0.0182: Flow 0 (INI): TAP [192.168.100.157]:11 -> [209.51.188.174]:11 => ?
0.0182: Flow 0 (TGT): INI -> TGT
0.0182: Flow 0 (TGT): TAP [192.168.100.157]:11 -> [209.51.188.174]:11 => HOST
[0.0.0.0]:0 -> [209.51.188.174]:11
0.0182: Flow 0 (ICMP ping sequence): TGT -> TYPED
0.0183: Flow 0 (ICMP ping sequence): TAP [192.168.100.157]:11 -> [209.51.188.174]:11
=> HOST [0.0.0.0]:0 -> [209.51.188.174]:11
0.0183: Flow 0 (ICMP ping sequence): new socket 95 for echo ID 11
0.0183: Flow 0 (ICMP ping sequence): Side 0 hash table insert: bucket: 150766
0.0184: Flow 0 (ICMP ping sequence): TYPED -> ACTIVE
0.0184: Flow 0 (ICMP ping sequence): TAP [192.168.100.157]:11 -> [209.51.188.174]:11
=> HOST [0.0.0.0]:0 -> [209.51.188.174]:11
0.0184: Flow 0 (ICMP ping sequence): echo request to socket, ID: 11, seq: 1
0.0214: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
0.0538: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
0.4423: pasta: epoll event on ICMP/ICMPv6 ping socket 95 (events: 0x00000001)
0.4424: Flow 0 (ICMP ping sequence): echo reply to tap, ID: 11, seq: 1
64 bytes from www.fsf.org (209.51.188.174): icmp_seq=1 ttl=255 time=424 ms
0.7857: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
1.0188: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
1.0189: tap: protocol 1, 192.168.100.157 -> 209.51.188.174 (1 packet)
1.0189: Flow 0 (ICMP ping sequence): echo request to socket, ID: 11, seq: 2
1.0736: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
1.1777: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
1.4302: pasta: epoll event on ICMP/ICMPv6 ping socket 95 (events: 0x00000001)
1.4303: Flow 0 (ICMP ping sequence): echo reply to tap, ID: 11, seq: 2
64 bytes from www.fsf.org (209.51.188.174): icmp_seq=2 ttl=255 time=412 ms
2.0188: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
2.0189: tap: protocol 1, 192.168.100.157 -> 209.51.188.174 (1 packet)
2.0190: Flow 0 (ICMP ping sequence): echo request to socket, ID: 11, seq: 3
2.4837: pasta: epoll event on ICMP/ICMPv6 ping socket 95 (events: 0x00000001)
2.4837: Flow 0 (ICMP ping sequence): echo reply to tap, ID: 11, seq: 3
64 bytes from www.fsf.org (209.51.188.174): icmp_seq=3 ttl=255 time=465 ms
3.0191: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
3.0191: tap: protocol 1, 192.168.100.157 -> 209.51.188.174 (1 packet)
3.0192: Flow 0 (ICMP ping sequence): echo request to socket, ID: 11, seq: 4
3.6917: pasta: epoll event on ICMP/ICMPv6 ping socket 95 (events: 0x00000001)
3.6918: Flow 0 (ICMP ping sequence): echo reply to tap, ID: 11, seq: 4
64 bytes from www.fsf.org (209.51.188.174): icmp_seq=4 ttl=255 time=673 ms
4.0186: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
4.0187: tap: protocol 1, 192.168.100.157 -> 209.51.188.174 (1 packet)
4.0188: Flow 0 (ICMP ping sequence): echo request to socket, ID: 11, seq: 5
4.4281: pasta: epoll event on ICMP/ICMPv6 ping socket 95 (events: 0x00000001)
4.4282: Flow 0 (ICMP ping sequence): echo reply to tap, ID: 11, seq: 5
64 bytes from www.fsf.org (209.51.188.174): icmp_seq=5 ttl=255 time=410 ms

--- fsf.org ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4001ms
rtt min/avg/max/mdev = 409.797/476.856/673.012/100.088 ms

There were no entries on the auditlog regarding pasta.

I wonder if these 2 issues are mutually exclusive: If I disable apparmor and let passt
run, it doesn't get DNS configs right; however, if I don't make any changes to
apparmor configs, while passt won't be able to create the socket at /run/*, it will
get DNS configs right (?)

Curioser and curioser.
...
  --
 Stefano 

On Sun, 02 Feb 2025 14:21:49 +0000
Prafulla Giri <prafulla.giri(a)protonmail.com> wrote:

...
  On Saturday, February 1st, 2025 at 2:05 AM, Stefano
Brivio <sbrivio(a)redhat.com> wrote:
 
  On Thu, 30 Jan 2025 10:05:14 +0000
 Prafulla Giri prafulla.giri(a)protonmail.com wrote:
   
  I didn't have auditd installed on Debian and
installed it, and
 running everything with the default auditd config (with my Apparmor
 disabled for passt, as mentioned previously) does not result in
 anything. Do I have to configure auditd manually? Any pointers on
 that, please?   
 
 
 No, the default configuration is just fine. But you should re-enable
 AppArmor for passt so that we can see meaningful messages in the logs.
    
 The following is the output of grep-ping 'passt' after re-enforcing
the apparmor config and trying to start a VM:
 $ grep passt /var/log/audit/audit.log # Debian Trixie
 type=AVC msg=audit(1738501259.829:124): apparmor="STATUS"
operation="profile_load" profile="unconfined" name="passt"
pid=1935 comm="apparmor_parser"
 type=AVC msg=audit(1738501309.118:135): apparmor="DENIED"
operation="file_mmap" class="file" profile="passt"
name="/usr/bin/passt" pid=2030 comm="passt"
requested_mask="r" denied_mask="r" fsuid=1000 ouid=0FSUID="larryboy" OUID="root"
 type=SYSCALL msg=audit(1738501309.118:135): arch=c000003e syscall=59 success=no exit=-13
a0=7faf24035fc0 a1=7faf24035210 a2=7ffc063280d0 a3=0 items=0 ppid=1964 pid=2030 auid=1000
uid=1000 gid=1000 euid=1000 suid=1000 fsuid=1000 egid=1000 sgid=1000 fsgid=1000 tty=(none)
ses=1 comm="passt" exe="/usr/bin/passt" subj=passt key=(null)ARCH=x86_64 SYSCALL=execve AUID="larryboy" UID="larryboy"
GID="larryboy" EUID="larryboy" SUID="larryboy"
FSUID="larryboy" EGID="larryboy" SGID="larryboy"
FSGID="larryboy"
 type=ANOM_ABEND msg=audit(1738501309.118:136): auid=1000 uid=1000 gid=1000 ses=1
subj=passt pid=2030 comm="passt" exe="/usr/bin/passt" sig=11 res=1AUID="larryboy" UID="larryboy" GID="larryboy" 
System call number 59 (this seems to be x86_64) is "execve":

  $ ausyscall 59
  execve

and this seems to be libvirt failing to execute passt itself, but:

 
https://gitlab.com/libvirt/libvirt/-/blob/0264a7704ada52f686cafe8f6402d5b60…

Do you see the libvirtd profile loaded if you run 'aa-status'?

Do you have this line:

  /usr/bin/passt Cx -> passt,

in /etc/apparmor.d/abstractions/libvirt-qemu? I wonder if something
bad happened during installation.

Can you perhaps grep a bit before and after those messages (say, grep
-A5 -B5) to see if we spot something else related to libvirt?

...
  type=AVC msg=audit(1738501923.727:148):
apparmor="DENIED" operation="file_mmap" class="file"
profile="passt" name="/usr/bin/passt" pid=2088 comm="passt"
requested_mask="r" denied_mask="r" fsuid=1000 ouid=0FSUID="larryboy" OUID="root"
 type=SYSCALL msg=audit(1738501923.727:148): arch=c000003e syscall=59 success=no exit=-13
a0=7ff564035d40 a1=7ff564039d00 a2=7fffe9aa1de0 a3=0 items=0 ppid=2060 pid=2088 auid=1000
uid=1000 gid=1000 euid=1000 suid=1000 fsuid=1000 egid=1000 sgid=1000 fsgid=1000 tty=(none)
ses=1 comm="passt" exe="/usr/bin/passt" subj=passt key=(null)ARCH=x86_64 SYSCALL=execve AUID="larryboy" UID="larryboy"
GID="larryboy" EUID="larryboy" SUID="larryboy"
FSUID="larryboy" EGID="larryboy" SGID="larryboy"
FSGID="larryboy"
 type=ANOM_ABEND msg=audit(1738501923.727:149): auid=1000 uid=1000 gid=1000 ses=1
subj=passt pid=2088 comm="passt" exe="/usr/bin/passt" sig=11 res=1AUID="larryboy" UID="larryboy" GID="larryboy"
 type=AVC msg=audit(1738502301.651:174): apparmor="DENIED"
operation="file_mmap" class="file" profile="passt"
name="/usr/bin/passt" pid=2145 comm="passt"
requested_mask="r" denied_mask="r" fsuid=1000 ouid=0FSUID="larryboy" OUID="root"
 type=SYSCALL msg=audit(1738502301.651:174): arch=c000003e syscall=59 success=no exit=-13
a0=7fe208034ce0 a1=7fe208034350 a2=7fffd2e60120 a3=0 items=0 ppid=2117 pid=2145 auid=1000
uid=1000 gid=1000 euid=1000 suid=1000 fsuid=1000 egid=1000 sgid=1000 fsgid=1000 tty=(none)
ses=1 comm="passt" exe="/usr/bin/passt" subj=passt key=(null)ARCH=x86_64 SYSCALL=execve AUID="larryboy" UID="larryboy"
GID="larryboy" EUID="larryboy" SUID="larryboy"
FSUID="larryboy" EGID="larryboy" SGID="larryboy"
FSGID="larryboy"
 type=ANOM_ABEND msg=audit(1738502301.651:175): auid=1000 uid=1000 gid=1000 ses=1
subj=passt pid=2145 comm="passt" exe="/usr/bin/passt" sig=11 res=1AUID="larryboy" UID="larryboy" GID="larryboy"
 
 
  $ passt
-f -d # on Debian Testing/Trixie
 0.0016: No interfaces with usable IPv6 routes
 0.0017: Failed to detect external interface for IPv6
 0.0028: UNIX domain socket bound at /tmp/passt_1.socket
 0.0029: Template interface: enp1s0 (IPv4)
 0.0029: MAC:
 0.0029: host: 9a:55:9a:55:9a:55
 0.0029: NAT to host 127.0.0.1: 192.168.100.1
 0.0029: DHCP:
 0.0029: assign: 192.168.100.157
 0.0029: mask: 255.255.255.0
 0.0029: router: 192.168.100.1
 0.0029: DNS:
 0.0029: 192.168.100.1   
 
 
 So, judging from this configuration, it looks like we advertise to
 the guest (via DHCP) 192.168.100.1 as resolver (copied from the host),
 and when we receive packets from the guest for 192.168.100.1, we'll
 re-map them to the host.
 
 Nothing strange so far, systemd-resolved is running on the host, it
 should get our queries and reply to them.
   
  $ cat /etc/resolv.conf # On Debian Trixie
 # This is /run/systemd/resolve/resolv.conf managed by
 man:systemd-resolved(8). [...]
 nameserver 192.168.100.1
 search .
 $ cat /etc/resolv.conf # On a Debian 11 OS
 # Generated by NetworkManager
 nameserver 192.168.100.1
 
 Also the output of `resolvectl status` for good measure:
 # On Fedora 41
 Global
 Protocols: LLMNR=resolve -mDNS -DNSOverTLS
 DNSSEC=no/unsupported resolv.conf mode: stub
 
 Link 2 (wlp0s20f3)
 Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
 Protocols: +DefaultRoute LLMNR=resolve -mDNS -DNSOverTLS
 DNSSEC=no/unsupported Current DNS Server: 192.168.100.1
 DNS Servers: 192.168.100.1
 
 # On Debian Trixie
 Global
 Protocols: +LLMNR +mDNS -DNSOverTLS DNSSEC=no/unsupported
 resolv.conf mode: uplink
 
 Link 2 (enp1s0)
 Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
 Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS
 DNSSEC=no/unsupported DNS Servers: 192.168.100.1
 Default Route: yes   
 
 
 Everything as expected here, I don't see any obvious reason why
 systemd-resolved should discard our queries.
   
  The log from Debian Trixie host for VM1:
 passt 0.0~git20250121.4f2c8e7-1: /usr/bin/passt.avx2 (6428)
 0.0017: info: No interfaces with usable IPv6 routes
 0.0029: info: UNIX domain socket bound at
 /run/user/1000/libvirt/qemu/run/passt/2-vm1-net0.socket 0.0030: info:
 Template interface: enp1s0 (IPv4) 0.0030: info: MAC:
 0.0030: info: host: 9a:55:9a:55:9a:55
 0.0030: info: NAT to host 127.0.0.1: 192.168.100.1
 0.0030: info: DHCP:
 0.0031: info: assign: 192.168.100.157
 0.0031: info: mask: 255.255.255.0
 0.0031: info: router: 192.168.100.1
 0.0031: info: DNS:
 0.0031: info: 192.168.100.1
 0.0031: info: DNS search list:
 0.0031: info: .
 0.0066: info:
 You can now start qemu (>= 7.2, with commit 13c6be96618c):
 0.0066: info: kvm ... -device virtio-net-pci,netdev=s -netdev

stream,id=s,server=off,addr.type=unix,addr.path=/run/user/1000/libvirt/qemu/run/passt/2-vm1-net0.socket
 0.0066: info: or qrap, for earlier qemu versions: 0.0066: info:
 ./qrap 5 kvm ... -net socket,fd=5 -net nic,model=virtio 0.0617:
 info: accepted connection from PID 0 38.6257: info: DHCP: offer
 to discover 38.6257: info: from 52:54:00:a0:e1:7c
 38.6471: info: DHCP: ack to request
 38.6471: info: from 52:54:00:a0:e1:7c
 451.4989: info: Client connection closed, exiting   
 
 
 Unfortunately libvirt doesn't let us enable more verbose logging. I
 hoped to see DNS queries there, but without --debug given to passt,
 that won't work.
 
 Another idea: pasta(1) does the same job as passt(1) (it's the same
 code and same binary) and it's intended for containers, but it has a
 stand-alone mode that can probably help us to debug this, because it's
 a network namespace that will look like your guest, and it can also
 take packet captures.
 
 What happens if you run:
 
 pasta --config-net --trace --pcap /tmp/dns.pcap -- nslookup fsf.org
 
 ?   
 This one errors out. dns.pcap is attached.
 $ pasta --config-net --trace --pcap /tmp/dns.pcap -- nslookup fsf.org # Debian
Trixie/Testing
 0.0015: No interfaces with usable IPv6 routes
 0.0015: Failed to detect external interface for IPv6
 0.0073: Template interface: enp1s0 (IPv4)
 0.0073: Namespace interface: enp1s0
 0.0074: MAC:
 0.0074:     host: 9a:55:9a:55:9a:55
 0.0074:     NAT to host 127.0.0.1: 192.168.100.1
 0.0074: DHCP:
 0.0074:     assign: 192.168.100.157
 0.0074:     mask: 255.255.255.0
 0.0075:     router: 192.168.100.1
 0.0075: DNS:
 0.0075:     192.168.100.1
 0.0076: DNS search list:
 0.0076:     .
 0.0146: SO_PEEK_OFF supported
 0.0146: TCP_INFO tcpi_snd_wnd field  supported
 0.0146: TCP_INFO tcpi_bytes_acked field  supported
 0.0146: TCP_INFO tcpi_min_rtt field  supported
 0.0147: Saving packet capture to /tmp/dns.pcap
 0.0197: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
 0.0371: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
 0.0372: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
 0.0372: tap: protocol 17, 192.168.100.157:41892 -> 192.168.100.1:53 (1 packet)
 0.0372: Flow 0 (NEW): FREE -> NEW
 0.0372: Flow 0 (INI): NEW -> INI
 0.0372: Flow 0 (INI): TAP [192.168.100.157]:41892 -> [192.168.100.1]:53 => ?
 0.0372: Flow 0 (TGT): INI -> TGT
 0.0373: Flow 0 (TGT): TAP [192.168.100.157]:41892 -> [192.168.100.1]:53 => HOST
[0.0.0.0]:41892 -> [127.0.0.1]:53
 0.0373: Flow 0 (UDP flow): TGT -> TYPED
 0.0373: Flow 0 (UDP flow): TAP [192.168.100.157]:41892 -> [192.168.100.1]:53 =>
HOST [0.0.0.0]:41892 -> [127.0.0.1]:53
 0.0373: Flow 0 (UDP flow): Side 0 hash table insert: bucket: 31049
 0.0374: Flow 0 (UDP flow): TYPED -> ACTIVE
 0.0374: Flow 0 (UDP flow): TAP [192.168.100.157]:41892 -> [192.168.100.1]:53 =>
HOST [0.0.0.0]:41892 -> [127.0.0.1]:53
 0.0374: pasta: epoll event on UDP reply socket 95 (events: 0x00000008)
 0.0374: ICMP error on UDP socket 95: Connection refused 
Ouch. I just sent a patch for this, you can test it by checking out
passt locally:

  git clone git://passt.top/passt; cd passt

applying it (you might need to install 'b4'):

  b4 shazam
  https://archives.passt.top/passt-dev/20250203082210.2114348-1-sbrivio@redha…

then:

  make

and ./pasta --config-net --trace --pcap /tmp/dns.pcap -- nslookup
fsf.org

You can also install it to /usr/local with 'make install', it's just a
couple of files and will uninstall cleanly with 'make uninstall' if
needed. Note that AppArmor profiles don't apply to binaries under
/usr/local/bin.

...
  [...]

 This is rather strange: from the shell I successfully managed to `ping fsf.org` and `ping
gnu.org`. 
That's because they were already cached on your host at this point (I
suppose by systemd-resolved) and ping didn't need to resolve anything,
just call getaddrinfo() and get the addresses back. There's no UDP at
all in the output below:

...
  I went back and ran
 $ pasta --config-net --trace --pcap /tmp/ping.pcap -- ping -c 5 fsf.org # and the
following output followed (ping.pcap is also attached)
 
 0.0013: No interfaces with usable IPv6 routes
 0.0013: Failed to detect external interface for IPv6
 0.0091: Template interface: enp1s0 (IPv4)
 0.0091: Namespace interface: enp1s0
 0.0092: MAC:
 0.0092:     host: 9a:55:9a:55:9a:55
 0.0092:     NAT to host 127.0.0.1: 192.168.100.1
 0.0092: DHCP:
 0.0092:     assign: 192.168.100.157
 0.0093:     mask: 255.255.255.0
 0.0093:     router: 192.168.100.1
 0.0093: DNS:
 0.0093:     192.168.100.1
 0.0093: DNS search list:
 0.0094:     .
 0.0161: SO_PEEK_OFF supported
 0.0161: TCP_INFO tcpi_snd_wnd field  supported
 0.0161: TCP_INFO tcpi_bytes_acked field  supported
 0.0161: TCP_INFO tcpi_min_rtt field  supported
 0.0162: Saving packet capture to /tmp/ping.pcap
 PING fsf.org (209.51.188.174) 56(84) bytes of data.
 0.0181: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
 0.0181: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
 0.0182: tap: protocol 1, 192.168.100.157 -> 209.51.188.174 (1 packet) 
-- 
Stefano

On Tue, 04 Feb 2025 08:21:53 +0000
Prafulla Giri <prafulla.giri(a)protonmail.com> wrote:

...
  type=SERVICE_START msg=audit(1738501309.082:134):
pid=1 uid=0 auid=4294967295 ses=4294967295 subj=unconfined msg='unit=polkit
comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=?
terminal=? res=success'UID="root" AUID="unset"
 type=AVC msg=audit(1738501309.118:135): apparmor="DENIED"
operation="file_mmap" class="file" profile="passt"
name="/usr/bin/passt" pid=2030 comm="passt"
requested_mask="r" denied_mask="r" fsuid=1000
ouid=0FSUID="larryboy" OUID="root"
 type=SYSCALL msg=audit(1738501309.118:135): arch=c000003e syscall=59 success=no exit=-13
a0=7faf24035fc0 a1=7faf24035210 a2=7ffc063280d0 a3=0 items=0 ppid=1964 pid=2030 auid=1000
uid=1000 gid=1000 euid=1000 suid=1000 fsuid=1000 egid=1000 sgid=1000 fsgid=1000 tty=(none)
ses=1 comm="passt" exe="/usr/bin/passt" subj=passt
key=(null)ARCH=x86_64 SYSCALL=execve AUID="larryboy" UID="larryboy"
GID="larryboy" EUID="larryboy" SUID="larryboy"
FSUID="larryboy" EGID="larryboy" SGID="larryboy"
FSGID="larryboy"
 type=PROCTITLE msg=audit(1738501309.118:135): proctitle="(null)"
 type=ANOM_ABEND msg=audit(1738501309.118:136): auid=1000 uid=1000 gid=1000 ses=1
subj=passt pid=2030 comm="passt" exe="/usr/bin/passt" sig=11
res=1AUID="larryboy" UID="larryboy" GID="larryboy" 
So, it looks like passt is running as its own profile. This shouldn't
happen because the libvirt profile has an own subprofile and we should
see that in "profile" on the type=AVC line but... I just reproduced
this! Clean Debian sid install, fresh install of libvirtd:

error: internal error: Child process (passt --one-off --socket
/run/user/1000/libvirt/qemu/run/passt/1-alpine-net0.socket --pid
/run/user/1000/libvirt/qemu/run/passt/1-alpine-net0-passt.pid --tcp-ports 40922:22)
unexpected fatal signal 11

I'll keep you posted.

...
 
 
https://archives.passt.top/passt-dev/20250203082210.2114348-1-sbrivio@redha…
 
 then:
 
 make
 
 and ./pasta --config-net --trace --pcap /tmp/dns.pcap -- nslookup
 fsf.org
    
 $ ./pasta --config-net --trace --pcap /tmp/dns.pcap -- nslookup fsf.org # On
Debian Trixie, dns.pcap attached
 0.0002: No interfaces with usable IPv6 routes
 0.0002: Failed to detect external interface for IPv6
 0.0035: Template interface: enp1s0 (IPv4)
 0.0035: Namespace interface: enp1s0
 0.0035: MAC:
 0.0035:     host: 9a:55:9a:55:9a:55
 0.0035:     NAT to host 127.0.0.1: 192.168.100.1
 0.0036: DHCP:
 0.0036:     assign: 192.168.100.157
 0.0036:     mask: 255.255.255.0
 0.0036:     router: 192.168.100.1
 0.0036: DNS:
 0.0036:     192.168.100.1
 0.0036: DNS search list:
 0.0036:     .
 0.0204: SO_PEEK_OFF supported
 0.0204: TCP_INFO tcpi_snd_wnd field  supported
 0.0205: TCP_INFO tcpi_bytes_acked field  supported
 0.0205: TCP_INFO tcpi_min_rtt field  supported
 0.0205: Saving packet capture to /tmp/dns.pcap
 0.0281: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
 0.0413: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
 0.0414: pasta: epoll event on /dev/net/tun device 16 (events: 0x00000001)
 0.0414: tap: protocol 17, 192.168.100.157:56205 -> 192.168.100.1:53 (1 packet)
 0.0415: Flow 0 (NEW): FREE -> NEW
 0.0415: Flow 0 (INI): NEW -> INI
 0.0415: Flow 0 (INI): TAP [192.168.100.157]:56205 -> [192.168.100.1]:53 => ?
 0.0416: Flow 0 (TGT): INI -> TGT
 0.0416: Flow 0 (TGT): TAP [192.168.100.157]:56205 -> [192.168.100.1]:53 => HOST
[0.0.0.0]:56205 -> [192.168.100.1]:53
 0.0416: Flow 0 (UDP flow): TGT -> TYPED
 0.0416: Flow 0 (UDP flow): TAP [192.168.100.157]:56205 -> [192.168.100.1]:53 =>
HOST [0.0.0.0]:56205 -> [192.168.100.1]:53
 0.0417: Flow 0 (UDP flow): Side 0 hash table insert: bucket: 121236
 0.0417: Flow 0 (UDP flow): TYPED -> ACTIVE
 0.0417: Flow 0 (UDP flow): TAP [192.168.100.157]:56205 -> [192.168.100.1]:53 =>
HOST [0.0.0.0]:56205 -> [192.168.100.1]:53
 0.3059: pasta: epoll event on UDP reply socket 96 (events: 0x00000001)
 0.3059: Flow 0 (UDP flow): Received 1 datagrams on reply socket
 Server:		192.168.100.1
 Address:	192.168.100.1#53
 
 Non-authoritative answer:
 Name:	fsf.org
 Address: 209.51.188.174 
Okay, at least the DNS issue is fixed. I'll apply the fix in a moment,
it will be available in an updated package in a while.

-- 
Stefano

On Tue, 4 Feb 2025 09:50:40 +0000
Andrea Bolognani <abologna(a)redhat.com> wrote:

...
  On Tue, Feb 04, 2025 at 09:50:00AM +0100, Stefano
Brivio wrote:
  On Tue, 04 Feb 2025 08:21:53 +0000 Prafulla Giri
<prafulla.giri(a)protonmail.com> wrote:  
  type=SERVICE_START msg=audit(1738501309.082:134):
pid=1 uid=0 auid=4294967295 ses=4294967295 subj=unconfined msg='unit=polkit
comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=?
terminal=? res=success'UID="root" AUID="unset"
 type=AVC msg=audit(1738501309.118:135): apparmor="DENIED"
operation="file_mmap" class="file" profile="passt"
name="/usr/bin/passt" pid=2030 comm="passt"
requested_mask="r" denied_mask="r" fsuid=1000
ouid=0FSUID="larryboy" OUID="root"
 type=SYSCALL msg=audit(1738501309.118:135): arch=c000003e syscall=59 success=no exit=-13
a0=7faf24035fc0 a1=7faf24035210 a2=7ffc063280d0 a3=0 items=0 ppid=1964 pid=2030 auid=1000
uid=1000 gid=1000 euid=1000 suid=1000 fsuid=1000 egid=1000 sgid=1000 fsgid=1000 tty=(none)
ses=1 comm="passt" exe="/usr/bin/passt" subj=passt
key=(null)ARCH=x86_64 SYSCALL=execve AUID="larryboy" UID="larryboy"
GID="larryboy" EUID="larryboy" SUID="larryboy"
FSUID="larryboy" EGID="larryboy" SGID="larryboy"
FSGID="larryboy"
 type=PROCTITLE msg=audit(1738501309.118:135): proctitle="(null)"
 type=ANOM_ABEND msg=audit(1738501309.118:136): auid=1000 uid=1000 gid=1000 ses=1
subj=passt pid=2030 comm="passt" exe="/usr/bin/passt" sig=11
res=1AUID="larryboy" UID="larryboy" GID="larryboy"   
 So, it looks like passt is running as its own profile. This shouldn't
 happen because the libvirt profile has an own subprofile and we should
 see that in "profile" on the type=AVC line but... I just reproduced
 this! Clean Debian sid install, fresh install of libvirtd:

 error: internal error: Child process (passt --one-off --socket
/run/user/1000/libvirt/qemu/run/passt/1-alpine-net0.socket --pid
/run/user/1000/libvirt/qemu/run/passt/1-alpine-net0-passt.pid --tcp-ports 40922:22)
unexpected fatal signal 11

 I'll keep you posted.   
 
 I've skimmed the conversation trying to understand whether there's
 anything that I need do from the libvirt side, but AFAICT no explicit
 action has been called for so far. 
Not yet, because I was hoping to figure out what's going on, but I'm
actually (almost?) stuck now. I don't think this is the same as
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1094583 by the way,
because:

$ find /etc/apparmor.d/ -ls | grep -i virt
   148926      4 drwxr-xr-x   2 root     root         4096 Feb  4 08:44
/etc/apparmor.d/libvirt
   148927      4 -rw-r--r--   1 root     root          192 Jan 15 08:06
/etc/apparmor.d/libvirt/TEMPLATE.qemu
   149882      4 -rw-r--r--   1 root     root          342 Jan 15 08:06
/etc/apparmor.d/libvirt/TEMPLATE.lxc
     6098      8 -rw-r--r--   1 root     root         4780 Jan 30 22:47
/etc/apparmor.d/usr.sbin.libvirtd
    20741      0 -rw-r--r--   1 root     root            0 Feb  4 08:44
/etc/apparmor.d/local/usr.sbin.libvirtd
    20572      0 -rw-r--r--   1 root     root            0 Feb  4 08:44
/etc/apparmor.d/local/usr.lib.libvirt.virt-aa-helper
     6826     12 -rw-r--r--   1 root     root         9258 Jan 30 22:47
/etc/apparmor.d/abstractions/libvirt-qemu
    20662      8 -rw-r--r--   1 root     root         4610 Jan 30 22:47
/etc/apparmor.d/abstractions/libvirt-lxc
     6099      4 -rw-r--r--   1 root     root         1898 Jan 30 22:47
/etc/apparmor.d/usr.lib.libvirt.virt-aa-helper
$ find /etc/libvirt/    -ls | grep -i conf
find: '/etc/libvirt/secrets': Permission denied
   268888     20 -rw-r--r--   1 root     root        17826 Jan 30 22:47
/etc/libvirt/libvirtd.conf
   269240      4 -rw-r--r--   1 root     root         2169 Jan 30 22:47
/etc/libvirt/libxl-lockd.conf
   324760      4 -rw-r--r--   1 root     root          547 Nov  1 09:13
/etc/libvirt/libvirt.conf
   269243      4 -rw-r--r--   1 root     root         3058 Jan 15 08:06
/etc/libvirt/virtlockd.conf
   263460      4 -rw-r--r--   1 root     root         2465 Jan 30 22:47
/etc/libvirt/qemu-sanlock.conf
   263459      4 -rw-r--r--   1 root     root         2169 Jan 30 22:47
/etc/libvirt/qemu-lockd.conf
   269238      4 -rw-r--r--   1 root     root         1175 Jan 15 08:06
/etc/libvirt/lxc.conf
   324759      4 -rw-r--r--   1 root     root          450 Nov  1 09:13
/etc/libvirt/libvirt-admin.conf
   269241      4 -rw-r--r--   1 root     root         2465 Jan 30 22:47
/etc/libvirt/libxl-sanlock.conf
   269242      4 -rw-r--r--   1 root     root         2268 Jan 15 08:06
/etc/libvirt/libxl.conf
   263461     40 -rw-------   1 root     root        39106 Jan 30 22:47
/etc/libvirt/qemu.conf
   262245      4 -rw-r--r--   1 root     root         4095 Jan 15 08:06
/etc/libvirt/virtlogd.conf
   268889      4 -rw-r--r--   1 root     root         1041 Jan 30 22:47
/etc/libvirt/network.conf

...
  It looks like you're making good progress in
figuring out what's
 going on. Being able to reproduce the issue yourself is certainly
 going to help. I'm happy to leave all the debugging to you, since as
 you know I'm not very good at the AppArmor stuff and I'm really,
 really bad at the networking stuff ;) 
...no, wait, I'm still failing to understand the bigger picture of what
happens AppArmor-wise when I do 'virsh start something'. :)

This is really pretty simple: fresh Debian sid image, all packages
updated to today. Then:

  virt-install -d --name alpine --memory 1024 --noreboot --osinfo alpinelinux3.20
--network
backend.type=passt,portForward0.proto=tcp,portForward0.range0.start=40922,portForward0.range0.to=22
--import --disk nocloud_alpine-3.21.2-x86_64-bios-tiny-r0.qcow2

this works. But:

  $ virsh start alpine
  error: Failed to start domain 'alpine'
  error: internal error: Child process (passt --one-off --socket
/run/user/1000/libvirt/qemu/run/passt/1-alpine-net0.socket --pid
/run/user/1000/libvirt/qemu/run/passt/1-alpine-net0-passt.pid --tcp-ports 40922:2)
unexpected fatal signal 11

execve() of passt is denied by AppArmor. Starting passt on its own
(passt -f) works, instead.

At this point, which libvirtd (?) process should associate with which
libvirtd profile? Once that's clear to me, I can probably debug further.

I can also give you access to the machine if needed.

...
  Once a clearer picture emerges, if it turns out that
changes are
 needed in either libvirt or its Debian packaging, I can definitely
 look into making that happen. 
I'm fairly sure it's libvirt, because I didn't change anything
substantial in passt, and it's anyway the AppArmor profile for libvirtd
that seems to be... missing? And yet it's there.

-- 
Stefano

On Tue, 4 Feb 2025 15:50:43 +0000
Andrea Bolognani <abologna(a)redhat.com> wrote:

...
  On Tue, Feb 04, 2025 at 11:17:24AM +0100, Stefano
Brivio wrote:
  On Tue, 4 Feb 2025 09:50:40 +0000 Andrea
Bolognani <abologna(a)redhat.com> wrote:  
  I've skimmed the conversation trying to
understand whether there's
 anything that I need do from the libvirt side, but AFAICT no explicit
 action has been called for so far.   
 Not yet, because I was hoping to figure out what's going on, but I'm
 actually (almost?) stuck now. I don't think this is the same as
 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1094583 by the way,   
 
 That issue can only manifest itself when upgrading from bookworm, so
 if you have performed a fresh install of sid you don't need to worry
 about it.
 
  This is really pretty simple: fresh Debian sid
image, all packages
 updated to today. Then:

   virt-install -d --name alpine --memory 1024 --noreboot --osinfo alpinelinux3.20
--network
backend.type=passt,portForward0.proto=tcp,portForward0.range0.start=40922,portForward0.range0.to=22
--import --disk nocloud_alpine-3.21.2-x86_64-bios-tiny-r0.qcow2

 this works. But:

   $ virsh start alpine
   error: Failed to start domain 'alpine'
   error: internal error: Child process (passt --one-off --socket
/run/user/1000/libvirt/qemu/run/passt/1-alpine-net0.socket --pid
/run/user/1000/libvirt/qemu/run/passt/1-alpine-net0-passt.pid --tcp-ports 40922:2)
unexpected fatal signal 11

 execve() of passt is denied by AppArmor. Starting passt on its own
 (passt -f) works, instead.   
 
 I was initially very surprised to read this, but it makes sense after
 spending some more time looking into it. 
Ah, sure, sorry! I didn't mean to waste your time with that, it was
clear to me that passt doesn't start there... I just wanted to show the
setup.

...
  [...]

 So there's no magic to that first VM start that apparently worked
 even when subsequent ones wouldn't. The VM start simply didn't happen
 in the first place.
 
  At this point, which libvirtd (?) process should
associate with which
 libvirtd profile? Once that's clear to me, I can probably debug further.
   
 [...]
 
 I'm fairly sure it's libvirt, because I didn't change anything
 substantial in passt, and it's anyway the AppArmor profile for libvirtd
 that seems to be... missing? And yet it's there.   
 
 We're going back to the question of how AppArmor works for
 unprivileged VMs... The short answer is that I'm not convinced it
 does.
 
 In order to make a direct comparison, I've create the very same
 Alpine VM, with no network interface, both on qemu:///system and
 qemu:///user.
 
 When I start the former, the (filtered) output for aa-status goes
 from
 
   22 profiles are in enforce mode.
      libvirtd
      libvirtd//qemu_bridge_helper
      virt-aa-helper
   25 profiles are in complain mode.
      dnsmasq//libvirt_leaseshelper
   2 processes are in enforce mode.
      /usr/sbin/libvirtd (862) libvirtd
 
 to
 
   24 profiles are in enforce mode.
      libvirt-1cdfdfd3-a020-45d9-8f88-8e0ce31745c4
      libvirt-1cdfdfd3-a020-45d9-8f88-8e0ce31745c4//passt
      libvirtd
      libvirtd//qemu_bridge_helper
      virt-aa-helper
   25 profiles are in complain mode.
      dnsmasq//libvirt_leaseshelper
   3 processes are in enforce mode.
      /usr/bin/qemu-system-x86_64 (1310)
 libvirt-1cdfdfd3-a020-45d9-8f88-8e0ce31745c4
      /usr/sbin/libvirtd (862) libvirtd
 
 The additional profiles (libvirt-1cdfdfd3-a020-45d9-8f88-8e0ce31745c4
 and its passt subprofile) are generated dynamically when the VM is
 started and the QEMU process gets the correct one assigned to it. So
 far so good. 
Why do we need additional profiles, I wonder? Are we trying to
replicate the MCS (Multi-Category Security) stuff from SELinux?

...
  After launching the qemu:///session VM, however, the
situation is a
 lot different:
 
   22 profiles are in enforce mode.
      libvirtd
      libvirtd//qemu_bridge_helper
      virt-aa-helper
   25 profiles are in complain mode.
      dnsmasq//libvirt_leaseshelper
   4 processes are in enforce mode.
      /usr/sbin/libvirtd (1589) libvirtd
      /usr/sbin/virtlogd (1632) libvirtd
 
 As you can see, the per-VM profile hasn't been created, and so
 obviously it couldn't be applied to the QEMU process either. 
Oh, now I understand the whole "template" thing finally! And now that
you mention virt-aa-helper (I wasn't aware of that) I also found:

  https://gitlab.com/apparmor/apparmor/-/wikis/Libvirt

Yes, of course, that won't work unless you're root.

...
  This is probably undesirable, but at the same time
I'm not really
 sure how it could be fixed. 
If I understood the purpose correctly: implementing equivalent MCS
functionality in AppArmor would probably be the only "complete" fix. But
for the moment (or more realistically):

...
  Creating a new profile requires dropping
 a file in /etc/apparmor.d/libvirt, and the unprivileged libvirtd
 intentionally doesn't have the necessary permissions to do that... 
Profiles could reside in other places too, but they won't be associated
"just like that". A privileged helper could... help. But if users can
edit their own profiles in their homes, that defies a bit the point of
AppArmor profiles altogether.

...
  Do you have any ideas? 
Probably you should ask somebody more familiar (openSUSE/Ubuntu
maintainers of libvirt, or the authors of the virt-aa-helper thing?),
but a couple of quick ideas:

1. user-specific subprofiles could be added at adduser time (is there a
   hook?) and libvirtd could use aa_change_hat(2) to select the
   appropriate one based on UID

2. (most reasonable I think) don't use per-VM profiles for the rootless
   case. Define a single "libvirt-user" (or "libvirt-session")
profile
   and use that. We could copy it from the existing ones I suppose.

I think that MCS-equivalent functionality is anyway much less critical
if guests are started as unprivileged users because you have a strong
separation given by the fact that guests are started as different users.

If all the guests are started as root, and multiple users have access
to that facility, user separation is much more seriously endangered,
hence a stronger need for per-VM profiles.

And, stating the obvious, it's counterproductive to force users to run
guests as root because we can't have that kind of functionality.

By the way, I recently happened to introduce an AppArmor profile for
guestfs-tools:

  https://salsa.debian.org/libvirt-team/guestfs-tools/-/merge_requests/1

there are no separate profiles, there.

I can try to work on this but I'm really a bit too busy right now. If
you can, great, otherwise, let me know. On the other hand this feels
pretty urgent. :(

-- 
Stefano

On Tue, 4 Feb 2025 18:46:37 +0000
Andrea Bolognani <abologna(a)redhat.com> wrote:

...
  On Tue, Feb 04, 2025 at 05:22:42PM +0100, Stefano
Brivio wrote:
  On Tue, 4 Feb 2025 15:50:43 +0000 Andrea
Bolognani <abologna(a)redhat.com> wrote:  
  The additional profiles
(libvirt-1cdfdfd3-a020-45d9-8f88-8e0ce31745c4
 and its passt subprofile) are generated dynamically when the VM is
 started and the QEMU process gets the correct one assigned to it. So
 far so good.   
 Why do we need additional profiles, I wonder? Are we trying to
 replicate the MCS (Multi-Category Security) stuff from SELinux?   
 
 I'm not well-versed enough in SELinux to be able to answer the latter
 question, but I can answer the former. The per-VM profile is needed
 to ensure that each VM is only granted access to its own resources.
 
   $ sudo tail -4
 /etc/apparmor.d/libvirt/libvirt-1cdfdfd3-a020-45d9-8f88-8e0ce31745c4
   profile libvirt-1cdfdfd3-a020-45d9-8f88-8e0ce31745c4
 flags=(attach_disconnected) {
     #include <abstractions/libvirt-qemu>
     #include if exists
 <libvirt/libvirt-1cdfdfd3-a020-45d9-8f88-8e0ce31745c4.files>
   }
 
   $ sudo cat /etc/apparmor.d/libvirt/libvirt-1cdfdfd3-a020-45d9-8f88-8e0ce31745c4.files
     "/var/log/libvirt/**/alpine.log" w,
     "/var/lib/libvirt/qemu/domain-alpine/monitor.sock" rw,
     "/var/lib/libvirt/qemu/domain-1-alpine/*" rw,
     "/run/libvirt/**/alpine.pid" rwk,
     "/run/libvirt/**/*.tunnelmigrate.dest.alpine" rw,
     "/var/lib/libvirt/images/alpine.qcow2" rwk,
     "/var/lib/libvirt/qemu/domain-1-alpine/{,**}" rwk,
     "/run/libvirt/qemu/channel/1-alpine/{,**}" rwk,
     "/var/lib/libvirt/qemu/domain-1-alpine/master-key.aes" rwk,
     "/dev/userfaultfd" rwk,
 
 The stuff in the libvirt-qemu abstraction is generic, all VMs get
 access to it. The stuff in .files is all specific to the VM. 
Ah, thanks, it never occurred to me to look into that. So, yes,
essentially the same thing as it's done with MCS and SELinux.

...
 
 
  Do you have any ideas?   
 Probably you should ask somebody more familiar (openSUSE/Ubuntu
 maintainers of libvirt, or the authors of the virt-aa-helper thing?),
 but a couple of quick ideas:

 1. user-specific subprofiles could be added at adduser time (is there a
    hook?) and libvirtd could use aa_change_hat(2) to select the
    appropriate one based on UID

 2. (most reasonable I think) don't use per-VM profiles for the rootless
    case. Define a single "libvirt-user" (or "libvirt-session")
profile
    and use that. We could copy it from the existing ones I suppose.   
 
 Sounds to me like this would require granting the QEMU process access
 to roughly the entire filesystem? The disk image could live anywhere
 after all, and if we can't dynamically add a rule for the exact path
 the only way out is a free-for-all approach. 
Right. That's what we did for libguestfs as well, the image can be
*almost* anywhere. But it's not free-for-all: you're just granting
*limited* filesystem access (not to sysfs, not to /etc, and so on).

And I had to build a *very* loose profile for libguestfs because that
applies to root as well, but for rootless libvirtd, it might even make
sense to restrict access to just @{HOME}/** and /tmp/** (that's what I
did for stand-alone passt, for example).

...
 
  I think that
MCS-equivalent functionality is anyway much less critical
 if guests are started as unprivileged users because you have a strong
 separation given by the fact that guests are started as different users.

 If all the guests are started as root, and multiple users have access
 to that facility, user separation is much more seriously endangered,
 hence a stronger need for per-VM profiles.   
 
 Ideally you'd still want to isolate unprivileged VMs from each other.
 If you don't, what's the point of using AppArmor in the first place? 
Well, you are still restricting them significantly, for example they
can't run random binaries, send arbitrary signals to other processes
or to each other, and access a ton of places on the filesystem.

Perhaps that's even more important than curbing filesystem access,
because that should already be significantly restricted.

...
 
  I can try to
work on this but I'm really a bit too busy right now. If
 you can, great, otherwise, let me know. On the other hand this feels
 pretty urgent. :(   
 
 I'm afraid I have neither the time nor the expertise to work on this
 myself. 
I'll try to submit a pull request at least for Debian in a couple of
days. I guess it would be nice if you could ask other maintainers
meanwhile.

-- 
Stefano

On Tue, 4 Feb 2025 14:19:34 -0800
Andrea Bolognani <abologna(a)redhat.com> wrote:

...
  On Tue, Feb 04, 2025 at 08:14:48PM +0100, Stefano
Brivio wrote:
  On Tue, 4 Feb 2025 18:46:37 +0000 Andrea
Bolognani <abologna(a)redhat.com> wrote:  
 
  2. (most
reasonable I think) don't use per-VM profiles for the rootless
    case. Define a single "libvirt-user" (or "libvirt-session")
profile
    and use that. We could copy it from the existing ones I suppose.   
 Sounds to me like this would require granting the QEMU process access
 to roughly the entire filesystem? The disk image could live anywhere
 after all, and if we can't dynamically add a rule for the exact path
 the only way out is a free-for-all approach.   
 Right. That's what we did for libguestfs as well, the image can be
 *almost* anywhere. But it's not free-for-all: you're just granting
 *limited* filesystem access (not to sysfs, not to /etc, and so on).

 And I had to build a *very* loose profile for libguestfs because that
 applies to root as well, but for rootless libvirtd, it might even make
 sense to restrict access to just @{HOME}/** and /tmp/** (that's what I
 did for stand-alone passt, for example).   
 
 That could work, I suppose. Needs to be discussed upstream, making
 sure to involve those who are more experienced with AppArmor than I
 am 
Sure, that makes sense of course.

...
  especially since it's not just a matter of
updating the policy
 but fundamentally changing how the driver works when operating in
 unprivileged mode. 
Well, right now it runs unconfined, and (at least with passt) networking
doesn't work. Pretty much any change would be good. :)

I've been disabling AppArmor when I start guests for quite a while now,
thinking that I just broke something on my setup while developing
stuff (I reported that to you but I wasn't sure how the whole thing
worked...). Oops.

...
 
  I'll try
to submit a pull request at least for Debian in a couple of
 days.   
 
 Be aware that I will emphatically refuse to introduce changes to the
 Debian package unless they have been merged upstream first. AppArmor
 support lives in the upstream repository, and all fixes and
 improvements have to go through it. 
Then never mind. I can help filing a Debian issue if needed, let me
know. Or let me know how I can help otherwise.

I would consider a workaround for passt for the moment, say, the whole
block:

    /usr/bin/passt r,

    signal (receive) set=("term") peer=/usr/sbin/libvirtd,
    signal (receive) set=("term") peer=libvirtd,
    signal (receive) set=("term") peer=virtqemud,

    owner @{run}/user/[0-9]*/libvirt/qemu/run/passt/* rw,
    owner @{run}/libvirt/qemu/passt/* rw,

as part of the profile for usr.bin.passt. If you don't see issues with
it, I'll go ahead with that. I still need to check openSUSE though (I
haven't tried for a while there).

-- 
Stefano