Re: [PATCH container/docs/manager/network/proxmox{-ebpf,-perl-rs}/qemu-server v3 00/17] sdn: implement DHCP for all zones using eBPF

[Stefan Hanreich <s.hanreich@proxmox.com>]

Did some testing:

* PVE IPAM / All zones / eBPF backend
* PVE IPAM / Simple zone / dnsmasq backend
* Netbox IPAM / All zones / eBPF backend
* Netbox IPAM / Simple zone / dnsmasq backend
* switching from dnsmasq -> eBPF and vice-versa
    -> pre-existing: dnsmasq doesn't clean its config folder
* changing bridge on network devices
* changing subnets on the vnet and then reacquiring a lease

Everything worked really well, also the pre-existing dnsmasq zone. This
revision seems a lot nicer already without the generation counter, which
seemed a bit clunky. This is a more elegant solution imo.

One thing I found:

The new DHCP backend type needs to be added to proxmox-ve-rs as well,
otherwise the config fails to parse (firewall). We should add fallback
variants there...

for code-related stuff see the respective patches.

On 10/20/26 10:00 AM, Hannes Laimer wrote:
> This series adds a second DHCP backend, ebpf, next to dnsmasq. A zone
> picks its backend. dnsmasq stays limited to simple zones, while ebpf
> answers on the guest's own interface and works on every zone type. A
> guest on a zone with the ebpf backend gets the address its NIC has in
> the IPAM. There is no daemon per zone and no lease file. The answers
> are held in the kernel and do not depend on the IPAM being reachable.
> 
> The responder is a BPF program on the ingress of each guest interface
> of a zone with the ebpf backend. It answers a request from the record
> of that interface, and the exchange never reaches the bridge. A
> request whose client MAC is not the interface's own passes on
> unanswered. So a guest cannot read another guest's record, and a
> nested client does not get the outer guest's address.
> 
> An edit through /cluster/sdn/vnets/{vnet}/ips reaches the guest's node
> by a detached call to a new node endpoint, POST
> /nodes/{node}/sdn/dhcp-mapping. The guest sees the change at its next
> renewal, so the lease time bounds how long an old answer survives.
> Subnets get a dhcp-lease-time property for both backends. Without it
> dnsmasq hands out infinite leases and the responder ten minutes. A
> failed push is logged in the journal, and the responder on the guest's
> node catches up at the node's next apply or the guest's next start. An
> apply also attaches the responder to running guests, so a zone
> switched to ebpf serves them without a restart.
> 
> Changes reach the kernel in the order they read their input. So no
> change overwrites a newer one with older input. A hotplug moves the
> interface before the guest config names the new bridge. An apply or an
> edit that read the older config in between leaves the moved interface
> as its plug left it. A change that fails only warns, and what was
> served stays served. Nothing of the responder survives a reboot, so it
> is loaded again at boot before the guests start.
> 
> Only DHCPv4 is answered. A request the guest tagged itself passes
> unanswered as well, so a trunk port keeps working as before. The
> request is answered on the guest interface, so the guest's firewall
> rules, its DHCP firewall option and its rate limit do not apply to it.
> The reply leaves through the interface's egress, where the rate limit
> shapes it. A request the responder does not answer passes on to the
> bridge and through the firewall as before. Mappings changed directly
> in an external IPAM are not picked up, as with dnsmasq.
> 
> In patch order, the series adds
>  - proxmox-ebpf, the dhcp subsystem, a tc program answering on the
>    guest interface and the per-interface map it answers from
>  - pve-rs, the bindings
>  - pve-network, the ebpf backend, the hooks that keep a backend current
>    when a guest interface or a mapping changes, dhcp on every zone
>    type, and fixes to the dnsmasq reservations and the MAC cache
>  - qemu-server and pve-container, the reports of a guest NIC coming,
>    going or moving, and for VMs the push at a migration's resume
>  - pve-manager, the backend and subnet options in the UI, and the
>    backends brought up at boot ahead of the guests
>  - pve-docs, documentation
> 
>  - proxmox-ebpf applies on top of the v4 of its own series [1]
>  - pve-rs needs proxmox-ebpf with the dhcp feature
>  - pve-network needs pve-rs, at build and run time
>  - qemu-server, pve-container and pve-manager need pve-network
> An older pve-network fails its apply on the unknown backend, so every
> node needs the new one before a zone gets ebpf.
> 
> Changes since v2:
>  * drop the generation counter. Every change takes the responder's
>    lock before it reads its input instead. An edit takes it
>    exclusively
>  * the resume at the end of a live migration pushes the guest's
>    mappings again on the target, so an edit made during the migration
>    reaches it
>  * new first pve-network commit, a dnsmasq fix that replaces a stale
>    reservation of another MAC instead of dropping it
>  * no MTU option for a zone without an MTU, where v2 handed out 1500
>  * a mapping edit without a MAC no longer reaches the backends
>  * rewrite commit messages, cover letter and parts of the docs
>  * rebase onto current master
> 
> (pre-build packages on sani)
> 
> [1] https://lore.proxmox.com/pve-devel/20261019142413.2255644-1-h.laimer@proxmox.com/
> 
> 
> proxmox-ebpf:
> 
> Hannes Laimer (2):
>   dhcp: add the per-tap DHCPv4 responder program
>   dhcp: add the subsystem that loads the responder and keeps its records
> 
>  Cargo.toml                     |    5 +
>  debian/control                 |    6 +-
>  src/bpf-shim/bpf/bpf_helpers.h |    3 +
>  src/bpf-shim/vmlinux.h         |    1 +
>  src/dhcp/bpf/dhcp.bpf.c        |  401 +++++++++++++
>  src/dhcp/bpf/types.h           |   24 +
>  src/dhcp/mod.rs                | 1031 ++++++++++++++++++++++++++++++++
>  src/dhcp/types.rs              |   64 ++
>  src/lib.rs                     |    3 +
>  src/subsystem.rs               |    2 +-
>  tests/common/mod.rs            |   63 +-
>  tests/dhcp.rs                  |  825 +++++++++++++++++++++++++
>  12 files changed, 2422 insertions(+), 6 deletions(-)
>  create mode 100644 src/dhcp/bpf/dhcp.bpf.c
>  create mode 100644 src/dhcp/bpf/types.h
>  create mode 100644 src/dhcp/mod.rs
>  create mode 100644 src/dhcp/types.rs
>  create mode 100644 tests/dhcp.rs
> 
> 
> proxmox-perl-rs:
> 
> Hannes Laimer (1):
>   pve-rs: sdn: add bindings for the eBPF DHCP responder
> 
>  pve-rs/Cargo.toml               |   2 +
>  pve-rs/Makefile                 |   3 +
>  pve-rs/debian/control           |   2 +
>  pve-rs/src/bindings/sdn/dhcp.rs | 229 ++++++++++++++++++++++++++++++++
>  pve-rs/src/bindings/sdn/mod.rs  |   1 +
>  5 files changed, 237 insertions(+)
>  create mode 100644 pve-rs/src/bindings/sdn/dhcp.rs
> 
> 
> pve-network:
> 
> Hannes Laimer (9):
>   sdn: dhcp: replace a stale dnsmasq reservation instead of dropping it
>   sdn: dhcp: update reservations when ip mappings change
>   sdn: ipam: key the MAC cache by lower-case MAC, stop caching misses
>   sdn: dhcp: make the lease time configurable per subnet
>   sdn: dhcp: require a backend only if a zone on this node uses it
>   sdn: dhcp: add an eBPF backend answering on each guest interface
>   sdn: zones: report interface plugs and unplugs to the DHCP backends
>   sdn: dhcp: push IP mapping edits to the guest's node
>   sdn: zones: allow the ebpf DHCP backend on every zone type
> 
>  debian/libpve-network-perl.prerm          |   13 +
>  src/PVE/API2/Network/SDN/Ips.pm           |   10 +
>  src/PVE/API2/Network/SDN/Nodes/Status.pm  |   37 +
>  src/PVE/API2/Network/SDN/Zones.pm         |   11 +-
>  src/PVE/Network/SDN/Dhcp.pm               |  200 ++-
>  src/PVE/Network/SDN/Dhcp/Dnsmasq.pm       |  114 +-
>  src/PVE/Network/SDN/Dhcp/Ebpf.pm          |  308 +++++
>  src/PVE/Network/SDN/Dhcp/Makefile         |    2 +-
>  src/PVE/Network/SDN/Dhcp/Plugin.pm        |   26 +-
>  src/PVE/Network/SDN/Ipams.pm              |   61 +-
>  src/PVE/Network/SDN/SubnetPlugin.pm       |   11 +
>  src/PVE/Network/SDN/Vnets.pm              |    5 +-
>  src/PVE/Network/SDN/Zones.pm              |   29 +-
>  src/PVE/Network/SDN/Zones/EvpnPlugin.pm   |   32 +
>  src/PVE/Network/SDN/Zones/FaucetPlugin.pm |    1 +
>  src/PVE/Network/SDN/Zones/QinQPlugin.pm   |    7 +
>  src/PVE/Network/SDN/Zones/SimplePlugin.pm |    2 +-
>  src/PVE/Network/SDN/Zones/VlanPlugin.pm   |    7 +
>  src/PVE/Network/SDN/Zones/VxlanPlugin.pm  |   25 +
>  src/test/run_test_vnets_blackbox.pl       | 1442 ++++++++++++++++++++-
>  20 files changed, 2263 insertions(+), 80 deletions(-)
>  create mode 100755 debian/libpve-network-perl.prerm
>  create mode 100644 src/PVE/Network/SDN/Dhcp/Ebpf.pm
> 
> 
> qemu-server:
> 
> Hannes Laimer (1):
>   network: sdn: keep the DHCP backends current on guest NICs
> 
>  src/PVE/CLI/qm.pm              |  4 ++--
>  src/PVE/QemuServer.pm          |  4 ++++
>  src/PVE/QemuServer/Network.pm  | 19 +++++++++++++++++--
>  src/PVE/QemuServer/RunState.pm |  2 ++
>  src/usr/pve-bridge             |  8 +++++++-
>  src/usr/pve-bridgedown         |  4 ++--
>  6 files changed, 34 insertions(+), 7 deletions(-)
> 
> 
> pve-container:
> 
> Hannes Laimer (1):
>   net: report NIC plugs and removals to the SDN DHCP backends
> 
>  src/PVE/LXC.pm            | 13 +++++++++++--
>  src/PVE/LXC/Config.pm     |  3 ++-
>  src/lxc-pve-poststop-hook |  6 +++---
>  3 files changed, 16 insertions(+), 6 deletions(-)
> 
> 
> pve-manager:
> 
> Hannes Laimer (2):
>   ui: sdn: add zone DHCP backend selector and subnet DHCP options
>   sdn: bring up the DHCP backends at boot before the guests start
> 
>  bin/pve-sdn-commit                   |  3 +++
>  services/pve-sdn-commit.service      |  1 +
>  www/manager6/sdn/SubnetEdit.js       | 23 +++++++++++++++++++++++
>  www/manager6/sdn/zones/Base.js       | 17 +++++++++++++++++
>  www/manager6/sdn/zones/SimpleEdit.js | 11 -----------
>  5 files changed, 44 insertions(+), 11 deletions(-)
> 
> 
> pve-docs:
> 
> Hannes Laimer (1):
>   sdn: dhcp: add eBPF backend section
> 
>  pvesdn.adoc | 101 ++++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 83 insertions(+), 18 deletions(-)
> 
> 
> Summary over all repositories:
>   52 files changed, 5099 insertions(+), 128 deletions(-)
>