298073 – Bridge VLAN tagging fails when using bhyve e1000 device emulation

Bug 298073 - Bridge VLAN tagging fails when using bhyve e1000 device emulation

Summary: Bridge VLAN tagging fails when using bhyve e1000 device emulation

Status:	New

Alias:	None

Product:	Base System
Classification:	Unclassified
Component:	bhyve (show other bugs)
Version:	15.1-RELEASE
Hardware:	amd64 Any

Importance:	--- Affects Only Me
Assignee:	freebsd-virtualization (Nobody)

URL:
Keywords:

Depends on:
Blocks:

Reported:	2026-08-31 11:46 UTC by Danny Danchev
Modified:	2026-09-02 08:25 UTC (History)
CC List:	1 user (show)

See Also:

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Description Danny Danchev 2026-08-31 11:46:02 UTC

Hello!
This issue is only present when using the e1000 device emulation instead of virtio-net.

Exact error: e82545: packet too small for writable header

Host machine
danny@freebsd-test:~ $ uname -a
FreeBSD freebsd-test 15.1-RELEASE-p3 FreeBSD 15.1-RELEASE-p3 releng/15.1-n283611-88e7371d9dc2 GENERIC amd64

Virtual machine:
danny@freebsd0:~ $ uname -a
FreeBSD freebsd0 15.1-RELEASE-p3 FreeBSD 15.1-RELEASE-p3 releng/15.1-n283611-88e7371d9dc2 GENERIC amd64

I have a VLAN bridge with several untagged ports (connected to VNET jails) as well as a tagged tap interface which goes to the virtual machine.

danny@freebsd-test:~ $ ifconfig bridge1
bridge1: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
	options=10<VLAN_HWTAGGING>
	ether 58:9c:fc:10:8e:4e
	id 00:00:00:00:00:00 priority 32768 hellotime 2 fwddelay 15
	maxage 20 holdcnt 6 proto rstp maxaddr 2000 timeout 1200
	root id 00:00:00:00:00:00 priority 32768 ifcost 0 port 0
	bridge flags=1<VLANFILTER>
	member: epair0a flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
	        port 9 priority 128 path cost 2000 vlan protocol 802.1q untagged 10
	member: epair5a flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
	        port 20 priority 128 path cost 2000 vlan protocol 802.1q untagged 250
	member: epair1a flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
	        port 11 priority 128 path cost 2000 vlan protocol 802.1q untagged 110
	member: epair3a flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
	        port 15 priority 128 path cost 2000 vlan protocol 802.1q untagged 110
	member: epair2a flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
	        port 13 priority 128 path cost 2000 vlan protocol 802.1q untagged 110
	member: epair4a flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
	        port 7 priority 128 path cost 2000 vlan protocol 802.1q untagged 210
	member: tap1 flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
	        port 6 priority 128 path cost 2000000 vlan protocol 802.1q tagged 10,110,210,250
	groups: bridge
	nd6 options=9<PERFORMNUD,IFDISABLED>


I use the bhyve_config(5) format to manage my virtual machines.
Here is the output of a working FreeBSD VM config with two tap interfaces using virtio-net

danny@freebsd-test:~ $ cat /etc/bhyve.conf.d/freebsd0.conf
rtc.use_localtime=false
x86.vmexit_on_hlt=true
x86.vmexit_on_pause=true
x86.strictmsr=false
#
name=freebsd0
cpus=2
cores=2
threads=1
sockets=1
memory.size=2G
memory.wired=true
bootrom=/usr/local/share/uefi-firmware/BHYVE_UEFI.fd
#
pci.0.0.0.device=hostbridge
pci.0.3.0.device=virtio-blk
pci.0.3.0.path=/dev/zvol/zroot/vm/freebsd0
pci.0.5.0.device=virtio-net
pci.0.5.0.backend=tap0
pci.0.6.0.device=virtio-net
pci.0.6.0.backend=tap1
pci.0.31.0.device=lpc
lpc.com1.path=/dev/nmdm1A

Here is the network setup of the virtual machine using virtio-net

danny@freebsd0:~ $ ifconfig 
vtnet0: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        options=880028<VLAN_MTU,JUMBO_MTU,LINKSTATE,HWSTATS>
        ether 00:a0:98:3f:19:75
        inet 172.19.3.100 netmask 0xffffff00 broadcast 172.19.3.255
        media: Ethernet autoselect (10Gbase-T <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
vtnet1: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        options=880028<VLAN_MTU,JUMBO_MTU,LINKSTATE,HWSTATS>
        ether 00:a0:98:2d:01:38
        media: Ethernet autoselect (10Gbase-T <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
lo0: flags=1008049<UP,LOOPBACK,RUNNING,MULTICAST,LOWER_UP> metric 0 mtu 16384
        options=680003<RXCSUM,TXCSUM,LINKSTATE,RXCSUM_IPV6,TXCSUM_IPV6>
        inet 127.0.0.1 netmask 0xff000000
        inet6 ::1 prefixlen 128
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3
        groups: lo
        nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
vtnet1.10: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        options=80000<LINKSTATE>
        ether 00:a0:98:2d:01:38
        inet 10.0.10.1 netmask 0xffffff00 broadcast 10.0.10.255
        groups: vlan
        vlan: 10 vlanproto: 802.1q vlanpcp: 0 parent interface: vtnet1
        media: Ethernet autoselect (10Gbase-T <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
vtnet1.110: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        options=80000<LINKSTATE>
        ether 00:a0:98:2d:01:38
        inet 10.0.110.1 netmask 0xffffff00 broadcast 10.0.110.255
        groups: vlan
        vlan: 110 vlanproto: 802.1q vlanpcp: 0 parent interface: vtnet1
        media: Ethernet autoselect (10Gbase-T <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
vtnet1.210: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        options=80000<LINKSTATE>
        ether 00:a0:98:2d:01:38
        inet 10.0.210.1 netmask 0xffffff00 broadcast 10.0.210.255
        groups: vlan
        vlan: 210 vlanproto: 802.1q vlanpcp: 0 parent interface: vtnet1
        media: Ethernet autoselect (10Gbase-T <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
vtnet1.250: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        options=80000<LINKSTATE>
        ether 00:a0:98:2d:01:38
        inet 10.0.250.1 netmask 0xffffff00 broadcast 10.0.250.255
        groups: vlan
        vlan: 250 vlanproto: 802.1q vlanpcp: 0 parent interface: vtnet1
        media: Ethernet autoselect (10Gbase-T <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>

The above is a fully working setup that allows me to use the FreeBSD VM as a firewall to filter traffic between the VLANs (different VNET jails) using a single bridge setup.

However if I were to switch away from virtio-net and change the configuration to e1000 (only on the tap1 interface which is connected to the VLAN bridge) I get an error.

danny@freebsd-test:~ $ cat /etc/bhyve.conf.d/freebsd0.conf
rtc.use_localtime=false
x86.vmexit_on_hlt=true
x86.vmexit_on_pause=true
x86.strictmsr=false
#
name=freebsd0
cpus=2
cores=2
threads=1
sockets=1
memory.size=2G
memory.wired=true
bootrom=/usr/local/share/uefi-firmware/BHYVE_UEFI.fd
#
pci.0.0.0.device=hostbridge
pci.0.3.0.device=virtio-blk
pci.0.3.0.path=/dev/zvol/zroot/vm/freebsd0
pci.0.5.0.device=virtio-net
pci.0.5.0.backend=tap0
pci.0.6.0.device=e1000
pci.0.6.0.backend=tap1
pci.0.31.0.device=lpc
lpc.com1.path=/dev/nmdm1A

The error is:
e82545: packet too small for writable header

Network layout inside the VM (adjusted for the new interface names and rebooted)

danny@freebsd0:~ $ ifconfig 
vtnet0: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        options=880028<VLAN_MTU,JUMBO_MTU,LINKSTATE,HWSTATS>
        ether 00:a0:98:3f:19:75
        inet 172.19.3.100 netmask 0xffffff00 broadcast 172.19.3.255
        media: Ethernet autoselect (10Gbase-T <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
em0: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        options=4e504bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,LRO,VLAN_HWFILTER,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6,HWSTATS,MEXTPG>
        ether 00:a0:98:2d:01:38
        media: Ethernet autoselect (1000baseT <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
lo0: flags=1008049<UP,LOOPBACK,RUNNING,MULTICAST,LOWER_UP> metric 0 mtu 16384
        options=680003<RXCSUM,TXCSUM,LINKSTATE,RXCSUM_IPV6,TXCSUM_IPV6>
        inet 127.0.0.1 netmask 0xff000000
        inet6 ::1 prefixlen 128
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3
        groups: lo
        nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
em0.10: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        options=4600403<RXCSUM,TXCSUM,LRO,RXCSUM_IPV6,TXCSUM_IPV6,MEXTPG>
        ether 00:a0:98:2d:01:38
        inet 10.0.10.1 netmask 0xffffff00 broadcast 10.0.10.255
        groups: vlan
        vlan: 10 vlanproto: 802.1q vlanpcp: 0 parent interface: em0
        media: Ethernet autoselect (1000baseT <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
em0.110: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        options=4600403<RXCSUM,TXCSUM,LRO,RXCSUM_IPV6,TXCSUM_IPV6,MEXTPG>
        ether 00:a0:98:2d:01:38
        inet 10.0.110.1 netmask 0xffffff00 broadcast 10.0.110.255
        groups: vlan
        vlan: 110 vlanproto: 802.1q vlanpcp: 0 parent interface: em0
        media: Ethernet autoselect (1000baseT <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
em0.210: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        options=4600403<RXCSUM,TXCSUM,LRO,RXCSUM_IPV6,TXCSUM_IPV6,MEXTPG>
        ether 00:a0:98:2d:01:38
        inet 10.0.210.1 netmask 0xffffff00 broadcast 10.0.210.255
        groups: vlan
        vlan: 210 vlanproto: 802.1q vlanpcp: 0 parent interface: em0
        media: Ethernet autoselect (1000baseT <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
em0.250: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        options=4600403<RXCSUM,TXCSUM,LRO,RXCSUM_IPV6,TXCSUM_IPV6,MEXTPG>
        ether 00:a0:98:2d:01:38
        inet 10.0.250.1 netmask 0xffffff00 broadcast 10.0.250.255
        groups: vlan
        vlan: 250 vlanproto: 802.1q vlanpcp: 0 parent interface: em0
        media: Ethernet autoselect (1000baseT <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>

The above does not work. Attempting to send packets through the VM on the VLAN tagged interface does not work and it triggers the "e82545: packet too small for writable header" error on the host machine.

Please note that I am using UEFI for the virtual machine and that the VLAN bridge does not have a physical interface connected to it.