https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=278245
Bug ID: 278245
Summary: sendfile to bhyve VM on same host fails with MEXTPG
Product: Base System
Version: 14.0-RELEASE
Hardware: amd64
OS: Any
Status: New
Severity: Affects Some People
Priority: ---
Component: kern
Assignee: [email protected]
Reporter: [email protected]
In debugging an issue with an nginx reverse proxy, I found an issue with
sendfile, MEXTPG, and one of more of bridge, tap, and bhyve. I am on FreeBSD
14-CURRENT-p6.
To replicate this issue, I used the following Python test harness:
import socket
HOST = 'target.host'
PORT = 50007
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s, open("blah.txt",
"rb") as f:
s.connect((HOST, PORT))
s.sendfile(f)
In this case, target.host is a Debian bhyve VM running on the same host. On
the target, something like 'nc -l -p 50007' can be run to receive the data.
On the networking side, I've got:
# ifconfig em0
em0: flags=1008943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST,LOWER_UP>
metric 0 mtu 1500
options=a520b9<RXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,WOL_MAGIC,VLAN_HWFILTER,VLAN_HWTSO,RXCSUM_IPV6,HWSTATS>
ether 6c:4b:90:1f:e9:a8
inet 192.168.11.15 netmask 0xffffff00 broadcast 192.168.11.255
inet6 fe80::6e4b:90ff:fe1f:e9a8%em0 prefixlen 64 scopeid 0x1
media: Ethernet autoselect (1000baseT <full-duplex>)
status: active
nd6 options=23<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL>
# ifconfig vm-public
vm-public: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP>
metric 0 mtu 1500
options=0
ether 3a:47:10:77:5b:4d
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
member: tap3 flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
ifmaxaddr 0 port 7 priority 128 path cost 2000000
member: tap2 flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
ifmaxaddr 0 port 6 priority 128 path cost 2000000
member: tap1 flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
ifmaxaddr 0 port 5 priority 128 path cost 2000000
member: tap0 flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
ifmaxaddr 0 port 4 priority 128 path cost 2000000
member: em0 flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
ifmaxaddr 0 port 1 priority 128 path cost 20000
groups: bridge vm-switch viid-4c918@
nd6 options=9<PERFORMNUD,IFDISABLED>
When MEXTPG is enabled on the em0 interface, the test fails when sending a file
larger than 224 bytes. When MEXTPG is enabled the test is successful. The
test is successful when sending to a VM on a different host, so the bhyve VM is
a requirement to replicate the issue.
https://www.reddit.com/r/freebsd/comments/1bxebaz/more_vm_networking_weirdness/
has a lot more detail and some narrowing down of the problem.
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