[Change History]
2025/09/25 change [Reproduce Steps] from Wireguard to "route -n monitor"
2025/09/27 add NOTE 2(why so many ARP, request in this environment), NOTE3 and workaround
Reproduce Steps
- connect network
- start route -n monitor
- start iperf -s on other machine
- start iperf on target machine
#!/bin/sh
IPERF_SERVER_IP=[IPERF Server IP]
IPERF=/usr/local/bin/iperf
while [ true ]; do
${IPERF} -c ${IPERF_SERVER_IP} -e -i 1
sleep 1
${IPERF} -c ${IPERF_SERVER_IP} -u -e -i 1 --isochronous=60:100m,10m --realtime
sleep 1
done
expected Result
no link down/up on USB Ethernet(ue)
Result
sometime link down/up on USB Ethernet(ue)
/var/log/messages
Sep 25 09:17:48 amd64 kernel: ue0: link state changed to DOWN
Sep 25 09:17:48 amd64 kernel: ue0: link state changed to UP
Sep 25 09:25:13 amd64 kernel: ue0: link state changed to DOWN
Sep 25 09:25:13 amd64 kernel: ue0: link state changed to UP
output from "route -n monitor"
09:17:48.536 PID 2391 add/repl neigh 192.168.10.254 state REACHABLE lladdr 00:a0:de:xx;xx:xx iface ue0
09:17:48.547 PID 2391 add/repl iface iface#3 ue0 admin UP oper UP mtu 1500
09:17:48.547 PID 0 add/repl iface iface#3 ue0 admin UP oper UP mtu 1500
09:17:48.547 PID 0 add/repl iface iface#3 ue0 admin UP oper UP mtu 1500
09:17:48.547 PID 0 add/repl iface iface#3 ue0 admin UP oper UP mtu 1500
09:17:49.537 PID 2391 add/repl neigh 192.168.10.254 state REACHABLE lladdr 00:a0:de:xx;xx:xx iface ue0
[SNIP]
09:25:12.572 PID 2391 add/repl neigh 192.168.10.254 state REACHABLE lladdr 00:a0:de:xx;xx:xx iface ue0
09:25:13.573 PID 2391 add/repl neigh 192.168.10.254 state REACHABLE lladdr 00:a0:de:xx;xx:xx iface ue0
09:25:13.583 PID 2391 add/repl iface iface#3 ue0 admin UP oper UP mtu 1500
09:25:13.583 PID 0 add/repl iface iface#3 ue0 admin UP oper UP mtu 1500
09:25:13.583 PID 0 add/repl iface iface#3 ue0 admin UP oper UP mtu 1500
09:25:13.583 PID 0 add/repl iface iface#3 ue0 admin UP oper UP mtu 1500
09:25:14.867 PID 2391 add/repl neigh 192.168.10.254 state REACHABLE lladdr 00:a0:de:xx;xx:xx iface ue0
09:25:16.777 PID 2391 add/repl neigh 192.168.10.254 state REACHABLE lladdr 00:a0:de:xx;xx:xx iface ue0
[NOTE 1]
"route -n monitor" command is used on WireGuard(/usr/local/bin/wg-quick shell script)
[NOTE 2]
Here's the reason why so many "state REACHABLE" entries (one to two, or even more, per second) are being outputted by "route -n monitor" in this environment.
When the Ricoh ScanSnap application "ScanSnap Home" is running on a PC (192.168.10.198) and the ScanSnap scanner is powered off, the application sends ARP Request commands to search for the scanner. The FreeBSD box on same subnet reacts to these packets, and they are outputted by route -n monitor. (The application continues to send ARP Requests until it's force-closed).
ScanSnap Home-related Packets
tcpdump results:
14:12:00.058366 ARP, Request who-has 192.168.10.250 tell 192.168.10.198, length 50
14:12:00.058413 ARP, Request who-has 192.168.10.251 tell 192.168.10.198, length 50
14:12:00.058426 ARP, Request who-has 192.168.10.252 tell 192.168.10.198, length 50
route -n monitor results from roughly the same time:
14:12:00.512 PID 0 add/repl neigh 192.168.10.198 state REACHABLE lladdr 00:50:b6:nn:nn:nn iface ue0
14:12:00.029 PID 0 add/repl neigh 192.168.10.198 state REACHABLE lladdr 00:50:b6:nn:nn:nn iface ue0
14:12:00.059 PID 0 add/repl neigh 192.168.10.198 state REACHABLE lladdr 00:50:b6:nn:nn:nn iface ue0
Additionally, ARP Requests are also periodically occurring for a NAT server in the route that is currently offline.
Router's Server Search Packets
tcpdump results:
14:17:35.772158 ARP, Request who-has 192.168.10.10 tell 192.168.10.254, length 50
14:17:36.773378 ARP, Request who-has 192.168.10.10 tell 192.168.10.254, length 50
14:17:37.774597 ARP, Request who-has 192.168.10.10 tell 192.168.10.254, length 50
route -n monitor results from roughly the same time:
14:18:06.709 PID 0 add/repl neigh 192.168.10.254 state REACHABLE lladdr 00:a0:de:nn:nn:nn iface ue0
14:18:08.711 PID 0 add/repl neigh 192.168.10.254 state REACHABLE lladdr 00:a0:de:nn:nn:nn iface ue0
[NOTE 3]
The issue (USB Ethernet link down/up) is that when an Ethernet driver without this problem (e.g., awg0) receives an ARP request, and NetLink processes it and reports it to route -n monitor, the affected USB Ethernet adapter (which is linked up and communicating separately) experiences a link down/up phenomenon despite not receiving the ARP packet on USB Ethernet.
Workaround
The root cause seems to be an issue between Netlink and the Ethernet Driver, but I don't have time to investigate it. Therefore, we're currently using the following workaround for FreeBSD-14 and later.
Workaround1 change /sbin/route
don't printout the neigh change
-
-- sbin/route/route_netlink.c.org 2025-09-27 14:26:39.289721000 +0900
+++ sbin/route/route_netlink.c 2025-09-27 14:27:21.644803000 +0900
@@ -753,7 +753,9 @@
int groups[] = {
RTNLGRP_LINK,
+#if 0
RTNLGRP_NEIGH,
+#endif
RTNLGRP_NEXTHOP,
#ifdef INET
RTNLGRP_IPV4_IFADDR,
Workaround2
just kill "route -n monitor" process after staring the Wireguard.
Current status
- Could changing the order of the interfaces shown by ifconfig from wg0 to ue0 solve the problem?
- Result: It won't solve it[NG].
- disable the ifconfig options (eg. -txcsum -rxcsum)
- Result: It won't solve it[NG].
Enviroment
USB Ethernet
- axe:
- BUFFALO LUA3-U2-ATX AX88772
<ASIX Elec. Corp. AX88772, rev 2.00/0.01, addr 2> on usbus0
ue0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=80008<VLAN_MTU,LINKSTATE>
miibus1: <MII bus> on axe0
ukphy0: <Generic IEEE 802.3u media interface> PHY 16 on miibus1
ukphy0: none, 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto - BUFFALO LUA3-U2-AGT AX88178
<BUFFALO INC. product 0x006e> at usbus1 ue0:flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500 options=80008<VLAN_MTU,LINKSTATE>
miibus1: <MII bus> on axe0
e1000phy0: <Marvell 88E1111 Gigabit PHY> PHY 24 on miibus1
e1000phy0: none, 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, 1000baseT, 1000baseT-master, 1000baseT-FDX, 1000baseT-FDX-master, auto, auto-flow - axge
- ELECOM EDC-GUC3L-W AX8179
axge0: <ASIX Elec. Corp. AX88179, rev 2.10/1.00, addr 2> on usbus7 miibus0: <MII bus> on axge0 rgephy0: <RTL8169S/8110S/8211 1000BASE-T media interface> PHY 3 on miibus0 rgephy0: none, 10baseT, 10baseT-FDX, 10baseT-FDX-flow, 100baseTX, 100baseTX-FDX, 100baseTX-FDX-flow, 1000baseT-FDX, 1000baseT-FDX-master, 1000baseT-FDX-flow, 1000baseT-FDX-flow-master, auto, auto-flow options=8000b<RXCSUM,TXCSUM,VLAN_MTU,LINKSTATE> - ure
- Lenovo USB-C to LAN RTL8153
ure0: <Lenovo Lenovo USB-C to LAN, class 0/0, rev 2.10/31.20, addr 2> on usbus7
miibus0: <MII bus> on ure0
rgephy0: <RTL8251/8153 1000BASE-T media interface> PHY 0 on miibus0
rgephy0: none, 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, 1000baseT-FDX, 1000baseT-FDX-master, auto
options=68009b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,LINKSTATE,RXCSUM_IPV6,TXCSUM_IPV6> - Planex USB-LAN2500R
ure0: <Planex USB 10/100/1G/2.5G LAN, class 0/0, rev 2.10/30.00, addr 2> on usbus7
options=60009b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,RXCSUM_IPV6,TXCSUM_IPV6> - cdce (setup info FreeBSD Bugzilla 252165)
- Lenovo USB-C to LAN RTL8251/8153
options=80000<LINKSTATE> - Planex USB-LAN2500R
- run0: <Ralink 802.11 n WLAN, class 0/0, rev 2.00/1.01, addr 2> on usbus7
run0: MAC/BBP RT3071 (rev 0x021C), RF RT3022 (MIMO 2T2R), address 4c:xx:xx:xx:xx
amd64 machine
- Lenovo ThinkPad T400s
arm64 machines
Related articles
FreeBSD Forums:
- Internet connection going up and down constantly
- Charlie Brown reported using the wg0 with ue0
- Interface flapping on ethernet USB adapter
- no information about Wireguard, finally use cdce.
- Link rapidly goes UP and DOWN
FreeBSD Bugzilla
- Bug 252165 - usb network and mii bus media status race condition
- Bug 267514 - AXGE(4) ASIX AX88179A ue0: link state changed to DOWN
- Bug 275026 - net/wireguard-tools: after service wireguard stop, route monitor keeps running in the background
- Bug 276414 - rtnetlink: destroying an interface generates spurious RTM_NEWLINKs
- Bug 272144 - netlink sets ifi_type to FreeBSD if_type instead of ARPHRD_*
