[issue] macvtap dropping all packets as errors

sundarpv

i am debugging an issue with Guest VM's ethernet interface isnt receving any packets

the packet path is as below;

Guest VM Host OS
me0 <-- --> macvtap0 <--> eth0

the tx direction from me0 packets are visible at macvtap0
while, the packets recvd through eth0 on HostOS are received well at macvtap0. but, all are dropped as error packets

i am unable to troubleshoot the issue

any pointers will help

root@local-node:~# ifconfig macvtap0 ; tcpdump -i macvtap0 -c 2 ;ifconfig macvtap0
macvtap0 Link encap:Ethernet HWaddr 74:e7:98:b6:e4:1a
inet addr:10.0.50.179 Bcast:10.0.255.255 Mask:255.255.0.0
inet6 addr: fe80::76e7:98ff:feb6:e41a/64 Scope:Link
UP BROADCAST RUNNING ALLMULTI MULTICAST MTU:1500 Metric:1
RX packets:4027390 errors:4023310 dropped:4023310 overruns:0 frame:0
TX packets:40317 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:432084441 (412.0 MiB) TX bytes:1723136 (1.6 MiB)

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on macvtap0, link-type EN10MB (Ethernet), capture size 262144 bytes
09:58:22.643089 IP6 fe80::4e73:4fff:fe09:6501.dhcpv6-client > ff02::1:2.dhcpv6-server: dhcp6 solicit
09:58:22.689583 IP 10.0.0.2 > 224.0.0.18: VRRPv2, Advertisement, vrid 7, prio 95, authtype none, intvl 1s, length 20
2 packets captured
4 packets received by filter
0 packets dropped by kernel
2 packets dropped by interface
macvtap0 Link encap:Ethernet HWaddr 74:e7:98:b6:e4:1a
inet addr:10.0.50.179 Bcast:10.0.255.255 Mask:255.255.0.0
inet6 addr: fe80::76e7:98ff:feb6:e41a/64 Scope:Link
UP BROADCAST RUNNING ALLMULTI MULTICAST MTU:1500 Metric:1
RX packets:4027392 errors:4023312 dropped:4023312 overruns:0 frame:0
TX packets:40317 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:432084650 (412.0 MiB) TX bytes:1723136 (1.6 MiB)

sundarpv

During ping from an external device, the arp resolution is happening. this means, the broadcast packets are being received. just that unicast packets are dropped all as error packets

lee42x

Hi, Can you please "ip add " on me0 & eth0 systems ? Which hypervisor are you using?

Thanks

sundarpv

i am using qemu-kvm. does the below info suffice, when you say "ip add" ?

-- Guest VM --
root@:/var/log # ifconfig me0
me0: encaps: ether; framing: ether
flags=0x3/0x8000 <PRESENT|RUNNING>
curr media: i802 74:e7:98:b6:e4:1a
me0.0: flags=0x8000 <UP|MULTICAST>
inet primary mtu 1500 local=10.0.50.179 dest=10.0.0.0/16 bcast=10.0.255.255

-- Host OS --
Last login: Thu Oct 6 22:24:45 2022 from 192.168.1.2
root@local-node:~# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 74:e7:98:b6:e4:27
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:4335804 errors:0 dropped:23124 overruns:0 frame:0
TX packets:43405 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:465215656 (443.6 MiB) TX bytes:1854012 (1.7 MiB)
Memory:90000000-9007ffff

sundarpv

i am able to tcpdump on macvtap0. so, packets are being well received on macvtap0, while it isnt received at Guest VM

root@local-node:~# tcpdump -i macvtap0 -c 3
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on macvtap0, link-type EN10MB (Ethernet), capture size 262144 bytes
22:37:06.696303 IP 10.0.0.2 > 224.0.0.18: VRRPv2, Advertisement, vrid 7, prio 95, authtype none, intvl 1s, length 20
22:37:06.731370 IP6 fe80::4e73:4fff:fe09:5581.dhcpv6-client > ff02::1:2.dhcpv6-server: dhcp6 solicit
22:37:06.731590 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from 4c:73:4f:09:65:01 (oui Unknown), length 298
3 packets captured
9 packets received by filter
0 packets dropped by kernel
3 packets dropped by interface

lee42x

The "ip" command has enhancements over "ifconfig". Please use the "ip" command.