Date: Fri, 19 Jul 2024 09:08:54 -0700 From: Alex Arslan <ararslan@comcast.net> To: mike tancsa <mike@sentex.net> Cc: freebsd-hackers@freebsd.org Subject: Re: Diagnosing virtual machine network issues Message-ID: <4AB1C33B-DD93-4484-B63A-9FF8FE612B15@comcast.net> In-Reply-To: <4a5a177a-5356-453c-8a09-f1d63d5d2e16@sentex.net> References: <FA265FAA-216D-4DCC-92C0-50017C17F7DE@comcast.net> <4a5a177a-5356-453c-8a09-f1d63d5d2e16@sentex.net>
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> I would start a pcap inside and outside of the VM for all udp port 53 =
traffic as a start to see if its a network issue going out of the box. =
If it happens frequently and you think it might be the network, perhaps =
try with the Intel em driver instead of the virtio network driver ?
Thanks so much for your help!
The way I implemented your pcap suggestion was to use tcpdump, hopefully
that's correct. I ran tcpdump simultaneously on the host and VM then ran
the code where libcurl gives a timeout rather than the expected domain
resolution failure. The output is below. I'm pretty well outside of my
depth here; what is it I'm looking for that would be indicative of a
network issue going out of the VM?
Linux host:
$ sudo /usr/sbin/tcpdump -v -i any 'host 192.168.122.35 and port 53'
tcpdump: listening on any, link-type LINUX_SLL (Linux cooked v1), =
capture size 262144 bytes
21:06:03.320754 IP (tos 0x0, ttl 64, id 29048, offset 0, flags [none], =
proto UDP (17), length 60)
192.168.122.35.24119 > amdci6.domain: 23532+ A? domain.invalid. (32)
21:06:03.320754 IP (tos 0x0, ttl 64, id 29048, offset 0, flags [none], =
proto UDP (17), length 60)
192.168.122.35.24119 > amdci6.domain: 23532+ A? domain.invalid. (32)
21:06:03.321633 IP (tos 0x0, ttl 64, id 27798, offset 0, flags [none], =
proto UDP (17), length 73)
192.168.122.35.18137 > amdci6.domain: 61699+ PTR? =
35.122.168.192.in-addr.arpa. (45)
21:06:03.321633 IP (tos 0x0, ttl 64, id 27798, offset 0, flags [none], =
proto UDP (17), length 73)
192.168.122.35.18137 > amdci6.domain: 61699+ PTR? =
35.122.168.192.in-addr.arpa. (45)
21:06:03.321701 IP (tos 0x0, ttl 64, id 44762, offset 0, flags [DF], =
proto UDP (17), length 113)
amdci6.domain > 192.168.122.35.18137: 61699* 1/0/0 =
35.122.168.192.in-addr.arpa. PTR freebsd-debugging-amdci6-0. (85)
21:06:03.321707 IP (tos 0x0, ttl 64, id 44762, offset 0, flags [DF], =
proto UDP (17), length 113)
amdci6.domain > 192.168.122.35.18137: 61699* 1/0/0 =
35.122.168.192.in-addr.arpa. PTR freebsd-debugging-amdci6-0. (85)
21:06:03.322188 IP (tos 0x0, ttl 64, id 27799, offset 0, flags [none], =
proto UDP (17), length 72)
192.168.122.35.37631 > amdci6.domain: 23871+ PTR? =
1.122.168.192.in-addr.arpa. (44)
21:06:03.322188 IP (tos 0x0, ttl 64, id 27799, offset 0, flags [none], =
proto UDP (17), length 72)
192.168.122.35.37631 > amdci6.domain: 23871+ PTR? =
1.122.168.192.in-addr.arpa. (44)
21:06:08.446737 IP (tos 0x0, ttl 64, id 29049, offset 0, flags [none], =
proto UDP (17), length 60)
192.168.122.35.24119 > amdci6.domain: 23532+ A? domain.invalid. (32)
21:06:08.446737 IP (tos 0x0, ttl 64, id 29049, offset 0, flags [none], =
proto UDP (17), length 60)
192.168.122.35.24119 > amdci6.domain: 23532+ A? domain.invalid. (32)
21:06:18.567376 IP (tos 0x0, ttl 64, id 29050, offset 0, flags [none], =
proto UDP (17), length 60)
192.168.122.35.37009 > amdci6.domain: 36459+ AAAA? domain.invalid. =
(32)
21:06:18.567376 IP (tos 0x0, ttl 64, id 29050, offset 0, flags [none], =
proto UDP (17), length 60)
192.168.122.35.37009 > amdci6.domain: 36459+ AAAA? domain.invalid. =
(32)
21:06:23.671046 IP (tos 0x0, ttl 64, id 29051, offset 0, flags [none], =
proto UDP (17), length 60)
192.168.122.35.37009 > amdci6.domain: 36459+ AAAA? domain.invalid. =
(32)
21:06:23.671046 IP (tos 0x0, ttl 64, id 29051, offset 0, flags [none], =
proto UDP (17), length 60)
192.168.122.35.37009 > amdci6.domain: 36459+ AAAA? domain.invalid. =
(32)
^C
14 packets captured
20 packets received by filter
2 packets dropped by kernel
FreeBSD VM:
$ sudo tcpdump -v port 53
tcpdump: listening on vtnet0, link-type EN10MB (Ethernet), capture size =
262144 bytes
21:06:06.179751 IP (tos 0x0, ttl 64, id 29048, offset 0, flags [none], =
proto UDP (17), length 60)
freebsd-debugging-amdci6-0.24119 > amdci6.domain: 23532+ A? =
domain.invalid. (32)
21:06:06.180634 IP (tos 0x0, ttl 64, id 27798, offset 0, flags [none], =
proto UDP (17), length 73)
freebsd-debugging-amdci6-0.18137 > amdci6.domain: 61699+ PTR? =
35.122.168.192.in-addr.arpa. (45)
21:06:06.180826 IP (tos 0x0, ttl 64, id 44762, offset 0, flags [DF], =
proto UDP (17), length 113)
amdci6.domain > freebsd-debugging-amdci6-0.18137: 61699* 1/0/0 =
35.122.168.192.in-addr.arpa. PTR freebsd-debugging-amdci6-0. (85)
21:06:06.181193 IP (tos 0x0, ttl 64, id 27799, offset 0, flags [none], =
proto UDP (17), length 72)
freebsd-debugging-amdci6-0.37631 > amdci6.domain: 23871+ PTR? =
1.122.168.192.in-addr.arpa. (44)
21:06:06.194107 IP (tos 0x0, ttl 64, id 44764, offset 0, flags [DF], =
proto UDP (17), length 118)
amdci6.domain > freebsd-debugging-amdci6-0.37631: 23871 2/0/0 =
1.122.168.192.in-addr.arpa. PTR amdci6., 1.122.168.192.in-addr.arpa. PTR =
amdci6.local. (90)
21:06:11.305743 IP (tos 0x0, ttl 64, id 29049, offset 0, flags [none], =
proto UDP (17), length 60)
freebsd-debugging-amdci6-0.24119 > amdci6.domain: 23532+ A? =
domain.invalid. (32)
21:06:21.426439 IP (tos 0x0, ttl 64, id 29050, offset 0, flags [none], =
proto UDP (17), length 60)
freebsd-debugging-amdci6-0.37009 > amdci6.domain: 36459+ AAAA? =
domain.invalid. (32)
21:06:26.530138 IP (tos 0x0, ttl 64, id 29051, offset 0, flags [none], =
proto UDP (17), length 60)
freebsd-debugging-amdci6-0.37009 > amdci6.domain: 36459+ AAAA? =
domain.invalid. (32)
^C
8 packets captured
427 packets received by filter
0 packets dropped by kernel
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