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Date: Fri, 20 Apr 2018 22:31:29 +0200
From: Riccardo Berto <riccardo@rcrdbrt.com>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Subject: Re: Troubleshooting WireGuard connections
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On 2018-04-20 21:51, Jason A. Donenfeld wrote:
> Could you let me know which kernel the non-working rapsis are running?
> Also, have you tried this over different internet connections and
> experienced the same thing?

I haven't tried this under different internet connection but one thing I 
must add is that the laptop is under the same local network of the 
raspberrys, they have the same gateway and the laptop works in 100% of 
the cases I tried it, both while pinging from the raspberrys and not.

Parallel execution on the raspberry of `tcpdump -vv -ni eth0 'port 
51820'` while pinging the server:

22:26:50.084184 IP (tos 0x88, ttl 64, id 45462, offset 0, flags [none], 
proto UDP (17), length 176)
     192.168.1.155.51820 > server-ip.51820: [bad udp cksum 0xf657 -> 
0xb3e7!] UDP, length 148
22:26:50.186665 IP (tos 0x0, ttl 48, id 31466, offset 0, flags [none], 
proto UDP (17), length 120)
     server-ip.51820 > 192.168.1.155.51820: [udp sum ok] UDP, length 92
22:26:50.187667 IP (tos 0x0, ttl 64, id 45466, offset 0, flags [none], 
proto UDP (17), length 156)
     192.168.1.155.51820 > server-ip.51820: [bad udp cksum 0xf643 -> 
0x0316!] UDP, length 128
22:26:51.098777 IP (tos 0x0, ttl 64, id 45520, offset 0, flags [none], 
proto UDP (17), length 156)
     192.168.1.155.51820 > server-ip.51820: [bad udp cksum 0xf643 -> 
0x6049!] UDP, length 128
22:26:52.138753 IP (tos 0x0, ttl 64, id 45595, offset 0, flags [none], 
proto UDP (17), length 156)
     192.168.1.155.51820 > server-ip.51820: [bad udp cksum 0xf643 -> 
0x5608!] UDP, length 128
22:26:53.178751 IP (tos 0x0, ttl 64, id 45691, offset 0, flags [none], 
proto UDP (17), length 156)
     192.168.1.155.51820 > server-ip.51820: [bad udp cksum 0xf643 -> 
0x7eb3!] UDP, length 128
22:26:54.218760 IP (tos 0x0, ttl 64, id 45734, offset 0, flags [none], 
proto UDP (17), length 156)
     192.168.1.155.51820 > server-ip.51820: [bad udp cksum 0xf643 -> 
0x240c!] UDP, length 128
22:27:05.259544 IP (tos 0x88, ttl 64, id 46342, offset 0, flags [none], 
proto UDP (17), length 176)
     192.168.1.155.51820 > server-ip.51820: [bad udp cksum 0xf657 -> 
0x5a78!] UDP, length 148
22:27:05.359976 IP (tos 0x0, ttl 48, id 33703, offset 0, flags [none], 
proto UDP (17), length 120)
     server-ip.51820 > 192.168.1.155.51820: [udp sum ok] UDP, length 92
22:27:05.360960 IP (tos 0x0, ttl 64, id 46348, offset 0, flags [none], 
proto UDP (17), length 60)
     192.168.1.155.51820 > server-ip.51820: [bad udp cksum 0xf5e3 -> 
0x7f66!] UDP, length 32

192.168.1.155 listed there is the static IP address of the raspberry pi 
in my local network.

Raspberry is running archlinuxarm with kernel: "Linux rpi3-two 
4.14.34-1-ARCH #1 SMP Mon Apr 16 19:15:19 UTC 2018 armv7l GNU/Linux"