On Tue, Oct 29, 2019 at 09:58:08AM -0600, Theo de Raadt wrote:

> I've been reporting this since the dawn of the architecture.  I
> saw it as a network hickup.  I didn't notice an earlier copy
> of the packet that was corrupted.
> 

So it *is* size related and can be reproduced with ping:

[otto@wand:61]$ ping -c 1 -s 31 10.1.1.3 
PING 10.1.1.3 (10.1.1.3): 31 data bytes

Outgoing:
# tcpdump -Xn -i fec0 -s 1500  -vvv icmp  
tcpdump: listening on fec0, link-type EN10MB
20:07:09.231929 10.1.1.9 > 10.1.1.3: icmp: echo request (id:9678
seq:0) [icmp cksum ok] (ttl 255, id 27755, len 59)
  0000: 4500 003b 6c6b 0000 ff01 3949 0a01 0109  E..;lk....9I....
  0010: 0a01 0103 0800 eb11 9678 0000 aabf 55f1  .........x....U.
  0020: 3356 ef18 87a0 ca13 74a6 c8ea 995c 4475  3V......t....\Du
  0030: 90dc e90f 1819 1a1b 1c1d 1e              ...........

Incoming:
# tcpdump -Xn -i em1 -s 1500  -vvv icmp 
tcpdump: listening on em1, link-type EN10MB
20:07:09.231896 10.1.1.9 > 10.1.1.3: icmp: echo request (id:9678
seq:0) [bad icmp cksum eb11! -> b11] (ttl 255, id 27755, len 59)
  0000: 4500 003b 6c6b 0000 ff01 3949 0a01 0109  E..;lk....9I....
  0010: 0a01 0103 0800 eb11 9678 0000 aabf 55f1  .........x....U.
  0020: 3356 ef18 87a0 ca13 74a6 c8ea 995c 4475  3V......t....\Du
  0030: 90dc e90f 1819 1a1b 1c1d fe              ...........

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