IPv6 Fragmentation

[Doug Hardie]

> On 19 February 2021, at 01:48, Michael Tuexen <michael.tuexen at lurchi.franken.de> wrote:
> 
>> On 19. Feb 2021, at 03:29, Doug Hardie <bc979 at lafn.org> wrote:
>> 
>> I don't know if this is a feature or a bug.  On FreeBSD 9, the following ping worked:
>> 
>> ping6 -s 5000 -b 6000 fe80::213:72ff:fec3:180f%dc0
> I don't have a dc0 interface, but using re0 at one side and bge at the other, I get
> with FreeBSD CURRENT:
> tuexen at cirrus:~ % ping6 -s 5000 -b 6000 fe80::2e09:4dff:fe00:c00%re0
> PING6(5048=40+8+5000 bytes) fe80::aaa1:59ff:fe0c:da92%re0 --> fe80::2e09:4dff:fe00:c00%re0
> 5008 bytes from fe80::2e09:4dff:fe00:c00%re0, icmp_seq=0 hlim=255 time=0.393 ms
> 5008 bytes from fe80::2e09:4dff:fe00:c00%re0, icmp_seq=1 hlim=255 time=0.419 ms
> 5008 bytes from fe80::2e09:4dff:fe00:c00%re0, icmp_seq=2 hlim=255 time=0.354 ms
> 5008 bytes from fe80::2e09:4dff:fe00:c00%re0, icmp_seq=3 hlim=255 time=0.446 ms
> 5008 bytes from fe80::2e09:4dff:fe00:c00%re0, icmp_seq=4 hlim=255 time=0.421 ms
> 5008 bytes from fe80::2e09:4dff:fe00:c00%re0, icmp_seq=5 hlim=255 time=0.372 ms
> ^C
> --- fe80::2e09:4dff:fe00:c00%re0 ping6 statistics ---
> 6 packets transmitted, 6 packets received, 0.0% packet loss
> round-trip min/avg/max/std-dev = 0.354/0.401/0.446/0.031 ms
> 
> Best regards
> Michael
>> 
>> It had to be stopped, but it returned the number of ping responses received along with statistics.
>> 
>> With FreeBSD 12.2 and 13.0-BETA2, it returns 100% packet loss.  tcpdump shows that it properly fragments the data, sends it, the other end receives it and sends back the ACKs.  The ACKs are received, but somehow ping doesn't find out that the packets were received.
>> 
>> Without the -s and -b arguments, it works and you get 100% packets received.

I brought up yet another system to see if I can isolate the problem.  I am using ping or ping6 with -s5000  -b6000

All of the systems have bge interfaces unfortunately, even though they are completely different machine.

ping from 12.1 to 13.0 works
ping from 12.1 to 12.2  fails
ping from 12.2 to 12.1 fails
ping from 12.2 to 13.0 fails
ping from 13.0 to 12.1 works
ping from 13.0 to 12.2 fails

From this the problem appears to lie with 12.2.  However, if I do the same ping on each machine, but to its own link-local address, all 3 systems work fine.

I suspect the problem does not lie in the bge driver as the ACKs are being received on all systems.  12.2 just seems to ignore them.