[tahoe-dev] [tahoe-lafs] #867: use ipv6

[Greg Troxel]

Randall Mason <clashthebunny at gmail.com> writes:

>> $ ping6 fc00::1234
>> PING fc00::1234(fc00::1234) 56 data bytes
>> --- fc00::1234 ping statistics ---
>> 4 packets transmitted, 0 received, 100% packet loss, time 3000ms
>
> works, whereas:
>
>> $ ping6 fe80::1234
>> connect: Invalid argument
>
> falls over hard.

(I'm guessing you are on Linux, but could be a different BSD.)  That's
probably because fe80::1234 doesn't have a scope identifer, so there is
no associated interface on which to send it.  Your system may not
allocate ifindex 0 (now, that seems wise).

On NetBSD:

> ping6 fe80::1234
PING6(56=40+8+8 bytes) fe80::1%lo0 --> fe80::1234
^C
--- fe80::1234 ping6 statistics ---
2 packets transmitted, 0 packets received, 100.0% packet loss

and I see the packet on lo0.

But, ping6 to

  fe80:1:0:0::[redacted, 4 x 16bits]

works to a neighbor which is on wm0 (which is ifindex 1 on that system).

Also, ping6 to fe80::1 works, because the missing ifindex slot is 0, and
lo0 is 0.

On NetBSD:

> ping6 fc00::1234
PING6(56=40+8+8 bytes) 2001:4978:1fb:6400::d2 --> fc00::1234
ping6: sendmsg: Network is unreachable
ping6: wrote fc00::1234 16 chars, ret=-1

because there is s reject route installed at boot to block this
not-really-allocated address space (that cjdns people will have to
remove):

> route get -inet6 fc00::
   route to: fc00::
destination: fc00::
       mask: fe00::
    gateway: localhost
 local addr: localhost
  interface: lo0
      flags: <UP,GATEWAY,REJECT,DONE,STATIC>
 recvpipe  sendpipe  ssthresh  rtt,msec    rttvar  hopcount      mtu	expire
       0         0         0         0         0         0         0	0 
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