Re: trapping to IPv6

Wes Hardaker wrote:
>>>>>> "MF" == Magnus Fromreide <magfr@lysator.liu.se> writes:
> MF> Could you please elaborate? What do you think is missing?
>
> Nope, my initial guess and memory was that it should work and Magnus is
> right, it does indeed work:
>
> # ./snmptrapd -f -Le --disableauthorization=true udp6:162
> [...]
> getaddrinfo: Name or service not known

Ah, that udp6: preface on the bind address looks to be the magic bits I'm
missing. Silly me expected --enable-ipv6 on the configure to cause it to
bind to IPv6 by default in addition to IPv4.

> You need to ignore the warning, but in the end:

That seems to have been introduced since 5.3.0.1... since with that version I
don't see that warning.

> # ./snmptrap -d -v 2c -c public udp6:'[::1]':162 0 coldStart.0

Argh, again the missing udp6: preface tripped us up making it appear not to
work. Admitedly, I only did a quick code scan before asking, and all I saw in
apps/ were AF_INET references, nothing touching AF_INET6. I see now that the
reason is that the code in question is over in snmplib/snmp_transport.c.

Hmm. So here's my problem with this. On the client side, I might not know that I
need to use IPv6 to get to the server. Say all I know is that I need to send
traps to entrapment.example.com. Hand that name off to DNS and it only comes
back with an AAAA record (an IPv6 address). How is a script or a user calling
snmptrap to report something or query something supposed to know that they need
to specify "udp6:" for this address?

IPv4 doesn't seem to need the user to tell it to use udp, it seems to default to
that. Any reason not to make the default switch to udp6 if dns returns *only* an
AAAA record? (I'm not even going to go into the insanity that could result from
trying to do both if DNS returns both an A and an AAAA address.)

It looks like a bit of code around line 380 of snmplib/snmp_transport.c might be
the ticket to accomplishing that.

> actually does make snmptrapd receive and print the trap.

Yup, technically it does work... just in a very user-un-friendly way.


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