[ntp:hackers] ntpd on ipv6 routers very chatty

John Hay jhay at meraka.org.za
Wed Oct 22 11:53:16 UTC 2008


On Wed, Oct 22, 2008 at 07:33:46AM -0400, Danny Mayer wrote:
> John Hay wrote:
> > Hi Guys,
> > 
> > I just updated some of my FreeBSD based routers to the latest 7-stable
> > code. This contains ntp 4.2.4p5-a. On these boxes ntpd fills up the
> > /var/log/messages file with these kinds of messages every few seconds:
> > 
> > ########################################
> > Oct 22 11:59:52 roof-bkp ntpd[1296]: bind() fd 33, family 28, port 123, scope 0, addr fd9c:6829:597c:10::, in6_is_addr_multicast=0 flags=0x11 fails: Can't assign requested address
> > Oct 22 11:59:52 roof-bkp ntpd[1296]: unable to create socket on wlan0 (7177) for fd9c:6829:597c:10::#123
> > Oct 22 11:59:52 roof-bkp ntpd[1296]: bind() fd 33, family 28, port 123, scope 0, addr fd9c:6829:597c:10::, in6_is_addr_multicast=0 flags=0x11 fails: Can't assign requested address
> > Oct 22 11:59:52 roof-bkp ntpd[1296]: unable to create socket on wlan1 (7178) for fd9c:6829:597c:10::#123
> > ########################################
> > 
> > The addresses that trip them up are ipv6 anycast addresses. They are
> > generated automatically if the box is a gateway. Ifconfig of an
> > interface looks like this:
> > 
> > ########################################
> > :~ > ifconfig wlan0
> > wlan0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
> >         ether 00:80:48:50:9a:0a
> >         inet6 fe80::280:48ff:fe50:9a0a%wlan0 prefixlen 64 scopeid 0x7 
> >         inet6 fd9c:6829:597c:10:280:48ff:fe50:9a0a prefixlen 64 
> >         inet6 fd9c:6829:597c:10:: prefixlen 64 anycast 
> >         media: IEEE 802.11 Wireless Ethernet autoselect mode 11a <adhoc>
> >         status: running
> >         ssid ptabb channel 64 (5320 Mhz 11a) bssid 02:15:6d:53:1f:ee
> >         regdomain 55 indoor ecm authmode OPEN privacy OFF txpower 18
> >         mcastrate 6 mgmtrate 6 scanvalid 60 wme burst
> > :~ >
> > ########################################
> > 
> > So what should happen here? Should it even try to bind to the anycast
> > address?
> > 
> > John
> 
> Hi John, it's been a long time.
> 
> This is kind of strange. It does not say that something else is bound to
> those addresses.

I doubt that there is, unless the kernel does it. You can ping6 that
address and one of the routers on that subnet will answer with its
full address, like this:

#########################
# ping6 -c1 2001:4200:7000:4::
PING6(56=40+8+8 bytes) 2001:4200:7000:4:204:61ff:fe93:7747 --> 2001:4200:7000:4::
16 bytes from 2001:4200:7000:4:2d0:12ff:fe03:2476, icmp_seq=0 hlim=64 time=2.092 ms

--- 2001:4200:7000:4:: ping6 statistics ---
1 packets transmitted, 1 packets received, 0.0% packet loss
round-trip min/avg/max/std-dev = 2.092/2.092/2.092/0.000 ms
#########################

> I'm not sure I understand what is meant here by the
> anycast addresses that the ifconfig shows, but it does seem like a
> prefix rather than an address.

On a freebsd box, you just put this in /etc/rc.conf (replacing wlanX
with whatever interfaces you have, I think it will even work on a
single interface as long as gateway is enabled):

#########################
ipv6_enable="YES"
ipv6_gateway_enable="YES"
ipv6_prefix_wlan0="fd9c:6829:597c:10"
ipv6_prefix_wlan1="fd9c:6829:597c:20"
#########################

That anycast address has been there since I started with IPv6 on FreeBSD,
but only on the routers, not on hosts.

> Can you file a bug report in bugzilla on
> this?

Will do, tonight. I got to run now.

John
-- 
John Hay -- John.Hay at meraka.csir.co.za / jhay at FreeBSD.org


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