On 12/10/13 10:48, Vladislav Grishenko wrote:
Hi, Simon,
Thanks for the implementation, works well with one issue is still there
RDNSS& DNS Search List RA options contain lifetimes calculated from
MaxRtrAdvInterval, where MaxRtrAdvInterval =<ra-interval>, and
MinRtrAdvInterval = 3/4*<ra-interval>
Since, there's no way to specify MinRtrAdvInterval& MaxRtrAdvInterval (as I
proposed before), RDNSS& DNS Search List lifetimes always equal
2*<ra-interval>.
So, if<ra-interval> is small, like 10sec, that lifetimes are small too,
just 20sec, without any connection to<router lifetime>. Hosts may refresh
RDNSS info with RS packets and trigger solicited RA answers in addition to
existing unsolicited RA packets.
In the same time, with working DHCPv6 stateless/full lifetime is taken from
dhcp-range, 600 sec as min.
In radvd, MinRtrAdvInterval, MaxRtrAdvInterval, DefaultLifetime and other
lifetimes can be set via conf file,
In dnsmasq they are automatic, guess automatic needs to be tuned up.
What do you think?
I think you're right that it needs tuning. The calculation for prefix
valid times is a good model. That's based on the lifetime in the
DHCP-range, but with a minimum of 3 * RA_interval as an imposed minimum.
The problem with that is that RDNSS and DNSSL are per interface, not
per-prefix. Maybe the calculation should the maximum valid time of any
prefix advertised on the interface?
Cheers,
Simon.
Best Regards, Vladislav Grishenko
-----Original Message-----
From: Simon Kelley [mailto:si...@thekelleys.org.uk]
Sent: Friday, October 11, 2013 2:01 AM
To: Vladislav Grishenko
Cc: dnsmasq-discuss@lists.thekelleys.org.uk
Subject: Re: [Dnsmasq-discuss] gatway
On 08/10/13 12:09, Vladislav Grishenko wrote:
From: Simon Kelley
Sent: Tuesday, October 08, 2013 4:20 PM On 06/10/13 11:32, Vladislav
Grishenko wrote:
Hi, RFC4861 says:
A router might want to send Router Advertisements without
advertising
itself as a default router. For instance, a router might
advertise
prefixes for stateless address autoconfiguration while not
wishing
to
forward packets. Such a router sets the Router Lifetime field in
outgoing advertisements to zero.
is it possible to tell dnsmasq not to announce itself as router?
So , yes, it's theoretically possible.
That's good information, thanks. In answer to the next question, no,
it's
not
possible to configure dnsmasq to send Router Lifetime == 0.
The lifetime, in dhcp-range is used to calculate the lifetimes for
prefixes, no
the router lifetime. In fact the router lifetime is always advertised
as
1800
seconds, I think.
Since this is a per-broadcast domain thing, and not per prefix thing,
it
needs
to be associated with an interface.
Simplest would be
no-router-interface=<interface>[,<interface>,....]
to set the interfaces that get router lifetime of zero.
More complex would be to allow explict setting of the router lifetime
per interface, that would have to be linked to the RA frequency: you
wouldn't want a router expiring before it could be re-advertised.
No-router-interface is simplest, and adds more option to control RA.
Currently we have already:
--dhcp-range=...ra-only|slaac|ra-names...
--enable-ra
--force-fast-ra
What if to logically split options to dhcp*-related and to
slaac-related?
--dhcp-range=
Sets only DHCP range/RA prefix parameters (including
lease/prefix/rdnss/domain lifetimes), but not RA timeouts
--enable-ra=<interface>[,<interface>,...][,AdvDefaultLifetime][,MinRtr
AdvInt
erval,MaxRtrAdvInterval]
Sets only RA timouts, if params absent - use defaults, 600 as max,
1/3*600 as min.
With this, both min& max can be configured, As per RFC,
max should be in range 4-1800 secodns, default 600
min should be in range 3-3/4*max, default 1/3*max, if max>=9,
otherwise equal to max
With this approach, --no-router-interface will be alias of
--enable-ra=interface,0
And --force-fast-ra will be an alias of
--enable-ra=interface,1800,5,20
Also, current code uses 600 as max, and 3/4*max as min ra intervals,
what fits RFC, bit, guessб isn't optimal, too big min delay.
As for startup advertisements and force-fast-ra, interval is 5-20, but
can be limited to range
MIN_DELAY_BETWEEN_RAS-MAX_INITIAL_RTR_ADVERT_INTERVAL, 3 and
16
respectively as RFC suggests Since RA can be very frequent, is it ever
worth to log with LOG_INFO level every unsolicited RTR-ADVERT? It just
floods syslog and has no other meaning in my opinion.
Best Regards, Vladislav Grishenko
OK, I just committed my take on this, which is --ra-param option, and
removed --force-fast-ra
--ra-param=<interface>,[high|low],[[<ra-interval>],<router
lifetime>]
Set non-default values for router advertisements sent
via an interface. The priority field for the router
may be altered from the default of medium with eg
--ra-param=eth0,high. The interval between router
advertisements may be set (in seconds) with --ra-
param=eth0,60. The lifetime of the route may be
changed or set to zero, which allows a router to
advertise prefixes but not a route via itself. --ra-
parm=eth0,0,0 (A value of zero for the interval means
the default value.) All three parameters may be set at
once. --ra-param=low,60,1200 The interface field may
include a wildcard.
I even added control of router priority as a bonus!
Cheers,
Simon.
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