From: Josh Rickmar Subject: Re: rad(8): Adjust rDNS lifetime to RFC 8106 default (minimum) value. To: tech Date: Sat, 28 Dec 2024 03:52:20 -0500 On Sat, Dec 28, 2024 at 09:29:54AM +0100, Florian Obser wrote: > This makes the rDNS lifetime the same as the router lifetime (1800 > seconds). rad(8) already lists 8106 under standards, but we used the old > value from 6106. > It also does not make any sense to expire the rDNS information before > the router itself. This is information that travels together. > > OK? > > diff --git rad.conf.5 rad.conf.5 > index b90934603f7..8abd51b9bed 100644 > --- rad.conf.5 > +++ rad.conf.5 > @@ -76,7 +76,7 @@ options are as follows: > .It Ic lifetime Ar seconds > The number of seconds the dns options are valid after receiving a router > advertisement message. > -The default is 900 seconds. > +The default is 1800 seconds. > .It Ic nameserver Pq Ar address Ns | Ns Brq Ar address ... > IPv6 address or list of IPv6 addresses of DNS name servers. > .It Ic search Pq Ar domain Ns | Ns Brq Ar domain ... > diff --git rad.h rad.h > index 46cdc51ea64..e0e59a31a38 100644 > --- rad.h > +++ rad.h > @@ -34,7 +34,7 @@ > #define MAX_RA_DELAY_TIME 500 /* 500 milliseconds */ > #define MIN_DELAY_BETWEEN_RAS 3 /* 3 seconds */ > #define MAX_SEARCH 1025 /* MAXDNAME in arpa/nameser.h */ > -#define DEFAULT_RDNS_LIFETIME 600 * 1.5 > +#define DEFAULT_RDNS_LIFETIME 3 * MAX_RTR_ADV_INTERVAL > #define PLTIME_DECAYING 1 > #define VLTIME_DECAYING 2 > > > -- > In my defence, I have been left unsupervised. > This is the same diff I was testing to try and fix my iphone from forgetting the advertised DNS servers and kicking back to LTE when connected to an IPv6-only wifi network. I also tried setting this lifetime up to 6x the maximum router interval, but the iphone would still lose wifi if I kept it sleeping long enough. This appears to be Apple's bug, and I've found other cases of people discovering this limitation after doing some additional internet searches. For my usage, I have increased the DNS lifetime to a week, but changing this default value still looks right to me. ok jrick