Issue with internal dns caching

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maillists

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Jul 5, 2021, 5:56:03 AM7/5/21
to IBrowse Users
If during a use session any site (re)loading stops, or access to a site previously accessed during same use session, unexpectedly returns access errors, (sites in question can have been accessed many days ago or just a moment ago), if this happens because of server side, firewall or dns lookup changes, then I am unable to verify or check if IB actually accesses the current, for the site valid ip, meaning it must be a current server problem, or if IB tries to access the site using an older now invalid dns result in/from its internal, very static and seemingly eternal lasting (within the use session) dns cache.

Does anyone have information on how to clear the IB internal dns cache?

Reloading certainly does not clear it, and no entries previously recorded therein seems to ever time out. Re-launching IB does absolutely clear it, but then any tabs or workflow already present is being killed off completely.

Would it be possible to add a menu entry to immediately clear the dns cache, so that any page/site reload will force new fresh dns lookups?

Perhaps a configuration option for cache timeout? I feel that dns lookups today should not seriously add too much of delays on many setups.

Have a quick look at about:networking#dns in firefox, where noteably the TTL's of its dns cache entries are very short-lived, I suspect for good reason.

rgds,
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Oliver Roberts

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Jul 9, 2021, 2:40:43 PM7/9/21
to ibrows...@googlegroups.com
On 05/07/2021, maillists <list...@nospammail.net> wrote:
> If during a use session any site (re)loading stops, or access to a site
> previously accessed during same use session, unexpectedly returns access
> errors, (sites in question can have been accessed many days ago or just a
> moment ago), if this happens because of server side, firewall or dns lookup
> changes, then I am unable to verify or check if IB actually accesses the
> current, for the site valid ip, meaning it must be a current server problem,
> or if IB tries to access the site using an older now invalid dns result
> in/from its internal, very static and seemingly eternal lasting (within the
> use session) dns cache.

Again, I guess you are in the minority that you leave IBrowse running
long enough for DNS issues to arise :)

> Does anyone have information on how to clear the IB internal dns cache?

It cannot be manually cleared. The DNS cache is not new, by the way -
it has been there since 2.0, and probably in 1.x too. I just increased
it from 64 to 256 entries, since these days, if you have a few tabs
open, it is easy to reach the 64 limit as one site can often access
many different hosts.

I've not looked into the cache logic in great detail, but it looks
like when the cache is full, least used hosts are released.

> Would it be possible to add a menu entry to immediately clear the dns cache,
> so that any page/site reload will force new fresh dns lookups?
>
> Perhaps a configuration option for cache timeout?

Yes, I'll look into this. I did wonder when I extended the cache size,
that perhaps this should be configurable in the settings (this also
means it could be disabled completely, if desired).

> I feel that dns lookups
> today should not seriously add too much of delays on many setups.

Maybe so, but when DNS-over-HTTPS support is available, the internal
DNS cache will certainly remain very useful. Also note that that many
TCP/IP stacks maintain their own built-in DNS cache also.

--
Oliver Roberts / @Futaura / www.futaura.co.uk

maillists

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Jul 10, 2021, 5:34:07 AM7/10/21
to 'Oliver Roberts' via IBrowse Users
On Fri, Jul 9, 2021, at 20:40, 'Oliver Roberts' via IBrowse Users wrote:
> On 05/07/2021, maillists <list...@nospammail.net> wrote:
> >
> > Does anyone have information on how to clear the IB internal dns cache?
>
> It cannot be manually cleared. The DNS cache is not new, by the way -
> it has been there since 2.0, and probably in 1.x too. I just increased
> it from 64 to 256 entries, since these days, if you have a few tabs
> open, it is easy to reach the 64 limit as one site can often access
> many different hosts.

it is probably static in aweb too, I recall having had the similar issues back then.

> I've not looked into the cache logic in great detail, but it looks
> like when the cache is full, least used hosts are released.

with the increase to 256 entries, I belive this particular change will prove even worse for the minority ;)

> > I feel that dns lookups
> > today should not seriously add too much of delays on many setups.
>
> Maybe so, but when DNS-over-HTTPS support is available, the internal
> DNS cache will certainly remain very useful. Also note that that many
> TCP/IP stacks maintain their own built-in DNS cache also.

I had a look at that as well, and with roadshow I dont see any caching in these particular instances, at least rs might adhere to short dns tables timeouts, dns ttl, as advertised in the dns communication protocole, which, if then ignored at the browser level, seems somewhat counter productive. I have not tested using any other stacks recently.

if dns-over-https support becomes available, please make this configurable as well, as this will otherwise kill off dns based parental- and/or adverts/tracking-filtering currently being set up locally.


rgds,
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maillists

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Mar 29, 2022, 9:07:52 AMMar 29
to 'Oliver Roberts' via IBrowse Users
Hello Oliver,

On Fri, Jul 9, 2021, at 20:40, 'Oliver Roberts' via IBrowse Users wrote:
> On 05/07/2021, maillists <list...@nospammail.net> wrote:
>> Would it be possible to add a menu entry to immediately clear the dns cache,
>> so that any page/site reload will force new fresh dns lookups?
>>
>> Perhaps a configuration option for DNS-cache timeout?
>
> Yes, I'll look into this. I did wonder when I extended the cache size,
> that perhaps this should be configurable in the settings (this also
> means it could be disabled completely, if desired).

did you have a look at this stale-dns-cache situation yet?

I have found that IBrowse seems to also internally cache possible NXDOMAIN replies, therefore forever presenting the user with a intuition popup window labeled IBrowse-error, containing a yellow warning sign and the text Network error: Connection refused, even if dns service and replies for the domain have since returned to normal.

Relaunching IBrowse when any odd possible related behaviour is experienced, loosing open tabs in the process too, this feels really akward. I hope that at least some kind of easy user accessible dns-cache clear/reset will be implemented, eventually. The fancy way of how FireFox solves this particular issue would be nice, visibility to the dns cache contents and automatic expirery, but less, like a manual cache clear, that would certainly do good too.

best rgds,
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Oliver Roberts

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Mar 29, 2022, 12:52:52 PMMar 29
to ibrows...@googlegroups.com
On 29/03/2022, maillists <list...@nospammail.net> wrote:
> Hello Oliver,
>
> On Fri, Jul 9, 2021, at 20:40, 'Oliver Roberts' via IBrowse Users wrote:
>> On 05/07/2021, maillists <list...@nospammail.net> wrote:
>>> Would it be possible to add a menu entry to immediately clear the dns
>>> cache,
>>> so that any page/site reload will force new fresh dns lookups?
>>>
>>> Perhaps a configuration option for DNS-cache timeout?
>>
>> Yes, I'll look into this. I did wonder when I extended the cache size,
>> that perhaps this should be configurable in the settings (this also
>> means it could be disabled completely, if desired).
>
> did you have a look at this stale-dns-cache situation yet?

Not yet. I've been too busy with AmiSSL v5.

> I have found that IBrowse seems to also internally cache possible NXDOMAIN
> replies, therefore forever presenting the user with a intuition popup window
> labeled IBrowse-error, containing a yellow warning sign and the text Network
> error: Connection refused, even if dns service and replies for the domain
> have since returned to normal.

All IBrowse ever does is cache successful gethostbyname() responses.

> Relaunching IBrowse when any odd possible related behaviour is experienced,
> loosing open tabs in the process too, this feels really akward. I hope that
> at least some kind of easy user accessible dns-cache clear/reset will be
> implemented, eventually. The fancy way of how FireFox solves this particular
> issue would be nice, visibility to the dns cache contents and automatic
> expirery, but less, like a manual cache clear, that would certainly do good
> too.

Something I'll hopefully be able to look at for IBrowse 2.5.7.
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