ANNOUNCEMENT: Live Wireshark University & Allegro Packets online APAC Wireshark Training Session
April 17th, 2024 | 14:30-16:00 SGT (UTC+8) | Online

Wireshark-dev: Re: [Wireshark-dev] Enabling linux kernel jit compiler from dumpcap?

From: Bálint Réczey <balint@xxxxxxxxxxxxxxx>
Date: Fri, 23 Aug 2013 12:58:43 +0200
2013/8/23 Anders Broman <anders.broman@xxxxxxxxxxxx>:
>> before we change it, should we remember the previous setting and restore it when dumpcap exits?
>
> Preferably yes but I'm not sure it's possible as I think root privileges are required to write to the file and I think dumpcap
> Drops those after starting to capture.
And in the configuration the documentation recommends dumpcap does not
run as root, it has permission to capture only.

Cheers,
Balint

>
> Regards
> Anders
>
> -----Original Message-----
> From: wireshark-dev-bounces@xxxxxxxxxxxxx [mailto:wireshark-dev-bounces@xxxxxxxxxxxxx] On Behalf Of Martin Kaiser
> Sent: den 23 augusti 2013 10:36
> To: wireshark-dev@xxxxxxxxxxxxx
> Subject: Re: [Wireshark-dev] Enabling linux kernel jit compiler from dumpcap?
>
> before we change it, should we remember the previous setting and restore it when dumpcap exits?
>
> Thus wrote Anders Broman (a.broman@xxxxxxxxxxxx):
>
>> Bálint Réczey skrev 2013-08-22 23:02:
>>> Hi,
>
>>> I would be happier if the applications I run did not change kernel
>>> configuration without my consent.
>> I see your point...
>
>>> Regarding Wireshark I would prefer suggesting "echo 1 >
>>> /proc/sys/net/core/bpf_jit_enable" in the documentation instead of
>>> adding code to enable JIT.
>>> There may be good reasons for not enabling it by default in the Linux kernel.
>> The problematic thing is that people seldom reads the documentation,
>> the setting gets reset at a reboot and it's easy to forget to
>> re-enable it. The ideal thing would be if dumpcap
>> - Had a preference/command line flag whether to use JIT or not.
>> - If told to use it check if it was enabled or not used JIT and put it
>> back to zero if not set when starting.
>> Wireshark could then default to use JIT and some warnings could be
>> displayed in the welcome screen and in dumpcaps help output.
>
>> netsniff-ng activates it by default it seems.
>> Regards
>> Anders
>
>>> Cheers,
>>> Balint
>
>>> 2013/8/22 Anders Broman <a.broman@xxxxxxxxxxxx>:
>>>> Guy Harris skrev 2013-08-22 18:16:
>
>>>>> On Aug 22, 2013, at 4:46 AM, Anders Broman
>>>>> <anders.broman@xxxxxxxxxxxx>
>>>>> wrote:
>
>>>>>> Should we add code to enable the JIT compiler from dumpcap?
>>>>> Should I add code to enable the JIT compiler to libpcap while I'm at it?
>
>>>>> Should the Linux kernel folks enable it by default?
>
>>>>> I'm inclined to answer "yes" to all three questions.  I think the
>>>>> FreeBSD JIT compiler is enabled by default.  I'm surprised that the Linux one isn't.
>>>> I checked in the dumpcap code. I agree that it might be useful in
>>>> libpcap too, root privileges are required to change it I think. and
>>>> Yes
>
>>>>> I'm surprised that the Linux one isn't
>>>> Regards
>>>> Anders
>
>>>>> ___________________________________________________________________________
>>>>> Sent via:    Wireshark-dev mailing list <wireshark-dev@xxxxxxxxxxxxx>
>>>>> Archives:    http://www.wireshark.org/lists/wireshark-dev
>>>>> Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev
>
>>>>> mailto:wireshark-dev-request@xxxxxxxxxxxxx?subject=unsubscribe
>
>>>> ___________________________________________________________________________
>>>> Sent via:    Wireshark-dev mailing list <wireshark-dev@xxxxxxxxxxxxx>
>>>> Archives:    http://www.wireshark.org/lists/wireshark-dev
>>>> Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev
>>>>
>>>> mailto:wireshark-dev-request@xxxxxxxxxxxxx?subject=unsubscribe
>>> ___________________________________________________________________________
>>> Sent via:    Wireshark-dev mailing list <wireshark-dev@xxxxxxxxxxxxx>
>>> Archives:    http://www.wireshark.org/lists/wireshark-dev
>>> Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev
>>>
>>> mailto:wireshark-dev-request@xxxxxxxxxxxxx?subject=unsubscribe
>
>
>> ___________________________________________________________________________
>> Sent via:    Wireshark-dev mailing list <wireshark-dev@xxxxxxxxxxxxx>
>> Archives:    http://www.wireshark.org/lists/wireshark-dev
>> Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev
>>
>> mailto:wireshark-dev-request@xxxxxxxxxxxxx?subject=unsubscribe
> ___________________________________________________________________________
> Sent via:    Wireshark-dev mailing list <wireshark-dev@xxxxxxxxxxxxx>
> Archives:    http://www.wireshark.org/lists/wireshark-dev
> Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev
>              mailto:wireshark-dev-request@xxxxxxxxxxxxx?subject=unsubscribe
> ___________________________________________________________________________
> Sent via:    Wireshark-dev mailing list <wireshark-dev@xxxxxxxxxxxxx>
> Archives:    http://www.wireshark.org/lists/wireshark-dev
> Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev
>              mailto:wireshark-dev-request@xxxxxxxxxxxxx?subject=unsubscribe