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Today's Topics:
1. Re: DHCP Server Fails When Forking (Jay Foster)
2. Re: DHCP Server Fails When Forking (Jay Foster)
3. Re: DHCP Server Fails When Forking (Jay Foster)
----------------------------------------------------------------------
Message: 1
Date: Mon, 6 Jan 2020 14:02:06 -0800
From: Jay Foster <j...@systech.com>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>, Christopher Barry
<christopher.r.ba...@gmail.com>
Subject: Re: DHCP Server Fails When Forking
Message-ID: <3c80ee93-be84-785d-07cc-c2e1b4995...@systech.com>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
dhcpd is running as root whether or not it forks (evidenced by ps). I do
not see how forking or not forking has any bearing on permissions.?
dhcpd does not report any errors writing the leases file (daemon.info
dhcpd: Wrote 1 leases to leases file.).
For grins, I chown dhcp:dhcp both the leases file and .conf file. Makes
no difference.? Also tried adding '-user dhcp -group dhcp'. Also makes
no difference.
There is no evidence of any kind of a permissions issue.? strace shows
that dhcpd creates 3 child processes via clone(2).? These processes seem
to be associated with the dhcp_context_create(), omapi_init(), etc.
function calls.? In the forking case, these get terminated along with
the parent process after the fork(2), but obviously do not when not
forking.? That is the only difference that I see between the forking and
non-forking invocations.
On 1/6/2020 1:49 PM, Christopher Barry wrote:
> Generally, when backgrounded, dhcpd runs with reduced privs, e.g. as
> dhcpd:dhcpd (your configured user/group may be different). Can you su
> as that user and run dhcpd in the foreground? I'm suspecting that user
> may not have write perms to the leases file.
>
>
> On Mon, Jan 6, 2020, 4:15 PM Jay Foster <j...@systech.com
> <mailto:j...@systech.com>> wrote:
>
> Can you be more specific?? /usr/sbin/dhcpd is root:root.?
> /usr/sbin/dhcpd is being run as root.
>
> On 1/6/2020 12:58 PM, Christopher Barry wrote:
>> Make sure user/group perms are valid.
>>
>>
>> On Mon, Jan 6, 2020, 1:42 PM Jay Foster <j...@systech.com
>> <mailto:j...@systech.com>> wrote:
>>
>> I am using the ISC DHCP server (dhcpd) version 4.3.6 from a
>> rocko Yocto
>> build.? When dhcpd is started without the '-f' or '-d'
>> options (forks to
>> the background) it does not work.? DHCP DISCOVER requests are
>> sent, but
>> the dhcpd application does not respond.? I can attach strace
>> to the
>> dhcpd process and see that dhcpd just sleeps in an futex() call.
>>
>> If I start dhcpd with either the '-f' or '-d' options so it
>> does not
>> fork, then it works properly.
>>
>> I have run dhcpd (both forking and non forking) using strace
>> to see if I
>> could spot any differences.? The only thing I notice is that
>> when
>> forking, the parent process terminates (expected) along with
>> 3 other
>> child processes/threads.? It looks like these other threads
>> are supposed
>> to handle the ISC tasks/messages, but are not cloned by the
>> fork and are
>> not present after forking.
>>
>> For reference, with an older version of ISC DHCP server
>> (4.1.1-P1) on an
>> older product, this problem does not occur.
>>
>> Any ideas where to look?
>>
>>
>>
>>
>>
>> _______________________________________________
>> dhcp-users mailing list
>> dhcp-users@lists.isc.org <mailto:dhcp-users@lists.isc.org>
>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>
>>
>> _______________________________________________
>> dhcp-users mailing list
>> dhcp-users@lists.isc.org <mailto:dhcp-users@lists.isc.org>
>> https://lists.isc.org/mailman/listinfo/dhcp-users
>
>
> _______________________________________________
> dhcp-users mailing list
> dhcp-users@lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users
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Message: 2
Date: Mon, 6 Jan 2020 14:39:48 -0800
From: Jay Foster <j...@systech.com>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>, Christopher Barry
<christopher.r.ba...@gmail.com>
Subject: Re: DHCP Server Fails When Forking
Message-ID: <25bd76c2-f9dc-7782-74c9-6c12bffc1...@systech.com>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
For now, I am working around this issue by telling dhcpd not to fork (-f
option) and instead forking the shell (append ' &' to the command line).
On 1/6/2020 2:02 PM, Jay Foster wrote:
> dhcpd is running as root whether or not it forks (evidenced by ps).? I
> do not see how forking or not forking has any bearing on permissions.?
> dhcpd does not report any errors writing the leases file (daemon.info
> dhcpd: Wrote 1 leases to leases file.).
>
> For grins, I chown dhcp:dhcp both the leases file and .conf file.
> Makes no difference.? Also tried adding '-user dhcp -group dhcp'. Also
> makes no difference.
>
> There is no evidence of any kind of a permissions issue.? strace shows
> that dhcpd creates 3 child processes via clone(2).? These processes
> seem to be associated with the dhcp_context_create(), omapi_init(),
> etc. function calls.? In the forking case, these get terminated along
> with the parent process after the fork(2), but obviously do not when
> not forking.? That is the only difference that I see between the
> forking and non-forking invocations.
>
> On 1/6/2020 1:49 PM, Christopher Barry wrote:
>> Generally, when backgrounded, dhcpd runs with reduced privs, e.g. as
>> dhcpd:dhcpd (your configured user/group may be different). Can you su
>> as that user and run dhcpd in the foreground? I'm suspecting that
>> user may not have write perms to the leases file.
>>
>>
>> On Mon, Jan 6, 2020, 4:15 PM Jay Foster <j...@systech.com
>> <mailto:j...@systech.com>> wrote:
>>
>> Can you be more specific?? /usr/sbin/dhcpd is root:root.?
>> /usr/sbin/dhcpd is being run as root.
>>
>> On 1/6/2020 12:58 PM, Christopher Barry wrote:
>>> Make sure user/group perms are valid.
>>>
>>>
>>> On Mon, Jan 6, 2020, 1:42 PM Jay Foster <j...@systech.com
>>> <mailto:j...@systech.com>> wrote:
>>>
>>> I am using the ISC DHCP server (dhcpd) version 4.3.6 from a
>>> rocko Yocto
>>> build.? When dhcpd is started without the '-f' or '-d'
>>> options (forks to
>>> the background) it does not work.? DHCP DISCOVER requests
>>> are sent, but
>>> the dhcpd application does not respond.? I can attach strace
>>> to the
>>> dhcpd process and see that dhcpd just sleeps in an futex() call.
>>>
>>> If I start dhcpd with either the '-f' or '-d' options so it
>>> does not
>>> fork, then it works properly.
>>>
>>> I have run dhcpd (both forking and non forking) using strace
>>> to see if I
>>> could spot any differences.? The only thing I notice is that
>>> when
>>> forking, the parent process terminates (expected) along with
>>> 3 other
>>> child processes/threads.? It looks like these other threads
>>> are supposed
>>> to handle the ISC tasks/messages, but are not cloned by the
>>> fork and are
>>> not present after forking.
>>>
>>> For reference, with an older version of ISC DHCP server
>>> (4.1.1-P1) on an
>>> older product, this problem does not occur.
>>>
>>> Any ideas where to look?
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> dhcp-users mailing list
>>> dhcp-users@lists.isc.org <mailto:dhcp-users@lists.isc.org>
>>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>>
>>>
>>> _______________________________________________
>>> dhcp-users mailing list
>>> dhcp-users@lists.isc.org <mailto:dhcp-users@lists.isc.org>
>>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>
>>
>> _______________________________________________
>> dhcp-users mailing list
>> dhcp-users@lists.isc.org
>> https://lists.isc.org/mailman/listinfo/dhcp-users
>
>
> _______________________________________________
> dhcp-users mailing list
> dhcp-users@lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users
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------------------------------
Message: 3
Date: Mon, 6 Jan 2020 15:16:37 -0800
From: Jay Foster <j...@systech.com>
To: Bruce Hudson <bruce.hud...@dal.ca>, Users of ISC DHCP
<dhcp-users@lists.isc.org>
Subject: Re: DHCP Server Fails When Forking
Message-ID: <314febde-927a-3ad3-b96c-57be8b3f9...@systech.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Yes, SELINUX is in use, but it is set to permissive.? Also, if SELINUX
was causing a problem, then it would do so in both the forking and
non-forking invocations.
On 1/6/2020 1:50 PM, Bruce Hudson wrote:
> Is your system running SELINUX? If it is a custom build, the
> secure environment rules, normally only envoked for daemons, may
> not be allowing the server to access things; even with the
> correct file permissions.
>
> Violations should be logged, or temporarily turn off security
> with "setenforce 0".
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