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Today's Topics:
1. Re: Accidentally found infinite recursion in Kea 1.3
Option... (Dave Cole)
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Message: 1
Date: Mon, 5 Feb 2018 22:39:26 +0000
From: Dave Cole <[email protected]>
To: Francis Dupont <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [kea-dev] Accidentally found infinite recursion in Kea
1.3 Option...
Message-ID:
<syxpr01mb172777fa0a97c5f428bb5de3f2...@syxpr01mb1727.ausprd01.prod.outlook.com>
Content-Type: text/plain; charset="utf-8"
I understand that the problem is in my code. I just thought I should tell
someone in case they cared ?
If the Option used a visited_ flag then recursive calls could detect cycles
established by callouts and throw an exception rather than crash.
________________________________
From: Francis Dupont <[email protected]>
Sent: Monday, 5 February 2018 9:34:59 PM
To: Dave Cole
Cc: [email protected]
Subject: Re: [kea-dev] Accidentally found infinite recursion in Kea 1.3
Option...
Dave Cole writes:
> While adding more tests for my code I stumbled on a problem in Kea. It is a
> small thing in the scheme of things, but it might be of interest.
=> IMHO the problem is in your code and is not prevented by Kea.
> >>> from kea import *
> >>> p = Pkt4(DHCPDISCOVER, 0)
> >>> o = Option(1)
> >>> o.addOption(o)
> >>> p.addOption(o)
> >>> p.pack()
=> if I understand well you created a loop with an option including
itself as a sub-option.
> Program received signal SIGSEGV, Segmentation fault.
=> even if the method is tail recursive its call consumes some stack
until the stack underflows...
> isc::dhcp::Option::len (this=0x555555ba3140) at option.cc:176
> 176 size_t length = getHeaderLen() + data_.size();
=> for documentation what is the source of the problem is:
// ... and sum of lengths of all suboptions
for (OptionCollection::const_iterator it = options_.begin();
it != options_.end();
++it) {
length += (*it).second->len();
^^^ recursive call
}
Thanks
Francis Dupont <[email protected]>
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