buglwIP - A Lightweight TCP/IP stack - Bugs: bug #51623, DHCP request XID should probably...

 
 

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bug #51623: DHCP request XID should probably be regenerated for INIT-REBOOT

Submitted by:  Ambroz Bizjak <abizjak>
Submitted on:  Sun 30 Jul 2017 03:27:36 PM UTC  
 
Category: DHCPSeverity: 3 - Normal
Item Group: Faulty BehaviourStatus: Fixed
Privacy: PublicAssigned to: Simon Goldschmidt <goldsimon>
Open/Closed: ClosedPlanned Release: None
lwIP version: git head

Mon 31 Jul 2017 06:22:02 PM UTC, comment #1:

Absolutely right. Fixed, thanks for reporting.

From my reading, Windows 10 is incorrect with creating a new xid in RENEWING/REBINDING. The RFC seems pretty clear to me there. Probably someone was more clever there as the authors of the RFC :-)

Simon Goldschmidt <goldsimon>
Project AdministratorIn charge of this item.
Sun 30 Jul 2017 03:27:36 PM UTC, original submission:

In bug #40303 the DHCP client was changed to never regenerate an XID when sending a DHCPREQUEST. This was because RFC 2131 requires that the DHCPREQUEST following a DHCPOFFER uses the same XID as the offer (and therefore the same as DHCPDISCOVER).

However it is required to generate a new XID when entering the INIT-REBOOT state (4.4.2 Initialization with known network address). Currently lwIP does not do that.

I have checked the behavior of Windows 10 and dhclient (Ubuntu 16.10) and both generate a new XID in this case (after link goes back up).

I also checked the XID generation of these systems for RENEWING and REBINDING, and Windows generates new XIDs while dhclient does not, so I suppose lwIP is fine in this respect if it keeps using the same XID as it is now, I only recommend to change to generating a new XID when the REBOOTING state is entered (in dhcp_network_changed).

Ambroz Bizjak <abizjak>

 

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  • -unavailable- added by goldsimon (Posted a comment)
  • -unavailable- added by abizjak (Submitted the item)
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    Follow 3 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Mon 31 Jul 2017 06:22:02 PM UTCgoldsimonStatusNone=>Fixed
      Assigned toNone=>goldsimon
      Open/ClosedOpen=>Closed

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