tasklwIP - A Lightweight TCP/IP stack - Tasks: task #13957, there is always a delay to send...

 
 

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task #13957: there is always a delay to send the first Neighbor Solicitation for the new add INCOMPLETE state neighbor entry

Submitter:  shu chen <chenshu>
Submitted:  Sat 09 Apr 2016 12:04:51 AM UTC
   
 
Category:  IPv6 Should Start On:  Fri 08 Apr 2016 12:00:00 AM UTC
Should be Finished on:  Fri 08 Apr 2016 12:00:00 AM UTC Priority:  5 - Normal
Status:  None Privacy:  Public
Assigned to:  None Percent Complete:  0%
Open/Closed:  Closed Planned Release:  None
Effort:  0.00

Tue 12 Apr 2016 07:12:13 PM UTC, comment #1: 

This is a duplicate to bug #47652. Please select bug or task to post, not both.

Simon Goldschmidt <goldsimon>
Group administrator
Sat 09 Apr 2016 12:04:51 AM UTC, original submission:  

The bug is found during the ping test in our project, all the first ping to the new neighbor exceeds one second.

In the current Neighbor Discovery implementation of LwIP, there is always a delay to send the first Neighbor Solicitation for the new add INCOMPLETE state neighbor entry. The delay blocks all the first packet to the neighbors.

In the RFC-4861, the INCOMPLETE state is described as follows (section 7.3.2):
"Address resolution is being performed on the entry. Specifically, a Neighbor Solicitation has been sent to the solicited-node multicast address of the target, but the corresponding Neighbor Advertisement has not yet been received."

But the current LwIP process:
 - create a new neighbor entry, init it as INCOMPLETE
 - wait for the nd6_tmr timer (once a second)
 - nd6_tmr is triggered, send neighbor solicit if the entry's state is INCOMPLETE

The current process is a little non-conformant with the RFC-4861, the correct way is to send Neighbor Solicitation immediately for the new neighbor entry, and then mark it as INCOMPLETE. So there should not be any delay to send the first Neighbor Discovery which blocks the first packet to the neighbor.

shu chen <chenshu>

 

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    Follows 1 latest change.

    Date Changed by Updated Field Previous Value => Replaced by
    2016-04-12 goldsimon Open/ClosedOpen Closed

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