[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[lwip-devel] [patch #9136] Device takes long to connect with some specif
From: |
Nirav Desai |
Subject: |
[lwip-devel] [patch #9136] Device takes long to connect with some specific Access Points like Aiport Extreme |
Date: |
Thu, 6 Oct 2016 07:37:23 +0000 (UTC) |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.94 Safari/537.36 |
URL:
<http://savannah.nongnu.org/patch/?9136>
Summary: Device takes long to connect with some specific
Access Points like Aiport Extreme
Project: lwIP - A Lightweight TCP/IP stack
Submitted by: niravisneo
Submitted on: Thu 06 Oct 2016 07:37:20 AM GMT
Category: ARP
Priority: 5 - Normal
Status: None
Privacy: Public
Assigned to: None
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Planned Release: None
_______________________________________________________
Details:
RFC 2131 : Dynamic Host Configuration Protocol
Here is brief workflow of DHCP address acquistion
1. Device to AP – DHCP discover
2. AP – broadcast ARP probe before offering an IPv4 address
3. AP to Device – DHCP offer
4. Device – broadcast ARP probe to check if that IPv4 address
is already in use
5. If no address conflict found then Device to AP – DHCP request
confirming that it is ready to use this IP
6. AP to Device – DHCP ACK
7. Else part of step 5, if there is some address conflict
found then Deviceto AP – DHCP Decline
However found an issue with Apple Airport Extreme, where it sends ARP packet
for same IP
while giving DHCP offer (Step 4)
In step 4, additional checks need to be done to correctly isolate "conflicting
ARP probes"
If both of the following conditions hold true, then only the given ARP packet
"may" be a "conflicting ARP Probe"
- Check if Source IP address is all-zero IP address,
so as to qualify the packet to be called as "ARP Probe"
- Check if sender MAC address is not same as our own
MAC to ensure that own ARP packet is not received back.
This can happen with some kinds of Ethernet hub and some WiFi
APs which may "rebroadcast" any received broadcast packets
If either of the above condition do not hold true, then the given ARP packet
is
NOT
an ARP Probe packet, hence should not be considered for address conflict use
case.
The ARP packets coming from Airport Extreme (mentioned in step 4 above) fall
in
the
second category - Source IP address NOT equal to all-zero IP address, as it
is
set
to IP address of Airport Extreme.
Hence these packets would not considered for address conflict use case.
_______________________________________________________
File Attachments:
-------------------------------------------------------
Date: Thu 06 Oct 2016 07:37:20 AM GMT Name: LWIP-ETHARP-Enhancements.patch
Size: 4kB By: niravisneo
<http://savannah.nongnu.org/patch/download.php?file_id=38669>
_______________________________________________________
Reply to this item at:
<http://savannah.nongnu.org/patch/?9136>
_______________________________________________
Message sent via/by Savannah
http://savannah.nongnu.org/
- [lwip-devel] [patch #9136] Device takes long to connect with some specific Access Points like Aiport Extreme,
Nirav Desai <=