Bug 41073 - IP packets have been lost when only 20 POP clients access at same time.
IP packets have been lost when only 20 POP clients access at same time.
Status: CLOSED NOTABUG
Product: Red Hat Linux
Classification: Retired
Component: kernel (Show other bugs)
7.1
i686 Linux
medium Severity high
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Assigned To: Arjan van de Ven
Brock Organ
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Depends On:
Blocks:
  Show dependency treegraph
 
Reported: 2001-05-17 05:20 EDT by Keiichi Mori
Modified: 2007-04-18 12:33 EDT (History)
0 users

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Environment:
Last Closed: 2001-05-20 23:06:13 EDT
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Regression: ---
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Documentation: ---
CRM:
Verified Versions:
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---


Attachments (Terms of Use)
Proposed patch (420 bytes, patch)
2001-05-17 07:14 EDT, Arjan van de Ven
no flags Details | Diff

  None (edit)
Description Keiichi Mori 2001-05-17 05:20:48 EDT
From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux 2.4.2-2 i686; en-US; 0.7) Gecko/20010316

Description of problem:
When 20 POP clients using "telnet <server></server> 110" and "expect"
access to at same time, xinetd can not fork only 18 process. Because
select() function in xinetd main_loop() catch the changed status at 110
port, only 18 times.

Packet dump by "ethereal" on POP Server is here:(station100 is a POP
Server, station67 is a POP Client)

    732 1.830000    station64  station100  TCP      32775 > pop3 [SYN]
Seq=3399523946 Ack=0 Win=5840 Len=0
    733 1.830000    station100 station64   TCP      pop3 > 32775 [SYN, ACK]
Seq=3802504036 Ack=3399523947 Win=5792 Len=0
!   750 1.830000    station64  station100  TCP      32775 > pop3 [ACK]
Seq=3399523947 Ack=3802504037 Win=5840 Len=0

* 18084 5.430000    station100 station64   TCP      pop3 > 32775 [SYN, ACK]
Seq=3802504036 Ack=3399523947 Win=5792 Len=0
* 22351 11.430000   station100 station64   TCP      pop3 > 32775 [SYN, ACK]
Seq=3802504036 Ack=3399523947 Win=5792 Len=0


Response to [SYN,ACK] reached the Link layer. But It seems not to reached
the Transport layer.

I think packet have been lost in Network layer.

Only 20 clients accessed, why packet have been lost?






How reproducible:
Always

Steps to Reproduce:
1.20 POP clients access to POP server at same time.(very critical)
2.
3.
	

Additional info:
Comment 1 Arjan van de Ven 2001-05-17 05:24:14 EDT
Dave: Could you take a look ?
Comment 2 Arjan van de Ven 2001-05-17 05:45:53 EDT
kmori@redhat.com: are you in a position to test a patch ?
Comment 3 Keiichi Mori 2001-05-17 06:57:39 EDT
I am not in development team, I am in service team.
But if you give me a patch, I'll test it.
Comment 4 Arjan van de Ven 2001-05-17 07:14:07 EDT
Created attachment 18732 [details]
Proposed patch
Comment 5 Keiichi Mori 2001-05-20 23:06:07 EDT
Thank you for creating attachment. I could get a patch.
I tested this patch, however, kernel had still lost packets.
Comment 6 Keiichi Mori 2001-05-22 03:37:34 EDT
This problem is caused by xinetd specification.

Because listen() backlog value defined by xinetd is low,
kernel drop client's requests.


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