Bug 82002 – Responding to bogus SYN, Linux repeats SYN+ACK despite RST

Bug 82002 - Responding to bogus SYN, Linux repeats SYN+ACK despite RST

Summary:	Responding to bogus SYN, Linux repeats SYN+ACK despite RST

Status:	CLOSED CURRENTRELEASE

Aliases:	None

Product:	Red Hat Linux
Classification:	Retired
Component:	kernel (Show other bugs)
Sub Component:
Version:	7.3
Hardware:	All Linux

Priority	medium Severity medium
Target Milestone:	---
Target Release:	---
Assigned To:	Arjan van de Ven
QA Contact:	Brian Brock
Docs Contact:

URL:
Whiteboard:
Keywords:

Depends On:
Blocks:
	Show dependency tree / graph

Reported:	2003-01-16 02:48 EST by Matthew Braithwaite
Modified:	2007-04-18 12:50 EDT (History)
CC List:	0 users

See Also:
Fixed In Version:
Doc Type:	Bug Fix
Doc Text:
Story Points:	---
Clone Of:
Environment:
Last Closed:	2003-02-25 18:52:34 EST
Type:	---
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
Solaris 7 reacting to a forged SYN (250 bytes, application/octet-stream) 2003-01-16 02:50 EST, Matthew Braithwaite	no flags	Details
Linux reacting to a forged SYN (1000 bytes, application/octet-stream) 2003-01-16 02:51 EST, Matthew Braithwaite	no flags	Details
Program to generate forged SYN (877 bytes, text/plain) 2003-01-16 03:03 EST, Matthew Braithwaite	no flags	Details
Add an attachment (proposed patch, testcase, etc.)

Groups: None (edit)

Description Matthew Braithwaite 2003-01-16 02:48:26 EST

From Bugzilla Helper:
User-Agent: Mozilla/5.0 Galeon/1.2.6 (X11; FreeBSD i386; U;) Gecko/0

Description of problem:
I can't quote chapter and verse, but the following behavior seems obviously
wrong, and it differs from another OS (Solaris) chosen at random for comparison.

Let A be a Linux box running RedHat 7.3, kernel=2.4.18-10bigmem.

When A receives a forged SYN from B, A sends B a SYN+ACK.  B then sends A a RST,
since the initial SYN is forged.

You'd think it'd end there.  But no, A keeps sending SYN+ACK to B for a long
time, despite receiving an RST in response to every one.

I will append tcpdumps showing how Linux and Solaris react differently.  As one
would expect, Solaris stops the three-way handshake immediately after receiving
the RST.

Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1. Using libnet, forge a SYN from your own IP address to a Linux box.  

Additional info:

Comment 1 Matthew Braithwaite 2003-01-16 02:50:10 EST

Created attachment 89404 [details]
Solaris 7 reacting to a forged SYN

This is the behavior that seems reasonable to me.

Comment 2 Matthew Braithwaite 2003-01-16 02:51:07 EST

Created attachment 89405 [details]
Linux reacting to a forged SYN

This is how Linux reacts.  This seems wrong to me.

Comment 3 Matthew Braithwaite 2003-01-16 03:03:54 EST

Created attachment 89406 [details]
Program to generate forged SYN

Requires libnet

Comment 4 Arjan van de Ven 2003-01-16 05:08:48 EST

this is something that should be fixed in a more recent erratum kernel.

Comment 5 Matthew Braithwaite 2003-01-16 10:49:00 EST

> this is something that should be fixed in a more recent erratum kernel.

I'm unclear whether that means that it *is* fixed or that it *will be* fixed. 
(If the former -- in what version?)

Comment 6 Arjan van de Ven 2003-01-16 10:57:34 EST

it's believed to be fixed in the current erratum for 7.3, eg version 2.4.18-19.7.x
(which is the 3rd erratum since 2.4.18-10)

Comment 7 Matthew Braithwaite 2003-02-25 18:52:34 EST

I confirm that this is fixed in 2.4.18-24.7.xbigmem.  Thanks.  Resolving
CURRENTRELEASE.

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