Kernel seems to be blocking messages

Hi all,
I have a server running 2.6.2-rc1, and I was happily installing vpopmail and reading the vpopmail gentoo guide (www.gentoo.org). Somehow (don't ask me
why) every net connections seem to stop and get blocked. Now I cannot make any socket connection. For example:

# ping localhost 
PING descartes.geniousdomain (127.0.0.1) 56(84) bytes of data. 
ping: sendmsg: Operation not permitted 
...

Any ideas on how to unblock the situation?

Cheers,

Paulo J. Matos : pocm [_at_] mega . ist . utl . pt
Instituto Superior Tecnico - Lisbon
Computer and Software Eng. - A.I.
 - > http://mega.ist.utl.pt/~pocm
---
        -> God had a deadline...
                So, he wrote it all in Lisp!

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I have seen this when iptables is running and pings are not permissioned.

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Hummm, that's very possible. I'm using iptables and I did tried somethings with them... I'll see what's happening when I get home from work.

Thanks a lot... :)
I'll then tell you if you were right.

Cheers,

Paulo Matos

Paulo J. Matos : pocm [_at_] mega . ist . utl . pt
Instituto Superior Tecnico - Lisbon
Computer and Software Eng. - A.I.
 - > http://mega.ist.utl.pt/~pocm
---
        -> God had a deadline...
                So, he wrote it all in Lisp!

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Hi,

You're right. The problem was the iptables configuration. I've done:
iptables -F
iptables -X

Then to share internet with my clients I've done:
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

however, it seems that it is not working, eth0 is my net connection. This should work, right? Maybe I'm doing something wrong in my clients config.

Cheers,

Paulo Matos

Paulo J. Matos : pocm [_at_] mega . ist . utl . pt
Instituto Superior Tecnico - Lisbon
Computer and Software Eng. - A.I.
 - > http://mega.ist.utl.pt/~pocm
---
        -> God had a deadline...
                So, he wrote it all in Lisp!

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There is one more change you need to make so that you are able to do NAT.

In /etc/sysctl.conf, you need to add/change the line:
net.ipv4.ip_forward = 1

The above might be set to zero, and if it is, change it to 1. Unfortunately, for this change to take effect, you'd need to reboot the system, but there's a quicker way. After you add the above line to the file, do the following:

echo "1" > /proc/sys/net/ipv4/ip_forward

If routing has been setup correctly for this machine, then any machine using it as its router should be able to access the outside.

Make sure that you set some rules for outside traffic, or else potential crackers could break the machine in little time, especially if you have services running on the box.

Good Luck!

: -----Original Message-----
: From: [email protected]
: [mailto:[email protected]] On Behalf Of Paulo : Jorge de Oliveira Cantante de Matos
: Sent: Sunday, 22 February, 2004 05:58
: To: asterr
: Cc: [email protected]; [email protected] : Subject: Re: Kernel seems to be blocking messages
:
: Hi,
:
: You're right. The problem was the iptables configuration. I've done:
: iptables -F
: iptables -X
:
: Then to share internet with my clients I've done:
: iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
:
: however, it seems that it is not working, eth0 is my net connection. : This should work, right? Maybe I'm doing something wrong in : my clients config.
:
: Cheers,
:
: Paulo Matos
:
:
: On Sat, 2004-02-21 at 03:22, asterr wrote:
: > I have seen this when iptables is running and pings are not : permissioned.
: >
: > On Sat, 21 Feb 2004, Paulo Jorge de Oliveira Cantante de : Matos wrote:
: >
: > > Hi all,
: > > I have a server running 2.6.2-rc1, and I was happily installing : > > vpopmail and reading the vpopmail gentoo guide (www.gentoo.org). : > > Somehow (don't ask me
: > > why) every net connections seem to stop and get blocked. Now I : > > cannot make any socket connection. For example:
: > >
: > > # ping localhost
: > > PING descartes.geniousdomain (127.0.0.1) 56(84) bytes of data. : > > ping: sendmsg: Operation not permitted ...
: > >
: > > Any ideas on how to unblock the situation?
: > >
: > > Cheers,
: > > --
: > >
: > > Paulo J. Matos : pocm [_at_] mega . ist . utl . pt Instituto : > > Superior Tecnico - Lisbon Computer and Software Eng. - A.I. : > > - > http://mega.ist.utl.pt/~pocm
: > > ---
: > > -> God had a deadline...
: > > So, he wrote it all in Lisp!
: > >
: > > -
: > > To unsubscribe from this list: send the line "unsubscribe : > > linux-admin" in the body of a message to
: [email protected]
: > > More majordomo info at http://vger.kernel.org/majordomo-info.html
: > >
: > >
: > >
: >
: > -
: > To unsubscribe from this list: send the line "unsubscribe : > linux-newbie" in the body of a message to [email protected] : > More majordomo info at http://vger.kernel.org/majordomo-info.html
: > Please read the FAQ at http://www.linux-learn.org/faqs
: --
:
: Paulo J. Matos : pocm [_at_] mega . ist . utl . pt Instituto : Superior Tecnico - Lisbon Computer and Software Eng. - A.I. : - > http://mega.ist.utl.pt/~pocm
: ---
: -> God had a deadline...
: So, he wrote it all in Lisp!
:
: -
: To unsubscribe from this list: send the line "unsubscribe : linux-admin" in the body of a message to
: [email protected] More majordomo info at
: http://vger.kernel.org/majordomo-info.html
:

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Paulo...

As Asterr suggested, you might have a iptable rules that are preventing data to go through. To clear those rules, try the following:
Iptables -F
Iptables -X
Iptables -P INPUT ACCEPT
Iptables -P OUTPUT ACCEPT
Iptables -P FORWARD ACCEPT

The above wipes out any instance of any rules existing for the time being. If you restart the server, they'll appear again. In that case, disable iptables from starting by using chkconfig.

Good Luck! =D

--Armen

: -----Original Message-----
: From: [email protected]
: [mailto:[email protected]] On Behalf Of Paulo : Jorge de Oliveira Cantante de Matos
: Sent: Friday, 20 February, 2004 19:46
: To: [email protected]; [email protected] : Subject: Kernel seems to be blocking messages
:
: Hi all,
: I have a server running 2.6.2-rc1, and I was happily : installing vpopmail and reading the vpopmail gentoo guide : (www.gentoo.org). Somehow (don't ask me
: why) every net connections seem to stop and get blocked. Now : I cannot make any socket connection. For example:
:
: # ping localhost
: PING descartes.geniousdomain (127.0.0.1) 56(84) bytes of data. : ping: sendmsg: Operation not permitted
: ...
:
: Any ideas on how to unblock the situation?
:
: Cheers,
: --
:
: Paulo J. Matos : pocm [_at_] mega . ist . utl . pt Instituto : Superior Tecnico - Lisbon Computer and Software Eng. - A.I. : - > http://mega.ist.utl.pt/~pocm
: ---
: -> God had a deadline...
: So, he wrote it all in Lisp!
:
: -
: To unsubscribe from this list: send the line "unsubscribe : linux-admin" in the body of a message to
: [email protected] More majordomo info at
: http://vger.kernel.org/majordomo-info.html
:

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