linux-kernel - Re: [PATCH] net: Remove a noisy printk

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Date:	Sun, 14 Dec 2008 21:15:20 +0100 (CET)
From:	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
To:	Jan Engelhardt <jengelh@...ozas.de>
cc:	David Miller <davem@...emloft.net>, ajax@...hat.com,
	linux-kernel@...r.kernel.org, davej@...hat.com,
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
	Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH] net: Remove a noisy printk

On Sun, 14 Dec 2008, Jan Engelhardt wrote:

> On Sunday 2008-12-14 18:09, Jozsef Kadlecsik wrote:
> >> 
> >> >> @@ -147,8 +147,6 @@ static unsigned int ipv4_conntrack_local(unsigned int hooknum,
> >> >>  	/* root is playing with raw sockets. */
> >> >>  	if (skb->len < sizeof(struct iphdr) ||
> >> >>  	    ip_hdrlen(skb) < sizeof(struct iphdr)) {
> >> >> -		if (net_ratelimit())
> >> >> -			printk("ipt_hook: happy cracking.\n");
> >> >>  		return NF_ACCEPT;
> >> >>  	}
> >> >>  	return nf_conntrack_in(dev_net(out), PF_INET, hooknum, skb);
> >> 
> >> I think this change is ok.
> >
> >In a >normal< system one usually does not use raw sockets. So if a root 
> >process do use raw socket, at least netfilter sends a notification and 
> >there's a chance that someone take notice it by checking the kernel logs.
> >[...]
> >But should we remove them due to nuisances on >test< systems?
> >
> >Rather make it a kernel compile option but do not remove.
> 
> This warning is in the conntrack calling code. Iff you play with
> raw sockets and do something wrong, the generic network code
> should barf IMHO, not nf_conntrack, and not [nf_conntrack_ipv4 only].

It is not about doing something wrong at using raw sockets - it's about 
using raw sockets.

I'm not quite convinced the generic network code should warn about raw 
sockets. I believe it belongs to the security-related subsystems - 
netfilter and (or) the security frameworks. [But as netfilter is much more 
widely used, the 'or' is just theoretical.)

But back to netfilter: this is more than strange. The logging is already 
removed from iptable_filter|mangle.c - and left in 
ip6table_filter|mangle.c. The only place in the IPv4 path where the 
checking happens is in nf_conntrack_l3proto_ipv4.c. IPv6 conntrack does
it as well, but uses another message text:

        if (skb->len < sizeof(struct ipv6hdr)) {
                if (net_ratelimit())
                        printk("ipv6_conntrack_local: packet too short\n");

[ISIC should check IPv6 too ;-).]

Best regards,
Jozsef
-
E-mail  : kadlec@...ckhole.kfki.hu, kadlec@...l.kfki.hu
PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt
Address : KFKI Research Institute for Particle and Nuclear Physics
          H-1525 Budapest 114, POB. 49, Hungary
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