linux-kernel - Re: When does Linux drop UDP packets?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20090605192933.GH2014@woodchuck>
Date:	Fri, 5 Jun 2009 20:29:34 +0100
From:	Alexander Clouter <alex@...riz.org.uk>
To:	david@...g.hm
Cc:	linux-kernel@...r.kernel.org, sefi@...-f-i.de
Subject: Re: When does Linux drop UDP packets?

Hi,

* david@...g.hm <david@...g.hm> [2009-06-05 12:15:27-0700]:
> 
> On Fri, 5 Jun 2009, Alexander Clouter wrote:
> 
> > * david@...g.hm <david@...g.hm> [2009-06-04 16:19:56-0700]:
> > > 
> > > On Thu, 4 Jun 2009, Alexander Clouter wrote:
> > > >
> > > > It's dead easy to transmit and receive multicast traffic, broadcasting
> > > > network traffic is so 1980's :)
> > > 
> > > there is only a difference between multicast and broadcast traffic if you
> > > are spanning subnets.
> > > 
> > Well yes and no.  Broadcast traffic is *always* handled by the kernel as
> > only the kernel can tell if it is interested in it or not.  With
> > multicast the NIC is configured to only pass particular
> > Ethernet multicast packets up to the kernel.
> > 
> > By using broadcast traffic the load (okay, hardly a big problem
> > now-a-days) hits *all* the workstations on the subnet, with multicast,
> > only those interested in the traffic receive it.
> 
> true, but only for some NICs, and even those tend to have a fairly small  
> number of slots for the filters. past these limits the OS handles it all  
> just like broadcasts.
> 
I *think* only the early ones have a naff non-hashing based to filter 
multicast flows, could be wrong though.

Either way, as a packet pusher by day, I dream of the venduh's 
discovering that multicast can be used for device discovery rather than 
expecting everything to be on the same subnet :-/

In this day and age, using broadcast to do a job is just plain lazy and 
braindead.

Cheers

-- 
Alexander Clouter
.sigmonster says: Misuse may cause suffocation.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/