netdev - Re: [PATCH] udp: Introduce special NULL pointers for hlist termination

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Date:	Fri, 31 Oct 2008 15:37:50 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Corey Minyard <minyard@....org>, David Miller <davem@...emloft.net>
CC:	Stephen Hemminger <shemminger@...tta.com>,
	paulmck@...ux.vnet.ibm.com, benny+usenet@...rsen.dk,
	netdev@...r.kernel.org,
	Christoph Lameter <cl@...ux-foundation.org>,
	a.p.zijlstra@...llo.nl, johnpol@....mipt.ru,
	Christian Bell <christian@...i.com>,
	Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [PATCH] udp: Introduce special NULL pointers for hlist termination

Corey Minyard a écrit :
  
> 
> It is annoying that it doesn't help the performance for multicast.  
> However, I think the current patch will solve the DOS issue for 
> multicast, since it switches to a normal spinlock and has a per-list lock.

About multicast, it should be possible to do something about it, if it happens
to be an issue.

That is, do a lockless lookup and accumulate matching sockets ptr in a table

(incrementing their refcount if not zero, checking key, adding in a local stack).

If lookup must be restarted, forget all accumulated sockets (sock_put(ptrs))
   goto begin;

Then, send the (cloned) packet to all accumulated sockets, and
 sock_put() them to release the refcount.



Well, looking at current implementation, I found that udp_v4_mcast_next()
doesnt take into account the 'struct net *net', so we have a bug here...

udp_v6_mcast_next() is buggy too (or at least its caller is)

David, please find a patch against net-2.6

Thanks

[PATCH] udp: multicast packets need to check namespace

Current UDP multicast delivery is not namespace aware.


Signed-off-by: Eric Dumazet <dada1@...mosbay.com>
---
 net/ipv4/udp.c |   14 ++++++++------
 net/ipv6/udp.c |    8 ++++----
 2 files changed, 12 insertions(+), 10 deletions(-)

View attachment "udp_multi.patch" of type "text/plain" (3014 bytes)