From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH] netlink: enable skb header refcounting before sending first broadcast Date: Mon, 13 Jul 2015 10:05:42 +0200 Message-ID: <1436774742.9402.3.camel@edumazet-glaptop2.roam.corp.google.com> References: <20150710115141.12980.88829.stgit@buzz> <20150713072352.GA8485@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Konstantin Khlebnikov , netdev@vger.kernel.org, "David S. Miller" , Eric Dumazet To: Herbert Xu Return-path: Received: from mail-wi0-f180.google.com ([209.85.212.180]:35210 "EHLO mail-wi0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751292AbbGMIFr (ORCPT ); Mon, 13 Jul 2015 04:05:47 -0400 Received: by wiga1 with SMTP id a1so61487952wig.0 for ; Mon, 13 Jul 2015 01:05:46 -0700 (PDT) In-Reply-To: <20150713072352.GA8485@gondor.apana.org.au> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2015-07-13 at 15:23 +0800, Herbert Xu wrote: > The real issue here is that the recv path no longer handles shared > skbs. So either we need to fix the recv path to not touch skbs > without cloning them, or we need to get rid of the use of shared > skbs in netlink. > > In fact it looks I introduced the bug way back in > > commit a59322be07c964e916d15be3df473fb7ba20c41e > Author: Herbert Xu > Date: Wed Dec 5 01:53:40 2007 -0800 > > [UDP]: Only increment counter on first peek/recv > > I will try to mend this error :) > > Cheers, Herbert, UDP peek support is very buggy anyway, because of deferred checksums __skb_checksum_complete() will happily manipulate csum, ip_summed, csum_complete_sw & csum_valid Ideally, peek should never touch skb (but skb->users)