netdev - Re: [PATCH] tcp: make sysctl_tcp

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Date:	Sun, 6 Jan 2013 02:18:49 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Stephen Hemminger <shemminger@...tta.com>, netdev@...r.kernel.org,
	eric.dumazet@...il.com, davem@...emloft.net
Subject: Re: [PATCH] tcp: make sysctl_tcp_ecn namespace aware

On Sat, Jan 05, 2013 at 08:05:08PM +0100, Hannes Frederic Sowa wrote:
> On Sat, Jan 05, 2013 at 11:00:05AM -0800, Stephen Hemminger wrote:
> > Rather than passing sysctl_tcp_ecn around as a parameter, I think it
> > would be clearer and more efficient to make the ECN functions namespace
> > aware.
> > 
> > Instead of:
> > > @@ -728,7 +728,8 @@ struct tcp_skb_cb {
> > >   * notifications, we disable TCP ECN negociation.
> > >   */
> > >  static inline void
> > > -TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb)
> > > +TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb,
> > > +		int sysctl_tcp_ecn)
> > >  {
> > >  	const struct tcphdr *th = tcp_hdr(skb);
> > >  
> > 
> > @@ -731,8 +730,9 @@ static inline void
> >  TCP_ECN_create_request(struct request_sock *req, const struct sk_buff *skb)
> >  {
> >         const struct tcphdr *th = tcp_hdr(skb);
> > -
> > -       if (sysctl_tcp_ecn && th->ece && th->cwr &&
> > +       
> > +       if (sock_net(req->sk)->ipv4.sysctl_tcp_ecn && 
> > +           th->ece && th->cwr &&
> >             INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield))
> >                 inet_rsk(req)->ecn_ok = 1;
> 
> Having a quick look, I think req->sk is not initialized at that moment, but
> I'll verify later.

I just verified that req->sk is indeed not initialized at that point. I
had a kernel panic on the first syn packet. So I would propose to keep
the patch as it is.

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