Re: [RFC PATCH] ipvs: skb defrag for L7 helpers

[Hans Schillstrom <hans@schillstrom.com>]

On Monday, November 08, 2010 23:23:54 Simon Horman wrote:
> On Mon, Nov 08, 2010 at 11:48:37PM +0200, Julian Anastasov wrote:
> > 
> > 	Hello,
> > 
> > On Mon, 8 Nov 2010, Hans Schillstrom wrote:
> > 
> > >Hello
> > >I have been struggling with SIP for a while ....
> > >L7 helpers like sip needs skb defrag
> > >ex virtio only copies the first 128 byte into the skb (incl mac hdr)
> > >in that case Call-Id will never be found.
> > >
> > >There is a skb_find_text() that might be used insead of this, but it requires some changes in ip_vs_pe_sip.c
> > >
> > >Signed-off-by: Hans Schillstrom <hans.schillstrom@ericsson.com>
> > >
> > >diff --git a/net/netfilter/ipvs/ip_vs_pe.c b/net/netfilter/ipvs/ip_vs_pe.c
> > >index e99f920..c0ac69a 100644
> > >--- a/net/netfilter/ipvs/ip_vs_pe.c
> > >+++ b/net/netfilter/ipvs/ip_vs_pe.c
> > >@@ -76,6 +72,24 @@ struct ip_vs_pe *ip_vs_pe_getbyname(const char *name)
> > >	return pe;
> > >}
> > >
> > >+/* skb defrag for L7 helpers */
> > >+char *ip_vs_skb_defrag(struct sk_buff *skb, int offset, int len)
> > >+{
> > >+	char *p = kmalloc(skb->len, GFP_ATOMIC);
> > >+	if (!p)
> > >+		goto err;
> > >+	if (skb_copy_bits(skb, offset, p, len))
> > >+		goto err;
> > 
> > 	Such copy already exists: skb_linearize(). If you
> > are lucky it does not copy data. But for your case the
> > copy should happen. In ip_vs_ftp we even use skb_make_writable
> > because we change the payload.
> 
> Good point.
> 
> > 	May be ip_vs_sip_fill_param() should deliver the status
> > from skb_linearize (-ENOMEM) after the iph.protocol != IPPROTO_UDP
> > check. ip_vs_conn_fill_param_persist should return this
> > error to ip_vs_sched_persist. What we need is ip_vs_sched_persist
> > to have new argument 'int *ignored' just like ip_vs_schedule, so
> > that we can return *ignored = 1 for the case when
> > ip_vs_conn_fill_param_persist returns any kind of error.
> > Even on ip_vs_conn_new failure we should return *ignored = 1.
> > *ignored = 0 remains only for the case when no dest is
> > selected.
> 
> Agreed.
> 
> Somewhat off topic: the *ignored and *verdict parameters
> seem to be a horrible way to pass this information around.
> I think we can use ERR_PTR instead, though I'd have to
> write the patch to see if that is true or not. If its
> not perhaps we can have a small structure used as
> the return value of ip_vs_schedule() and pp->conn_schedule().
> 
> 	struct ip_vs_scheduler_status {
> 		ip_vs_conn *cp;
> 		int flag;
> 	}
> 
> However, I do wonder if the defrag change is stable material.
> If so, I'll hold off on any re-working ideas.

I have been runing it for two days now with SIP
and that seems to work.

I can send an update version tomorrow.
 It's time for a power nap now.

Regards 
Hans