Subject: Re: [net-next v4] vxlan: Notify drivers for listening UDP port changes

From: Joseph Gasparakis <[email-masked]>
Date: Fri, 6 Sep 2013 16:42:26 -0700 (PDT)

On Fri, 6 Sep 2013, Daniel Borkmann wrote:

> On 09/04/2013 11:13 AM, Jeff Kirsher wrote:
> > From: Joseph Gasparakis <[email-masked]>
> > 
> > This patch adds two more ndo ops: ndo_add_rx_vxlan_port() and
> > ndo_del_rx_vxlan_port().
> > 
> > Drivers can get notifications through the above functions about changes
> > of the UDP listening port of VXLAN. Also, when physical ports come up,
> > now they can call vxlan_get_rx_port() in order to obtain the port number(s)
> > of the existing VXLAN interface in case they already up before them.
> > 
> > This information about the listening UDP port would be used for VXLAN
> > related offloads.
> > 
> > A big thank you to John Fastabend ([email-masked]) for his
> > input and his suggestions on this patch set.
> > 
> > CC: John Fastabend <[email-masked]>
> > CC: Stephen Hemminger <[email-masked]>
> > Signed-off-by: Joseph Gasparakis <[email-masked]>
> > Signed-off-by: Jeff Kirsher <[email-masked]>
> > ---
> >   drivers/net/vxlan.c       | 68
> > ++++++++++++++++++++++++++++++++++++++++++++++-
> >   include/linux/netdevice.h | 19 +++++++++++++
> >   include/net/vxlan.h       |  1 +
> >   3 files changed, 87 insertions(+), 1 deletion(-)
> [...]
> > +/* Calls the ndo_add_vxlan_port of the caller in order to
> > + * supply the listening VXLAN udp ports.
> > + */
> > +void vxlan_get_rx_port(struct net_device *dev)
> > +{
> > +	struct vxlan_sock *vs;
> > +	struct net *net = dev_net(dev);
> > +	struct vxlan_net *vn = net_generic(net, vxlan_net_id);
> > +	sa_family_t sa_family;
> > +	u16 port;
> > +	int i;
> > +
> > +	if (!dev || !dev->netdev_ops || !dev->netdev_ops->ndo_add_vxlan_port)
> > +		return;
> 
> Here, either parts of this if statement are unnecessary, or in case they are
> necessary then vars 'net' and 'vn' should have been assigned after that I
> think
> as we would first get an offset and then dereference it before actually
> checking
> if dev is NULL.

That is correct, I started assuming dev will be a valid pointer, but then 
I thought I shouldn't trust the caller, so I ended up with this. In fact I 
have some upcoming sparse fixes too, so I will incorporate all this in one 
patch. For this particular comment I will be checking dev first and 
assigning net and vn after that.

> 
> > +	spin_lock(&vn->sock_lock);
> > +	for (i = 0; i < PORT_HASH_SIZE; ++i) {
> > +		hlist_for_each_entry_rcu(vs, vs_head(net, i), hlist) {
> > +			port = htons(inet_sk(vs->sock->sk)->inet_sport);
> > +			sa_family = vs->sock->sk->sk_family;
> > +			dev->netdev_ops->ndo_add_vxlan_port(dev, sa_family,
> > +							    port);
> > +		}
> > +	}
> > +	spin_unlock(&vn->sock_lock);
> > +}
> > +EXPORT_SYMBOL_GPL(vxlan_get_rx_port);
>