netdev - Re: [PATCH net-next 3/3] vxlan: virtual extensible lan

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Message-ID: <20120924141133.3c97e9de@nehalam.linuxnetplumber.net>
Date:	Mon, 24 Sep 2012 14:11:33 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Chris Wright <chrisw@...hat.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 3/3] vxlan: virtual extensible lan

On Mon, 24 Sep 2012 13:58:22 -0700
Chris Wright <chrisw@...hat.com> wrote:

> * Stephen Hemminger (shemminger@...tta.com) wrote:
> > This is an implementation of Virtual eXtensible Local Area Network
> > as described in draft RFC:
> >   http://tools.ietf.org/html/draft-mahalingam-dutt-dcops-vxlan-02
> > 
> > The driver integrates a Virtual Tunnel Endpoint (VTEP) functionality
> > that learns MAC to IP address mapping. 
> > 
> > This implementation has not been tested for Interoperation with
> > other equipment.
> 
> I'm working on doing some interop
> 
> > --- a/drivers/net/Kconfig	2012-09-24 10:56:57.080291529 -0700
> > +++ b/drivers/net/Kconfig	2012-09-24 11:08:02.865416523 -0700
> > @@ -149,6 +149,19 @@ config MACVTAP
> >  	  To compile this driver as a module, choose M here: the module
> >  	  will be called macvtap.
> >  
> > +config VXLAN
> > +       tristate "Virtual eXtensible Local Area Network (VXLAN)"
> > +       depends on EXPERIMENTAL
> > +       ---help---
> > +	  This allows one to create vxlan virtual interfaces that provide
> > +	  Layer 2 Networks over Layer 3 Networks. VXLAN is often used
> > +	  to tunnel virtual network infrastructure in virtualized environments.
> > +	  For more information see:
> > +	    http://tools.ietf.org/html/draft-mahalingam-dutt-dcops-vxlan-02
> > +
> > +	  To compile this driver as a module, choose M here: the module
> > +	  will be called macvlan.
>                          ^^^^^^^
> Cut 'n paste error, s/macvlan/vxlan/
> 
> > +/* Add static entry (via netlink) */
> > +static int vxlan_fdb_add(struct ndmsg *ndm, struct nlattr *tb[],
> > +			 struct net_device *dev,
> > +			 const unsigned char *addr, u16 flags)
> > +{
> > +	struct vxlan_dev *vxlan = netdev_priv(dev);
> > +	__be32 ip;
> > +	int err;
> > +
> > +	if (tb[NDA_DST] == NULL)
> > +		return -EINVAL;
> > +
> > +	if (nla_len(tb[NDA_DST]) != sizeof(__be32))
> > +		return -EAFNOSUPPORT;
> > +
> > +	ip = nla_get_be32(tb[NDA_DST]);
> > +
> > +	spin_lock_bh(&vxlan->hash_lock);
> > +	err = vxlan_fdb_create(vxlan, addr, ip, VXLAN_FDB_PERM);
> 
> Any reason to force permanent when created from userspace?

Should use neighbour flag (NUD_PERMANENT) instead.

> 
> > +static bool vxlan_group_used(struct vxlan_net *vn,
> > +			     const struct vxlan_dev *this)
> > +{
> > +	const struct vxlan_dev *vxlan;
> > +	struct hlist_node *node;
> > +	unsigned h;
> > +
> > +	for (h = 0; h < VNI_HASH_SIZE; ++h)
> > +		hlist_for_each_entry(vxlan, node, &vn->vni_list[h], hlist) {
> 
> is walking this chain only protected with rtnl?

Yes. that should be enough, only used when creating new vxlan
to avoid joining same group twice.

> 
> > +/* Propogate ECN from outer IP header to tunneled packet */
> > +static inline void vxlan_ecn_decap(const struct iphdr *iph, struct sk_buff *skb)
> > +{
> > +	if (INET_ECN_is_ce(iph->tos)) {
> > +		if (skb->protocol == htons(ETH_P_IP))
> > +			IP_ECN_set_ce(ip_hdr(skb));
> > +		else if (skb->protocol == htons(ETH_P_IPV6))
> > +			IP6_ECN_set_ce(ipv6_hdr(skb));
> > +	}
> > +}
> <snip>
> > +/* Propogate ECN bits out */
> > +static inline u8 vxlan_ecn_encap(u8 tos,
> > +				 const struct iphdr *iph,
> > +				 const struct sk_buff *skb)
> > +{
> > +	u8 inner = vxlan_get_dsfield(iph, skb);
> > +
> > +	return INET_ECN_encapsulate(tos, inner);
> > +}
> 
> Goal is to be RFC 6040 compliant, and it looks like some edge cases aren't
> met, for example, should drop on decap when inner is not supporting ECN
> and outer has set CE.

The code was taken from existing GRE in Linux.
Looks like both VXLAN and GRE need to handle that.


> 
> <snip>
> > +/* Callback from net/ipv4/udp.c to receive packets */
> > +	/* Mark socket as an encapsulation socket. */
> > +	udp_sk(sk)->encap_type = UDP_ENCAP_L2TPINUDP;
> 
> I don't think we need this particular encap_type value, just != 0

Is there any value in defining new value?


> 
> > +	udp_sk(sk)->encap_rcv = vxlan_udp_encap_recv;
> > +	udp_encap_enable();

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