Pavel Emelianov wrote:
Patrick McHardy wrote:
Pavel Emelianov wrote:
Veth stands for Virtual ETHernet. It is a simple tunnel driver
that works at the link layer and looks like a pair of ethernet
devices interconnected with each other.
Mainly it allows to communicate between network namespaces but
it can be used as is as well.
Eric recently sent a similar driver called etun. This
implementation uses another interface - the RTM_NRELINK
message introduced by Patric. The patch fits today netdev
tree with Patrick's patches.
The newlink callback is organized that way to make it easy
to create the peer device in the separate namespace when we
have them in kernel.
+struct veth_priv {
+ struct net_device *peer;
+ struct net_device *dev;
+ struct list_head list;
+ struct net_device_stats stats;
You can use dev->stats instead.
OK. Actually I planned to use percpu stats to reduce cacheline
trashing (Stephen has noticed it also). The reason I didn't do it
here is that the patch would look more complicated, but I wanted to
show and approve the netlink interface first.
+static int veth_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+ struct net_device *rcv = NULL;
+ struct veth_priv *priv, *rcv_priv;
+ int length;
+
+ skb_orphan(skb);
+
+ priv = netdev_priv(dev);
+ rcv = priv->peer;
+ rcv_priv = netdev_priv(rcv);
+
+ if (!(rcv->flags & IFF_UP))
+ goto outf;
+
+ skb->dev = rcv;
eth_type_trans already sets skb->dev.
Ok. Thanks.
+ skb->pkt_type = PACKET_HOST;
+ skb->protocol = eth_type_trans(skb, rcv);
+ if (dev->features & NETIF_F_NO_CSUM)
+ skb->ip_summed = rcv_priv->ip_summed;
+
+ dst_release(skb->dst);
+ skb->dst = NULL;
+
+ secpath_reset(skb);
+ nf_reset(skb);
Is skb->mark supposed to survive communication between different
namespaces?
I guess it must not. Thanks.
+static const struct nla_policy veth_policy[VETH_INFO_MAX] = {
+ [VETH_INFO_MAC] = { .type = NLA_BINARY, .len = ETH_ALEN },
+ [VETH_INFO_PEER] = { .type = NLA_STRING },
+ [VETH_INFO_PEER_MAC] = { .type = NLA_BINARY, .len = ETH_ALEN },
+};
The rtnl_link codes looks fine. I don't like the VETH_INFO_MAC attribute
very much though, we already have a generic device attribute for MAC
addresses. Of course that only allows you to supply one MAC address, so
I'm wondering what you think of allocating only a single device per
newlink operation and binding them in a seperate enslave operation?
I did this at the very first version, but Alexey showed me that this
would be wrong. Look. When we create the second device it must be in
the other namespace as it is useless to have them in one namespace.
But if we have the device in the other namespace the RTNL_NEWLINK
message from kernel would come into this namespace thus confusing ip
utility in the init namespace. Creating the device in the init ns and
moving it into the new one is rather a complex task.
Pavel,
moving the netdevice to another namespace is not a complex task. Eric
Biederman did it in its patchset ( cf. http://lxc.sf.net/network )
When the pair device is created, both extremeties are into the init
namespace and you can choose to which namespace to move one extremity.
When the network namespace dies, the netdev is moved back to the init
namespace.
That facilitate network device management.
Concerning netlink events, this is automatically generated when the
network device is moved through namespaces.
IMHO, we should have the network device movement between namespaces in
order to be able to move a physical network device too (eg. you have 4
NIC and you want to create 3 containers and assign 3 NIC to each of them)
But with such approach the creation looks really logical. We send a
packet to the kernel and have a single response about the new device
appearance. At the same time we have a RTNL_NEWLINK message arrived at
the destination namespace informing that a new device has appeared
there as well.
+enum {
+ VETH_INFO_UNSPEC,
+ VETH_INFO_MAC,
+ VETH_INFO_PEER,
+ VETH_INFO_PEER_MAC,
+
+ VETH_INFO_MAX
+};
Please follow the
#define VETH_INFO_MAX (__VETH_INFO_MAX - 1)
convention here.
Could you please clarify this point. I saw the lines
enum {
...
RTNL_NEWLINK
#define RTNL_NEWLINK RTNL_NEWLINK
...
}
and had my brains exploded imagining what this would mean :(
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