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Date: Fri, 4 May 2012 03:11:52 +0400
From: Basil Gor <basil.gor@...il.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>,
"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH v3 2/2] macvtap: restore vlan header on user read
On Thu, May 03, 2012 at 07:22:25PM +0400, Basil Gor wrote:
> On Thu, May 03, 2012 at 05:31:10PM +0300, Michael S. Tsirkin wrote:
> > On Thu, May 03, 2012 at 06:37:46AM -0700, Eric W. Biederman wrote:
> > > "Michael S. Tsirkin" <mst@...hat.com> writes:
> > >
> > > > On Wed, Apr 25, 2012 at 10:31:25PM -0700, Eric W. Biederman wrote:
> > > >> Basil Gor <basil.gor@...il.com> writes:
> > > >>
> > > >> > Vlan tag is restored during buffer transmit to a network device (bridge
> > > >> > port) in bridging code in case of tun/tap driver. In case of macvtap it
> > > >> > has to be done explicitly. Otherwise vlan_tci is ignored and user always
> > > >> > gets untagged packets.
> > > >>
> > > >> We could quibble about efficiencies but this looks good except for
> > > >> macvtap_recvmsg which isn't setting the auxdata for the vlan header.
> > > >>
> > > >> Eric
> > > >
> > > > Right. I'm guessing we need to support old userspace
> > > > so if there's auxdata, put vlan there but if not,
> > > > put the vlan in the packet like this patch does.
> > >
> > > This patch isn't horrible.
> > >
> > > Still why copy the skb when you can just split the copy to userspace
> > > into a couple of pieces?
> > >
> > > We don't need to change the skb and changing the skb looks like
> > > it is likely to confuse things and cause bugs because we are
> > > not working with a consistent model of how vlan information
> > > is encoded.
> > >
> > > Still something needs to happen and this works in more cases even if it
> > > isn't perfect.
> > >
> > > Eric
> >
> > Absolutely. And it's easier than I thought.
> > So we can do something like the below (warning: compiled only).
> > Basil - want to take a look?
>
> Sure, I'll give it a try.
> Thanks
>
> Basil Gor
>
> > My only concern if we put this logic in an out of way
> > driver like macvtap will people remember to update it?
> > Maybe better to update skb_copy_datagram_const_iovec which is in core?
> >
> >
> > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> >
> > diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> > index 0427c65..5a1724c 100644
> > --- a/drivers/net/macvtap.c
> > +++ b/drivers/net/macvtap.c
> > @@ -1,5 +1,6 @@
> > #include <linux/etherdevice.h>
> > #include <linux/if_macvlan.h>
> > +#include <linux/if_vlan.h>
> > #include <linux/interrupt.h>
> > #include <linux/nsproxy.h>
> > #include <linux/compat.h>
> > @@ -759,6 +760,7 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
> > struct macvlan_dev *vlan;
> > int ret;
> > int vnet_hdr_len = 0;
> > + int vlan_offset = 0;
> >
> > if (q->flags & IFF_VNET_HDR) {
> > struct virtio_net_hdr vnet_hdr;
> > @@ -776,8 +778,29 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
> >
> > len = min_t(int, skb->len, len);
skb->len + VLAN_HLEN if vlan tag present
> >
> > - ret = skb_copy_datagram_const_iovec(skb, 0, iv, vnet_hdr_len, len);
> > + if (vlan_tx_tag_present(skb)) {
> > + struct {
> > + __be16 h_vlan_proto;
> > + __be16 h_vlan_TCI;
> > + } veth;
> > + veth.h_vlan_proto = htons(ETH_P_8021Q);
> > + veth.h_vlan_TCI = vlan_tx_tag_get(skb);
htons(vlan_tx_tag_get(skb))
> > +
> > + vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
> > + ret = skb_copy_datagram_const_iovec(skb, 0, iv, vnet_hdr_len,
> > + vlan_offset);
do we need to count how much we copy carefully?
> > + if (ret)
> > + goto done;
> > + ret = memcpy_toiovecend(iv, (unsigned char *)&veth, vlan_offset,
> > + sizeof veth);
offset has to be vnet_hdr_len + vlan_offset
> > + if (ret)
> > + goto done;
> > + vlan_offset += sizeof veth;
offset to use in next copy: vnet_hdr_len + vlan_offset + sizeof(veth)
> > + }
> > + ret = skb_copy_datagram_const_iovec(skb, vlan_offset, iv, vnet_hdr_len,
> > + len);
> >
> > +done:
> > rcu_read_lock_bh();
> > vlan = rcu_dereference_bh(q->vlan);
> > if (vlan)
Below is a bit reworked version I've tested.
---
drivers/net/macvtap.c | 43 ++++++++++++++++++++++++++++++++++++++-----
1 files changed, 38 insertions(+), 5 deletions(-)
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 0427c65..cb8fd50 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -1,5 +1,6 @@
#include <linux/etherdevice.h>
#include <linux/if_macvlan.h>
+#include <linux/if_vlan.h>
#include <linux/interrupt.h>
#include <linux/nsproxy.h>
#include <linux/compat.h>
@@ -759,6 +760,8 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
struct macvlan_dev *vlan;
int ret;
int vnet_hdr_len = 0;
+ int vlan_offset = 0;
+ int copied;
if (q->flags & IFF_VNET_HDR) {
struct virtio_net_hdr vnet_hdr;
@@ -773,18 +776,48 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
if (memcpy_toiovecend(iv, (void *)&vnet_hdr, 0, sizeof(vnet_hdr)))
return -EFAULT;
}
+ copied = vnet_hdr_len;
+
+ if (!vlan_tx_tag_present(skb))
+ len = min_t(int, skb->len, len);
+ else {
+ int copy;
+ struct {
+ __be16 h_vlan_proto;
+ __be16 h_vlan_TCI;
+ } veth;
+ veth.h_vlan_proto = htons(ETH_P_8021Q);
+ veth.h_vlan_TCI = htons(vlan_tx_tag_get(skb));
+
+ vlan_offset = offsetof(struct vlan_ethhdr, h_vlan_proto);
+ len = min_t(int, skb->len + VLAN_HLEN, len);
+
+ copy = min_t(int, vlan_offset, len);
+ ret = skb_copy_datagram_const_iovec(skb, 0, iv, copied, copy);
+ len -= copy;
+ copied += copy;
+ if (ret || !len)
+ goto done;
+
+ copy = min_t(int, sizeof(veth), len);
+ ret = memcpy_toiovecend(iv, (void *)&veth, copied, copy);
+ len -= copy;
+ copied += copy;
+ if (ret || !len)
+ goto done;
+ }
- len = min_t(int, skb->len, len);
-
- ret = skb_copy_datagram_const_iovec(skb, 0, iv, vnet_hdr_len, len);
+ ret = skb_copy_datagram_const_iovec(skb, vlan_offset, iv, copied, len);
+ copied += len;
+done:
rcu_read_lock_bh();
vlan = rcu_dereference_bh(q->vlan);
if (vlan)
- macvlan_count_rx(vlan, len, ret == 0, 0);
+ macvlan_count_rx(vlan, copied - vnet_hdr_len, ret == 0, 0);
rcu_read_unlock_bh();
- return ret ? ret : (len + vnet_hdr_len);
+ return ret ? ret : copied;
}
static ssize_t macvtap_do_read(struct macvtap_queue *q, struct kiocb *iocb,
--
1.7.6.5
--
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