Re: [PATCH V2 net-next 5/7] tun: support receiving skb through msg_control

[Jason Wang]

On 2017年03月30日 23:06, Michael S. Tsirkin wrote:

On Thu, Mar 30, 2017 at 03:22:28PM +0800, Jason Wang wrote:

This patch makes tun_recvmsg() can receive from skb from its caller
through msg_control. Vhost_net will be the first user.

Signed-off-by: Jason Wang

Do we need to bother with tun? I didn't realize one
can even use that with vhost. What would be the point of
all the virtio header stuff dealing with checksums etc?

Even if you see a use-case is it worth optimizing?




It's for tap in fact. I use "tun" just because we have already had a 
tap.c which is used by macvtap.


Thanks

Re: [PATCH V2 net-next 5/7] tun: support receiving skb through msg_control

[Jason Wang]

On 2017年03月30日 23:06, Michael S. Tsirkin wrote:

On Thu, Mar 30, 2017 at 03:22:28PM +0800, Jason Wang wrote:

This patch makes tun_recvmsg() can receive from skb from its caller
through msg_control. Vhost_net will be the first user.

Signed-off-by: Jason Wang

Do we need to bother with tun? I didn't realize one
can even use that with vhost. What would be the point of
all the virtio header stuff dealing with checksums etc?

Even if you see a use-case is it worth optimizing?




It's for tap in fact. I use "tun" just because we have already had a 
tap.c which is used by macvtap.


Thanks

Re: [PATCH V2 net-next 5/7] tun: support receiving skb through msg_control

[Michael S. Tsirkin]

On Thu, Mar 30, 2017 at 03:22:28PM +0800, Jason Wang wrote:
> This patch makes tun_recvmsg() can receive from skb from its caller
> through msg_control. Vhost_net will be the first user.
> 
> Signed-off-by: Jason Wang 

Do we need to bother with tun? I didn't realize one
can even use that with vhost. What would be the point of
all the virtio header stuff dealing with checksums etc?

Even if you see a use-case is it worth optimizing?


> ---
>  drivers/net/tun.c | 18 ++
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 70dd9ec..a82bced 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1498,9 +1498,8 @@ static struct sk_buff *tun_ring_recv(struct tun_file 
> *tfile, int noblock,
>  
>  static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
>  struct iov_iter *to,
> -int noblock)
> +int noblock, struct sk_buff *skb)
>  {
> - struct sk_buff *skb;
>   ssize_t ret;
>   int err;
>  
> @@ -1509,10 +1508,12 @@ static ssize_t tun_do_read(struct tun_struct *tun, 
> struct tun_file *tfile,
>   if (!iov_iter_count(to))
>   return 0;
>  
> - /* Read frames from ring */
> - skb = tun_ring_recv(tfile, noblock, );
> - if (!skb)
> - return err;
> + if (!skb) {
> + /* Read frames from ring */
> + skb = tun_ring_recv(tfile, noblock, );
> + if (!skb)
> + return err;
> + }
>  
>   ret = tun_put_user(tun, tfile, skb, to);
>   if (unlikely(ret < 0))
> @@ -1532,7 +1533,7 @@ static ssize_t tun_chr_read_iter(struct kiocb *iocb, 
> struct iov_iter *to)
>  
>   if (!tun)
>   return -EBADFD;
> - ret = tun_do_read(tun, tfile, to, file->f_flags & O_NONBLOCK);
> + ret = tun_do_read(tun, tfile, to, file->f_flags & O_NONBLOCK, NULL);
>   ret = min_t(ssize_t, ret, len);
>   if (ret > 0)
>   iocb->ki_pos = ret;
> @@ -1634,7 +1635,8 @@ static int tun_recvmsg(struct socket *sock, struct 
> msghdr *m, size_t total_len,
>SOL_PACKET, TUN_TX_TIMESTAMP);
>   goto out;
>   }
> - ret = tun_do_read(tun, tfile, >msg_iter, flags & MSG_DONTWAIT);
> + ret = tun_do_read(tun, tfile, >msg_iter, flags & MSG_DONTWAIT,
> +   m->msg_control);
>   if (ret > (ssize_t)total_len) {
>   m->msg_flags |= MSG_TRUNC;
>   ret = flags & MSG_TRUNC ? ret : total_len;
> -- 
> 2.7.4

Re: [PATCH V2 net-next 5/7] tun: support receiving skb through msg_control

[Michael S. Tsirkin]

On Thu, Mar 30, 2017 at 03:22:28PM +0800, Jason Wang wrote:
> This patch makes tun_recvmsg() can receive from skb from its caller
> through msg_control. Vhost_net will be the first user.
> 
> Signed-off-by: Jason Wang 

Do we need to bother with tun? I didn't realize one
can even use that with vhost. What would be the point of
all the virtio header stuff dealing with checksums etc?

Even if you see a use-case is it worth optimizing?


> ---
>  drivers/net/tun.c | 18 ++
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 70dd9ec..a82bced 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1498,9 +1498,8 @@ static struct sk_buff *tun_ring_recv(struct tun_file 
> *tfile, int noblock,
>  
>  static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
>  struct iov_iter *to,
> -int noblock)
> +int noblock, struct sk_buff *skb)
>  {
> - struct sk_buff *skb;
>   ssize_t ret;
>   int err;
>  
> @@ -1509,10 +1508,12 @@ static ssize_t tun_do_read(struct tun_struct *tun, 
> struct tun_file *tfile,
>   if (!iov_iter_count(to))
>   return 0;
>  
> - /* Read frames from ring */
> - skb = tun_ring_recv(tfile, noblock, );
> - if (!skb)
> - return err;
> + if (!skb) {
> + /* Read frames from ring */
> + skb = tun_ring_recv(tfile, noblock, );
> + if (!skb)
> + return err;
> + }
>  
>   ret = tun_put_user(tun, tfile, skb, to);
>   if (unlikely(ret < 0))
> @@ -1532,7 +1533,7 @@ static ssize_t tun_chr_read_iter(struct kiocb *iocb, 
> struct iov_iter *to)
>  
>   if (!tun)
>   return -EBADFD;
> - ret = tun_do_read(tun, tfile, to, file->f_flags & O_NONBLOCK);
> + ret = tun_do_read(tun, tfile, to, file->f_flags & O_NONBLOCK, NULL);
>   ret = min_t(ssize_t, ret, len);
>   if (ret > 0)
>   iocb->ki_pos = ret;
> @@ -1634,7 +1635,8 @@ static int tun_recvmsg(struct socket *sock, struct 
> msghdr *m, size_t total_len,
>SOL_PACKET, TUN_TX_TIMESTAMP);
>   goto out;
>   }
> - ret = tun_do_read(tun, tfile, >msg_iter, flags & MSG_DONTWAIT);
> + ret = tun_do_read(tun, tfile, >msg_iter, flags & MSG_DONTWAIT,
> +   m->msg_control);
>   if (ret > (ssize_t)total_len) {
>   m->msg_flags |= MSG_TRUNC;
>   ret = flags & MSG_TRUNC ? ret : total_len;
> -- 
> 2.7.4