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Message-ID: <4AA8FCD9.3040600@gmail.com>
Date: Thu, 10 Sep 2009 15:19:21 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
CC: David Miller <davem@...emloft.net>, m.s.tsirkin@...il.com,
netdev@...r.kernel.org, herbert@...dor.apana.org.au
Subject: Re: [PATCH RFC] tun: export underlying socket
Michael S. Tsirkin a écrit :
> Tun device looks similar to a packet socket
> in that both pass complete frames from/to userspace.
>
> This patch fills in enough fields in the socket underlying tun driver
> to support sendmsg/recvmsg operations, and exports access to this socket
> to modules.
>
> This way, code using raw sockets to inject packets
> into a physical device, can support injecting
> packets into host network stack almost without modification.
>
> First user of this interface will be vhost virtualization
> accelerator.
>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
>
> This patch is on top of net-next master.
> An alternative approach would be to add an ioctl to tun, to export the
> underlying socket to userspace: a uniform way to work with a network
> device and the host stack might be useful there, as well.
> Kernel users could then do sockfd_lookup to get the socket.
> I decided against it for now as it requires more code.
> Please comment.
>
> drivers/net/tun.c | 78 +++++++++++++++++++++++++++++++++++++++++++----
> include/linux/if_tun.h | 14 ++++++++
> 2 files changed, 85 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 589a44a..76f5faa 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -151,6 +151,7 @@ static int tun_attach(struct tun_struct *tun, struct file *file)
> err = 0;
> tfile->tun = tun;
> tun->tfile = tfile;
> + tun->socket.file = file;
> dev_hold(tun->dev);
> sock_hold(tun->socket.sk);
> atomic_inc(&tfile->count);
> @@ -165,6 +166,7 @@ static void __tun_detach(struct tun_struct *tun)
> /* Detach from net device */
> netif_tx_lock_bh(tun->dev);
> tun->tfile = NULL;
> + tun->socket.file = NULL;
> netif_tx_unlock_bh(tun->dev);
>
> /* Drop read queue */
> @@ -750,7 +752,7 @@ static __inline__ ssize_t tun_put_user(struct tun_struct *tun,
> len = min_t(int, skb->len, len);
>
> skb_copy_datagram_const_iovec(skb, 0, iv, total, len);
> - total += len;
> + total += skb->len;
Why are you changing this ? This is very strange that read() can return
a bigger length than what was asked by user...
>
> tun->dev->stats.tx_packets++;
> tun->dev->stats.tx_bytes += len;
> @@ -758,12 +760,10 @@ static __inline__ ssize_t tun_put_user(struct tun_struct *tun,
> return total;
> }
>
> -static ssize_t tun_chr_aio_read(struct kiocb *iocb, const struct iovec *iv,
> - unsigned long count, loff_t pos)
> +static ssize_t tun_do_read(struct tun_struct *tun,
> + struct kiocb *iocb, const struct iovec *iv,
> + unsigned long count, int noblock)
> {
> - struct file *file = iocb->ki_filp;
> - struct tun_file *tfile = file->private_data;
> - struct tun_struct *tun = __tun_get(tfile);
> DECLARE_WAITQUEUE(wait, current);
> struct sk_buff *skb;
> ssize_t len, ret = 0;
> @@ -785,7 +785,7 @@ static ssize_t tun_chr_aio_read(struct kiocb *iocb, const struct iovec *iv,
>
> /* Read frames from the queue */
> if (!(skb=skb_dequeue(&tun->socket.sk->sk_receive_queue))) {
> - if (file->f_flags & O_NONBLOCK) {
> + if (noblock) {
> ret = -EAGAIN;
> break;
> }
> @@ -813,6 +813,21 @@ static ssize_t tun_chr_aio_read(struct kiocb *iocb, const struct iovec *iv,
> remove_wait_queue(&tun->socket.wait, &wait);
>
> out:
> + return ret;
> +}
> +
> +static ssize_t tun_chr_aio_read(struct kiocb *iocb, const struct iovec *iv,
> + unsigned long count, loff_t pos)
> +{
> + struct file *file = iocb->ki_filp;
> + struct tun_file *tfile = file->private_data;
> + struct tun_struct *tun = __tun_get(tfile);
> + ssize_t ret;
> +
> + if (!tun)
> + return -EBADFD;
> + ret = tun_do_read(tun, iocb, iv, count, file->f_flags & O_NONBLOCK);
> + ret = min_t(ssize_t, ret, count);
> tun_put(tun);
> return ret;
> }
> @@ -865,6 +880,37 @@ static void tun_sock_destruct(struct sock *sk)
> free_netdev(container_of(sk, struct tun_sock, sk)->tun->dev);
> }
>
> +static int tun_sendmsg(struct kiocb *iocb, struct socket *sock,
> + struct msghdr *m, size_t total_len)
> +{
> + struct tun_struct *tun = container_of(sock, struct tun_struct, socket);
> + return tun_get_user(tun, m->msg_iov, total_len,
> + m->msg_flags & MSG_DONTWAIT);
> +}
> +
> +static int tun_recvmsg(struct kiocb *iocb, struct socket *sock,
> + struct msghdr *m, size_t total_len,
> + int flags)
> +{
> + struct tun_struct *tun = container_of(sock, struct tun_struct, socket);
> + int ret;
> + if (flags & ~(MSG_DONTWAIT|MSG_TRUNC))
> + return -EINVAL;
> + ret = tun_do_read(tun, iocb, m->msg_iov, total_len,
> + flags & MSG_DONTWAIT);
> + if (ret > total_len) {
> + m->msg_flags |= MSG_TRUNC;
> + ret = flags & MSG_TRUNC ? ret : total_len;
> + }
> + return ret;
> +}
> +
> +/* Ops structure to mimic raw sockets with tun */
> +static const struct proto_ops tun_socket_ops = {
> + .sendmsg = tun_sendmsg,
> + .recvmsg = tun_recvmsg,
> +};
> +
> static struct proto tun_proto = {
> .name = "tun",
> .owner = THIS_MODULE,
> @@ -982,6 +1028,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
> goto err_free_dev;
>
> init_waitqueue_head(&tun->socket.wait);
> + tun->socket.ops = &tun_socket_ops;
> sock_init_data(&tun->socket, sk);
> sk->sk_write_space = tun_sock_write_space;
> sk->sk_sndbuf = INT_MAX;
> @@ -1483,6 +1530,23 @@ static void tun_cleanup(void)
> rtnl_link_unregister(&tun_link_ops);
> }
>
> +/* Get an underlying socket object from tun file. Returns error unless file is
> + * attached to a device. The returned object works like a packet socket, it
> + * can be used for sock_sendmsg/sock_recvmsg. The caller is responsible for
> + * holding a reference to the file for as long as the socket is in use. */
> +struct socket *tun_get_socket(struct file *file)
> +{
> + struct tun_struct *tun;
> + if (file->f_op != &tun_fops)
> + return ERR_PTR(-EINVAL);
> + tun = tun_get(file);
> + if (!tun)
> + return ERR_PTR(-EBADFD);
> + tun_put(tun);
> + return &tun->socket;
> +}
> +EXPORT_SYMBOL_GPL(tun_get_socket);
> +
> module_init(tun_init);
> module_exit(tun_cleanup);
> MODULE_DESCRIPTION(DRV_DESCRIPTION);
> diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h
> index 3f5fd52..404abe0 100644
> --- a/include/linux/if_tun.h
> +++ b/include/linux/if_tun.h
> @@ -86,4 +86,18 @@ struct tun_filter {
> __u8 addr[0][ETH_ALEN];
> };
>
> +#ifdef __KERNEL__
> +#if defined(CONFIG_TUN) || defined(CONFIG_TUN_MODULE)
> +struct socket *tun_get_socket(struct file *);
> +#else
> +#include <linux/err.h>
> +#include <linux/errno.h>
> +struct file;
> +struct socket;
> +static inline struct socket *tun_get_socket(struct file *f)
> +{
> + return ERR_PTR(-EINVAL);
> +}
> +#endif /* CONFIG_TUN */
> +#endif /* __KERNEL__ */
> #endif /* __IF_TUN_H */
--
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