Re: [PATCH net-next 08/11] tun: switch to new type of msg_control
From: Jason Wang
Date: Thu Sep 06 2018 - 23:35:26 EST
On 2018å09æ07æ 00:54, Michael S. Tsirkin wrote:
On Thu, Sep 06, 2018 at 12:05:23PM +0800, Jason Wang wrote:
This patch introduces to a new tun/tap specific msg_control:
#define TUN_MSG_UBUF 1
#define TUN_MSG_PTR 2
struct tun_msg_ctl {
int type;
void *ptr;
};
This allows us to pass different kinds of msg_control through
sendmsg(). The first supported type is ubuf (TUN_MSG_UBUF) which will
be used by the existed vhost_net zerocopy code. The second is XDP
buff, which allows vhost_net to pass XDP buff to TUN. This could be
used to implement accepting an array of XDP buffs from vhost_net in
the following patches.
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
At this point, do we want to just add a new sock opt for tap's
benefit? Seems cleaner than (ab)using sendmsg.
I think it won't be much difference, we still need a void pointer.
---
drivers/net/tap.c | 18 ++++++++++++------
drivers/net/tun.c | 6 +++++-
drivers/vhost/net.c | 7 +++++--
include/linux/if_tun.h | 7 +++++++
4 files changed, 29 insertions(+), 9 deletions(-)
diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index f0f7cd977667..7996ed7cbf18 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -619,7 +619,7 @@ static inline struct sk_buff *tap_alloc_skb(struct sock *sk, size_t prepad,
#define TAP_RESERVE HH_DATA_OFF(ETH_HLEN)
/* Get packet from user space buffer */
-static ssize_t tap_get_user(struct tap_queue *q, struct msghdr *m,
+static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
struct iov_iter *from, int noblock)
{
int good_linear = SKB_MAX_HEAD(TAP_RESERVE);
@@ -663,7 +663,7 @@ static ssize_t tap_get_user(struct tap_queue *q, struct msghdr *m,
if (unlikely(len < ETH_HLEN))
goto err;
- if (m && m->msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
+ if (msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
struct iov_iter i;
copylen = vnet_hdr.hdr_len ?
@@ -724,11 +724,11 @@ static ssize_t tap_get_user(struct tap_queue *q, struct msghdr *m,
tap = rcu_dereference(q->tap);
/* copy skb_ubuf_info for callback when skb has no error */
if (zerocopy) {
- skb_shinfo(skb)->destructor_arg = m->msg_control;
+ skb_shinfo(skb)->destructor_arg = msg_control;
skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
- } else if (m && m->msg_control) {
- struct ubuf_info *uarg = m->msg_control;
+ } else if (msg_control) {
+ struct ubuf_info *uarg = msg_control;
uarg->callback(uarg, false);
}
@@ -1150,7 +1150,13 @@ static int tap_sendmsg(struct socket *sock, struct msghdr *m,
size_t total_len)
{
struct tap_queue *q = container_of(sock, struct tap_queue, sock);
- return tap_get_user(q, m, &m->msg_iter, m->msg_flags & MSG_DONTWAIT);
+ struct tun_msg_ctl *ctl = m->msg_control;
+
+ if (ctl && ctl->type != TUN_MSG_UBUF)
+ return -EINVAL;
+
+ return tap_get_user(q, ctl ? ctl->ptr : NULL, &m->msg_iter,
+ m->msg_flags & MSG_DONTWAIT);
}
static int tap_recvmsg(struct socket *sock, struct msghdr *m,
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index ff1cbf3ebd50..c839a4bdcbd9 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2429,11 +2429,15 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
int ret;
struct tun_file *tfile = container_of(sock, struct tun_file, socket);
struct tun_struct *tun = tun_get(tfile);
+ struct tun_msg_ctl *ctl = m->msg_control;
if (!tun)
return -EBADFD;
- ret = tun_get_user(tun, tfile, m->msg_control, &m->msg_iter,
+ if (ctl && ctl->type != TUN_MSG_UBUF)
+ return -EINVAL;
+
+ ret = tun_get_user(tun, tfile, ctl ? ctl->ptr : NULL, &m->msg_iter,
m->msg_flags & MSG_DONTWAIT,
m->msg_flags & MSG_MORE);
tun_put(tun);
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 4e656f89cb22..fb01ce6d981c 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -620,6 +620,7 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
.msg_controllen = 0,
.msg_flags = MSG_DONTWAIT,
};
+ struct tun_msg_ctl ctl;
size_t len, total_len = 0;
int err;
struct vhost_net_ubuf_ref *uninitialized_var(ubufs);
@@ -664,8 +665,10 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
ubuf->ctx = nvq->ubufs;
ubuf->desc = nvq->upend_idx;
refcount_set(&ubuf->refcnt, 1);
- msg.msg_control = ubuf;
- msg.msg_controllen = sizeof(ubuf);
+ msg.msg_control = &ctl;
+ ctl.type = TUN_MSG_UBUF;
+ ctl.ptr = ubuf;
+ msg.msg_controllen = sizeof(ctl);
ubufs = nvq->ubufs;
atomic_inc(&ubufs->refcount);
nvq->upend_idx = (nvq->upend_idx + 1) % UIO_MAXIOV;
diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h
index 3d2996dc7d85..ba46dced1f38 100644
--- a/include/linux/if_tun.h
+++ b/include/linux/if_tun.h
@@ -19,6 +19,13 @@
#define TUN_XDP_FLAG 0x1UL
+#define TUN_MSG_UBUF 1
+#define TUN_MSG_PTR 2
Looks like TUN_MSG_PTR should be pushed out to a follow-up patch?
Ok.
+struct tun_msg_ctl {
+ int type;
+ void *ptr;
+};
+
type actually includes a size. Why not two short fields then?
Yes, this sounds better.
Thanks
#if defined(CONFIG_TUN) || defined(CONFIG_TUN_MODULE)
struct socket *tun_get_socket(struct file *);
struct ptr_ring *tun_get_tx_ring(struct file *file);
--
2.17.1