tun: experimental zero copy tx support
Let vhost-net utilize zero copy tx when used with tun. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Michael S. Tsirkin
David S. Miller
parent
dcc0fb782b
commit
0690899b4d
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@ -100,6 +100,8 @@ do { \
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} while (0)
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#endif
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#define GOODCOPY_LEN 128
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#define FLT_EXACT_COUNT 8
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struct tap_filter {
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unsigned int count; /* Number of addrs. Zero means disabled */
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@ -604,19 +606,100 @@ static struct sk_buff *tun_alloc_skb(struct tun_struct *tun,
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return skb;
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}
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/* set skb frags from iovec, this can move to core network code for reuse */
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static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
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int offset, size_t count)
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{
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int len = iov_length(from, count) - offset;
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int copy = skb_headlen(skb);
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int size, offset1 = 0;
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int i = 0;
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/* Skip over from offset */
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while (count && (offset >= from->iov_len)) {
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offset -= from->iov_len;
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++from;
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--count;
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}
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/* copy up to skb headlen */
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while (count && (copy > 0)) {
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size = min_t(unsigned int, copy, from->iov_len - offset);
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if (copy_from_user(skb->data + offset1, from->iov_base + offset,
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size))
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return -EFAULT;
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if (copy > size) {
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++from;
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--count;
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offset = 0;
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} else
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offset += size;
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copy -= size;
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offset1 += size;
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}
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if (len == offset1)
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return 0;
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while (count--) {
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struct page *page[MAX_SKB_FRAGS];
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int num_pages;
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unsigned long base;
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unsigned long truesize;
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len = from->iov_len - offset;
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if (!len) {
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offset = 0;
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++from;
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continue;
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}
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base = (unsigned long)from->iov_base + offset;
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size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT;
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if (i + size > MAX_SKB_FRAGS)
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return -EMSGSIZE;
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num_pages = get_user_pages_fast(base, size, 0, &page[i]);
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if (num_pages != size) {
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for (i = 0; i < num_pages; i++)
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put_page(page[i]);
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return -EFAULT;
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}
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truesize = size * PAGE_SIZE;
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skb->data_len += len;
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skb->len += len;
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skb->truesize += truesize;
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atomic_add(truesize, &skb->sk->sk_wmem_alloc);
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while (len) {
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int off = base & ~PAGE_MASK;
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int size = min_t(int, len, PAGE_SIZE - off);
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__skb_fill_page_desc(skb, i, page[i], off, size);
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skb_shinfo(skb)->nr_frags++;
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/* increase sk_wmem_alloc */
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base += size;
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len -= size;
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i++;
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}
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offset = 0;
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++from;
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}
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return 0;
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}
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/* Get packet from user space buffer */
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static ssize_t tun_get_user(struct tun_struct *tun,
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const struct iovec *iv, size_t count,
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int noblock)
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static ssize_t tun_get_user(struct tun_struct *tun, void *msg_control,
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const struct iovec *iv, size_t total_len,
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size_t count, int noblock)
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{
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struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };
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struct sk_buff *skb;
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size_t len = count, align = NET_SKB_PAD;
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size_t len = total_len, align = NET_SKB_PAD;
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struct virtio_net_hdr gso = { 0 };
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int offset = 0;
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int copylen;
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bool zerocopy = false;
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int err;
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if (!(tun->flags & TUN_NO_PI)) {
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if ((len -= sizeof(pi)) > count)
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if ((len -= sizeof(pi)) > total_len)
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return -EINVAL;
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if (memcpy_fromiovecend((void *)&pi, iv, 0, sizeof(pi)))
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@ -625,7 +708,7 @@ static ssize_t tun_get_user(struct tun_struct *tun,
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}
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if (tun->flags & TUN_VNET_HDR) {
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if ((len -= tun->vnet_hdr_sz) > count)
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if ((len -= tun->vnet_hdr_sz) > total_len)
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return -EINVAL;
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if (memcpy_fromiovecend((void *)&gso, iv, offset, sizeof(gso)))
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@ -647,14 +730,46 @@ static ssize_t tun_get_user(struct tun_struct *tun,
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return -EINVAL;
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}
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skb = tun_alloc_skb(tun, align, len, gso.hdr_len, noblock);
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if (msg_control)
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zerocopy = true;
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if (zerocopy) {
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/* Userspace may produce vectors with count greater than
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* MAX_SKB_FRAGS, so we need to linearize parts of the skb
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* to let the rest of data to be fit in the frags.
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*/
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if (count > MAX_SKB_FRAGS) {
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copylen = iov_length(iv, count - MAX_SKB_FRAGS);
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if (copylen < offset)
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copylen = 0;
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else
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copylen -= offset;
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} else
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copylen = 0;
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/* There are 256 bytes to be copied in skb, so there is enough
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* room for skb expand head in case it is used.
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* The rest of the buffer is mapped from userspace.
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*/
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if (copylen < gso.hdr_len)
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copylen = gso.hdr_len;
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if (!copylen)
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copylen = GOODCOPY_LEN;
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} else
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copylen = len;
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skb = tun_alloc_skb(tun, align, copylen, gso.hdr_len, noblock);
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if (IS_ERR(skb)) {
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if (PTR_ERR(skb) != -EAGAIN)
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tun->dev->stats.rx_dropped++;
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return PTR_ERR(skb);
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}
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if (skb_copy_datagram_from_iovec(skb, 0, iv, offset, len)) {
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if (zerocopy)
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err = zerocopy_sg_from_iovec(skb, iv, offset, count);
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else
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err = skb_copy_datagram_from_iovec(skb, 0, iv, offset, len);
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if (err) {
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tun->dev->stats.rx_dropped++;
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kfree_skb(skb);
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return -EFAULT;
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@ -728,12 +843,18 @@ static ssize_t tun_get_user(struct tun_struct *tun,
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skb_shinfo(skb)->gso_segs = 0;
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}
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/* copy skb_ubuf_info for callback when skb has no error */
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if (zerocopy) {
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skb_shinfo(skb)->destructor_arg = msg_control;
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skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
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}
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netif_rx_ni(skb);
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tun->dev->stats.rx_packets++;
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tun->dev->stats.rx_bytes += len;
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return count;
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return total_len;
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}
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static ssize_t tun_chr_aio_write(struct kiocb *iocb, const struct iovec *iv,
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@ -748,7 +869,7 @@ static ssize_t tun_chr_aio_write(struct kiocb *iocb, const struct iovec *iv,
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tun_debug(KERN_INFO, tun, "tun_chr_write %ld\n", count);
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result = tun_get_user(tun, iv, iov_length(iv, count),
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result = tun_get_user(tun, NULL, iv, iov_length(iv, count), count,
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file->f_flags & O_NONBLOCK);
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tun_put(tun);
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@ -962,8 +1083,8 @@ static int tun_sendmsg(struct kiocb *iocb, struct socket *sock,
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struct msghdr *m, size_t total_len)
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{
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struct tun_struct *tun = container_of(sock, struct tun_struct, socket);
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return tun_get_user(tun, m->msg_iov, total_len,
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m->msg_flags & MSG_DONTWAIT);
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return tun_get_user(tun, m->msg_control, m->msg_iov, total_len,
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m->msg_iovlen, m->msg_flags & MSG_DONTWAIT);
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}
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static int tun_recvmsg(struct kiocb *iocb, struct socket *sock,
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@ -1133,6 +1254,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
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sock_init_data(&tun->socket, sk);
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sk->sk_write_space = tun_sock_write_space;
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sk->sk_sndbuf = INT_MAX;
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sock_set_flag(sk, SOCK_ZEROCOPY);
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tun_sk(sk)->tun = tun;
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