This patch modifies tun to allow a vringfd to specify the send
buffer. The user does a write to push out packets from the buffer.
Again, more thought needs to be put into the possible races with ring
registration.
Again we use the 'struct virtio_net_hdr' to allow userspace to send
GSO packets. In this case, it can hint how much to copy, and the
other pages will be made into skb fragments.
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
diff -r 8270b5fdf03f drivers/net/tun.c
--- a/drivers/net/tun.c Sat Apr 05 22:49:10 2008 +1100
+++ b/drivers/net/tun.c Sat Apr 05 22:51:10 2008 +1100
@@ -101,7 +101,7 @@ struct tun_struct {
u32 chr_filter[2];
u32 net_filter[2];
- struct vring_info *inring;
+ struct vring_info *inring, *outring;
#ifdef TUN_DEBUG
int debug;
@@ -258,6 +258,162 @@ static void tun_net_init(struct net_devi
}
}
+/* We don't consolidate consecutive iovecs, so huge iovecs can break here.
+ * Users will learn not to do that. */
+static int get_user_skb_frags(const struct iovec *iv, size_t len,
+ struct skb_frag_struct *f)
+{
+ unsigned int i, j, num_pg = 0;
+ int err;
+ struct page *pages[MAX_SKB_FRAGS];
+
+ down_read(¤t->mm->mmap_sem);
+ while (len) {
+ int n, npages;
+ unsigned long base, len;
+ base = (unsigned long)iv->iov_base;
+ len = (unsigned long)iv->iov_len;
+
+ if (len == 0) {
+ iv++;
+ continue;
+ }
+
+ /* How many pages will this take? */
+ npages = 1 + (base + len - 1)/PAGE_SIZE - base/PAGE_SIZE;
+ if (unlikely(num_pg + npages > MAX_SKB_FRAGS)) {
+ err = -ENOSPC;
+ goto fail;
+ }
+ n = get_user_pages(current, current->mm, base, npages,
+ 0, 0, pages, NULL);
+ if (unlikely(n < 0)) {
+ err = n;
+ goto fail;
+ }
+
+ /* Transfer pages to the frag array */
+ for (j = 0; j < n; j++) {
+ f[num_pg].page = pages[j];
+ if (j == 0) {
+ f[num_pg].page_offset = offset_in_page(base);
+ f[num_pg].size = min(len, PAGE_SIZE -
+ f[num_pg].page_offset);
+ } else {
+ f[num_pg].page_offset = 0;
+ f[num_pg].size = min(len, PAGE_SIZE);
+ }
+ len -= f[num_pg].size;
+ base += f[num_pg].size;
+ num_pg++;
+ }
+
+ if (unlikely(n != npages)) {
+ err = -EFAULT;
+ goto fail;
+ }
+ }
+ up_read(¤t->mm->mmap_sem);
+ return num_pg;
+
+fail:
+ for (i = 0; i < num_pg; i++)
+ put_page(f[i].page);
+ up_read(¤t->mm->mmap_sem);
+ return err;
+}
+
+/* Get packet from user space buffer. copylen is a hint as to how
+ * much to copy (rest is pinned). */
+static struct sk_buff *get_user_skb(struct tun_struct *tun, struct iovec *iv,
+ size_t copylen, size_t len, int extra)
+{
+ struct tun_pi pi = { 0, __constant_htons(ETH_P_IP) };
+ struct sk_buff *skb;
+ size_t align = 0;
+ int err;
+
+ /* You can't have user fragments without room for destruction info. */
+ BUG_ON(!extra && copylen != len);
+
+ if (!(tun->flags & TUN_NO_PI)) {
+ if (len < sizeof(pi)) {
+ err = -EINVAL;
+ goto fail;
+ }
+ len -= sizeof(pi);
+
+ if (memcpy_fromiovec((void *)&pi, iv, sizeof(pi))) {
+ err = -EFAULT;
+ goto fail;
+ }
+ if (copylen > len)
+ copylen = len;
+ }
+
+ if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV) {
+ align = NET_IP_ALIGN;
+ if (unlikely(copylen < ETH_HLEN)) {
+ if (len < ETH_HLEN) {
+ err = -EINVAL;
+ goto fail;
+ }
+ copylen = ETH_HLEN;
+ }
+ }
+
+ /* We don't need a destructor if we don't have fragments. */
+ if (extra && copylen == len)
+ extra = 0;
+
+ if (!(skb = __alloc_skb(copylen + align, GFP_KERNEL, 0, extra, -1))) {
+ err = -ENOMEM;
+ goto fail;
+ }
+
+ if (align)
+ skb_reserve(skb, align);
+ if (memcpy_fromiovec(skb_put(skb, copylen), iv, copylen)) {
+ err = -EFAULT;
+ goto free_skb;
+ }
+
+ switch (tun->flags & TUN_TYPE_MASK) {
+ case TUN_TUN_DEV:
+ skb_reset_mac_header(skb);
+ skb->protocol = pi.proto;
+ skb->dev = tun->dev;
+ break;
+ case TUN_TAP_DEV:
+ skb->protocol = eth_type_trans(skb, tun->dev);
+ break;
+ };
+
+ if (tun->flags & TUN_NOCHECKSUM)
+ skb->ip_summed = CHECKSUM_UNNECESSARY;
+
+ /* Anything left gets put into frags. */
+ if (extra) {
+ struct skb_shared_info *sinfo = skb_shinfo(skb);
+ int err = get_user_skb_frags(iv, len - copylen, sinfo->frags);
+ if (err < 0)
+ goto free_skb;
+ sinfo->nr_frags = err;
+ }
+ tun->dev->last_rx = jiffies;
+
+ tun->dev->stats.rx_packets++;
+ tun->dev->stats.rx_bytes += len;
+
+ return skb;
+
+free_skb:
+ kfree_skb(skb);
+fail:
+ tun->dev->stats.rx_dropped++;
+ return ERR_PTR(err);
+}
+
#ifdef CONFIG_VRINGFD
static void unset_recv(void *_tun)
{
@@ -362,8 +518,118 @@ static int set_recv_vring(struct tun_str
tun->inring = vi;
return 0;
}
+
+static void unset_xmit(void *_tun)
+{
+ struct tun_struct *tun = _tun;
+
+ tun->outring = NULL;
+}
+
+struct skb_shinfo_tun {
+ struct tun_struct *tun;
+
+ unsigned int id;
+ unsigned int len;
+};
+
+/* We are done with this skb: put it in the used pile. */
+static void skb_finished(struct skb_shared_info *sinfo)
+{
+ struct skb_shinfo_tun *sht = (void *)(sinfo + 1);
+
+ /* FIXME: Race prevention */
+ vring_used_buffer_atomic(sht->tun->outring, sht->id, sht->len);
+ vring_wake(sht->tun->outring);
+
+ /* Release device. */
+ dev_put(sht->tun->dev);
+}
+
+static int xmit_packets(void *_tun)
+{
+ struct tun_struct *tun = _tun;
+ struct iovec iov[1+MAX_SKB_FRAGS];
+ unsigned int iovnum = ARRAY_SIZE(iov);
+ int id, err, wake = 0;
+ unsigned long len;
+
+ while ((id = vring_get_buffer(tun->outring, NULL, NULL, NULL,
+ iov, &iovnum, &len)) > 0) {
+ struct virtio_net_hdr h;
+ struct sk_buff *skb;
+ struct skb_shared_info *shinfo;
+ struct skb_shinfo_tun *sht;
+
+ if (unlikely(len < sizeof(h)))
+ return -EINVAL;
+
+ err = memcpy_fromiovec((void *)&h, iov, sizeof(h));
+ if (unlikely(err))
+ return -EFAULT;
+
+ len -= sizeof(h);
+ if (h.hdr_len > len)
+ return -EINVAL;
+
+ /* Without GSO, we copy entire packet. */
+ if (h.gso_type == VIRTIO_NET_HDR_GSO_NONE)
+ h.hdr_len = len;
+
+ skb = get_user_skb(tun, iov, h.hdr_len, len, sizeof(*sht));
+ if (IS_ERR(skb))
+ return PTR_ERR(skb);
+
+ if ((h.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
+ !skb_partial_csum_set(skb, h.csum_start, h.csum_offset)) {
+ kfree_skb(skb);
+ return -EINVAL;
+ }
+
+ shinfo = skb_shinfo(skb);
+ /* If it has fragments, set up destructor for later. */
+ if (shinfo->nr_frags) {
+ sht = (void *)(shinfo + 1);
+ shinfo->destructor = skb_finished;
+ sht->id = id;
+ sht->len = sizeof(h) + skb->len;
+ } else {
+ vring_used_buffer(tun->outring, id, sizeof(h)+skb->len);
+ wake = 1;
+ }
+ netif_rx_ni(skb);
+ }
+
+ if (wake)
+ vring_wake(tun->outring);
+
+ /* 0 or error. */
+ return id;
+}
+
+static struct vring_ops xmitops = {
+ .destroy = unset_xmit,
+ .push = xmit_packets,
+};
+
+static int set_xmit_vring(struct tun_struct *tun, int fd)
+{
+ struct vring_info *vi;
+
+ /* FIXME: Racy. */
+ vi = vring_attach(fd, &xmitops, tun, false);
+ if (IS_ERR(vi))
+ return PTR_ERR(vi);
+ tun->outring = vi;
+ return 0;
+}
#else /* ... !CONFIG_VRINGFD */
static int set_recv_vring(struct tun_struct *tun, int fd)
+{
+ return -ENOTTY;
+}
+
+static int set_xmit_vring(struct tun_struct *tun, int fd)
{
return -ENOTTY;
}
@@ -390,74 +656,26 @@ static unsigned int tun_chr_poll(struct
return mask;
}
-/* Get packet from user space buffer */
-static __inline__ ssize_t tun_get_user(struct tun_struct *tun, struct iovec *iv, size_t count)
-{
- struct tun_pi pi = { 0, __constant_htons(ETH_P_IP) };
- struct sk_buff *skb;
- size_t len = count, align = 0;
-
- if (!(tun->flags & TUN_NO_PI)) {
- if ((len -= sizeof(pi)) > count)
- return -EINVAL;
-
- if(memcpy_fromiovec((void *)&pi, iv, sizeof(pi)))
- return -EFAULT;
- }
-
- if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV) {
- align = NET_IP_ALIGN;
- if (unlikely(len < ETH_HLEN))
- return -EINVAL;
- }
-
- if (!(skb = alloc_skb(len + align, GFP_KERNEL))) {
- tun->dev->stats.rx_dropped++;
- return -ENOMEM;
- }
-
- if (align)
- skb_reserve(skb, align);
- if (memcpy_fromiovec(skb_put(skb, len), iv, len)) {
- tun->dev->stats.rx_dropped++;
- kfree_skb(skb);
- return -EFAULT;
- }
-
- switch (tun->flags & TUN_TYPE_MASK) {
- case TUN_TUN_DEV:
- skb_reset_mac_header(skb);
- skb->protocol = pi.proto;
- skb->dev = tun->dev;
- break;
- case TUN_TAP_DEV:
- skb->protocol = eth_type_trans(skb, tun->dev);
- break;
- };
-
- if (tun->flags & TUN_NOCHECKSUM)
- skb->ip_summed = CHECKSUM_UNNECESSARY;
-
- netif_rx_ni(skb);
- tun->dev->last_rx = jiffies;
-
- tun->dev->stats.rx_packets++;
- tun->dev->stats.rx_bytes += len;
-
- return count;
-}
-
static ssize_t tun_chr_aio_write(struct kiocb *iocb, const struct iovec *iv,
unsigned long count, loff_t pos)
{
struct tun_struct *tun = iocb->ki_filp->private_data;
+ size_t len;
+ struct sk_buff *skb;
if (!tun)
return -EBADFD;
DBG(KERN_INFO "%s: tun_chr_write %ld\n", tun->dev->name, count);
- return tun_get_user(tun, (struct iovec *) iv, iov_length(iv, count));
+ len = iov_length(iv, count);
+
+ skb = get_user_skb(tun, (struct iovec *)iv, len, len, 0);
+ if (IS_ERR(skb))
+ return PTR_ERR(skb);
+
+ netif_rx_ni(skb);
+ return len;
}
/* Put packet to the user space buffer */
@@ -795,7 +1013,10 @@ static int tun_chr_ioctl(struct inode *i
#endif
case TUNSETRECVVRING:
- return set_recv_vring(tun, arg);
+ return set_recv_vring(tun, arg);
+
+ case TUNSETXMITVRING:
+ return set_xmit_vring(tun, arg);
case SIOCGIFFLAGS:
ifr.ifr_flags = tun->if_flags;
diff -r 8270b5fdf03f include/linux/if_tun.h
--- a/include/linux/if_tun.h Sat Apr 05 22:49:10 2008 +1100
+++ b/include/linux/if_tun.h Sat Apr 05 22:51:10 2008 +1100
@@ -43,6 +43,7 @@
#define TUNSETLINK _IOW('T', 205, int)
#define TUNSETGROUP _IOW('T', 206, int)
#define TUNSETRECVVRING _IOW('T', 207, int)
+#define TUNSETXMITVRING _IOW('T', 208, int)
/* TUNSETIFF ifr flags */
#define IFF_TUN 0x0001
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