tap: XDP support

This patch tries to implement XDP for tun. The implementation was
split into two parts:

- fast path: small and no gso packet. We try to do XDP at page level
  before build_skb(). For XDP_TX, since creating/destroying queues
  were completely under control of userspace, it was implemented
  through generic XDP helper after skb has been built. This could be
  optimized in the future.
- slow path: big or gso packet. We try to do it after skb was created
  through generic XDP helpers.

Test were done through pktgen with small packets.

xdp1 test shows ~41.1% improvement:

Before: ~1.7Mpps
After:  ~2.3Mpps

xdp_redirect to ixgbe shows ~60% improvement:

Before: ~0.8Mpps
After:  ~1.38Mpps

Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Wang 2017-08-11 19:41:18 +08:00 committed by David S. Miller
parent 7c4974786f
commit 761876c857

View File

@ -73,6 +73,8 @@
#include <linux/seq_file.h>
#include <linux/uio.h>
#include <linux/skb_array.h>
#include <linux/bpf.h>
#include <linux/bpf_trace.h>
#include <linux/uaccess.h>
@ -105,7 +107,8 @@ do { \
} while (0)
#endif
#define TUN_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD)
#define TUN_HEADROOM 256
#define TUN_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD + TUN_HEADROOM)
/* TUN device flags */
@ -224,6 +227,7 @@ struct tun_struct {
u32 flow_count;
u32 rx_batched;
struct tun_pcpu_stats __percpu *pcpu_stats;
struct bpf_prog __rcu *xdp_prog;
};
#ifdef CONFIG_TUN_VNET_CROSS_LE
@ -590,6 +594,7 @@ static void tun_detach(struct tun_file *tfile, bool clean)
static void tun_detach_all(struct net_device *dev)
{
struct tun_struct *tun = netdev_priv(dev);
struct bpf_prog *xdp_prog = rtnl_dereference(tun->xdp_prog);
struct tun_file *tfile, *tmp;
int i, n = tun->numqueues;
@ -622,6 +627,9 @@ static void tun_detach_all(struct net_device *dev)
}
BUG_ON(tun->numdisabled != 0);
if (xdp_prog)
bpf_prog_put(xdp_prog);
if (tun->flags & IFF_PERSIST)
module_put(THIS_MODULE);
}
@ -1008,6 +1016,46 @@ tun_net_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
stats->tx_dropped = tx_dropped;
}
static int tun_xdp_set(struct net_device *dev, struct bpf_prog *prog,
struct netlink_ext_ack *extack)
{
struct tun_struct *tun = netdev_priv(dev);
struct bpf_prog *old_prog;
old_prog = rtnl_dereference(tun->xdp_prog);
rcu_assign_pointer(tun->xdp_prog, prog);
if (old_prog)
bpf_prog_put(old_prog);
return 0;
}
static u32 tun_xdp_query(struct net_device *dev)
{
struct tun_struct *tun = netdev_priv(dev);
const struct bpf_prog *xdp_prog;
xdp_prog = rtnl_dereference(tun->xdp_prog);
if (xdp_prog)
return xdp_prog->aux->id;
return 0;
}
static int tun_xdp(struct net_device *dev, struct netdev_xdp *xdp)
{
switch (xdp->command) {
case XDP_SETUP_PROG:
return tun_xdp_set(dev, xdp->prog, xdp->extack);
case XDP_QUERY_PROG:
xdp->prog_id = tun_xdp_query(dev);
xdp->prog_attached = !!xdp->prog_id;
return 0;
default:
return -EINVAL;
}
}
static const struct net_device_ops tun_netdev_ops = {
.ndo_uninit = tun_net_uninit,
.ndo_open = tun_net_open,
@ -1038,6 +1086,7 @@ static const struct net_device_ops tap_netdev_ops = {
.ndo_features_check = passthru_features_check,
.ndo_set_rx_headroom = tun_set_headroom,
.ndo_get_stats64 = tun_net_get_stats64,
.ndo_xdp = tun_xdp,
};
static void tun_flow_init(struct tun_struct *tun)
@ -1217,16 +1266,22 @@ static bool tun_can_build_skb(struct tun_struct *tun, struct tun_file *tfile,
return true;
}
static struct sk_buff *tun_build_skb(struct tun_file *tfile,
static struct sk_buff *tun_build_skb(struct tun_struct *tun,
struct tun_file *tfile,
struct iov_iter *from,
int len)
struct virtio_net_hdr *hdr,
int len, int *generic_xdp)
{
struct page_frag *alloc_frag = &tfile->alloc_frag;
struct sk_buff *skb;
struct bpf_prog *xdp_prog;
int buflen = SKB_DATA_ALIGN(len + TUN_RX_PAD) +
SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
unsigned int delta = 0;
char *buf;
size_t copied;
bool xdp_xmit = false;
int err;
if (unlikely(!skb_page_frag_refill(buflen, alloc_frag, GFP_KERNEL)))
return ERR_PTR(-ENOMEM);
@ -1238,16 +1293,77 @@ static struct sk_buff *tun_build_skb(struct tun_file *tfile,
if (copied != len)
return ERR_PTR(-EFAULT);
skb = build_skb(buf, buflen);
if (!skb)
return ERR_PTR(-ENOMEM);
if (hdr->gso_type)
*generic_xdp = 1;
else
*generic_xdp = 0;
skb_reserve(skb, TUN_RX_PAD);
skb_put(skb, len);
rcu_read_lock();
xdp_prog = rcu_dereference(tun->xdp_prog);
if (xdp_prog && !*generic_xdp) {
struct xdp_buff xdp;
void *orig_data;
u32 act;
xdp.data_hard_start = buf;
xdp.data = buf + TUN_RX_PAD;
xdp.data_end = xdp.data + len;
orig_data = xdp.data;
act = bpf_prog_run_xdp(xdp_prog, &xdp);
switch (act) {
case XDP_REDIRECT:
get_page(alloc_frag->page);
alloc_frag->offset += buflen;
err = xdp_do_redirect(tun->dev, &xdp, xdp_prog);
if (err)
goto err_redirect;
return NULL;
case XDP_TX:
xdp_xmit = true;
/* fall through */
case XDP_PASS:
delta = orig_data - xdp.data;
break;
default:
bpf_warn_invalid_xdp_action(act);
/* fall through */
case XDP_ABORTED:
trace_xdp_exception(tun->dev, xdp_prog, act);
/* fall through */
case XDP_DROP:
goto err_xdp;
}
}
skb = build_skb(buf, buflen);
if (!skb) {
rcu_read_unlock();
return ERR_PTR(-ENOMEM);
}
skb_reserve(skb, TUN_RX_PAD - delta);
skb_put(skb, len + delta);
get_page(alloc_frag->page);
alloc_frag->offset += buflen;
if (xdp_xmit) {
skb->dev = tun->dev;
generic_xdp_tx(skb, xdp_prog);
rcu_read_lock();
return NULL;
}
rcu_read_unlock();
return skb;
err_redirect:
put_page(alloc_frag->page);
err_xdp:
rcu_read_unlock();
this_cpu_inc(tun->pcpu_stats->rx_dropped);
return NULL;
}
/* Get packet from user space buffer */
@ -1266,6 +1382,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
bool zerocopy = false;
int err;
u32 rxhash;
int generic_xdp = 1;
if (!(tun->dev->flags & IFF_UP))
return -EIO;
@ -1324,11 +1441,13 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
}
if (tun_can_build_skb(tun, tfile, len, noblock, zerocopy)) {
skb = tun_build_skb(tfile, from, len);
skb = tun_build_skb(tun, tfile, from, &gso, len, &generic_xdp);
if (IS_ERR(skb)) {
this_cpu_inc(tun->pcpu_stats->rx_dropped);
return PTR_ERR(skb);
}
if (!skb)
return total_len;
} else {
if (!zerocopy) {
copylen = len;
@ -1402,6 +1521,22 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
skb_reset_network_header(skb);
skb_probe_transport_header(skb, 0);
if (generic_xdp) {
struct bpf_prog *xdp_prog;
int ret;
rcu_read_lock();
xdp_prog = rcu_dereference(tun->xdp_prog);
if (xdp_prog) {
ret = do_xdp_generic(xdp_prog, skb);
if (ret != XDP_PASS) {
rcu_read_unlock();
return total_len;
}
}
rcu_read_unlock();
}
rxhash = __skb_get_hash_symmetric(skb);
#ifndef CONFIG_4KSTACKS
tun_rx_batched(tun, tfile, skb, more);