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
David S. Miller
parent
7c4974786f
commit
761876c857
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@ -73,6 +73,8 @@
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#include <linux/seq_file.h>
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#include <linux/uio.h>
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#include <linux/skb_array.h>
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#include <linux/bpf.h>
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#include <linux/bpf_trace.h>
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#include <linux/uaccess.h>
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@ -105,7 +107,8 @@ do { \
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} while (0)
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#endif
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#define TUN_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD)
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#define TUN_HEADROOM 256
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#define TUN_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD + TUN_HEADROOM)
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/* TUN device flags */
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@ -224,6 +227,7 @@ struct tun_struct {
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u32 flow_count;
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u32 rx_batched;
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struct tun_pcpu_stats __percpu *pcpu_stats;
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struct bpf_prog __rcu *xdp_prog;
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};
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#ifdef CONFIG_TUN_VNET_CROSS_LE
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@ -590,6 +594,7 @@ static void tun_detach(struct tun_file *tfile, bool clean)
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static void tun_detach_all(struct net_device *dev)
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{
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struct tun_struct *tun = netdev_priv(dev);
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struct bpf_prog *xdp_prog = rtnl_dereference(tun->xdp_prog);
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struct tun_file *tfile, *tmp;
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int i, n = tun->numqueues;
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@ -622,6 +627,9 @@ static void tun_detach_all(struct net_device *dev)
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}
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BUG_ON(tun->numdisabled != 0);
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if (xdp_prog)
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bpf_prog_put(xdp_prog);
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if (tun->flags & IFF_PERSIST)
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module_put(THIS_MODULE);
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}
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@ -1008,6 +1016,46 @@ tun_net_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
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stats->tx_dropped = tx_dropped;
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}
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static int tun_xdp_set(struct net_device *dev, struct bpf_prog *prog,
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struct netlink_ext_ack *extack)
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{
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struct tun_struct *tun = netdev_priv(dev);
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struct bpf_prog *old_prog;
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old_prog = rtnl_dereference(tun->xdp_prog);
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rcu_assign_pointer(tun->xdp_prog, prog);
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if (old_prog)
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bpf_prog_put(old_prog);
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return 0;
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}
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static u32 tun_xdp_query(struct net_device *dev)
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{
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struct tun_struct *tun = netdev_priv(dev);
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const struct bpf_prog *xdp_prog;
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xdp_prog = rtnl_dereference(tun->xdp_prog);
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if (xdp_prog)
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return xdp_prog->aux->id;
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return 0;
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}
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static int tun_xdp(struct net_device *dev, struct netdev_xdp *xdp)
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{
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switch (xdp->command) {
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case XDP_SETUP_PROG:
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return tun_xdp_set(dev, xdp->prog, xdp->extack);
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case XDP_QUERY_PROG:
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xdp->prog_id = tun_xdp_query(dev);
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xdp->prog_attached = !!xdp->prog_id;
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return 0;
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default:
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return -EINVAL;
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}
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}
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static const struct net_device_ops tun_netdev_ops = {
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.ndo_uninit = tun_net_uninit,
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.ndo_open = tun_net_open,
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@ -1038,6 +1086,7 @@ static const struct net_device_ops tap_netdev_ops = {
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.ndo_features_check = passthru_features_check,
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.ndo_set_rx_headroom = tun_set_headroom,
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.ndo_get_stats64 = tun_net_get_stats64,
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.ndo_xdp = tun_xdp,
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};
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static void tun_flow_init(struct tun_struct *tun)
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@ -1217,16 +1266,22 @@ static bool tun_can_build_skb(struct tun_struct *tun, struct tun_file *tfile,
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return true;
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}
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static struct sk_buff *tun_build_skb(struct tun_file *tfile,
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static struct sk_buff *tun_build_skb(struct tun_struct *tun,
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struct tun_file *tfile,
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struct iov_iter *from,
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int len)
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struct virtio_net_hdr *hdr,
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int len, int *generic_xdp)
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{
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struct page_frag *alloc_frag = &tfile->alloc_frag;
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struct sk_buff *skb;
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struct bpf_prog *xdp_prog;
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int buflen = SKB_DATA_ALIGN(len + TUN_RX_PAD) +
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SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
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unsigned int delta = 0;
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char *buf;
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size_t copied;
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bool xdp_xmit = false;
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int err;
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if (unlikely(!skb_page_frag_refill(buflen, alloc_frag, GFP_KERNEL)))
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return ERR_PTR(-ENOMEM);
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@ -1238,16 +1293,77 @@ static struct sk_buff *tun_build_skb(struct tun_file *tfile,
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if (copied != len)
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return ERR_PTR(-EFAULT);
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skb = build_skb(buf, buflen);
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if (!skb)
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return ERR_PTR(-ENOMEM);
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if (hdr->gso_type)
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*generic_xdp = 1;
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else
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*generic_xdp = 0;
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skb_reserve(skb, TUN_RX_PAD);
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skb_put(skb, len);
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rcu_read_lock();
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xdp_prog = rcu_dereference(tun->xdp_prog);
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if (xdp_prog && !*generic_xdp) {
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struct xdp_buff xdp;
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void *orig_data;
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u32 act;
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xdp.data_hard_start = buf;
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xdp.data = buf + TUN_RX_PAD;
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xdp.data_end = xdp.data + len;
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orig_data = xdp.data;
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act = bpf_prog_run_xdp(xdp_prog, &xdp);
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switch (act) {
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case XDP_REDIRECT:
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get_page(alloc_frag->page);
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alloc_frag->offset += buflen;
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err = xdp_do_redirect(tun->dev, &xdp, xdp_prog);
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if (err)
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goto err_redirect;
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return NULL;
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case XDP_TX:
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xdp_xmit = true;
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/* fall through */
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case XDP_PASS:
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delta = orig_data - xdp.data;
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break;
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default:
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bpf_warn_invalid_xdp_action(act);
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/* fall through */
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case XDP_ABORTED:
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trace_xdp_exception(tun->dev, xdp_prog, act);
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/* fall through */
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case XDP_DROP:
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goto err_xdp;
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}
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}
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skb = build_skb(buf, buflen);
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if (!skb) {
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rcu_read_unlock();
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return ERR_PTR(-ENOMEM);
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}
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skb_reserve(skb, TUN_RX_PAD - delta);
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skb_put(skb, len + delta);
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get_page(alloc_frag->page);
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alloc_frag->offset += buflen;
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if (xdp_xmit) {
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skb->dev = tun->dev;
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generic_xdp_tx(skb, xdp_prog);
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rcu_read_lock();
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return NULL;
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}
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rcu_read_unlock();
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return skb;
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err_redirect:
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put_page(alloc_frag->page);
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err_xdp:
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rcu_read_unlock();
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this_cpu_inc(tun->pcpu_stats->rx_dropped);
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return NULL;
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}
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/* Get packet from user space buffer */
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@ -1266,6 +1382,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
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bool zerocopy = false;
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int err;
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u32 rxhash;
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int generic_xdp = 1;
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if (!(tun->dev->flags & IFF_UP))
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return -EIO;
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@ -1324,11 +1441,13 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
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}
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if (tun_can_build_skb(tun, tfile, len, noblock, zerocopy)) {
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skb = tun_build_skb(tfile, from, len);
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skb = tun_build_skb(tun, tfile, from, &gso, len, &generic_xdp);
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if (IS_ERR(skb)) {
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this_cpu_inc(tun->pcpu_stats->rx_dropped);
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return PTR_ERR(skb);
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}
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if (!skb)
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return total_len;
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} else {
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if (!zerocopy) {
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copylen = len;
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@ -1402,6 +1521,22 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
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skb_reset_network_header(skb);
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skb_probe_transport_header(skb, 0);
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if (generic_xdp) {
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struct bpf_prog *xdp_prog;
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int ret;
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rcu_read_lock();
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xdp_prog = rcu_dereference(tun->xdp_prog);
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if (xdp_prog) {
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ret = do_xdp_generic(xdp_prog, skb);
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if (ret != XDP_PASS) {
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rcu_read_unlock();
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return total_len;
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}
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}
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rcu_read_unlock();
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}
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rxhash = __skb_get_hash_symmetric(skb);
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#ifndef CONFIG_4KSTACKS
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tun_rx_batched(tun, tfile, skb, more);
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