[PATCH net-next V2 09/11] tuntap: accept an array of XDP buffs through sendmsg()

Jason Wang
2018-09-12T03:17:07Z

This patch implement TUN_MSG_PTR msg_control type. This type allows
the caller to pass an array of XDP buffs to tuntap through ptr field
of the tun_msg_control. If an XDP program is attached, tuntap can run
XDP program directly. If not, tuntap will build skb and do a fast
receiving since part of the work has been done by vhost_net.

This will avoid lots of indirect calls thus improves the icache
utilization and allows to do XDP batched flushing when doing XDP
redirection.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/net/tun.c | 117 ++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 114 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 89779b58c7ca..2a2cd35853b7 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2426,22 +2426,133 @@ static void tun_sock_write_space(struct sock *sk)
kill_fasync(&tfile->fasync, SIGIO, POLL_OUT);
}

+static int tun_xdp_one(struct tun_struct *tun,
+ struct tun_file *tfile,
+ struct xdp_buff *xdp, int *flush)
+{
+ struct tun_xdp_hdr *hdr = xdp->data_hard_start;
+ struct virtio_net_hdr *gso = &hdr->gso;
+ struct tun_pcpu_stats *stats;
+ struct bpf_prog *xdp_prog;
+ struct sk_buff *skb = NULL;
+ u32 rxhash = 0, act;
+ int buflen = hdr->buflen;
+ int err = 0;
+ bool skb_xdp = false;
+
+ xdp_prog = rcu_dereference(tun->xdp_prog);
+ if (xdp_prog) {
+ if (gso->gso_type) {
+ skb_xdp = true;
+ goto build;
+ }
+ xdp_set_data_meta_invalid(xdp);
+ xdp->rxq = &tfile->xdp_rxq;
+
+ act = bpf_prog_run_xdp(xdp_prog, xdp);
+ err = tun_xdp_act(tun, xdp_prog, xdp, act);
+ if (err < 0) {
+ put_page(virt_to_head_page(xdp->data));
+ return err;
+ }
+
+ switch (err) {
+ case XDP_REDIRECT:
+ *flush = true;
+ /* fall through */
+ case XDP_TX:
+ return 0;
+ case XDP_PASS:
+ break;
+ default:
+ put_page(virt_to_head_page(xdp->data));
+ return 0;
+ }
+ }
+
+build:
+ skb = build_skb(xdp->data_hard_start, buflen);
+ if (!skb) {
+ err = -ENOMEM;
+ goto out;
+ }
+
+ skb_reserve(skb, xdp->data - xdp->data_hard_start);
+ skb_put(skb, xdp->data_end - xdp->data);
+
+ if (virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
+ this_cpu_inc(tun->pcpu_stats->rx_frame_errors);
+ kfree_skb(skb);
+ err = -EINVAL;
+ goto out;
+ }
+
+ skb->protocol = eth_type_trans(skb, tun->dev);
+ skb_reset_network_header(skb);
+ skb_probe_transport_header(skb, 0);
+
+ if (skb_xdp) {
+ err = do_xdp_generic(xdp_prog, skb);
+ if (err != XDP_PASS)
+ goto out;
+ }
+
+ if (!rcu_dereference(tun->steering_prog))
+ rxhash = __skb_get_hash_symmetric(skb);
+
+ netif_receive_skb(skb);
+
+ stats = get_cpu_ptr(tun->pcpu_stats);
+ u64_stats_update_begin(&stats->syncp);
+ stats->rx_packets++;
+ stats->rx_bytes += skb->len;
+ u64_stats_update_end(&stats->syncp);
+ put_cpu_ptr(stats);
+
+ if (rxhash)
+ tun_flow_update(tun, rxhash, tfile);
+
+out:
+ return err;
+}
+
static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
{
- int ret;
+ int ret, i;
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;
+ struct xdp_buff *xdp;

if (!tun)
return -EBADFD;

- if (ctl && ctl->type != TUN_MSG_UBUF)
- return -EINVAL;
+ if (ctl && (ctl->type == TUN_MSG_PTR)) {
+ int n = ctl->num;
+ int flush = 0;
+
+ local_bh_disable();
+ rcu_read_lock();
+
+ for (i = 0; i < n; i++) {
+ xdp = &((struct xdp_buff *)ctl->ptr)[i];
+ tun_xdp_one(tun, tfile, xdp, &flush);
+ }
+
+ if (flush)
+ xdp_do_flush_map();
+
+ rcu_read_unlock();
+ local_bh_enable();
+
+ ret = total_len;
+ goto out;
+ }

ret = tun_get_user(tun, tfile, ctl ? ctl->ptr : NULL, &m->msg_iter,
m->msg_flags & MSG_DONTWAIT,
m->msg_flags & MSG_MORE);
+out:
tun_put(tun);
return ret;
}
--
2.17.1