[RFC PATCH net-next 09/12] tuntap: split out XDP logic

Jason Wang
2018-05-21T09:05:33Z

This patch split out XDP logic into a single function. This make it to
be reused by XDP batching path in the following patch.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/net/tun.c | 85 +++++++++++++++++++++++++++++++++----------------------
1 file changed, 51 insertions(+), 34 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index ed04291..2560378 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1605,6 +1605,44 @@ static bool tun_can_build_skb(struct tun_struct *tun, struct tun_file *tfile,
return true;
}

+static u32 tun_do_xdp(struct tun_struct *tun,
+ struct tun_file *tfile,
+ struct bpf_prog *xdp_prog,
+ struct xdp_buff *xdp,
+ int *err)
+{
+ u32 act = bpf_prog_run_xdp(xdp_prog, xdp);
+
+ switch (act) {
+ case XDP_REDIRECT:
+ *err = xdp_do_redirect(tun->dev, xdp, xdp_prog);
+ xdp_do_flush_map();
+ if (*err)
+ break;
+ goto out;
+ case XDP_TX:
+ *err = tun_xdp_tx(tun->dev, xdp);
+ if (*err)
+ break;
+ tun_xdp_flush(tun->dev);
+ goto out;
+ case XDP_PASS:
+ goto out;
+ 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:
+ break;
+ }
+
+ put_page(virt_to_head_page(xdp->data_hard_start));
+out:
+ return act;
+}
+
static struct sk_buff *tun_build_skb(struct tun_struct *tun,
struct tun_file *tfile,
struct iov_iter *from,
@@ -1615,10 +1653,10 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
struct sk_buff *skb = NULL;
struct bpf_prog *xdp_prog;
int buflen = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
- unsigned int delta = 0;
char *buf;
size_t copied;
- int err, pad = TUN_RX_PAD;
+ int pad = TUN_RX_PAD;
+ int err = 0;

rcu_read_lock();
xdp_prog = rcu_dereference(tun->xdp_prog);
@@ -1655,9 +1693,8 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
preempt_disable();
rcu_read_lock();
xdp_prog = rcu_dereference(tun->xdp_prog);
- if (xdp_prog && !*skb_xdp) {
+ if (xdp_prog) {
struct xdp_buff xdp;
- void *orig_data;
u32 act;

xdp.data_hard_start = buf;
@@ -1665,34 +1702,14 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
xdp_set_data_meta_invalid(&xdp);
xdp.data_end = xdp.data + len;
xdp.rxq = &tfile->xdp_rxq;
- orig_data = xdp.data;
- act = bpf_prog_run_xdp(xdp_prog, &xdp);
-
- switch (act) {
- case XDP_REDIRECT:
- err = xdp_do_redirect(tun->dev, &xdp, xdp_prog);
- xdp_do_flush_map();
- if (err)
- goto err_xdp;
- goto out;
- case XDP_TX:
- if (tun_xdp_tx(tun->dev, &xdp))
- goto err_xdp;
- tun_xdp_flush(tun->dev);
- goto out;
- case XDP_PASS:
- delta = orig_data - xdp.data;
- len = xdp.data_end - 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:
+ act = tun_do_xdp(tun, tfile, xdp_prog, &xdp, &err);
+ if (err)
goto err_xdp;
- }
+ if (act != XDP_PASS)
+ goto out;
+
+ pad = xdp.data - xdp.data_hard_start;
+ len = xdp.data_end - xdp.data;
}
rcu_read_unlock();
preempt_enable();
@@ -1700,18 +1717,18 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
build:
skb = build_skb(buf, buflen);
if (!skb) {
+ put_page(alloc_frag->page);
skb = ERR_PTR(-ENOMEM);
goto out;
}

- skb_reserve(skb, pad - delta);
+ skb_reserve(skb, pad);
skb_put(skb, len);

return skb;

err_xdp:
- alloc_frag->offset -= buflen;
- put_page(alloc_frag->page);
+ this_cpu_inc(tun->pcpu_stats->rx_dropped);
out:
rcu_read_unlock();
preempt_enable();
--
2.7.4