Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

Daniel Borkmann says:

====================
bpf 2022-07-08

We've added 3 non-merge commits during the last 2 day(s) which contain
a total of 7 files changed, 40 insertions(+), 24 deletions(-).

The main changes are:

1) Fix cBPF splat triggered by skb not having a mac header, from Eric Dumazet.

2) Fix spurious packet loss in generic XDP when pushing packets out (note
   that native XDP is not affected by the issue), from Johan Almbladh.

3) Fix bpf_dynptr_{read,write}() helper signatures with flag argument before
   its set in stone as UAPI, from Joanne Koong.

* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf:
  bpf: Add flags arg to bpf_dynptr_read and bpf_dynptr_write APIs
  bpf: Make sure mac_header was set before using it
  xdp: Fix spurious packet loss in generic XDP TX path
====================

Link: https://lore.kernel.org/r/20220708213418.19626-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 8e6f22961206..30a1603a7225 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4863,7 +4863,10 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
 }
 
 /* When doing generic XDP we have to bypass the qdisc layer and the
- * network taps in order to match in-driver-XDP behavior.
+ * network taps in order to match in-driver-XDP behavior. This also means
+ * that XDP packets are able to starve other packets going through a qdisc,
+ * and DDOS attacks will be more effective. In-driver-XDP use dedicated TX
+ * queues, so they do not have this starvation issue.
  */
 void generic_xdp_tx(struct sk_buff *skb, struct bpf_prog *xdp_prog)
 {
@@ -4875,7 +4878,7 @@ void generic_xdp_tx(struct sk_buff *skb, struct bpf_prog *xdp_prog)
 	txq = netdev_core_pick_tx(dev, skb, NULL);
 	cpu = smp_processor_id();
 	HARD_TX_LOCK(dev, txq, cpu);
-	if (!netif_xmit_stopped(txq)) {
+	if (!netif_xmit_frozen_or_drv_stopped(txq)) {
 		rc = netdev_start_xmit(skb, dev, txq, 0);
 		if (dev_xmit_complete(rc))
 			free_skb = false;
@@ -4883,6 +4886,7 @@ void generic_xdp_tx(struct sk_buff *skb, struct bpf_prog *xdp_prog)
 	HARD_TX_UNLOCK(dev, txq);
 	if (free_skb) {
 		trace_xdp_exception(dev, xdp_prog, XDP_TX);
+		dev_core_stats_tx_dropped_inc(dev);
 		kfree_skb(skb);
 	}
 }