bpf: make programs see skb->data == L2 for ingress and egress
eBPF programs attached to ingress and egress qdiscs see inconsistent skb->data.
For ingress L2 header is already pulled, whereas for egress it's present.
This is known to program writers which are currently forced to use
BPF_LL_OFF workaround.
Since programs don't change skb internal pointers it is safe to do
pull/push right around invocation of the program and earlier taps and
later pt->func() will not be affected.
Multiple taps via packet_rcv(), tpacket_rcv() are doing the same trick
around run_filter/BPF_PROG_RUN even if skb_shared.
This fix finally allows programs to use optimized LD_ABS/IND instructions
without BPF_LL_OFF for higher performance.
tc ingress + cls_bpf + samples/bpf/tcbpf1_kern.o
w/o JIT w/JIT
before 20.5 23.6 Mpps
after 21.8 26.6 Mpps
Old programs with BPF_LL_OFF will still work as-is.
We can now undo most of the earlier workaround commit:
a166151cbe33 ("bpf: fix bpf helpers to use skb->mac_header relative offsets")
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c
index 91bd9c1..c79ecfd 100644
--- a/net/sched/cls_bpf.c
+++ b/net/sched/cls_bpf.c
@@ -64,6 +64,11 @@
{
struct cls_bpf_head *head = rcu_dereference_bh(tp->root);
struct cls_bpf_prog *prog;
+#ifdef CONFIG_NET_CLS_ACT
+ bool at_ingress = G_TC_AT(skb->tc_verd) & AT_INGRESS;
+#else
+ bool at_ingress = false;
+#endif
int ret = -1;
if (unlikely(!skb_mac_header_was_set(skb)))
@@ -72,7 +77,16 @@
/* Needed here for accessing maps. */
rcu_read_lock();
list_for_each_entry_rcu(prog, &head->plist, link) {
- int filter_res = BPF_PROG_RUN(prog->filter, skb);
+ int filter_res;
+
+ if (at_ingress) {
+ /* It is safe to push/pull even if skb_shared() */
+ __skb_push(skb, skb->mac_len);
+ filter_res = BPF_PROG_RUN(prog->filter, skb);
+ __skb_pull(skb, skb->mac_len);
+ } else {
+ filter_res = BPF_PROG_RUN(prog->filter, skb);
+ }
if (filter_res == 0)
continue;