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authorAlexei Starovoitov <ast@plumgrid.com>2015-06-04 10:11:53 -0700
committerDavid S. Miller <davem@davemloft.net>2015-06-07 02:01:33 -0700
commit3431205e03977aaf32bce6d4b16fb8244b510056 (patch)
tree0d9405acb8ac34a6bc5ad93a9b9ae674c4d3879e /net
parent98da81a426a76c351f3c2854d5bc31f17bba3194 (diff)
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>
Diffstat (limited to 'net')
-rw-r--r--net/core/filter.c26
-rw-r--r--net/sched/act_bpf.c9
-rw-r--r--net/sched/cls_bpf.c16
3 files changed, 26 insertions, 25 deletions
diff --git a/net/core/filter.c b/net/core/filter.c
index 09b2062eb5b8..36a69e33d76b 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1238,21 +1238,6 @@ int sk_attach_bpf(u32 ufd, struct sock *sk)
return 0;
}
-/**
- * bpf_skb_clone_not_writable - is the header of a clone not writable
- * @skb: buffer to check
- * @len: length up to which to write, can be negative
- *
- * Returns true if modifying the header part of the cloned buffer
- * does require the data to be copied. I.e. this version works with
- * negative lengths needed for eBPF case!
- */
-static bool bpf_skb_clone_unwritable(const struct sk_buff *skb, int len)
-{
- return skb_header_cloned(skb) ||
- (int) skb_headroom(skb) + len > skb->hdr_len;
-}
-
#define BPF_RECOMPUTE_CSUM(flags) ((flags) & 1)
static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
@@ -1275,9 +1260,8 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
if (unlikely((u32) offset > 0xffff || len > sizeof(buf)))
return -EFAULT;
- offset -= skb->data - skb_mac_header(skb);
if (unlikely(skb_cloned(skb) &&
- bpf_skb_clone_unwritable(skb, offset + len)))
+ !skb_clone_writable(skb, offset + len)))
return -EFAULT;
ptr = skb_header_pointer(skb, offset, len, buf);
@@ -1321,9 +1305,8 @@ static u64 bpf_l3_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
if (unlikely((u32) offset > 0xffff))
return -EFAULT;
- offset -= skb->data - skb_mac_header(skb);
if (unlikely(skb_cloned(skb) &&
- bpf_skb_clone_unwritable(skb, offset + sizeof(sum))))
+ !skb_clone_writable(skb, offset + sizeof(sum))))
return -EFAULT;
ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum);
@@ -1369,9 +1352,8 @@ static u64 bpf_l4_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
if (unlikely((u32) offset > 0xffff))
return -EFAULT;
- offset -= skb->data - skb_mac_header(skb);
if (unlikely(skb_cloned(skb) &&
- bpf_skb_clone_unwritable(skb, offset + sizeof(sum))))
+ !skb_clone_writable(skb, offset + sizeof(sum))))
return -EFAULT;
ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum);
@@ -1425,8 +1407,6 @@ static u64 bpf_clone_redirect(u64 r1, u64 ifindex, u64 flags, u64 r4, u64 r5)
if (unlikely(!skb2))
return -ENOMEM;
- skb_push(skb2, skb2->data - skb_mac_header(skb2));
-
if (BPF_IS_REDIRECT_INGRESS(flags))
return dev_forward_skb(dev, skb2);
diff --git a/net/sched/act_bpf.c b/net/sched/act_bpf.c
index dc6a2d324bd8..1d56903fd4c7 100644
--- a/net/sched/act_bpf.c
+++ b/net/sched/act_bpf.c
@@ -37,6 +37,7 @@ static int tcf_bpf(struct sk_buff *skb, const struct tc_action *act,
{
struct tcf_bpf *prog = act->priv;
int action, filter_res;
+ bool at_ingress = G_TC_AT(skb->tc_verd) & AT_INGRESS;
if (unlikely(!skb_mac_header_was_set(skb)))
return TC_ACT_UNSPEC;
@@ -48,7 +49,13 @@ static int tcf_bpf(struct sk_buff *skb, const struct tc_action *act,
/* Needed here for accessing maps. */
rcu_read_lock();
- filter_res = BPF_PROG_RUN(prog->filter, skb);
+ if (at_ingress) {
+ __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);
+ }
rcu_read_unlock();
/* A BPF program may overwrite the default action opcode.
diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c
index 91bd9c19471d..c79ecfd36e0f 100644
--- a/net/sched/cls_bpf.c
+++ b/net/sched/cls_bpf.c
@@ -64,6 +64,11 @@ static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
{
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 @@ static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
/* 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;

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