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Few minor BPF helper improvements

PATCH In review Daniel Borkmann 2 participants 5 messages Sep 22, 2016 – Sep 23, 2016

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Networking Network drivers BPF BPF networking
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Daniel Borkmann

author maintainer
#0 lore raw

cover Few minor BPF helper improvements

Just a few minor improvements around BPF helpers, first one is a fix but given this late stage and that it's not really a critical one, I think net-next is just fine. For details please see the individual patches.

Thanks!

Daniel Borkmann (3):
bpf: use skb_to_full_sk helper in bpf_skb_under_cgroup
bpf: use bpf_get_smp_processor_id_proto instead of raw one
bpf: add helper to invalidate hash

 include/uapi/linux/bpf.h |  7 +++++++
 net/core/filter.c        | 22 +++++++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)
Signature · 1 line
1.9.3
author maintainer
#1 lore raw

PATCH 1/3 bpf: use skb_to_full_sk helper in bpf_skb_under_cgroup

We need to use skb_to_full_sk() helper introduced in commit bd5eb35f16a9 ("xfrm: take care of request sockets") as otherwise we miss tcp synack messages, since ownership is on request socket and therefore it would miss the sk_fullsock() check. Use skb_to_full_sk() as also done similarly in the bpf_get_cgroup_classid() helper via 2309236c13fe ("cls_cgroup:
get sk_classid only from full sockets") fix to not let this fall through.

Fixes 4a482f34afcc ("cgroup: bpf: Add bpf_skb_in_cgroup_proto")
Signed-off-by Daniel Borkmann <[email protected]>
Acked-by Alexei Starovoitov <[email protected]>
---
 net/core/filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
net/core/filter.c +1 -1
index 0920c2a..e5d9977 100644
@@ -2408,7 +2408,7 @@ BPF_CALL_3(bpf_skb_under_cgroup, struct sk_buff *, skb, struct bpf_map *, map,
 	struct cgroup *cgrp;
 	struct sock *sk;
 
-	sk = skb->sk;
+	sk = skb_to_full_sk(skb);
 	if (!sk || !sk_fullsock(sk))
 		return -ENOENT;
 	if (unlikely(idx >= array->map.max_entries))
Signature · 1 line
1.9.3
author maintainer
#2 lore raw

PATCH 2/3 bpf: use bpf_get_smp_processor_id_proto instead of raw one

In reply to Daniel Borkmann

Same motivation as in commit 80b48c445797 ("bpf: don't use raw processor id in generic helper"), but this time for XDP typed programs. Thus, allow for preemption checks when we have DEBUG_PREEMPT enabled, and otherwise use the raw variant.

Signed-off-by Daniel Borkmann <[email protected]>
Acked-by Alexei Starovoitov <[email protected]>
---
 net/core/filter.c | 2 ++
 1 file changed, 2 insertions(+)
net/core/filter.c +2 -0
index e5d9977..acf84fb 100644
@@ -2551,6 +2551,8 @@ xdp_func_proto(enum bpf_func_id func_id)
 	switch (func_id) {
 	case BPF_FUNC_perf_event_output:
 		return &bpf_xdp_event_output_proto;
+	case BPF_FUNC_get_smp_processor_id:
+		return &bpf_get_smp_processor_id_proto;
 	default:
 		return sk_filter_func_proto(func_id);
 	}
Signature · 1 line
1.9.3
author maintainer
#3 lore raw

PATCH 3/3 bpf: add helper to invalidate hash

In reply to Daniel Borkmann

Add a small helper that complements 36bbef52c7eb ("bpf: direct packet write and access for helpers for clsact progs") for invalidating the current skb->hash after mangling on headers via direct packet write.

Signed-off-by Daniel Borkmann <[email protected]>
Acked-by Alexei Starovoitov <[email protected]>
---
 include/uapi/linux/bpf.h |  7 +++++++
 net/core/filter.c        | 18 ++++++++++++++++++
 2 files changed, 25 insertions(+)
include/uapi/linux/bpf.h +7 -0
index e07432b..f09c70b 100644
@@ -419,6 +419,13 @@ enum bpf_func_id {
 	 */
 	BPF_FUNC_csum_update,
 
+	/**
+	 * bpf_set_hash_invalid(skb)
+	 * Invalidate current skb>hash.
+	 * @skb: pointer to skb
+	 */
+	BPF_FUNC_set_hash_invalid,
+
 	__BPF_FUNC_MAX_ID,
 };
net/core/filter.c +18 -0
index acf84fb..00351cd 100644
@@ -1777,6 +1777,22 @@ static const struct bpf_func_proto bpf_get_hash_recalc_proto = {
 	.arg1_type	= ARG_PTR_TO_CTX,
 };
 
+BPF_CALL_1(bpf_set_hash_invalid, struct sk_buff *, skb)
+{
+	/* After all direct packet write, this can be used once for
+	 * triggering a lazy recalc on next skb_get_hash() invocation.
+	 */
+	skb_clear_hash(skb);
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_set_hash_invalid_proto = {
+	.func		= bpf_set_hash_invalid,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+};
+
 BPF_CALL_3(bpf_skb_vlan_push, struct sk_buff *, skb, __be16, vlan_proto,
 	   u16, vlan_tci)
 {

@@ -2534,6 +2550,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
 		return &bpf_get_route_realm_proto;
 	case BPF_FUNC_get_hash_recalc:
 		return &bpf_get_hash_recalc_proto;
+	case BPF_FUNC_set_hash_invalid:
+		return &bpf_set_hash_invalid_proto;
 	case BPF_FUNC_perf_event_output:
 		return &bpf_skb_event_output_proto;
 	case BPF_FUNC_get_smp_processor_id:
Signature · 1 line
1.9.3
maintainer
#4 lore raw
In reply to Daniel Borkmann

From: Daniel Borkmann <[email protected]>
Date: Fri, 23 Sep 2016 01:28:34 +0200

Quoted 4 lines

Just a few minor improvements around BPF helpers, first one is a fix but given this late stage and that it's not really a critical one, I think net-next is just fine. For details please see the individual patches.

Series applied, thanks.