Allow for tc BPF programs to set a skb->hash, apart from clearing
and triggering a recalc that we have right now. It allows for BPF
to implement a custom hashing routine for skb_get_hash().
Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
Acked-by: Alexei Starovoitov <a...@kernel.org>
---
include/uapi/linux/bpf.h | 8 +++++++-
net/core/filter.c | 20 ++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 8 +++++++-
3 files changed, 34 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 9b2c10b..f94b48b 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -513,6 +513,11 @@ enum bpf_attach_type {
* Get the owner uid of the socket stored inside sk_buff.
* @skb: pointer to skb
* Return: uid of the socket owner on success or overflowuid if failed.
+ *
+ * u32 bpf_set_hash(skb, hash)
+ * Set full skb->hash.
+ * @skb: pointer to skb
+ * @hash: hash to set
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -562,7 +567,8 @@ enum bpf_attach_type {
FN(xdp_adjust_head), \
FN(probe_read_str), \
FN(get_socket_cookie), \
- FN(get_socket_uid),
+ FN(get_socket_uid), \
+ FN(set_hash),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
diff --git a/net/core/filter.c b/net/core/filter.c
index 4867391..a65a3b2 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1874,6 +1874,24 @@ int skb_do_redirect(struct sk_buff *skb)
.arg1_type = ARG_PTR_TO_CTX,
};
+BPF_CALL_2(bpf_set_hash, struct sk_buff *, skb, u32, hash)
+{
+ /* Set user specified hash as L4(+), so that it gets returned
+ * on skb_get_hash() call unless BPF prog later on triggers a
+ * skb_clear_hash().
+ */
+ __skb_set_sw_hash(skb, hash, true);
+ return 0;
+}
+
+static const struct bpf_func_proto bpf_set_hash_proto = {
+ .func = bpf_set_hash,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_ANYTHING,
+};
+
BPF_CALL_3(bpf_skb_vlan_push, struct sk_buff *, skb, __be16, vlan_proto,
u16, vlan_tci)
{
@@ -2744,6 +2762,8 @@ static unsigned long bpf_xdp_copy(void *dst_buff, const
void *src_buff,
return &bpf_get_hash_recalc_proto;
case BPF_FUNC_set_hash_invalid:
return &bpf_set_hash_invalid_proto;
+ case BPF_FUNC_set_hash:
+ return &bpf_set_hash_proto;
case BPF_FUNC_perf_event_output:
return &bpf_skb_event_output_proto;
case BPF_FUNC_get_smp_processor_id:
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 9b2c10b..f94b48b 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -513,6 +513,11 @@ enum bpf_attach_type {
* Get the owner uid of the socket stored inside sk_buff.
* @skb: pointer to skb
* Return: uid of the socket owner on success or overflowuid if failed.
+ *
+ * u32 bpf_set_hash(skb, hash)
+ * Set full skb->hash.
+ * @skb: pointer to skb
+ * @hash: hash to set
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -562,7 +567,8 @@ enum bpf_attach_type {
FN(xdp_adjust_head), \
FN(probe_read_str), \
FN(get_socket_cookie), \
- FN(get_socket_uid),
+ FN(get_socket_uid), \
+ FN(set_hash),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
--
1.9.3
