This patch adds a helper function called bpf_get_xdp_hash to calculate
the hash for a packet at the XDP layer. In the helper function, we call
the kernel flow dissector in non-skb mode by passing the net pointer
to calculate the hash.
Changes since RFC:
- accounted for vlans(David Ahern)
- return the correct hash by not using skb_get_hash(David Ahern)
- call __skb_flow_dissect in non-skb mode
Signed-off-by: Harshitha Ramamurthy <harshitha.ramamurthy@xxxxxxxxx>
---
include/uapi/linux/bpf.h | 9 +++++++++
net/core/filter.c | 29 +++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 9 +++++++++
3 files changed, 47 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index a613750d5515..bffe93b526e7 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3576,6 +3576,14 @@ union bpf_attr {
* the data in *dst*. This is a wrapper of copy_from_user().
* Return
* 0 on success, or a negative error in case of failure.
+ *
+ * u32 bpf_get_xdp_hash(struct xdp_buff *xdp_md)
+ * Description
+ * Return the hash for the xdp context passed. This function
+ * calls skb_flow_dissect in non-skb mode to calculate the
+ * hash for the packet.
+ * Return
+ * The 32-bit hash.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3727,6 +3735,7 @@ union bpf_attr {
FN(inode_storage_delete), \
FN(d_path), \
FN(copy_from_user), \
+ FN(get_xdp_hash), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/net/core/filter.c b/net/core/filter.c
index 47eef9a0be6a..cfb5a6aea6c3 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3765,6 +3765,33 @@ static const struct bpf_func_proto bpf_xdp_redirect_map_proto = {
.arg3_type = ARG_ANYTHING,
};
+BPF_CALL_1(bpf_get_xdp_hash, struct xdp_buff *, xdp)
+{
+ void *data_end = xdp->data_end;
+ struct ethhdr *eth = xdp->data;
+ void *data = xdp->data;
+ struct flow_keys keys;
+ u32 ret = 0;
+ int len;
+
+ len = data_end - data;
+ if (len <= 0)
+ return ret;
+ memset(&keys, 0, sizeof(keys));
+ __skb_flow_dissect(dev_net(xdp->rxq->dev), NULL, &flow_keys_dissector,
+ &keys, data, eth->h_proto, sizeof(*eth), len,
+ FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL);
+ ret = flow_hash_from_keys(&keys);
+ return ret;
+}
+
+static const struct bpf_func_proto bpf_get_xdp_hash_proto = {
+ .func = bpf_get_xdp_hash,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+};
+
static unsigned long bpf_skb_copy(void *dst_buff, const void *skb,
unsigned long off, unsigned long len)
{
@@ -6837,6 +6864,8 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_xdp_adjust_tail_proto;
case BPF_FUNC_fib_lookup:
return &bpf_xdp_fib_lookup_proto;
+ case BPF_FUNC_get_xdp_hash:
+ return &bpf_get_xdp_hash_proto;
#ifdef CONFIG_INET
case BPF_FUNC_sk_lookup_udp:
return &bpf_xdp_sk_lookup_udp_proto;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index a613750d5515..bffe93b526e7 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3576,6 +3576,14 @@ union bpf_attr {
* the data in *dst*. This is a wrapper of copy_from_user().
* Return
* 0 on success, or a negative error in case of failure.
+ *
+ * u32 bpf_get_xdp_hash(struct xdp_buff *xdp_md)
+ * Description
+ * Return the hash for the xdp context passed. This function
+ * calls skb_flow_dissect in non-skb mode to calculate the
+ * hash for the packet.
+ * Return
+ * The 32-bit hash.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3727,6 +3735,7 @@ union bpf_attr {
FN(inode_storage_delete), \
FN(d_path), \
FN(copy_from_user), \
+ FN(get_xdp_hash), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.20.1
