[PATCH v12 bpf-next 11/18] bpf: introduce bpf_xdp_get_buff_len helper

[Lorenzo Bianconi <lorenzo@kernel.org>]

Introduce bpf_xdp_get_buff_len helper in order to return the xdp buffer
total size (linear and paged area)

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 include/uapi/linux/bpf.h       |  7 +++++++
 net/core/filter.c              | 23 +++++++++++++++++++++++
 tools/include/uapi/linux/bpf.h |  7 +++++++
 3 files changed, 37 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c4f7892edb2b..9e2c3b12ea49 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4871,6 +4871,12 @@ union bpf_attr {
  * 	Return
  *		Value specified by user at BPF link creation/attachment time
  *		or 0, if it was not specified.
+ *
+ * u64 bpf_xdp_get_buff_len(struct xdp_buff *xdp_md)
+ *	Description
+ *		Get the total size of a given xdp buff (linear and paged area)
+ *	Return
+ *		The total size of a given xdp buffer.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5048,6 +5054,7 @@ union bpf_attr {
 	FN(timer_cancel),		\
 	FN(get_func_ip),		\
 	FN(get_attach_cookie),		\
+	FN(xdp_get_buff_len),		\
 	/* */
 
 /* 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 e6a589705813..53eaae2a5463 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3784,6 +3784,27 @@ static const struct bpf_func_proto sk_skb_change_head_proto = {
 	.arg2_type	= ARG_ANYTHING,
 	.arg3_type	= ARG_ANYTHING,
 };
+
+BPF_CALL_1(bpf_xdp_get_buff_len, struct  xdp_buff*, xdp)
+{
+	u64 len = xdp->data_end - xdp->data;
+
+	if (unlikely(xdp_buff_is_mb(xdp))) {
+		struct skb_shared_info *sinfo;
+
+		sinfo = xdp_get_shared_info_from_buff(xdp);
+		len += sinfo->xdp_frags_size;
+	}
+	return len;
+}
+
+static const struct bpf_func_proto bpf_xdp_get_buff_len_proto = {
+	.func		= bpf_xdp_get_buff_len,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+};
+
 static unsigned long xdp_get_metalen(const struct xdp_buff *xdp)
 {
 	return xdp_data_meta_unsupported(xdp) ? 0 :
@@ -7513,6 +7534,8 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_xdp_redirect_map_proto;
 	case BPF_FUNC_xdp_adjust_tail:
 		return &bpf_xdp_adjust_tail_proto;
+	case BPF_FUNC_xdp_get_buff_len:
+		return &bpf_xdp_get_buff_len_proto;
 	case BPF_FUNC_fib_lookup:
 		return &bpf_xdp_fib_lookup_proto;
 	case BPF_FUNC_check_mtu:
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index c4f7892edb2b..9e2c3b12ea49 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4871,6 +4871,12 @@ union bpf_attr {
  * 	Return
  *		Value specified by user at BPF link creation/attachment time
  *		or 0, if it was not specified.
+ *
+ * u64 bpf_xdp_get_buff_len(struct xdp_buff *xdp_md)
+ *	Description
+ *		Get the total size of a given xdp buff (linear and paged area)
+ *	Return
+ *		The total size of a given xdp buffer.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5048,6 +5054,7 @@ union bpf_attr {
 	FN(timer_cancel),		\
 	FN(get_func_ip),		\
 	FN(get_attach_cookie),		\
+	FN(xdp_get_buff_len),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
-- 
2.31.1