[PATCH bpf-next v2 1/2] bpf: add hardware timestamp field to __sk_buff

[Vadim Fedorenko <vfedorenko@xxxxxxxx>]

BPF programs may want to know hardware timestamps if NIC supports
such timestamping.

Expose this data as hwtstamp field of __sk_buff the same way as
gso_segs/gso_size. This field could be accessed from the same
programs as tstamp field, but it's read-only field. Explicit test
to deny access to padding data is added to bpf_skb_is_valid_access.

Also update BPF_PROG_TEST_RUN tests of the feature.

Signed-off-by: Vadim Fedorenko <vfedorenko@xxxxxxxx>
---
 include/uapi/linux/bpf.h       |  2 ++
 net/core/filter.c              | 21 +++++++++++++++++++++
 tools/include/uapi/linux/bpf.h |  2 ++
 3 files changed, 25 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 791f31dd0abe..51cfd91cc387 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5284,6 +5284,8 @@ struct __sk_buff {
 	__u32 gso_segs;
 	__bpf_md_ptr(struct bpf_sock *, sk);
 	__u32 gso_size;
+	__u32 :32;		/* Padding, future use. */
+	__u64 hwtstamp;
 };
 
 struct bpf_tunnel_key {
diff --git a/net/core/filter.c b/net/core/filter.c
index 2e32cee2c469..4bace37a6a44 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7765,6 +7765,10 @@ static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type
 		break;
 	case bpf_ctx_range_ptr(struct __sk_buff, flow_keys):
 		return false;
+	case bpf_ctx_range(struct __sk_buff, hwtstamp):
+		if (type == BPF_WRITE || size != sizeof(__u64))
+			return false;
+		break;
 	case bpf_ctx_range(struct __sk_buff, tstamp):
 		if (size != sizeof(__u64))
 			return false;
@@ -7774,6 +7778,9 @@ static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type
 			return false;
 		info->reg_type = PTR_TO_SOCK_COMMON_OR_NULL;
 		break;
+	case offsetofend(struct __sk_buff, gso_size) ... offsetof(struct __sk_buff, hwtstamp) - 1:
+		/* Explicitly prohibit access to padding in __sk_buff. */
+		return false;
 	default:
 		/* Only narrow read access allowed for now. */
 		if (type == BPF_WRITE) {
@@ -7802,6 +7809,7 @@ static bool sk_filter_is_valid_access(int off, int size,
 	case bpf_ctx_range_till(struct __sk_buff, family, local_port):
 	case bpf_ctx_range(struct __sk_buff, tstamp):
 	case bpf_ctx_range(struct __sk_buff, wire_len):
+	case bpf_ctx_range(struct __sk_buff, hwtstamp):
 		return false;
 	}
 
@@ -7872,6 +7880,7 @@ static bool lwt_is_valid_access(int off, int size,
 	case bpf_ctx_range(struct __sk_buff, data_meta):
 	case bpf_ctx_range(struct __sk_buff, tstamp):
 	case bpf_ctx_range(struct __sk_buff, wire_len):
+	case bpf_ctx_range(struct __sk_buff, hwtstamp):
 		return false;
 	}
 
@@ -8373,6 +8382,7 @@ static bool sk_skb_is_valid_access(int off, int size,
 	case bpf_ctx_range(struct __sk_buff, data_meta):
 	case bpf_ctx_range(struct __sk_buff, tstamp):
 	case bpf_ctx_range(struct __sk_buff, wire_len):
+	case bpf_ctx_range(struct __sk_buff, hwtstamp):
 		return false;
 	}
 
@@ -8884,6 +8894,17 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
 				      si->dst_reg, si->src_reg,
 				      offsetof(struct sk_buff, sk));
 		break;
+	case offsetof(struct __sk_buff, hwtstamp):
+		BUILD_BUG_ON(sizeof_field(struct skb_shared_hwtstamps, hwtstamp) != 8);
+		BUILD_BUG_ON(offsetof(struct skb_shared_hwtstamps, hwtstamp) != 0);
+
+		insn = bpf_convert_shinfo_access(si, insn);
+		*insn++ = BPF_LDX_MEM(BPF_DW,
+				      si->dst_reg, si->dst_reg,
+				      bpf_target_off(struct skb_shared_info,
+						     hwtstamps, 8,
+						     target_size));
+		break;
 	}
 
 	return insn - insn_buf;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 791f31dd0abe..51cfd91cc387 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5284,6 +5284,8 @@ struct __sk_buff {
 	__u32 gso_segs;
 	__bpf_md_ptr(struct bpf_sock *, sk);
 	__u32 gso_size;
+	__u32 :32;		/* Padding, future use. */
+	__u64 hwtstamp;
 };
 
 struct bpf_tunnel_key {
-- 
2.18.4