Subject: [PATCH net-next 1/9] net-timestamp: add bpf infrastructure to allow exposing more information later

From: Jason Xing <[email-masked]>
Date: Tue, 8 Oct 2024 17:51:01 +0800

From: Jason Xing <[email-masked]>

Implement basic codes so that we later can easily add each tx points.
Introducing BPF_SOCK_OPS_ALL_CB_FLAGS used as a test statement can help use
control whether to output or not.

Signed-off-by: Jason Xing <[email-masked]>
---
 include/uapi/linux/bpf.h       |  5 ++++-
 net/core/skbuff.c              | 18 ++++++++++++++++++
 tools/include/uapi/linux/bpf.h |  5 ++++-
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c6cd7c7aeeee..157e139ed6fc 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -6900,8 +6900,11 @@ enum {
 	 * options first before the BPF program does.
 	 */
 	BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG = (1<<6),
+	/* Call bpf when the kernel is generating tx timestamps.
+	 */
+	BPF_SOCK_OPS_TX_TIMESTAMPING_OPT_CB_FLAG = (1<<7),
 /* Mask of all currently supported cb flags */
-	BPF_SOCK_OPS_ALL_CB_FLAGS       = 0x7F,
+	BPF_SOCK_OPS_ALL_CB_FLAGS       = 0xFF,
 };
 
 /* List of known BPF sock_ops operators.
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 74149dc4ee31..5ff1a91c1204 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5539,6 +5539,21 @@ void skb_complete_tx_timestamp(struct sk_buff *skb,
 }
 EXPORT_SYMBOL_GPL(skb_complete_tx_timestamp);
 
+static bool bpf_skb_tstamp_tx(struct sock *sk, u32 scm_flag,
+			      struct skb_shared_hwtstamps *hwtstamps)
+{
+	struct tcp_sock *tp;
+
+	if (!sk_is_tcp(sk))
+		return false;
+
+	tp = tcp_sk(sk);
+	if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_TX_TIMESTAMPING_OPT_CB_FLAG))
+		return true;
+
+	return false;
+}
+
 void __skb_tstamp_tx(struct sk_buff *orig_skb,
 		     const struct sk_buff *ack_skb,
 		     struct skb_shared_hwtstamps *hwtstamps,
@@ -5551,6 +5566,9 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
 	if (!sk)
 		return;
 
+	if (bpf_skb_tstamp_tx(sk, tstype, hwtstamps))
+		return;
+
 	tsflags = READ_ONCE(sk->sk_tsflags);
 	if (!hwtstamps && !(tsflags & SOF_TIMESTAMPING_OPT_TX_SWHW) &&
 	    skb_shinfo(orig_skb)->tx_flags & SKBTX_IN_PROGRESS)
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 1fb3cb2636e6..93853d9d4922 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -6899,8 +6899,11 @@ enum {
 	 * options first before the BPF program does.
 	 */
 	BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG = (1<<6),
+	/* Call bpf when the kernel is generating tx timestamps.
+	 */
+	BPF_SOCK_OPS_TX_TIMESTAMPING_OPT_CB_FLAG = (1<<7),
 /* Mask of all currently supported cb flags */
-	BPF_SOCK_OPS_ALL_CB_FLAGS       = 0x7F,
+	BPF_SOCK_OPS_ALL_CB_FLAGS       = 0xFF,
 };
 
 /* List of known BPF sock_ops operators.
-- 
2.37.3