Subject: [PATCH net-next 6/9] net-timestamp: add tx OPT_ID_TCP support for bpf case

From: Jason Xing <[email-masked]>
Date: Tue, 8 Oct 2024 17:51:06 +0800

From: Jason Xing <[email-masked]>

We can set OPT_ID|OPT_ID_TCP before we initialize the last skb
from each sendmsg. We only set the socket once like how we use
setsockopt() with OPT_ID|OPT_ID_TCP flags.

Signed-off-by: Jason Xing <[email-masked]>
---
 net/core/skbuff.c | 16 +++++++++++++---
 net/ipv4/tcp.c    | 19 +++++++++++++++----
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 2b1b2f7d271a..a60aec450970 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5540,6 +5540,7 @@ 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 sk_buff *skb,
 			      struct skb_shared_hwtstamps *hwtstamps)
 {
 	struct tcp_sock *tp;
@@ -5550,7 +5551,7 @@ static bool bpf_skb_tstamp_tx(struct sock *sk, u32 scm_flag,
 	tp = tcp_sk(sk);
 	if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_TX_TIMESTAMPING_OPT_CB_FLAG)) {
 		struct timespec64 tstamp;
-		u32 cb_flag;
+		u32 cb_flag, key = 0;
 
 		switch (scm_flag) {
 		case SCM_TSTAMP_SCHED:
@@ -5566,11 +5567,20 @@ static bool bpf_skb_tstamp_tx(struct sock *sk, u32 scm_flag,
 			return true;
 		}
 
+		/* We require user to set OPT_ID_TCP to generate key value
+		 * in a robust way.
+		 */
+		if (READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_OPT_ID &&
+		    READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_OPT_ID_TCP) {
+			key = skb_shinfo(skb)->tskey;
+			key -= atomic_read(&sk->sk_tskey);
+		}
+
 		if (hwtstamps)
 			tstamp = ktime_to_timespec64(hwtstamps->hwtstamp);
 		else
 			tstamp = ktime_to_timespec64(ktime_get_real());
-		tcp_call_bpf_2arg(sk, cb_flag, tstamp.tv_sec, tstamp.tv_nsec);
+		tcp_call_bpf_3arg(sk, cb_flag, key, tstamp.tv_sec, tstamp.tv_nsec);
 		return true;
 	}
 
@@ -5589,7 +5599,7 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
 	if (!sk)
 		return;
 
-	if (bpf_skb_tstamp_tx(sk, tstype, hwtstamps))
+	if (bpf_skb_tstamp_tx(sk, tstype, orig_skb, hwtstamps))
 		return;
 
 	tsflags = READ_ONCE(sk->sk_tsflags);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ddf4089779b5..1d52640f9ff4 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -477,7 +477,7 @@ void tcp_init_sock(struct sock *sk)
 }
 EXPORT_SYMBOL(tcp_init_sock);
 
-static u32 bpf_tcp_tx_timestamp(struct sock *sk)
+static u32 bpf_tcp_tx_timestamp(struct sock *sk, int copied)
 {
 	u32 flags;
 
@@ -491,10 +491,21 @@ static u32 bpf_tcp_tx_timestamp(struct sock *sk)
 	if (!(flags & SOF_TIMESTAMPING_TX_RECORD_MASK))
 		return 0;
 
+	/* We require users to set both OPT_ID and OPT_ID_TCP flags
+	 * together here, or else the key might be inaccurate.
+	 */
+	if (flags & SOF_TIMESTAMPING_OPT_ID &&
+	    flags & SOF_TIMESTAMPING_OPT_ID_TCP &&
+	    !(sk->sk_tsflags & (SOF_TIMESTAMPING_OPT_ID | SOF_TIMESTAMPING_OPT_ID_TCP))) {
+		atomic_set(&sk->sk_tskey, (tcp_sk(sk)->write_seq - copied));
+		sk->sk_tsflags |= (SOF_TIMESTAMPING_OPT_ID | SOF_TIMESTAMPING_OPT_ID_TCP);
+	}
+
 	return flags;
 }
 
-static void tcp_tx_timestamp(struct sock *sk, struct sockcm_cookie *sockc)
+static void tcp_tx_timestamp(struct sock *sk, struct sockcm_cookie *sockc,
+			     int copied)
 {
 	struct sk_buff *skb = tcp_write_queue_tail(sk);
 	u32 tsflags = sockc->tsflags;
@@ -503,7 +514,7 @@ static void tcp_tx_timestamp(struct sock *sk, struct sockcm_cookie *sockc)
 	if (!skb)
 		return;
 
-	flags = bpf_tcp_tx_timestamp(sk);
+	flags = bpf_tcp_tx_timestamp(sk, copied);
 	if (flags)
 		tsflags = flags;
 
@@ -1347,7 +1358,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 
 out:
 	if (copied) {
-		tcp_tx_timestamp(sk, &sockc);
+		tcp_tx_timestamp(sk, &sockc, copied);
 		tcp_push(sk, flags, mss_now, tp->nonagle, size_goal);
 	}
 out_nopush:
-- 
2.37.3