Merge branch 'net-timestamp-introduce-a-flag-to-filter-out-rx-software-and-hardware-report'

Jason Xing says:

====================
net-timestamp: introduce a flag to filter out rx software and hardware report

When one socket is set SOF_TIMESTAMPING_RX_SOFTWARE which means the
whole system turns on the netstamp_needed_key button, other sockets
that only have SOF_TIMESTAMPING_SOFTWARE will be affected and then
print the rx timestamp information even without setting
SOF_TIMESTAMPING_RX_SOFTWARE generation flag.

How to solve it without breaking users?
We introduce a new flag named SOF_TIMESTAMPING_OPT_RX_FILTER. Using
it together with SOF_TIMESTAMPING_SOFTWARE can stop reporting the
rx software timestamp.

Similarly, we also filter out the hardware case where one process
enables the rx hardware generation flag, then another process only
passing SOF_TIMESTAMPING_RAW_HARDWARE gets the timestamp. So we can set
both SOF_TIMESTAMPING_RAW_HARDWARE and SOF_TIMESTAMPING_OPT_RX_FILTER
to stop reporting rx hardware timestamp after this patch applied.

v6: https://lore.kernel.org/20240906095640.77533-1-kerneljasonxing@gmail.com
v5: https://lore.kernel.org/20240905071738.3725-1-kerneljasonxing@gmail.com
v4: https://lore.kernel.org/20240830153751.86895-1-kerneljasonxing@gmail.com
v3: https://lore.kernel.org/20240828160145.68805-1-kerneljasonxing@gmail.com
v2: https://lore.kernel.org/20240825152440.93054-1-kerneljasonxing@gmail.com
====================

Link: https://patch.msgid.link/20240909015612.3856-1-kerneljasonxing@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

6 files changed, 53 insertions, 5 deletions

diff --git a/Documentation/networking/timestamping.rst b/Documentation/networking/timestamping.rst
index 9c7773271393..8199e6917671 100644
--- a/Documentation/networking/timestamping.rst
+++ b/Documentation/networking/timestamping.rst
@@ -267,6 +267,23 @@ SOF_TIMESTAMPING_OPT_TX_SWHW:
   two separate messages will be looped to the socket's error queue,
   each containing just one timestamp.
 
+SOF_TIMESTAMPING_OPT_RX_FILTER:
+  Filter out spurious receive timestamps: report a receive timestamp
+  only if the matching timestamp generation flag is enabled.
+
+  Receive timestamps are generated early in the ingress path, before a
+  packet's destination socket is known. If any socket enables receive
+  timestamps, packets for all socket will receive timestamped packets.
+  Including those that request timestamp reporting with
+  SOF_TIMESTAMPING_SOFTWARE and/or SOF_TIMESTAMPING_RAW_HARDWARE, but
+  do not request receive timestamp generation. This can happen when
+  requesting transmit timestamps only.
+
+  Receiving spurious timestamps is generally benign. A process can
+  ignore the unexpected non-zero value. But it makes behavior subtly
+  dependent on other sockets. This flag isolates the socket for more
+  deterministic behavior.
+
 New applications are encouraged to pass SOF_TIMESTAMPING_OPT_ID to
 disambiguate timestamps and SOF_TIMESTAMPING_OPT_TSONLY to operate
 regardless of the setting of sysctl net.core.tstamp_allow_data.
diff --git a/include/uapi/linux/net_tstamp.h b/include/uapi/linux/net_tstamp.h
index a2c66b3d7f0f..858339d1c1c4 100644
--- a/include/uapi/linux/net_tstamp.h
+++ b/include/uapi/linux/net_tstamp.h
@@ -32,8 +32,9 @@ enum {
 	SOF_TIMESTAMPING_OPT_TX_SWHW = (1<<14),
 	SOF_TIMESTAMPING_BIND_PHC = (1 << 15),
 	SOF_TIMESTAMPING_OPT_ID_TCP = (1 << 16),
+	SOF_TIMESTAMPING_OPT_RX_FILTER = (1 << 17),
 
-	SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_ID_TCP,
+	SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_RX_FILTER,
 	SOF_TIMESTAMPING_MASK = (SOF_TIMESTAMPING_LAST - 1) |
 				 SOF_TIMESTAMPING_LAST
 };
diff --git a/net/ethtool/common.c b/net/ethtool/common.c
index 781834ef57c3..6c245e59bbc1 100644
--- a/net/ethtool/common.c
+++ b/net/ethtool/common.c
@@ -427,6 +427,7 @@ const char sof_timestamping_names[][ETH_GSTRING_LEN] = {
 	[const_ilog2(SOF_TIMESTAMPING_OPT_TX_SWHW)]  = "option-tx-swhw",
 	[const_ilog2(SOF_TIMESTAMPING_BIND_PHC)]     = "bind-phc",
 	[const_ilog2(SOF_TIMESTAMPING_OPT_ID_TCP)]   = "option-id-tcp",
+	[const_ilog2(SOF_TIMESTAMPING_OPT_RX_FILTER)] = "option-rx-filter",
 };
 static_assert(ARRAY_SIZE(sof_timestamping_names) == __SOF_TIMESTAMPING_CNT);
 
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 8a5680b4e786..e359a9161445 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2235,6 +2235,7 @@ void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
 			struct scm_timestamping_internal *tss)
 {
 	int new_tstamp = sock_flag(sk, SOCK_TSTAMP_NEW);
+	u32 tsflags = READ_ONCE(sk->sk_tsflags);
 	bool has_timestamping = false;
 
 	if (tss->ts[0].tv_sec || tss->ts[0].tv_nsec) {
@@ -2274,14 +2275,18 @@ void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
 			}
 		}
 
-		if (READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_SOFTWARE)
+		if (tsflags & SOF_TIMESTAMPING_SOFTWARE &&
+		    (tsflags & SOF_TIMESTAMPING_RX_SOFTWARE ||
+		     !(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER)))
 			has_timestamping = true;
 		else
 			tss->ts[0] = (struct timespec64) {0};
 	}
 
 	if (tss->ts[2].tv_sec || tss->ts[2].tv_nsec) {
-		if (READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_RAW_HARDWARE)
+		if (tsflags & SOF_TIMESTAMPING_RAW_HARDWARE &&
+		    (tsflags & SOF_TIMESTAMPING_RX_HARDWARE ||
+		     !(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER)))
 			has_timestamping = true;
 		else
 			tss->ts[2] = (struct timespec64) {0};
diff --git a/net/socket.c b/net/socket.c
index 0a2bd22ec105..8d8b84fa404a 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -946,11 +946,17 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
 
 	memset(&tss, 0, sizeof(tss));
 	tsflags = READ_ONCE(sk->sk_tsflags);
-	if ((tsflags & SOF_TIMESTAMPING_SOFTWARE) &&
+	if ((tsflags & SOF_TIMESTAMPING_SOFTWARE &&
+	     (tsflags & SOF_TIMESTAMPING_RX_SOFTWARE ||
+	      skb_is_err_queue(skb) ||
+	      !(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER))) &&
 	    ktime_to_timespec64_cond(skb->tstamp, tss.ts + 0))
 		empty = 0;
 	if (shhwtstamps &&
-	    (tsflags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
+	    (tsflags & SOF_TIMESTAMPING_RAW_HARDWARE &&
+	     (tsflags & SOF_TIMESTAMPING_RX_HARDWARE ||
+	      skb_is_err_queue(skb) ||
+	      !(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER))) &&
 	    !skb_is_swtx_tstamp(skb, false_tstamp)) {
 		if_index = 0;
 		if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP_NETDEV)
diff --git a/tools/testing/selftests/net/rxtimestamp.c b/tools/testing/selftests/net/rxtimestamp.c
index 9eb42570294d..16ac4df55fdb 100644
--- a/tools/testing/selftests/net/rxtimestamp.c
+++ b/tools/testing/selftests/net/rxtimestamp.c
@@ -57,6 +57,8 @@ static struct sof_flag sof_flags[] = {
 	SOF_FLAG(SOF_TIMESTAMPING_SOFTWARE),
 	SOF_FLAG(SOF_TIMESTAMPING_RX_SOFTWARE),
 	SOF_FLAG(SOF_TIMESTAMPING_RX_HARDWARE),
+	SOF_FLAG(SOF_TIMESTAMPING_OPT_RX_FILTER),
+	SOF_FLAG(SOF_TIMESTAMPING_RAW_HARDWARE),
 };
 
 static struct socket_type socket_types[] = {
@@ -98,6 +100,22 @@ static struct test_case test_cases[] = {
 		{}
 	},
 	{
+		{ .so_timestamping = SOF_TIMESTAMPING_RAW_HARDWARE
+			| SOF_TIMESTAMPING_OPT_RX_FILTER },
+		{}
+	},
+	{
+		{ .so_timestamping = SOF_TIMESTAMPING_SOFTWARE
+			| SOF_TIMESTAMPING_OPT_RX_FILTER },
+		{}
+	},
+	{
+		{ .so_timestamping = SOF_TIMESTAMPING_SOFTWARE
+			| SOF_TIMESTAMPING_RX_SOFTWARE
+			| SOF_TIMESTAMPING_OPT_RX_FILTER },
+		{ .swtstamp = true }
+	},
+	{
 		{ .so_timestamping = SOF_TIMESTAMPING_SOFTWARE
 			| SOF_TIMESTAMPING_RX_SOFTWARE },
 		{ .swtstamp = true }