net-timestamp: introduce SOF_TIMESTAMPING_OPT_RX_FILTER flag

introduce a new flag SOF_TIMESTAMPING_OPT_RX_FILTER in the receive path. User can set it with SOF_TIMESTAMPING_SOFTWARE to filter out rx software timestamp report, especially after a process turns on netstamp_needed_key which can time stamp every incoming skb. Previously, we found out if an application starts first which turns on netstamp_needed_key, then another one only passing SOF_TIMESTAMPING_SOFTWARE could also get rx timestamp. Now we handle this case by introducing this new flag without breaking users. Quoting Willem to explain why we need the flag: "why a process would want to request software timestamp reporting, but not receive software timestamp generation. The only use I see is when the application does request SOF_TIMESTAMPING_SOFTWARE | SOF_TIMESTAMPING_TX_SOFTWARE." Similarly, this new flag could also be used for hardware case where we can set it with SOF_TIMESTAMPING_RAW_HARDWARE, then we won't receive hardware receive timestamp. Another thing about errqueue in this patch I have a few words to say: In this case, we need to handle the egress path carefully, or else reporting the tx timestamp will fail. Egress path and ingress path will finally call sock_recv_timestamp(). We have to distinguish them. Errqueue is a good indicator to reflect the flow direction.

Jason Xing committed 2 years ago

Commit be8e9eb1 parent e503f825 files · +35 −5Browse files

Unified · Split

5 files

Documentation/networking/timestamping.rst +17 −0
include/uapi/linux/net_tstamp.h +2 −1
net/ethtool/common.c +1 −0
net/ipv4/tcp.c +7 −2
net/socket.c +8 −2

Documentation/networking/timestamping.rst+17−0

@@ -267,6 +267,23 @@ SOF_TIMESTAMPING_OPT_TX_SWHW: · 266 unmodified lines
267	267	two separate messages will be looped to the socket's error queue,
268	268	each containing just one timestamp.
269	269
	270	+SOF_TIMESTAMPING_OPT_RX_FILTER:
	271	+ Filter out spurious receive timestamps: report a receive timestamp
	272	+ only if the matching timestamp generation flag is enabled.
	273	+
	274	+ Receive timestamps are generated early in the ingress path, before a
	275	+ packet's destination socket is known. If any socket enables receive
	276	+ timestamps, packets for all socket will receive timestamped packets.
	277	+ Including those that request timestamp reporting with
	278	+ SOF_TIMESTAMPING_SOFTWARE and/or SOF_TIMESTAMPING_RAW_HARDWARE, but
	279	+ do not request receive timestamp generation. This can happen when
	280	+ requesting transmit timestamps only.
	281	+
	282	+ Receiving spurious timestamps is generally benign. A process can
	283	+ ignore the unexpected non-zero value. But it makes behavior subtly
	284	+ dependent on other sockets. This flag isolates the socket for more
	285	+ deterministic behavior.
	286	+
270	287	New applications are encouraged to pass SOF_TIMESTAMPING_OPT_ID to
271	288	disambiguate timestamps and SOF_TIMESTAMPING_OPT_TSONLY to operate
272	289	regardless of the setting of sysctl net.core.tstamp_allow_data.

include/uapi/linux/net_tstamp.h+2−1

@@ -32,8 +32,9 @@ enum { · 31 unmodified lines
32	32	SOF_TIMESTAMPING_OPT_TX_SWHW = (1<<14),
33	33	SOF_TIMESTAMPING_BIND_PHC = (1 << 15),
34	34	SOF_TIMESTAMPING_OPT_ID_TCP = (1 << 16),
	35	+ SOF_TIMESTAMPING_OPT_RX_FILTER = (1 << 17),
35	36
36		− SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_ID_TCP,
	37	+ SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_RX_FILTER,
37	38	SOF_TIMESTAMPING_MASK = (SOF_TIMESTAMPING_LAST - 1) \|
38	39	SOF_TIMESTAMPING_LAST
39	40	};

net/ethtool/common.c+1−0

@@ -427,6 +427,7 @@ const char sof_timestamping_names[][ETH_GSTRING_LEN] = { · 426 unmodified lines
427	427	[const_ilog2(SOF_TIMESTAMPING_OPT_TX_SWHW)] = "option-tx-swhw",
428	428	[const_ilog2(SOF_TIMESTAMPING_BIND_PHC)] = "bind-phc",
429	429	[const_ilog2(SOF_TIMESTAMPING_OPT_ID_TCP)] = "option-id-tcp",
	430	+ [const_ilog2(SOF_TIMESTAMPING_OPT_RX_FILTER)] = "option-rx-filter",
430	431	};
431	432	static_assert(ARRAY_SIZE(sof_timestamping_names) == __SOF_TIMESTAMPING_CNT);
432	433

net/ipv4/tcp.c+7−2

@@ -2235,6 +2235,7 @@ void tcp_recv_timestamp(struct msghdr msg, const struct sock sk, · 2234 unmodified lines
2235	2235	struct scm_timestamping_internal *tss)
2236	2236	{
2237	2237	int new_tstamp = sock_flag(sk, SOCK_TSTAMP_NEW);
	2238	+ u32 tsflags = READ_ONCE(sk->sk_tsflags);
2238	2239	bool has_timestamping = false;
2239	2240
2240	2241	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, · 33 unmodified lines
2274	2275	}
2275	2276	}
2276	2277
2277		− if (READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_SOFTWARE)
	2278	+ if (tsflags & SOF_TIMESTAMPING_SOFTWARE &&
	2279	+ (tsflags & SOF_TIMESTAMPING_RX_SOFTWARE \|\|
	2280	+ !(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER)))
2278	2281	has_timestamping = true;
2279	2282	else
2280	2283	tss->ts[0] = (struct timespec64) {0};
2281	2284	}
2282	2285
2283	2286	if (tss->ts[2].tv_sec \|\| tss->ts[2].tv_nsec) {
2284		− if (READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_RAW_HARDWARE)
	2287	+ if (tsflags & SOF_TIMESTAMPING_RAW_HARDWARE &&
	2288	+ (tsflags & SOF_TIMESTAMPING_RX_HARDWARE \|\|
	2289	+ !(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER)))
2285	2290	has_timestamping = true;
2286	2291	else
2287	2292	tss->ts[2] = (struct timespec64) {0};

net/socket.c+8−2

@@ -946,11 +946,17 @@ void __sock_recv_timestamp(struct msghdr msg, struct sock sk, · 945 unmodified lines
946	946
947	947	memset(&tss, 0, sizeof(tss));
948	948	tsflags = READ_ONCE(sk->sk_tsflags);
949		− if ((tsflags & SOF_TIMESTAMPING_SOFTWARE) &&
	949	+ if ((tsflags & SOF_TIMESTAMPING_SOFTWARE &&
	950	+ (tsflags & SOF_TIMESTAMPING_RX_SOFTWARE \|\|
	951	+ skb_is_err_queue(skb) \|\|
	952	+ !(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER))) &&
950	953	ktime_to_timespec64_cond(skb->tstamp, tss.ts + 0))
951	954	empty = 0;
952	955	if (shhwtstamps &&
953		− (tsflags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
	956	+ (tsflags & SOF_TIMESTAMPING_RAW_HARDWARE &&
	957	+ (tsflags & SOF_TIMESTAMPING_RX_HARDWARE \|\|
	958	+ skb_is_err_queue(skb) \|\|
	959	+ !(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER))) &&
954	960	!skb_is_swtx_tstamp(skb, false_tstamp)) {
955	961	if_index = 0;
956	962	if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP_NETDEV)