tcp: SOF_TIMESTAMPING_OPT_STATS option for SO_TIMESTAMPING

This patch exports the sender chronograph stats via the socket
SO_TIMESTAMPING channel. Currently we can instrument how long a
particular application unit of data was queued in TCP by tracking
SOF_TIMESTAMPING_TX_SOFTWARE and SOF_TIMESTAMPING_TX_SCHED. Having
these sender chronograph stats exported simultaneously along with
these timestamps allow further breaking down the various sender
limitation.  For example, a video server can tell if a particular
chunk of video on a connection takes a long time to deliver because
TCP was experiencing small receive window. It is not possible to
tell before this patch without packet traces.

To prepare these stats, the user needs to set
SOF_TIMESTAMPING_OPT_STATS and SOF_TIMESTAMPING_OPT_TSONLY flags
while requesting other SOF_TIMESTAMPING TX timestamps. When the
timestamps are available in the error queue, the stats are returned
in a separate control message of type SCM_TIMESTAMPING_OPT_STATS,
in a list of TLVs (struct nlattr) of types: TCP_NLA_BUSY_TIME,
TCP_NLA_RWND_LIMITED, TCP_NLA_SNDBUF_LIMITED. Unit is microsecond.

Signed-off-by: Francis Yan <francisyyan@gmail.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

20 files changed, 90 insertions, 5 deletions

diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt
index 671cccf0dcd2..96f50694a748 100644
--- a/Documentation/networking/timestamping.txt
+++ b/Documentation/networking/timestamping.txt
@@ -182,6 +182,16 @@ SOF_TIMESTAMPING_OPT_TSONLY:
   the timestamp even if sysctl net.core.tstamp_allow_data is 0.
   This option disables SOF_TIMESTAMPING_OPT_CMSG.
 
+SOF_TIMESTAMPING_OPT_STATS:
+
+  Optional stats that are obtained along with the transmit timestamps.
+  It must be used together with SOF_TIMESTAMPING_OPT_TSONLY. When the
+  transmit timestamp is available, the stats are available in a
+  separate control message of type SCM_TIMESTAMPING_OPT_STATS, as a
+  list of TLVs (struct nlattr) of types. These stats allow the
+  application to associate various transport layer stats with
+  the transmit timestamps, such as how long a certain block of
+  data was limited by peer's receiver window.
 
 New applications are encouraged to pass SOF_TIMESTAMPING_OPT_ID to
 disambiguate timestamps and SOF_TIMESTAMPING_OPT_TSONLY to operate
diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
index 9e46d6e656d9..afc901b7a6f6 100644
--- a/arch/alpha/include/uapi/asm/socket.h
+++ b/arch/alpha/include/uapi/asm/socket.h
@@ -97,4 +97,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SCM_TIMESTAMPING_OPT_STATS	54
+
 #endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/frv/include/uapi/asm/socket.h b/arch/frv/include/uapi/asm/socket.h
index afbc98f02d27..81e03530ed39 100644
--- a/arch/frv/include/uapi/asm/socket.h
+++ b/arch/frv/include/uapi/asm/socket.h
@@ -90,5 +90,7 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SCM_TIMESTAMPING_OPT_STATS	54
+
 #endif /* _ASM_SOCKET_H */
 
diff --git a/arch/ia64/include/uapi/asm/socket.h b/arch/ia64/include/uapi/asm/socket.h
index 0018fad9039f..57feb0c1f7d7 100644
--- a/arch/ia64/include/uapi/asm/socket.h
+++ b/arch/ia64/include/uapi/asm/socket.h
@@ -99,4 +99,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SCM_TIMESTAMPING_OPT_STATS	54
+
 #endif /* _ASM_IA64_SOCKET_H */
diff --git a/arch/m32r/include/uapi/asm/socket.h b/arch/m32r/include/uapi/asm/socket.h
index 5fe42fc7b6c5..5853f8e92c20 100644
--- a/arch/m32r/include/uapi/asm/socket.h
+++ b/arch/m32r/include/uapi/asm/socket.h
@@ -90,4 +90,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SCM_TIMESTAMPING_OPT_STATS	54
+
 #endif /* _ASM_M32R_SOCKET_H */
diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
index 2027240aafbb..566ecdcb5b4b 100644
--- a/arch/mips/include/uapi/asm/socket.h
+++ b/arch/mips/include/uapi/asm/socket.h
@@ -108,4 +108,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SCM_TIMESTAMPING_OPT_STATS	54
+
 #endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/mn10300/include/uapi/asm/socket.h b/arch/mn10300/include/uapi/asm/socket.h
index 5129f23a9ee1..0e12527c4b0e 100644
--- a/arch/mn10300/include/uapi/asm/socket.h
+++ b/arch/mn10300/include/uapi/asm/socket.h
@@ -90,4 +90,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SCM_TIMESTAMPING_OPT_STATS	54
+
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h
index 9c935d717df9..7a109b73ddf7 100644
--- a/arch/parisc/include/uapi/asm/socket.h
+++ b/arch/parisc/include/uapi/asm/socket.h
@@ -89,4 +89,6 @@
 
 #define SO_CNX_ADVICE		0x402E
 
+#define SCM_TIMESTAMPING_OPT_STATS	0x402F
+
 #endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/powerpc/include/uapi/asm/socket.h b/arch/powerpc/include/uapi/asm/socket.h
index 1672e3398270..44583a52f882 100644
--- a/arch/powerpc/include/uapi/asm/socket.h
+++ b/arch/powerpc/include/uapi/asm/socket.h
@@ -97,4 +97,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SCM_TIMESTAMPING_OPT_STATS	54
+
 #endif	/* _ASM_POWERPC_SOCKET_H */
diff --git a/arch/s390/include/uapi/asm/socket.h b/arch/s390/include/uapi/asm/socket.h
index 41b51c2f4f1b..b24a64cbfeb1 100644
--- a/arch/s390/include/uapi/asm/socket.h
+++ b/arch/s390/include/uapi/asm/socket.h
@@ -96,4 +96,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SCM_TIMESTAMPING_OPT_STATS	54
+
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
index 31aede3af088..a25dc32f5d6a 100644
--- a/arch/sparc/include/uapi/asm/socket.h
+++ b/arch/sparc/include/uapi/asm/socket.h
@@ -86,6 +86,8 @@
 
 #define SO_CNX_ADVICE		0x0037
 
+#define SCM_TIMESTAMPING_OPT_STATS	0x0038
+
 /* Security levels - as per NRL IPv6 - don't actually do anything */
 #define SO_SECURITY_AUTHENTICATION		0x5001
 #define SO_SECURITY_ENCRYPTION_TRANSPORT	0x5002
diff --git a/arch/xtensa/include/uapi/asm/socket.h b/arch/xtensa/include/uapi/asm/socket.h
index 81435d995e11..9fdbe1fe0473 100644
--- a/arch/xtensa/include/uapi/asm/socket.h
+++ b/arch/xtensa/include/uapi/asm/socket.h
@@ -101,4 +101,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SCM_TIMESTAMPING_OPT_STATS	54
+
 #endif	/* _XTENSA_SOCKET_H */
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index d5d3bd814338..00e0ee8f001f 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -428,4 +428,6 @@ static inline void tcp_saved_syn_free(struct tcp_sock *tp)
 	tp->saved_syn = NULL;
 }
 
+struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk);
+
 #endif	/* _LINUX_TCP_H */
diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
index 67d632f1743d..2c748ddad5f8 100644
--- a/include/uapi/asm-generic/socket.h
+++ b/include/uapi/asm-generic/socket.h
@@ -92,4 +92,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SCM_TIMESTAMPING_OPT_STATS	54
+
 #endif /* __ASM_GENERIC_SOCKET_H */
diff --git a/include/uapi/linux/net_tstamp.h b/include/uapi/linux/net_tstamp.h
index 264e515de16f..464dcca5ed68 100644
--- a/include/uapi/linux/net_tstamp.h
+++ b/include/uapi/linux/net_tstamp.h
@@ -25,8 +25,9 @@ enum {
 	SOF_TIMESTAMPING_TX_ACK = (1<<9),
 	SOF_TIMESTAMPING_OPT_CMSG = (1<<10),
 	SOF_TIMESTAMPING_OPT_TSONLY = (1<<11),
+	SOF_TIMESTAMPING_OPT_STATS = (1<<12),
 
-	SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_TSONLY,
+	SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_STATS,
 	SOF_TIMESTAMPING_MASK = (SOF_TIMESTAMPING_LAST - 1) |
 				 SOF_TIMESTAMPING_LAST
 };
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 2863b661d6e1..c53de2691cec 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -220,6 +220,14 @@ struct tcp_info {
 	__u64	tcpi_sndbuf_limited; /* Time (usec) limited by send buffer */
 };
 
+/* netlink attributes types for SCM_TIMESTAMPING_OPT_STATS */
+enum {
+	TCP_NLA_PAD,
+	TCP_NLA_BUSY,		/* Time (usec) busy sending data */
+	TCP_NLA_RWND_LIMITED,	/* Time (usec) limited by receive window */
+	TCP_NLA_SNDBUF_LIMITED,	/* Time (usec) limited by send buffer */
+};
+
 /* for TCP_MD5SIG socket option */
 #define TCP_MD5SIG_MAXKEYLEN	80
 
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index d1d1a5a5ad24..ea6fa954c7a0 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3839,10 +3839,18 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
 	if (!skb_may_tx_timestamp(sk, tsonly))
 		return;
 
-	if (tsonly)
-		skb = alloc_skb(0, GFP_ATOMIC);
-	else
+	if (tsonly) {
+#ifdef CONFIG_INET
+		if ((sk->sk_tsflags & SOF_TIMESTAMPING_OPT_STATS) &&
+		    sk->sk_protocol == IPPROTO_TCP &&
+		    sk->sk_type == SOCK_STREAM)
+			skb = tcp_get_timestamping_opt_stats(sk);
+		else
+#endif
+			skb = alloc_skb(0, GFP_ATOMIC);
+	} else {
 		skb = skb_clone(orig_skb, GFP_ATOMIC);
+	}
 	if (!skb)
 		return;
 
diff --git a/net/core/sock.c b/net/core/sock.c
index 14e6145be33b..d8c7f8c877ca 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -854,6 +854,13 @@ set_rcvbuf:
 				sk->sk_tskey = 0;
 			}
 		}
+
+		if (val & SOF_TIMESTAMPING_OPT_STATS &&
+		    !(val & SOF_TIMESTAMPING_OPT_TSONLY)) {
+			ret = -EINVAL;
+			break;
+		}
+
 		sk->sk_tsflags = val;
 		if (val & SOF_TIMESTAMPING_RX_SOFTWARE)
 			sock_enable_timestamp(sk,
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index cdde20f49999..1149b48700a1 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2841,6 +2841,26 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info)
 }
 EXPORT_SYMBOL_GPL(tcp_get_info);
 
+struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *stats;
+	struct tcp_info info;
+
+	stats = alloc_skb(3 * nla_total_size_64bit(sizeof(u64)), GFP_ATOMIC);
+	if (!stats)
+		return NULL;
+
+	tcp_get_info_chrono_stats(tp, &info);
+	nla_put_u64_64bit(stats, TCP_NLA_BUSY,
+			  info.tcpi_busy_time, TCP_NLA_PAD);
+	nla_put_u64_64bit(stats, TCP_NLA_RWND_LIMITED,
+			  info.tcpi_rwnd_limited, TCP_NLA_PAD);
+	nla_put_u64_64bit(stats, TCP_NLA_SNDBUF_LIMITED,
+			  info.tcpi_sndbuf_limited, TCP_NLA_PAD);
+	return stats;
+}
+
 static int do_tcp_getsockopt(struct sock *sk, int level,
 		int optname, char __user *optval, int __user *optlen)
 {
diff --git a/net/socket.c b/net/socket.c
index e2584c51aa1f..e6318943ad07 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -693,9 +693,14 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
 	    (sk->sk_tsflags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
 	    ktime_to_timespec_cond(shhwtstamps->hwtstamp, tss.ts + 2))
 		empty = 0;
-	if (!empty)
+	if (!empty) {
 		put_cmsg(msg, SOL_SOCKET,
 			 SCM_TIMESTAMPING, sizeof(tss), &tss);
+
+		if (skb->len && (sk->sk_tsflags & SOF_TIMESTAMPING_OPT_STATS))
+			put_cmsg(msg, SOL_SOCKET, SCM_TIMESTAMPING_OPT_STATS,
+				 skb->len, skb->data);
+	}
 }
 EXPORT_SYMBOL_GPL(__sock_recv_timestamp);