net: add new control message for incoming HW-timestamped packets

Add SOF_TIMESTAMPING_OPT_PKTINFO option to request a new control message
for incoming packets with hardware timestamps. It contains the index of
the real interface which received the packet and the length of the
packet at layer 2.

The index is useful with bonding, bridges and other interfaces, where
IP_PKTINFO doesn't allow applications to determine which PHC made the
timestamp. With the L2 length (and link speed) it is possible to
transpose preamble timestamps to trailer timestamps, which are used in
the NTP protocol.

While this information could be provided by two new socket options
independently from timestamping, it doesn't look like they would be very
useful. With this option any performance impact is limited to hardware
timestamping.

Use dev_get_by_napi_id() to get the device and its index. On kernels
with disabled CONFIG_NET_RX_BUSY_POLL or drivers not using NAPI, a zero
index will be returned in the control message.

CC: Richard Cochran <richardcochran@gmail.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt
index 96f50694a74837735a60a5b83d3b83a58ae72c23..ce11e3a08c0d18faf4d75ab43f4b01c18af4de99 100644 (file)
--- a/Documentation/networking/timestamping.txt
+++ b/Documentation/networking/timestamping.txt
@@ -193,6 +193,16 @@ SOF_TIMESTAMPING_OPT_STATS:
   the transmit timestamps, such as how long a certain block of
   data was limited by peer's receiver window.
 
+SOF_TIMESTAMPING_OPT_PKTINFO:
+
+  Enable the SCM_TIMESTAMPING_PKTINFO control message for incoming
+  packets with hardware timestamps. The message contains struct
+  scm_ts_pktinfo, which supplies the index of the real interface which
+  received the packet and its length at layer 2. A valid (non-zero)
+  interface index will be returned only if CONFIG_NET_RX_BUSY_POLL is
+  enabled and the driver is using NAPI. The struct contains also two
+  other fields, but they are reserved and undefined.
+
 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/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
index 2b488565599daf73b8942fe6482890830af94dff..a5f6e819fafd9c9cbd92f18cd13383fb04d9f2fa 100644 (file)
--- a/include/uapi/asm-generic/socket.h
+++ b/include/uapi/asm-generic/socket.h
@@ -100,4 +100,6 @@
 
 #define SO_COOKIE              57
 
+#define SCM_TIMESTAMPING_PKTINFO       58
+
 #endif /* __ASM_GENERIC_SOCKET_H */

diff --git a/include/uapi/linux/net_tstamp.h b/include/uapi/linux/net_tstamp.h
index 0749fb13e5171083e3b7beb20228b682f136fa1c..dee74d39da9462d295f1620e925b81031d721ebd 100644 (file)
--- a/include/uapi/linux/net_tstamp.h
+++ b/include/uapi/linux/net_tstamp.h
@@ -9,6 +9,7 @@
 #ifndef _NET_TIMESTAMPING_H
 #define _NET_TIMESTAMPING_H
 
+#include <linux/types.h>
 #include <linux/socket.h>   /* for SO_TIMESTAMPING */
 
 /* SO_TIMESTAMPING gets an integer bit field comprised of these values */
@@ -26,8 +27,9 @@ enum {
        SOF_TIMESTAMPING_OPT_CMSG = (1<<10),
        SOF_TIMESTAMPING_OPT_TSONLY = (1<<11),
        SOF_TIMESTAMPING_OPT_STATS = (1<<12),
+       SOF_TIMESTAMPING_OPT_PKTINFO = (1<<13),
 
-       SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_STATS,
+       SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_PKTINFO,
        SOF_TIMESTAMPING_MASK = (SOF_TIMESTAMPING_LAST - 1) |
                                 SOF_TIMESTAMPING_LAST
 };
@@ -130,4 +132,11 @@ enum hwtstamp_rx_filters {
        HWTSTAMP_FILTER_NTP_ALL,
 };
 
+/* SCM_TIMESTAMPING_PKTINFO control message */
+struct scm_ts_pktinfo {
+       __u32 if_index;
+       __u32 pkt_length;
+       __u32 reserved[2];
+};
+
 #endif /* _NET_TIMESTAMPING_H */

diff --git a/net/socket.c b/net/socket.c
index c2564eb25c6b8faf5c99504ef1d3c90f9bb57c73..67db7d8a3b8137990217811304eab0f67a6ec6a4 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -662,6 +662,27 @@ static bool skb_is_err_queue(const struct sk_buff *skb)
        return skb->pkt_type == PACKET_OUTGOING;
 }
 
+static void put_ts_pktinfo(struct msghdr *msg, struct sk_buff *skb)
+{
+       struct scm_ts_pktinfo ts_pktinfo;
+       struct net_device *orig_dev;
+
+       if (!skb_mac_header_was_set(skb))
+               return;
+
+       memset(&ts_pktinfo, 0, sizeof(ts_pktinfo));
+
+       rcu_read_lock();
+       orig_dev = dev_get_by_napi_id(skb_napi_id(skb));
+       if (orig_dev)
+               ts_pktinfo.if_index = orig_dev->ifindex;
+       rcu_read_unlock();
+
+       ts_pktinfo.pkt_length = skb->len - skb_mac_offset(skb);
+       put_cmsg(msg, SOL_SOCKET, SCM_TIMESTAMPING_PKTINFO,
+                sizeof(ts_pktinfo), &ts_pktinfo);
+}
+
 /*
  * called from sock_recv_timestamp() if sock_flag(sk, SOCK_RCVTSTAMP)
  */
@@ -699,8 +720,12 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
                empty = 0;
        if (shhwtstamps &&
            (sk->sk_tsflags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
-           ktime_to_timespec_cond(shhwtstamps->hwtstamp, tss.ts + 2))
+           ktime_to_timespec_cond(shhwtstamps->hwtstamp, tss.ts + 2)) {
                empty = 0;
+               if ((sk->sk_tsflags & SOF_TIMESTAMPING_OPT_PKTINFO) &&
+                   !skb_is_err_queue(skb))
+                       put_ts_pktinfo(msg, skb);
+       }
        if (!empty) {
                put_cmsg(msg, SOL_SOCKET,
                         SCM_TIMESTAMPING, sizeof(tss), &tss);