tcp: Extend SOF_TIMESTAMPING_RX_SOFTWARE to TCP recvmsg
When SOF_TIMESTAMPING_RX_SOFTWARE is enabled for tcp sockets, return the
timestamp corresponding to the highest sequence number data returned.
Previously the skb->tstamp is overwritten when a TCP packet is placed
in the out of order queue. While the packet is in the ooo queue, save the
timestamp in the TCB_SKB_CB. This space is shared with the gso_*
options which are only used on the tx path, and a previously unused 4
byte hole.
When skbs are coalesced either in the sk_receive_queue or the
out_of_order_queue always choose the timestamp of the appended skb to
maintain the invariant of returning the timestamp of the last byte in
the recvmsg buffer.
Signed-off-by: Mike Maloney <maloney@google.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index a995004..c614ff1 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -774,6 +774,12 @@
u16 tcp_gso_segs;
u16 tcp_gso_size;
};
+
+ /* Used to stash the receive timestamp while this skb is in the
+ * out of order queue, as skb->tstamp is overwritten by the
+ * rbnode.
+ */
+ ktime_t swtstamp;
};
__u8 tcp_flags; /* TCP header flags. (tcp[13]) */
@@ -790,7 +796,8 @@
__u8 ip_dsfield; /* IPv4 tos or IPv6 dsfield */
__u8 txstamp_ack:1, /* Record TX timestamp for ack? */
eor:1, /* Is skb MSG_EOR marked? */
- unused:6;
+ has_rxtstamp:1, /* SKB has a RX timestamp */
+ unused:5;
__u32 ack_seq; /* Sequence number ACK'd */
union {
struct {