tcp: Add snd_wnd to TCP_INFO

Neal Cardwell mentioned that snd_wnd would be useful for diagnosing TCP
performance problems --
> (1) Usually when we're diagnosing TCP performance problems, we do so
> from the sender, since the sender makes most of the
> performance-critical decisions (cwnd, pacing, TSO size, TSQ, etc).
> From the sender-side the thing that would be most useful is to see
> tp->snd_wnd, the receive window that the receiver has advertised to
> the sender.

This serves the purpose of adding an additional __u32 to avoid the
would-be hole caused by the addition of the tcpi_rcvi_ooopack field.

Signed-off-by: Thomas Higdon <tph@fb.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 20237987ccc825592a7a76ff19b72aa839f88c50..81e697978e8b5d1d2f6861dba8dd59ce669ede0d 100644 (file)
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -272,6 +272,10 @@ struct tcp_info {
        __u32   tcpi_reord_seen;     /* reordering events seen */
 
        __u32   tcpi_rcv_ooopack;    /* Out-of-order packets received */
+
+       __u32   tcpi_snd_wnd;        /* peer's advertised receive window after
+                                     * scaling (bytes)
+                                     */
 };
 
 /* netlink attributes types for SCM_TIMESTAMPING_OPT_STATS */

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 4cf58208270e7253dc427a60d2ec92149f33ff9c..79c325a07ba5dc7cfad0a846d1f03bf1787f840b 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3297,6 +3297,7 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info)
        info->tcpi_dsack_dups = tp->dsack_dups;
        info->tcpi_reord_seen = tp->reord_seen;
        info->tcpi_rcv_ooopack = tp->rcv_ooopack;
+       info->tcpi_snd_wnd = tp->snd_wnd;
        unlock_sock_fast(sk, slow);
 }
 EXPORT_SYMBOL_GPL(tcp_get_info);