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 <t...@fb.com>
---
changes since v4:
- clarify comment
include/uapi/linux/tcp.h | 4 ++++
net/ipv4/tcp.c | 1 +
2 files changed, 5 insertions(+)
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 20237987ccc8..81e697978e8b 100644
--- 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 4cf58208270e..79c325a07ba5 100644
--- 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);
--
2.17.1
