tcp: introduce tcp_rto_delta_us() helper for xmit timer fix

commit e1a10ef7fa876f8510aaec36ea5c0cf34baba410 upstream.

Pure refactor. This helper will be required in the xmit timer fix
later in the patch series. (Because the TLP logic will want to make
this calculation.)

[This version of the commit was compiled and briefly tested
based on top of v3.10.107.]

Change-Id: I1ccfba0b00465454bf5ce22e6fef5f7b5dd94d15
Fixes: 6ba8a3b19e76 ("tcp: Tail loss probe (TLP)")
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Nandita Dukkipati <nanditad@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 79cd118d59946c73e4754fc8ba3dfea39f9e8c1d..c4db9acefa9c242ac038a3ff243f3083c09d0a4b 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1592,4 +1592,14 @@ struct tcp_request_sock_ops {
 extern void tcp_v4_init(void);
 extern void tcp_init(void);
 
+/* At how many jiffies into the future should the RTO fire? */
+static inline s32 tcp_rto_delta(const struct sock *sk)
+{
+       const struct sk_buff *skb = tcp_write_queue_head(sk);
+       const u32 rto = inet_csk(sk)->icsk_rto;
+       const u32 rto_time_stamp = TCP_SKB_CB(skb)->when + rto;
+
+       return (s32)(rto_time_stamp - tcp_time_stamp);
+}
+
 #endif /* _TCP_H */

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 0680058fe6937c43b42e37784549c1f72d37c91a..a36b7c55b76bd74dedb31a6d1e852c159d1ab5fc 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2972,9 +2972,7 @@ void tcp_rearm_rto(struct sock *sk)
                /* Offset the time elapsed after installing regular RTO */
                if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
                    icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
-                       struct sk_buff *skb = tcp_write_queue_head(sk);
-                       const u32 rto_time_stamp = TCP_SKB_CB(skb)->when + rto;
-                       s32 delta = (s32)(rto_time_stamp - tcp_time_stamp);
+                       s32 delta = tcp_rto_delta(sk);
                        /* delta may not be positive if the socket is locked
                         * when the retrans timer fires and is rescheduled.
                         */