[DCCP]: Provide function for RTT sampling

[powerpc.git] / net / dccp / input.c

diff --git a/net/dccp/input.c b/net/dccp/input.c
index a190015..bd578c8 100644 (file)
--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -577,3 +577,43 @@ discard:
 }
 
 EXPORT_SYMBOL_GPL(dccp_rcv_state_process);
+
+/**
+ * dccp_sample_rtt  -  Sample RTT from packet exchange
+ *
+ * @sk:     connected dccp_sock
+ * @t_recv: receive timestamp of packet with timestamp echo
+ * @t_hist: packet history timestamp or NULL
+ */
+u32 dccp_sample_rtt(struct sock *sk, struct timeval *t_recv,
+                                    struct timeval *t_hist)
+{
+       struct dccp_sock *dp = dccp_sk(sk);
+       struct dccp_options_received *or = &dp->dccps_options_received;
+       suseconds_t delta;
+
+       if (t_hist == NULL) {
+               if (!or->dccpor_timestamp_echo) {
+                       DCCP_WARN("packet without timestamp echo\n");
+                       return DCCP_SANE_RTT_MAX;
+               }
+               timeval_sub_usecs(t_recv, or->dccpor_timestamp_echo * 10);
+               delta = timeval_usecs(t_recv);
+       } else
+               delta = timeval_delta(t_recv, t_hist);
+
+       delta -= or->dccpor_elapsed_time * 10;          /* either set or 0 */
+
+       if (unlikely(delta <= 0)) {
+               DCCP_WARN("unusable RTT sample %ld, using min\n", (long)delta);
+               return DCCP_SANE_RTT_MIN;
+       }
+       if (unlikely(delta - (suseconds_t)DCCP_SANE_RTT_MAX > 0)) {
+               DCCP_WARN("RTT sample %ld too large, using max\n", (long)delta);
+               return DCCP_SANE_RTT_MAX;
+       }
+
+       return delta;
+}
+
+EXPORT_SYMBOL_GPL(dccp_sample_rtt);