[CCID3]: Reorganise timeval handling

Introducing functions to add to or subtract from a timeval variable
and renaming now_delta to timeval_new_delta that calls do_gettimeofday
and then timeval_delta, that should be used when there are several
deltas made relative to the current time or setting variables to it,
so as to avoid calling do_gettimeofday excessively.

I'm leaving these "timeval_" prefixed funcions internal to DCCP for a
while till we're sure there are no subtle bugs in it.

It also is more correct as it checks if the number of usecs added to
or subtracted from a tv_usec field is more than 2 seconds.

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 98 insertions, 78 deletions

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 225c5301317..60e3a5f9fcb 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -156,26 +156,6 @@ static inline void ccid3_hc_tx_set_state(struct sock *sk,
         hctx->ccid3hctx_state = state;
 }
 
-static void timeval_sub(struct timeval large, struct timeval small,
-                        struct timeval *result)
-{
-        result->tv_sec = large.tv_sec-small.tv_sec;
-        if (large.tv_usec < small.tv_usec) {
-                (result->tv_sec)--;
-                result->tv_usec = USEC_PER_SEC +
-                                  large.tv_usec - small.tv_usec;
-        } else
-                result->tv_usec = large.tv_usec-small.tv_usec;
-}
-
-static inline void timeval_fix(struct timeval *tv)
-{
-        if (tv->tv_usec >= USEC_PER_SEC) {
-                tv->tv_sec++;
-                tv->tv_usec -= USEC_PER_SEC;
-        }
-}
-
 #define CALCX_ARRSIZE 500
 
 #define CALCX_SPLIT 50000
@@ -816,18 +796,22 @@ static void ccid3_hc_tx_update_x(struct sock *sk)
                                                           2 * hctx->ccid3hctx_x_recv),
                                                (hctx->ccid3hctx_s /
                                                 TFRC_MAX_BACK_OFF_TIME));
-        } else if (now_delta(hctx->ccid3hctx_t_ld) >= hctx->ccid3hctx_rtt) {
-                u32 rtt = hctx->ccid3hctx_rtt;
-                if (rtt < 10) {
-                        rtt = 10;
-                } /* avoid divide by zero below */
-                
-                hctx->ccid3hctx_x = max_t(u32, min_t(u32, 2 * hctx->ccid3hctx_x_recv,
-                                                          2 * hctx->ccid3hctx_x),
-                                               ((hctx->ccid3hctx_s * 100000) /
-                                                (rtt / 10)));
-                /* Using 100000 and 10 to avoid 32 bit overflow for jumbo frames */
-                do_gettimeofday(&hctx->ccid3hctx_t_ld);
+        } else {
+                struct timeval now;
+
+                do_gettimeofday(&now);
+                if (timeval_delta(&now, &hctx->ccid3hctx_t_ld) >=
+                    hctx->ccid3hctx_rtt) {
+                        /* Avoid divide by zero below */
+                        const u32 rtt = max_t(u32, hctx->ccid3hctx_rtt, 10);
+                        
+                        hctx->ccid3hctx_x = max_t(u32, min_t(u32, 2 * hctx->ccid3hctx_x_recv,
+                                                                  2 * hctx->ccid3hctx_x),
+                                                       ((hctx->ccid3hctx_s * 100000) /
+                                                        (rtt / 10)));
+                        /* Using 100000 and 10 to avoid 32 bit overflow for jumbo frames */
+                        hctx->ccid3hctx_t_ld = now;
+                }
         }
 
         if (hctx->ccid3hctx_x == 0) {
@@ -999,14 +983,15 @@ static int ccid3_hc_tx_send_packet(struct sock *sk,
 
                 /* Set nominal send time for initial packet */
                 hctx->ccid3hctx_t_nom = now;
-                (hctx->ccid3hctx_t_nom).tv_usec += hctx->ccid3hctx_t_ipi;
-                timeval_fix(&(hctx->ccid3hctx_t_nom));
+                timeval_add_usecs(&hctx->ccid3hctx_t_nom,
+                                  hctx->ccid3hctx_t_ipi);
                 ccid3_calc_new_delta(hctx);
                 rc = 0;
                 break;
         case TFRC_SSTATE_NO_FBACK:
         case TFRC_SSTATE_FBACK:
-                delay = now_delta(hctx->ccid3hctx_t_nom) - hctx->ccid3hctx_delta;
+                delay = (timeval_delta(&now, &hctx->ccid3hctx_t_nom) -
+                         hctx->ccid3hctx_delta);
                 ccid3_pr_debug("send_packet delay=%ld\n", delay);
                 delay /= -1000;
                 /* divide by -1000 is to convert to ms and get sign right */
@@ -1068,7 +1053,7 @@ static void ccid3_hc_tx_packet_sent(struct sock *sk, int more, int len)
                  * Algorithm in "8.1. Window Counter Valuer" in
                  * draft-ietf-dccp-ccid3-11.txt
                  */
-                quarter_rtt = now_delta(hctx->ccid3hctx_t_last_win_count) /
+                quarter_rtt = timeval_delta(&now, &hctx->ccid3hctx_t_last_win_count) /
                               (hctx->ccid3hctx_rtt / 4);
                 if (quarter_rtt > 0) {
                         hctx->ccid3hctx_t_last_win_count = now;
@@ -1102,8 +1087,8 @@ static void ccid3_hc_tx_packet_sent(struct sock *sk, int more, int len)
                         hctx->ccid3hctx_t_nom = now;
                         ccid3_calc_new_t_ipi(hctx);
                         ccid3_calc_new_delta(hctx);
-                        (hctx->ccid3hctx_t_nom).tv_usec += hctx->ccid3hctx_t_ipi;
-                        timeval_fix(&(hctx->ccid3hctx_t_nom));
+                        timeval_add_usecs(&hctx->ccid3hctx_t_nom,
+                                          hctx->ccid3hctx_t_ipi);
                 }
                 break;
         default:
@@ -1167,7 +1152,7 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                 }
 
                 /* Update RTT */
-                r_sample = now_delta(packet->dccphtx_tstamp);
+                r_sample = timeval_now_delta(&packet->dccphtx_tstamp);
                 /* FIXME: */
                 // r_sample -= usecs_to_jiffies(t_elapsed * 10);
 
@@ -1224,15 +1209,11 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                 ccid3_hc_tx_update_x(sk);
 
                 /* Update next send time */
-                if (hctx->ccid3hctx_t_ipi > (hctx->ccid3hctx_t_nom).tv_usec) {
-                        hctx->ccid3hctx_t_nom.tv_usec += USEC_PER_SEC;
-                        (hctx->ccid3hctx_t_nom).tv_sec--;
-                }
-                /* FIXME - if no feedback then t_ipi can go > 1 second */
-                (hctx->ccid3hctx_t_nom).tv_usec -= hctx->ccid3hctx_t_ipi;
+                timeval_sub_usecs(&hctx->ccid3hctx_t_nom,
+                                  hctx->ccid3hctx_t_ipi);
                 ccid3_calc_new_t_ipi(hctx);
-                (hctx->ccid3hctx_t_nom).tv_usec += hctx->ccid3hctx_t_ipi;
-                timeval_fix(&(hctx->ccid3hctx_t_nom));
+                timeval_add_usecs(&hctx->ccid3hctx_t_nom,
+                                  hctx->ccid3hctx_t_ipi);
                 ccid3_calc_new_delta(hctx);
 
                 /* remove all packets older than the one acked from history */
@@ -1559,20 +1540,24 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk)
         struct dccp_sock *dp = dccp_sk(sk);
         struct ccid3_hc_rx_sock *hcrx = dp->dccps_hc_rx_ccid_private;
         struct dccp_rx_hist_entry *packet;
+        struct timeval now;
 
         ccid3_pr_debug("%s, sk=%p\n", dccp_role(sk), sk);
 
+        do_gettimeofday(&now);
+
         switch (hcrx->ccid3hcrx_state) {
         case TFRC_RSTATE_NO_DATA:
                 hcrx->ccid3hcrx_x_recv = 0;
                 break;
         case TFRC_RSTATE_DATA: {
-                u32 delta = now_delta(hcrx->ccid3hcrx_tstamp_last_feedback);
+                const u32 delta = timeval_delta(&now,
+                                        &hcrx->ccid3hcrx_tstamp_last_feedback);
 
-                if (delta == 0)
-                        delta = 1; /* to prevent divide by zero */
                 hcrx->ccid3hcrx_x_recv = (hcrx->ccid3hcrx_bytes_recv *
-                                          USEC_PER_SEC) / delta;
+                                          USEC_PER_SEC);
+                if (likely(delta > 1))
+                        hcrx->ccid3hcrx_x_recv /= delta;
         }
                 break;
         default:
@@ -1590,13 +1575,14 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk)
                 return;
         }
 
-        do_gettimeofday(&(hcrx->ccid3hcrx_tstamp_last_feedback));
+        hcrx->ccid3hcrx_tstamp_last_feedback = now;
         hcrx->ccid3hcrx_last_counter         = packet->dccphrx_ccval;
         hcrx->ccid3hcrx_seqno_last_counter   = packet->dccphrx_seqno;
         hcrx->ccid3hcrx_bytes_recv           = 0;
 
         /* Convert to multiples of 10us */
-        hcrx->ccid3hcrx_elapsed_time = now_delta(packet->dccphrx_tstamp) / 10;
+        hcrx->ccid3hcrx_elapsed_time =
+                        timeval_delta(&now, &packet->dccphrx_tstamp) / 10;
         if (hcrx->ccid3hcrx_p == 0)
                 hcrx->ccid3hcrx_pinv = ~0;
         else
@@ -1676,7 +1662,7 @@ static u32 ccid3_hc_rx_calc_first_li(struct sock *sk)
         struct ccid3_hc_rx_sock *hcrx = dp->dccps_hc_rx_ccid_private;
         struct dccp_rx_hist_entry *entry, *next, *tail = NULL;
         u32 rtt, delta, x_recv, fval, p, tmp2;
-        struct timeval tstamp = { 0 }, tmp_tv;
+        struct timeval tstamp = { 0, };
         int interval = 0;
         int win_count = 0;
         int step = 0;
@@ -1718,18 +1704,16 @@ static u32 ccid3_hc_rx_calc_first_li(struct sock *sk)
                 interval = 1;
         }
 found:
-        timeval_sub(tstamp,tail->dccphrx_tstamp,&tmp_tv);
-        rtt = (tmp_tv.tv_sec * USEC_PER_SEC + tmp_tv.tv_usec) * 4 / interval;
+        rtt = timeval_delta(&tstamp, &tail->dccphrx_tstamp) * 4 / interval;
         ccid3_pr_debug("%s, sk=%p, approximated RTT to %uus\n",
                        dccp_role(sk), sk, rtt);
         if (rtt == 0)
                 rtt = 1;
 
-        delta = now_delta(hcrx->ccid3hcrx_tstamp_last_feedback);
-        if (delta == 0)
-                delta = 1;
-
-        x_recv = (hcrx->ccid3hcrx_bytes_recv * USEC_PER_SEC) / delta;
+        delta = timeval_now_delta(&hcrx->ccid3hcrx_tstamp_last_feedback);
+        x_recv = hcrx->ccid3hcrx_bytes_recv * USEC_PER_SEC;
+        if (likely(delta > 1))
+                x_recv /= delta;
 
         tmp1 = (u64)x_recv * (u64)rtt;
         do_div(tmp1,10000000);
@@ -1926,7 +1910,6 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
         const struct dccp_options_received *opt_recv;
         struct dccp_rx_hist_entry *packet;
         struct timeval now;
-        u32 now_usecs;
         u8 win_count;
         u32 p_prev;
         int ins;
@@ -1948,8 +1931,7 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
                         break;
                 p_prev = hcrx->ccid3hcrx_rtt;
                 do_gettimeofday(&now);
-                now_usecs = now.tv_sec * USEC_PER_SEC + now.tv_usec;
-                hcrx->ccid3hcrx_rtt = now_usecs -
+                hcrx->ccid3hcrx_rtt = timeval_usecs(&now) -
                                      (opt_recv->dccpor_timestamp_echo -
                                       opt_recv->dccpor_elapsed_time) * 10;
                 if (p_prev != hcrx->ccid3hcrx_rtt)
@@ -1994,15 +1976,16 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
         case TFRC_RSTATE_DATA:
                 hcrx->ccid3hcrx_bytes_recv += skb->len -
                                               dccp_hdr(skb)->dccph_doff * 4;
-                if (ins == 0) {
-                        if (now_delta(hcrx->ccid3hcrx_tstamp_last_ack) >=
-                            hcrx->ccid3hcrx_rtt) {
-                                do_gettimeofday(&hcrx->ccid3hcrx_tstamp_last_ack);
-                                ccid3_hc_rx_send_feedback(sk);
-                        }
-                        return;
+                if (ins != 0)
+                        break;
+
+                do_gettimeofday(&now);
+                if (timeval_delta(&now, &hcrx->ccid3hcrx_tstamp_last_ack) >=
+                    hcrx->ccid3hcrx_rtt) {
+                        hcrx->ccid3hcrx_tstamp_last_ack = now;
+                        ccid3_hc_rx_send_feedback(sk);
                 }
-                break;
+                return;
         default:
                 printk(KERN_CRIT "%s: %s, sk=%p, Illegal state (%d)!\n",
                        __FUNCTION__, dccp_role(sk), sk, hcrx->ccid3hcrx_state);
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 6ba21509e79..5cd9e794bbe 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -429,17 +429,53 @@ extern int dccp_ackpkts_add(struct dccp_ackpkts *ap, u64 ackno, u8 state);
 extern void dccp_ackpkts_check_rcv_ackno(struct dccp_ackpkts *ap,
                                          struct sock *sk, u64 ackno);
 
+static inline suseconds_t timeval_usecs(const struct timeval *tv)
+{
+        return tv->tv_sec * USEC_PER_SEC + tv->tv_usec;
+}
+
+static inline suseconds_t timeval_delta(const struct timeval *large,
+                                        const struct timeval *small)
+{
+        time_t      secs  = large->tv_sec  - small->tv_sec;
+        suseconds_t usecs = large->tv_usec - small->tv_usec;
+
+        if (usecs < 0) {
+                secs--;
+                usecs += USEC_PER_SEC;
+        }
+        return secs * USEC_PER_SEC + usecs;
+}
+
+static inline void timeval_add_usecs(struct timeval *tv,
+                                     const suseconds_t usecs)
+{
+        tv->tv_usec += usecs;
+        while (tv->tv_usec >= USEC_PER_SEC) {
+                tv->tv_sec++;
+                tv->tv_usec -= USEC_PER_SEC;
+        }
+}
+
+static inline void timeval_sub_usecs(struct timeval *tv,
+                                     const suseconds_t usecs)
+{
+        tv->tv_usec -= usecs;
+        while (tv->tv_usec < 0) {
+                tv->tv_sec--;
+                tv->tv_usec += USEC_PER_SEC;
+        }
+}
+
 /*
  * Returns the difference in usecs between timeval
  * passed in and current time
  */
-static inline u32 now_delta(struct timeval tv)
+static inline suseconds_t timeval_now_delta(const struct timeval *tv)
 {
         struct timeval now;
-        
         do_gettimeofday(&now);
-        return (now.tv_sec  - tv.tv_sec) * USEC_PER_SEC +
-               (now.tv_usec - tv.tv_usec);
+        return timeval_delta(&now, tv);
 }
 
 #ifdef CONFIG_IP_DCCP_DEBUG
diff --git a/net/dccp/options.c b/net/dccp/options.c
index eabcc8f1c62..382c5894acb 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -359,7 +359,7 @@ static void dccp_insert_option_ack_vector(struct sock *sk, struct sk_buff *skb)
 #endif
         struct dccp_ackpkts *ap = dp->dccps_hc_rx_ackpkts;
         int len = ap->dccpap_buf_vector_len + 2;
-        const u32 elapsed_time = now_delta(ap->dccpap_time) / 10;
+        const u32 elapsed_time = timeval_now_delta(&ap->dccpap_time) / 10;
         unsigned char *to, *from;
 
         if (elapsed_time != 0)
@@ -451,7 +451,8 @@ static void dccp_insert_option_timestamp_echo(struct sock *sk,
                                         "CLIENT TX opt: " : "server TX opt: ";
 #endif
         u32 tstamp_echo;
-        const u32 elapsed_time = now_delta(dp->dccps_timestamp_time) / 10;
+        const u32 elapsed_time =
+                        timeval_now_delta(&dp->dccps_timestamp_time) / 10;
         const int elapsed_time_len = dccp_elapsed_time_len(elapsed_time);
         const int len = 6 + elapsed_time_len;
         unsigned char *to;