[DCCP]: Debug timeval operations

Problem:

 Most target types in the CCID3 code are u32, so subtle conversion errors
 can occur if signed time calculations yield negative results: the original
 values are lost in the conversion to unsigned, calculation errors go undetected.

 This patch therefore
   * sets all critical time types from unsigned to suseconds_t
   * avoids comparison between signed/unsigned via type-casting
   * provides ample warning messages in case time calculations are negative

 These warning messages can be removed at a later stage when the code
 has undergone more testing.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

2 files changed, 33 insertions, 24 deletions

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 89ef1183e48c..820bc25e14dc 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -128,8 +128,8 @@ static void ccid3_hc_tx_update_x(struct sock *sk, struct timeval *now)
                 hctx->ccid3hctx_x = max_t(u64, hctx->ccid3hctx_x,
                                           (hctx->ccid3hctx_s << 6)/TFRC_T_MBI);
 
-        } else if (timeval_delta(now, &hctx->ccid3hctx_t_ld) >=
-                                                          hctx->ccid3hctx_rtt) {
+        } else if (timeval_delta(now, &hctx->ccid3hctx_t_ld) -
+                        (suseconds_t)hctx->ccid3hctx_rtt >= 0 ) {
 
                 hctx->ccid3hctx_x = max(2 * min(hctx->ccid3hctx_x,
                                                 hctx->ccid3hctx_x_recv),
@@ -271,7 +271,7 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
         struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
         struct dccp_tx_hist_entry *new_packet;
         struct timeval now;
-        long delay;
+        suseconds_t delay;
 
         BUG_ON(hctx == NULL);
 
@@ -331,7 +331,7 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
                  * else
                  *       // send the packet in (t_nom - t_now) milliseconds.
                  */
-                if (delay - (long)hctx->ccid3hctx_delta >= 0)
+                if (delay - (suseconds_t)hctx->ccid3hctx_delta >= 0)
                         return delay / 1000L;
                 break;
         case TFRC_SSTATE_TERM:
@@ -353,7 +353,7 @@ static void ccid3_hc_tx_packet_sent(struct sock *sk, int more, unsigned int len)
         const struct dccp_sock *dp = dccp_sk(sk);
         struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
         struct timeval now;
-        unsigned long quarter_rtt;
+        suseconds_t quarter_rtt;
         struct dccp_tx_hist_entry *packet;
 
         BUG_ON(hctx == NULL);
@@ -450,10 +450,8 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                 r_sample  = timeval_delta(&now, &packet->dccphtx_tstamp);
                 t_elapsed = dp->dccps_options_received.dccpor_elapsed_time * 10;
 
-                if (unlikely(r_sample <= 0)) {
-                        DCCP_WARN("WARNING: R_sample (%ld) <= 0!\n", r_sample);
-                        r_sample = 0;
-                } else if (unlikely(r_sample <= t_elapsed))
+                DCCP_BUG_ON(r_sample < 0);
+                if (unlikely(r_sample <= t_elapsed))
                         DCCP_WARN("WARNING: r_sample=%ldus <= t_elapsed=%ldus\n",
                                   r_sample, t_elapsed);
                 else
@@ -698,6 +696,7 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk)
         struct dccp_sock *dp = dccp_sk(sk);
         struct dccp_rx_hist_entry *packet;
         struct timeval now;
+        suseconds_t delta;
 
         ccid3_pr_debug("%s, sk=%p\n", dccp_role(sk), sk);
 
@@ -707,12 +706,12 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk)
         case TFRC_RSTATE_NO_DATA:
                 hcrx->ccid3hcrx_x_recv = 0;
                 break;
-        case TFRC_RSTATE_DATA: {
-                const u32 delta = timeval_delta(&now,
-                                        &hcrx->ccid3hcrx_tstamp_last_feedback);
+        case TFRC_RSTATE_DATA:
+                delta = timeval_delta(&now,
+                                      &hcrx->ccid3hcrx_tstamp_last_feedback);
+                DCCP_BUG_ON(delta < 0);
                 hcrx->ccid3hcrx_x_recv =
                         scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta);
-        }
                 break;
         case TFRC_RSTATE_TERM:
                 DCCP_BUG("Illegal %s state TERM, sk=%p", dccp_role(sk), sk);
@@ -730,9 +729,10 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk)
         hcrx->ccid3hcrx_ccval_last_counter   = packet->dccphrx_ccval;
         hcrx->ccid3hcrx_bytes_recv           = 0;
 
-        /* Convert to multiples of 10us */
-        hcrx->ccid3hcrx_elapsed_time =
-                        timeval_delta(&now, &packet->dccphrx_tstamp) / 10;
+        /* Elapsed time information [RFC 4340, 13.2] in units of 10 * usecs */
+        delta = timeval_delta(&now, &packet->dccphrx_tstamp);
+        DCCP_BUG_ON(delta < 0);
+        hcrx->ccid3hcrx_elapsed_time = delta / 10;
 
         if (hcrx->ccid3hcrx_p == 0)
                 hcrx->ccid3hcrx_pinv = ~0U;     /* see RFC 4342, 8.5 */
@@ -785,7 +785,8 @@ static u32 ccid3_hc_rx_calc_first_li(struct sock *sk)
 {
         struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
         struct dccp_rx_hist_entry *entry, *next, *tail = NULL;
-        u32 rtt, delta, x_recv, p;
+        u32 x_recv, p;
+        suseconds_t rtt, delta;
         struct timeval tstamp = { 0, };
         int interval = 0;
         int win_count = 0;
@@ -830,8 +831,12 @@ found:
                 DCCP_CRIT("tail is null\n");
                 return ~0;
         }
-        rtt = timeval_delta(&tstamp, &tail->dccphrx_tstamp) * 4 / interval;
-        ccid3_pr_debug("%s, sk=%p, approximated RTT to %uus\n",
+
+        delta = timeval_delta(&tstamp, &tail->dccphrx_tstamp);
+        DCCP_BUG_ON(delta < 0);
+
+        rtt = delta * 4 / interval;
+        ccid3_pr_debug("%s, sk=%p, approximated RTT to %ldus\n",
                        dccp_role(sk), sk, rtt);
 
         /*
@@ -849,8 +854,9 @@ found:
 
         dccp_timestamp(sk, &tstamp);
         delta = timeval_delta(&tstamp, &hcrx->ccid3hcrx_tstamp_last_feedback);
-        x_recv = scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta);
+        DCCP_BUG_ON(delta <= 0);
 
+        x_recv = scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta);
         if (x_recv == 0) {              /* would also trigger divide-by-zero */
                 DCCP_WARN("X_recv==0\n");
                 if ((x_recv = hcrx->ccid3hcrx_x_recv) == 0) {
@@ -977,7 +983,8 @@ 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 p_prev, rtt_prev, r_sample, t_elapsed;
+        u32 p_prev, rtt_prev;
+        suseconds_t r_sample, t_elapsed;
         int loss, payload_size;
 
         BUG_ON(hcrx == NULL);
@@ -997,8 +1004,9 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
                 r_sample = timeval_usecs(&now);
                 t_elapsed = opt_recv->dccpor_elapsed_time * 10;
 
+                DCCP_BUG_ON(r_sample < 0);
                 if (unlikely(r_sample <= t_elapsed))
-                        DCCP_WARN("r_sample=%uus, t_elapsed=%uus\n",
+                        DCCP_WARN("r_sample=%ldus, t_elapsed=%ldus\n",
                                   r_sample, t_elapsed);
                 else
                         r_sample -= t_elapsed;
@@ -1051,8 +1059,8 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
                         break;
 
                 dccp_timestamp(sk, &now);
-                if (timeval_delta(&now, &hcrx->ccid3hcrx_tstamp_last_ack) >=
-                    hcrx->ccid3hcrx_rtt) {
+                if (timeval_delta(&now, &hcrx->ccid3hcrx_tstamp_last_ack) -
+                                        (suseconds_t)hcrx->ccid3hcrx_rtt >= 0) {
                         hcrx->ccid3hcrx_tstamp_last_ack = now;
                         ccid3_hc_rx_send_feedback(sk);
                 }
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 44829d636c93..a0900bf98e6b 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -432,6 +432,7 @@ static inline void timeval_sub_usecs(struct timeval *tv,
                 tv->tv_sec--;
                 tv->tv_usec += USEC_PER_SEC;
         }
+        DCCP_BUG_ON(tv->tv_sec < 0);
 }
 
 #ifdef CONFIG_SYSCTL