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[DCCP]: Debug timeval operations
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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>
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Gerrit Renker authored and David S. Miller committed Dec 11, 2006
1 parent bfe24a6 commit 0f9e5b5
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Showing 2 changed files with 33 additions and 24 deletions.
56 changes: 32 additions & 24 deletions net/dccp/ccids/ccid3.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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),
Expand Down Expand Up @@ -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);

Expand Down Expand Up @@ -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:
Expand All @@ -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);
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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);

Expand All @@ -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);
Expand All @@ -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 */
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -830,8 +831,12 @@ static u32 ccid3_hc_rx_calc_first_li(struct sock *sk)
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);

/*
Expand All @@ -849,8 +854,9 @@ static u32 ccid3_hc_rx_calc_first_li(struct sock *sk)

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) {
Expand Down Expand Up @@ -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);
Expand All @@ -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;
Expand Down Expand Up @@ -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);
}
Expand Down
1 change: 1 addition & 0 deletions net/dccp/dccp.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down

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