diff options
| -rw-r--r-- | net/dccp/ccids/ccid3.c | 39 |
1 files changed, 22 insertions, 17 deletions
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c index bdd13de..89ef118 100644 --- a/net/dccp/ccids/ccid3.c +++ b/net/dccp/ccids/ccid3.c @@ -785,12 +785,12 @@ 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, fval, p, tmp2; + u32 rtt, delta, x_recv, p; struct timeval tstamp = { 0, }; int interval = 0; int win_count = 0; int step = 0; - u64 tmp1; + u64 fval; list_for_each_entry_safe(entry, next, &hcrx->ccid3hcrx_hist, dccphrx_node) { @@ -834,30 +834,35 @@ found: ccid3_pr_debug("%s, sk=%p, approximated RTT to %uus\n", dccp_role(sk), sk, rtt); - if (rtt == 0) { - DCCP_WARN("RTT==0, setting to 1\n"); - rtt = 1; + /* + * Determine the length of the first loss interval via inverse lookup. + * Assume that X_recv can be computed by the throughput equation + * s + * X_recv = -------- + * R * fval + * Find some p such that f(p) = fval; return 1/p [RFC 3448, 6.3.1]. + */ + if (rtt == 0) { /* would result in divide-by-zero */ + DCCP_WARN("RTT==0, returning 1/p = 1\n"); + return 1000000; } dccp_timestamp(sk, &tstamp); delta = timeval_delta(&tstamp, &hcrx->ccid3hcrx_tstamp_last_feedback); x_recv = scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta); - if (x_recv == 0) - x_recv = hcrx->ccid3hcrx_x_recv; - - tmp1 = (u64)x_recv * (u64)rtt; - do_div(tmp1,10000000); - tmp2 = (u32)tmp1; - - if (!tmp2) { - DCCP_CRIT("tmp2 = 0, x_recv = %u, rtt =%u\n", x_recv, rtt); - return ~0; + if (x_recv == 0) { /* would also trigger divide-by-zero */ + DCCP_WARN("X_recv==0\n"); + if ((x_recv = hcrx->ccid3hcrx_x_recv) == 0) { + DCCP_BUG("stored value of X_recv is zero"); + return 1000000; + } } - fval = (hcrx->ccid3hcrx_s * 100000) / tmp2; - /* do not alter order above or you will get overflow on 32 bit */ + fval = scaled_div(hcrx->ccid3hcrx_s, rtt); + fval = scaled_div32(fval, x_recv); p = tfrc_calc_x_reverse_lookup(fval); + ccid3_pr_debug("%s, sk=%p, receive rate=%u bytes/s, implied " "loss rate=%u\n", dccp_role(sk), sk, x_recv, p); |
