[CCID3]: Ignore trivial amounts of elapsed time
This patch fixes a previously undiscovered bug; the problem is in computing the elapsed time as the time between `receiving' the packet (i.e. skb enters CCID module) and sending feedback: - there is no layer-processing, queueing, or delay involved, - hence the elapsed time is in the order of 1 function call - this is in the dimension of maximally 50..100usec - which renders the use of elapsed time almost entirely useless. The fix is simply to ignore such trivial amounts of elapsed time. As a further advantage, the now useless elapsed_time field can be removed from the socket, which reduces the socket structure by another four bytes. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -744,11 +744,6 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk)
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hcrx->ccid3hcrx_ccval_last_counter = packet->dccphrx_ccval;
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hcrx->ccid3hcrx_bytes_recv = 0;
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/* Elapsed time information [RFC 4340, 13.2] in units of 10 * usecs */
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delta = ktime_us_delta(now, packet->dccphrx_tstamp);
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DCCP_BUG_ON(delta < 0);
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hcrx->ccid3hcrx_elapsed_time = delta / 10;
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if (hcrx->ccid3hcrx_p == 0)
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hcrx->ccid3hcrx_pinv = ~0U; /* see RFC 4342, 8.5 */
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else if (hcrx->ccid3hcrx_p > 1000000) {
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@ -778,10 +773,7 @@ static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
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x_recv = htonl(hcrx->ccid3hcrx_x_recv);
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pinv = htonl(hcrx->ccid3hcrx_pinv);
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if ((hcrx->ccid3hcrx_elapsed_time != 0 &&
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dccp_insert_option_elapsed_time(sk, skb,
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hcrx->ccid3hcrx_elapsed_time)) ||
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dccp_insert_option_timestamp(sk, skb) ||
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if (dccp_insert_option_timestamp(sk, skb) ||
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dccp_insert_option(sk, skb, TFRC_OPT_LOSS_EVENT_RATE,
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&pinv, sizeof(pinv)) ||
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dccp_insert_option(sk, skb, TFRC_OPT_RECEIVE_RATE,
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@ -147,7 +147,6 @@ enum ccid3_hc_rx_states {
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* @ccid3hcrx_li_hist - Loss Interval History
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* @ccid3hcrx_s - Received packet size in bytes
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* @ccid3hcrx_pinv - Inverse of Loss Event Rate (RFC 4342, sec. 8.5)
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* @ccid3hcrx_elapsed_time - Time since packet reception
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*/
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struct ccid3_hc_rx_sock {
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struct tfrc_rx_info ccid3hcrx_tfrc;
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@ -165,7 +164,6 @@ struct ccid3_hc_rx_sock {
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struct list_head ccid3hcrx_li_hist;
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u16 ccid3hcrx_s;
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u32 ccid3hcrx_pinv;
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u32 ccid3hcrx_elapsed_time;
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};
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static inline struct ccid3_hc_rx_sock *ccid3_hc_rx_sk(const struct sock *sk)
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