dccp ccid-3: Fix a loss detection bug
This fixes a bug in the logic of the TFRC loss detection: * new_loss_indicated() should not be called while a loss is pending; * but the code allows this; * thus, for two subsequent gaps in the sequence space, when loss_count has not yet reached NDUPACK=3, the loss_count is falsely reduced to 1. To avoid further and similar problems, all loss handling and loss detection is now done inside tfrc_rx_hist_handle_loss(), using an appropriate routine to track new losses. Further changes: ---------------- * added a reminder that no RX history operations should be performed when rx_handle_loss() has identified a (new) loss, since the function takes care of packet reordering during loss detection; * made tfrc_rx_hist_loss_pending() bool (thanks to an earlier suggestion by Arnaldo); * removed unused functions. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
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@ -825,18 +825,16 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
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}
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/*
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* Handle pending losses and otherwise check for new loss
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* Perform loss detection and handle pending losses
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*/
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if (tfrc_rx_hist_loss_pending(&hcrx->ccid3hcrx_hist) &&
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tfrc_rx_handle_loss(&hcrx->ccid3hcrx_hist,
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&hcrx->ccid3hcrx_li_hist,
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skb, ndp, ccid3_first_li, sk) ) {
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if (tfrc_rx_handle_loss(&hcrx->ccid3hcrx_hist, &hcrx->ccid3hcrx_li_hist,
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skb, ndp, ccid3_first_li, sk)) {
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do_feedback = CCID3_FBACK_PARAM_CHANGE;
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goto done_receiving;
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}
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if (tfrc_rx_hist_new_loss_indicated(&hcrx->ccid3hcrx_hist, skb, ndp))
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goto update_records;
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if (tfrc_rx_hist_loss_pending(&hcrx->ccid3hcrx_hist))
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return; /* done receiving */
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/*
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* Handle data packets: RTT sampling and monitoring p
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@ -206,10 +206,21 @@ static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
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*
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* In the descriptions, `Si' refers to the sequence number of entry number i,
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* whose NDP count is `Ni' (lower case is used for variables).
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* Note: All __after_loss functions expect that a test against duplicates has
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* been performed already: the seqno of the skb must not be less than the
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* seqno of loss_prev; and it must not equal that of any valid hist_entry.
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* Note: All __xxx_loss functions expect that a test against duplicates has been
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* performed already: the seqno of the skb must not be less than the seqno
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* of loss_prev; and it must not equal that of any valid history entry.
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*/
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static void __do_track_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u64 n1)
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{
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u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
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s1 = DCCP_SKB_CB(skb)->dccpd_seq;
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if (!dccp_loss_free(s0, s1, n1)) { /* gap between S0 and S1 */
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h->loss_count = 1;
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tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n1);
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}
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}
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static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
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{
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u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
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@ -353,6 +364,9 @@ static void __three_after_loss(struct tfrc_rx_hist *h)
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* Chooses action according to pending loss, updates LI database when a new
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* loss was detected, and does required post-processing. Returns 1 when caller
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* should send feedback, 0 otherwise.
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* Since it also takes care of reordering during loss detection and updates the
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* records accordingly, the caller should not perform any more RX history
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* operations when loss_count is greater than 0 after calling this function.
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*/
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int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
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struct tfrc_loss_hist *lh,
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@ -361,7 +375,9 @@ int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
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{
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int is_new_loss = 0;
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if (h->loss_count == 1) {
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if (h->loss_count == 0) {
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__do_track_loss(h, skb, ndp);
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} else if (h->loss_count == 1) {
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__one_after_loss(h, skb, ndp);
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} else if (h->loss_count != 2) {
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DCCP_BUG("invalid loss_count %d", h->loss_count);
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@ -118,30 +118,10 @@ static inline struct tfrc_rx_hist_entry *
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return h->ring[h->loss_start];
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}
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/* initialise loss detection and disable RTT sampling */
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static inline void tfrc_rx_hist_loss_indicated(struct tfrc_rx_hist *h)
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{
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h->loss_count = 1;
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}
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/* indicate whether previously a packet was detected missing */
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static inline int tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
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static inline bool tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
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{
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return h->loss_count;
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}
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/* any data packets missing between last reception and skb ? */
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static inline int tfrc_rx_hist_new_loss_indicated(struct tfrc_rx_hist *h,
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const struct sk_buff *skb,
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u32 ndp)
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{
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int delta = dccp_delta_seqno(tfrc_rx_hist_last_rcv(h)->tfrchrx_seqno,
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DCCP_SKB_CB(skb)->dccpd_seq);
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if (delta > 1 && ndp < delta)
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tfrc_rx_hist_loss_indicated(h);
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return tfrc_rx_hist_loss_pending(h);
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return h->loss_count > 0;
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}
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extern void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
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