dccp: generalise data-loss condition
This patch generalises the task of determining data loss from RFC 4340, 7.7.1. Let S_A, S_B be sequence numbers such that S_B is "after" S_A, and let N_B be the NDP count of packet S_B. Then, using modulo-2^48 arithmetic, D = S_B - S_A - 1 is an upper bound of the number of lost data packets, D - N_B is an approximation of the number of lost data packets (there are cases where this is not exact). The patch implements this as dccp_loss_count(S_A, S_B, N_B) := max(S_B - S_A - 1 - N_B, 0) Signed-off-by: Ivo Calado <ivocalado@embedded.ufcg.edu.br> Signed-off-by: Erivaldo Xavier <desadoc@gmail.com> Signed-off-by: Leandro Sales <leandroal@gmail.com> Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
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@ -153,18 +153,27 @@ static inline u64 max48(const u64 seq1, const u64 seq2)
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}
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/**
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* dccp_loss_free - Evaluates condition for data loss from RFC 4340, 7.7.1
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* @s1: start sequence number
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* @s2: end sequence number
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* dccp_loss_count - Approximate the number of lost data packets in a burst loss
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* @s1: last known sequence number before the loss ('hole')
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* @s2: first sequence number seen after the 'hole'
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* @ndp: NDP count on packet with sequence number @s2
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* Returns true if the sequence range s1...s2 has no data loss.
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*/
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static inline bool dccp_loss_free(const u64 s1, const u64 s2, const u64 ndp)
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static inline u64 dccp_loss_count(const u64 s1, const u64 s2, const u64 ndp)
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{
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s64 delta = dccp_delta_seqno(s1, s2);
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WARN_ON(delta < 0);
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return (u64)delta <= ndp + 1;
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delta -= ndp + 1;
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return delta > 0 ? delta : 0;
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}
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/**
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* dccp_loss_free - Evaluate condition for data loss from RFC 4340, 7.7.1
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*/
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static inline bool dccp_loss_free(const u64 s1, const u64 s2, const u64 ndp)
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{
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return dccp_loss_count(s1, s2, ndp) == 0;
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}
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enum {
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