From: Ivo Calado Date: Mon, 11 Oct 2010 18:40:04 +0000 (+0200) Subject: dccp: generalise data-loss condition X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=d196c9a5d4e150cdff675662214c80c69b906958;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git 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 Signed-off-by: Erivaldo Xavier Signed-off-by: Leandro Sales Signed-off-by: Gerrit Renker --- diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h index e051c774ef5c..60f4f9622ab3 100644 --- a/net/dccp/dccp.h +++ b/net/dccp/dccp.h @@ -153,18 +153,27 @@ static inline u64 max48(const u64 seq1, const u64 seq2) } /** - * dccp_loss_free - Evaluates condition for data loss from RFC 4340, 7.7.1 - * @s1: start sequence number - * @s2: end sequence number + * dccp_loss_count - Approximate the number of lost data packets in a burst loss + * @s1: last known sequence number before the loss ('hole') + * @s2: first sequence number seen after the 'hole' * @ndp: NDP count on packet with sequence number @s2 - * Returns true if the sequence range s1...s2 has no data loss. */ -static inline bool dccp_loss_free(const u64 s1, const u64 s2, const u64 ndp) +static inline u64 dccp_loss_count(const u64 s1, const u64 s2, const u64 ndp) { s64 delta = dccp_delta_seqno(s1, s2); WARN_ON(delta < 0); - return (u64)delta <= ndp + 1; + delta -= ndp + 1; + + return delta > 0 ? delta : 0; +} + +/** + * dccp_loss_free - Evaluate condition for data loss from RFC 4340, 7.7.1 + */ +static inline bool dccp_loss_free(const u64 s1, const u64 s2, const u64 ndp) +{ + return dccp_loss_count(s1, s2, ndp) == 0; } enum {