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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2007-04-20 16:02:55 -0400
committerDavid S. Miller <davem@sunset.davemloft.net>2007-04-26 01:28:54 -0400
commitb2449fdc30ccac550344df5e60d38bb8427b109c (patch)
treee0371a1474a6d28cbb2826c2401abf2a1a7fcbcf /net/dccp
parentcb8c181f288a1157bc717cc7a02412d4d1dc19bc (diff)
[DCCP]: Fix bug in the calculation of very low sending rates
This fixes an error in the calculation of t_ipi when X converges towards very low sending rates (between 1 and 64 bytes per second). Although this case may not sound likely, it can be reproduced by connecting, hitting enter (1 byte sent) and waiting for some time, during which the nofeedback timer halves the sending rate until finally it reaches the region 1..64 bytes/sec. Computing X is handled correctly (tested separately); but by dividing X _before_ entering the calculation of t_ipi, X becomes zero as a result. This in turn triggers a BUG condition caught in scaled_div(). Fixed by replacing with equivalent statement and explicit typecast for good measure. Calculation verified and effect of patch tested - reduced never below 1 byte per 64 seconds afterwards, i.e. not allowing divide-by-zero. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz> Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/dccp')
-rw-r--r--net/dccp/ccids/ccid3.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index c3abd7695d55..d7d9ce737244 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -102,8 +102,8 @@ static inline u64 rfc3390_initial_rate(struct sock *sk)
102static inline void ccid3_update_send_interval(struct ccid3_hc_tx_sock *hctx) 102static inline void ccid3_update_send_interval(struct ccid3_hc_tx_sock *hctx)
103{ 103{
104 /* Calculate new t_ipi = s / X_inst (X_inst is in 64 * bytes/second) */ 104 /* Calculate new t_ipi = s / X_inst (X_inst is in 64 * bytes/second) */
105 hctx->ccid3hctx_t_ipi = scaled_div(hctx->ccid3hctx_s, 105 hctx->ccid3hctx_t_ipi = scaled_div32(((u64)hctx->ccid3hctx_s) << 6,
106 hctx->ccid3hctx_x >> 6); 106 hctx->ccid3hctx_x);
107 107
108 /* Calculate new delta by delta = min(t_ipi / 2, t_gran / 2) */ 108 /* Calculate new delta by delta = min(t_ipi / 2, t_gran / 2) */
109 hctx->ccid3hctx_delta = min_t(u32, hctx->ccid3hctx_t_ipi / 2, 109 hctx->ccid3hctx_delta = min_t(u32, hctx->ccid3hctx_t_ipi / 2,