: Modulo-16 arithmetic for window counters
PATCH 1/43 : Modulo-16 arithmetic for window counters
[CCID 3]: Modulo-16 arithmetic for window counters
This implements modulo-16 arithmetic which is needed to compare the 4-bit CCID 3 window counter (CCVal) values; it respects circular wraparound and returns a-b mod 16.
Implemented as a macro, since required in several places.
Signed-off-by Gerrit Renker <[email protected]>
--- net/dccp/ccids/ccid3.c | 4 +--- net/dccp/ccids/lib/packet_history.c | 4 +--- net/dccp/ccids/lib/packet_history.h | 3 ++- 3 files changed, 4 insertions(+), 7 deletions(-)
net/dccp/ccids/lib/packet_history.h +2 -1
@@ -47,7 +47,8 @@#define TFRC_RECV_NUM_LATE_LOSS 3#define TFRC_WIN_COUNT_PER_RTT 4 -#define TFRC_WIN_COUNT_LIMIT 16 +/* Subtraction a-b modulo-16, respects circular wrap-around */ +#define SUB16 (a,b) (((a) + 16 - (b)) & 0xF)/* * Transmitter History data structures and declarations
net/dccp/ccids/ccid3.c +1 -3
@@ -841,9 +841,7 @@ static u32 ccid3_hc_rx_calc_first_li(str step =1 ;break ;case 1 : - interval = win_count - entry->dccphrx_ccval; -if (interval <0 ) - interval +=TFRC_WIN_COUNT_LIMIT ; + interval =SUB16 (win_count, entry->dccphrx_ccval);if (interval >4 ) goto found;break ;
net/dccp/ccids/lib/packet_history.c +1 -3
@@ -291,9 +291,7 @@ void dccp_rx_hist_add_packet(struct dccp win_count = entry->dccphrx_ccval;break ;case 2 : - tmp = win_count - entry->dccphrx_ccval; -if (tmp <0 ) - tmp +=TFRC_WIN_COUNT_LIMIT ; + tmp =SUB16 (win_count, entry->dccphrx_ccval);if (tmp >TFRC_WIN_COUNT_PER_RTT +1 ) {/* * We have found a packet older