Merge git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-2.6-fixes

[pandora-kernel.git] / drivers / staging / batman-adv / bitarray.c

diff --git a/drivers/staging/batman-adv/bitarray.c b/drivers/staging/batman-adv/bitarray.c
index 212eef9..2fef6e3 100644 (file)
--- a/drivers/staging/batman-adv/bitarray.c
+++ b/drivers/staging/batman-adv/bitarray.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2006-2009 B.A.T.M.A.N. contributors:
+ * Copyright (C) 2006-2010 B.A.T.M.A.N. contributors:
  *
  * Simon Wunderlich, Marek Lindner
  *
@@ -68,7 +68,7 @@ void bit_shift(TYPE_OF_WORD *seq_bits, int32_t n)
        int32_t word_offset, word_num;
        int32_t i;
 
-       if (n <= 0)
+       if (n <= 0 || n >= TQ_LOCAL_WINDOW_SIZE)
                return;
 
        word_offset = n % WORD_BIT_SIZE;/* shift how much inside each word */
@@ -111,48 +111,76 @@ void bit_shift(TYPE_OF_WORD *seq_bits, int32_t n)
                seq_bits[i] = 0;
 }
 
+static void bit_reset_window(TYPE_OF_WORD *seq_bits)
+{
+       int i;
+       for (i = 0; i < NUM_WORDS; i++)
+               seq_bits[i] = 0;
+}
+
 
-/* receive and process one packet, returns 1 if received seq_num is considered
- * new, 0 if old  */
+/* receive and process one packet within the sequence number window.
+ *
+ * returns:
+ *  1 if the window was moved (either new or very old)
+ *  0 if the window was not moved/shifted.
+ */
 char bit_get_packet(TYPE_OF_WORD *seq_bits, int16_t seq_num_diff,
                    int8_t set_mark)
 {
-       int i;
+       /* sequence number is slightly older. We already got a sequence number
+        * higher than this one, so we just mark it. */
 
-       /* we already got a sequence number higher than this one, so we just
-        * mark it. this should wrap around the integer just fine */
-       if ((seq_num_diff < 0) && (seq_num_diff >= -TQ_LOCAL_WINDOW_SIZE)) {
+       if ((seq_num_diff <= 0) && (seq_num_diff > -TQ_LOCAL_WINDOW_SIZE)) {
                if (set_mark)
                        bit_mark(seq_bits, -seq_num_diff);
                return 0;
        }
 
-       /* it seems we missed a lot of packets or the other host restarted */
-       if ((seq_num_diff > TQ_LOCAL_WINDOW_SIZE) ||
-           (seq_num_diff < -TQ_LOCAL_WINDOW_SIZE)) {
+       /* sequence number is slightly newer, so we shift the window and
+        * set the mark if required */
 
-               if (seq_num_diff > TQ_LOCAL_WINDOW_SIZE)
-                       bat_dbg(DBG_BATMAN,
-                               "We missed a lot of packets (%i) !\n",
-                               seq_num_diff-1);
+       if ((seq_num_diff > 0) && (seq_num_diff < TQ_LOCAL_WINDOW_SIZE)) {
+               bit_shift(seq_bits, seq_num_diff);
 
-               if (-seq_num_diff > TQ_LOCAL_WINDOW_SIZE)
-                       bat_dbg(DBG_BATMAN,
-                               "Other host probably restarted !\n");
+               if (set_mark)
+                       bit_mark(seq_bits, 0);
+               return 1;
+       }
 
-               for (i = 0; i < NUM_WORDS; i++)
-                       seq_bits[i] = 0;
+       /* sequence number is much newer, probably missed a lot of packets */
 
+       if ((seq_num_diff >= TQ_LOCAL_WINDOW_SIZE)
+               || (seq_num_diff < EXPECTED_SEQNO_RANGE)) {
+               bat_dbg(DBG_BATMAN,
+                       "We missed a lot of packets (%i) !\n",
+                       seq_num_diff - 1);
+               bit_reset_window(seq_bits);
                if (set_mark)
-                       seq_bits[0] = 1;  /* we only have the latest packet */
-       } else {
-               bit_shift(seq_bits, seq_num_diff);
+                       bit_mark(seq_bits, 0);
+               return 1;
+       }
+
+       /* received a much older packet. The other host either restarted
+        * or the old packet got delayed somewhere in the network. The
+        * packet should be dropped without calling this function if the
+        * seqno window is protected. */
+
+       if ((seq_num_diff <= -TQ_LOCAL_WINDOW_SIZE)
+               || (seq_num_diff >= EXPECTED_SEQNO_RANGE)) {
 
+               bat_dbg(DBG_BATMAN,
+                       "Other host probably restarted!\n");
+
+               bit_reset_window(seq_bits);
                if (set_mark)
                        bit_mark(seq_bits, 0);
+
+               return 1;
        }
 
-       return 1;
+       /* never reached */
+       return 0;
 }
 
 /* count the hamming weight, how many good packets did we receive? just count