1 files changed, 56 insertions, 47 deletions

diff --git a/net/dccp/ackvec.h b/net/dccp/ackvec.h
index 7ea557b7c6b1..ebcbbc726cff 100644
--- a/net/dccp/ackvec.h
+++ b/net/dccp/ackvec.h
@@ -3,9 +3,9 @@
 /*
  *  net/dccp/ackvec.h
  *
- *  An implementation of the DCCP protocol
+ *  An implementation of Ack Vectors for the DCCP protocol
+ *  Copyright (c) 2007 University of Aberdeen, Scotland, UK
  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@mandriva.com>
- *
  *      This program is free software; you can redistribute it and/or modify it
  *      under the terms of the GNU General Public License version 2 as
  *      published by the Free Software Foundation.
@@ -13,75 +13,84 @@
 
 #include <linux/dccp.h>
 #include <linux/compiler.h>
-#include <linux/ktime.h>
 #include <linux/list.h>
 #include <linux/types.h>
 
-/* We can spread an ack vector across multiple options */
-#define DCCP_MAX_ACKVEC_LEN (DCCP_SINGLE_OPT_MAXLEN * 2)
+/*
+ * Ack Vector buffer space is static, in multiples of %DCCP_SINGLE_OPT_MAXLEN,
+ * the maximum size of a single Ack Vector. Setting %DCCPAV_NUM_ACKVECS to 1
+ * will be sufficient for most cases of low Ack Ratios, using a value of 2 gives
+ * more headroom if Ack Ratio is higher or when the sender acknowledges slowly.
+ */
+#define DCCPAV_NUM_ACKVECS      2
+#define DCCPAV_MAX_ACKVEC_LEN   (DCCP_SINGLE_OPT_MAXLEN * DCCPAV_NUM_ACKVECS)
 
 /* Estimated minimum average Ack Vector length - used for updating MPS */
 #define DCCPAV_MIN_OPTLEN       16
 
-#define DCCP_ACKVEC_STATE_RECEIVED      0
-#define DCCP_ACKVEC_STATE_ECN_MARKED    (1 << 6)
-#define DCCP_ACKVEC_STATE_NOT_RECEIVED  (3 << 6)
+enum dccp_ackvec_states {
+        DCCPAV_RECEIVED =       0x00,
+        DCCPAV_ECN_MARKED =     0x40,
+        DCCPAV_RESERVED =       0x80,
+        DCCPAV_NOT_RECEIVED =   0xC0
+};
+#define DCCPAV_MAX_RUNLEN       0x3F
 
-#define DCCP_ACKVEC_STATE_MASK          0xC0 /* 11000000 */
-#define DCCP_ACKVEC_LEN_MASK            0x3F /* 00111111 */
+static inline u8 dccp_ackvec_runlen(const u8 *cell)
+{
+        return *cell & DCCPAV_MAX_RUNLEN;
+}
 
-/** struct dccp_ackvec - ack vector
- *
- * This data structure is the one defined in RFC 4340, Appendix A.
- *
- * @av_buf_head - circular buffer head
- * @av_buf_tail - circular buffer tail
- * @av_buf_ackno - ack # of the most recent packet acknowledgeable in the
- *                     buffer (i.e. %av_buf_head)
- * @av_buf_nonce - the one-bit sum of the ECN Nonces on all packets acked
- *                     by the buffer with State 0
- *
- * Additionally, the HC-Receiver must keep some information about the
- * Ack Vectors it has recently sent. For each packet sent carrying an
- * Ack Vector, it remembers four variables:
+static inline u8 dccp_ackvec_state(const u8 *cell)
+{
+        return *cell & ~DCCPAV_MAX_RUNLEN;
+}
+
+/** struct dccp_ackvec - Ack Vector main data structure
  *
- * @av_records - list of dccp_ackvec_record
- * @av_ack_nonce - the one-bit sum of the ECN Nonces for all State 0.
+ * This implements a fixed-size circular buffer within an array and is largely
+ * based on Appendix A of RFC 4340.
  *
- * @av_time - the time in usecs
- * @av_buf - circular buffer of acknowledgeable packets
+ * @av_buf:        circular buffer storage area
+ * @av_buf_head:   head index; begin of live portion in @av_buf
+ * @av_buf_tail:   tail index; first index _after_ the live portion in @av_buf
+ * @av_buf_ackno:  highest seqno of acknowledgeable packet recorded in @av_buf
+ * @av_buf_nonce:  ECN nonce sums, each covering subsequent segments of up to
+ *                 %DCCP_SINGLE_OPT_MAXLEN cells in the live portion of @av_buf
+ * @av_records:    list of %dccp_ackvec_record (Ack Vectors sent previously)
+ * @av_veclen:     length of the live portion of @av_buf
  */
 struct dccp_ackvec {
-        u64                     av_buf_ackno;
-        struct list_head        av_records;
-        ktime_t                 av_time;
+        u8                      av_buf[DCCPAV_MAX_ACKVEC_LEN];
         u16                     av_buf_head;
+        u16                     av_buf_tail;
+        u64                     av_buf_ackno:48;
+        bool                    av_buf_nonce[DCCPAV_NUM_ACKVECS];
+        struct list_head        av_records;
         u16                     av_vec_len;
-        u8                      av_buf_nonce;
-        u8                      av_ack_nonce;
-        u8                      av_buf[DCCP_MAX_ACKVEC_LEN];
 };
 
-/** struct dccp_ackvec_record - ack vector record
+/** struct dccp_ackvec_record - Records information about sent Ack Vectors
  *
- * ACK vector record as defined in Appendix A of spec.
+ * These list entries define the additional information which the HC-Receiver
+ * keeps about recently-sent Ack Vectors; again refer to RFC 4340, Appendix A.
  *
- * The list is sorted by avr_ack_seqno
+ * @avr_node:       the list node in @av_records
+ * @avr_ack_seqno:  sequence number of the packet the Ack Vector was sent on
+ * @avr_ack_ackno:  the Ack number that this record/Ack Vector refers to
+ * @avr_ack_ptr:    pointer into @av_buf where this record starts
+ * @avr_ack_runlen: run length of @avr_ack_ptr at the time of sending
+ * @avr_ack_nonce:  the sum of @av_buf_nonce's at the time this record was sent
  *
- * @avr_node - node in av_records
- * @avr_ack_seqno - sequence number of the packet this record was sent on
- * @avr_ack_ackno - sequence number being acknowledged
- * @avr_ack_ptr - pointer into av_buf where this record starts
- * @avr_ack_nonce - av_ack_nonce at the time this record was sent
- * @avr_sent_len - lenght of the record in av_buf
+ * The list as a whole is sorted in descending order by @avr_ack_seqno.
  */
 struct dccp_ackvec_record {
         struct list_head avr_node;
-        u64              avr_ack_seqno;
-        u64              avr_ack_ackno;
+        u64              avr_ack_seqno:48;
+        u64              avr_ack_ackno:48;
         u16              avr_ack_ptr;
-        u16              avr_sent_len;
-        u8               avr_ack_nonce;
+        u8               avr_ack_runlen;
+        u8               avr_ack_nonce:1;
 };
 
 struct sock;