[DCCP] ackvec: Introduce ack vector records

Based on a patch by Andrea Bittau.

Signed-off-by: Andrea Bittau <a.bittau@cs.ucl.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 173 insertions, 98 deletions

diff --git a/net/dccp/ackvec.c b/net/dccp/ackvec.c
index 64408253b14..b4ff14f3d4f 100644
--- a/net/dccp/ackvec.c
+++ b/net/dccp/ackvec.c
@@ -22,6 +22,47 @@
 #include <net/sock.h>
 
 static kmem_cache_t *dccp_ackvec_slab;
+static kmem_cache_t *dccp_ackvec_record_slab;
+
+static struct dccp_ackvec_record *dccp_ackvec_record_new(void)
+{
+        struct dccp_ackvec_record *avr =
+                        kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
+
+        if (avr != NULL)
+                INIT_LIST_HEAD(&avr->dccpavr_node);
+
+        return avr;
+}
+
+static void dccp_ackvec_record_delete(struct dccp_ackvec_record *avr)
+{
+        if (unlikely(avr == NULL))
+                return;
+        /* Check if deleting a linked record */
+        WARN_ON(!list_empty(&avr->dccpavr_node));
+        kmem_cache_free(dccp_ackvec_record_slab, avr);
+}
+
+static void dccp_ackvec_insert_avr(struct dccp_ackvec *av,
+                                   struct dccp_ackvec_record *avr)
+{
+        /*
+         * AVRs are sorted by seqno. Since we are sending them in order, we
+         * just add the AVR at the head of the list.
+         * -sorbo.
+         */
+        if (!list_empty(&av->dccpav_records)) {
+                const struct dccp_ackvec_record *head =
+                                        list_entry(av->dccpav_records.next,
+                                                   struct dccp_ackvec_record,
+                                                   dccpavr_node);
+                BUG_ON(before48(avr->dccpavr_ack_seqno,
+                                head->dccpavr_ack_seqno));
+        }
+
+        list_add(&avr->dccpavr_node, &av->dccpav_records);
+}
 
 int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
 {
@@ -35,6 +76,14 @@ int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
         struct timeval now;
         u32 elapsed_time;
         unsigned char *to, *from;
+        struct dccp_ackvec_record *avr;
+
+        if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
+                return -1;
+
+        avr = dccp_ackvec_record_new();
+        if (avr == NULL)
+                return -1;
 
         dccp_timestamp(sk, &now);
         elapsed_time = timeval_delta(&now, &av->dccpav_time) / 10;
@@ -42,19 +91,6 @@ int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
         if (elapsed_time != 0)
                 dccp_insert_option_elapsed_time(sk, skb, elapsed_time);
 
-        if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
-                return -1;
-
-        /*
-         * XXX: now we have just one ack vector sent record, so
-         * we have to wait for it to be cleared.
-         *
-         * Of course this is not acceptable, but this is just for
-         * basic testing now.
-         */
-        if (av->dccpav_ack_seqno != DCCP_MAX_SEQNO + 1)
-                return -1;
-
         DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 
         to    = skb_push(skb, len);
@@ -65,8 +101,8 @@ int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
         from = av->dccpav_buf + av->dccpav_buf_head;
 
         /* Check if buf_head wraps */
-        if ((int)av->dccpav_buf_head + len > av->dccpav_vec_len) {
-                const u32 tailsize = av->dccpav_vec_len - av->dccpav_buf_head;
+        if ((int)av->dccpav_buf_head + len > DCCP_MAX_ACKVEC_LEN) {
+                const u32 tailsize = DCCP_MAX_ACKVEC_LEN - av->dccpav_buf_head;
 
                 memcpy(to, from, tailsize);
                 to   += tailsize;
@@ -83,21 +119,21 @@ int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
          *      sequence number it used for the ack packet; ack_ptr will equal
          *      buf_head; ack_ackno will equal buf_ackno; and ack_nonce will
          *      equal buf_nonce.
-         *
-         * This implemention uses just one ack record for now.
          */
-        av->dccpav_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
-        av->dccpav_ack_ptr   = av->dccpav_buf_head;
-        av->dccpav_ack_ackno = av->dccpav_buf_ackno;
-        av->dccpav_ack_nonce = av->dccpav_buf_nonce;
-        av->dccpav_sent_len  = av->dccpav_vec_len;
+        avr->dccpavr_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
+        avr->dccpavr_ack_ptr   = av->dccpav_buf_head;
+        avr->dccpavr_ack_ackno = av->dccpav_buf_ackno;
+        avr->dccpavr_ack_nonce = av->dccpav_buf_nonce;
+        avr->dccpavr_sent_len  = av->dccpav_vec_len;
+
+        dccp_ackvec_insert_avr(av, avr);
 
         dccp_pr_debug("%sACK Vector 0, len=%d, ack_seqno=%llu, "
                       "ack_ackno=%llu\n",
-                      debug_prefix, av->dccpav_sent_len,
-                      (unsigned long long)av->dccpav_ack_seqno,
-                      (unsigned long long)av->dccpav_ack_ackno);
-        return -1;
+                      debug_prefix, avr->dccpavr_sent_len,
+                      (unsigned long long)avr->dccpavr_ack_seqno,
+                      (unsigned long long)avr->dccpavr_ack_ackno);
+        return 0;
 }
 
 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
@@ -107,13 +143,13 @@ struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
         if (av != NULL) {
                 av->dccpav_buf_head     =
                         av->dccpav_buf_tail = DCCP_MAX_ACKVEC_LEN - 1;
-                av->dccpav_buf_ackno    =
-                        av->dccpav_ack_ackno = av->dccpav_ack_seqno = ~0LLU;
+                av->dccpav_buf_ackno    = DCCP_MAX_SEQNO + 1;
                 av->dccpav_buf_nonce = av->dccpav_buf_nonce = 0;
                 av->dccpav_ack_ptr      = 0;
                 av->dccpav_time.tv_sec  = 0;
                 av->dccpav_time.tv_usec = 0;
                 av->dccpav_sent_len     = av->dccpav_vec_len = 0;
+                INIT_LIST_HEAD(&av->dccpav_records);
         }
 
         return av;
@@ -121,6 +157,9 @@ struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
 
 void dccp_ackvec_free(struct dccp_ackvec *av)
 {
+        if (unlikely(av == NULL))
+                return;
+        WARN_ON(!list_empty(&av->dccpav_records));
         kmem_cache_free(dccp_ackvec_slab, av);
 }
 
@@ -299,44 +338,50 @@ void dccp_ackvec_print(const struct dccp_ackvec *av)
 }
 #endif
 
-static void dccp_ackvec_throw_away_ack_record(struct dccp_ackvec *av)
+static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
+                                     struct dccp_ackvec_record *avr)
 {
-        /*
-         * As we're keeping track of the ack vector size (dccpav_vec_len) and
-         * the sent ack vector size (dccpav_sent_len) we don't need
-         * dccpav_buf_tail at all, but keep this code here as in the future
-         * we'll implement a vector of ack records, as suggested in
-         * draft-ietf-dccp-spec-11.txt Appendix A. -acme
-         */
-#if 0
-        u32 new_buf_tail = av->dccpav_ack_ptr + 1;
-        if (new_buf_tail >= av->dccpav_vec_len)
-                new_buf_tail -= av->dccpav_vec_len;
-        av->dccpav_buf_tail = new_buf_tail;
-#endif
-        av->dccpav_vec_len -= av->dccpav_sent_len;
+        struct dccp_ackvec_record *next;
+
+        av->dccpav_buf_tail = avr->dccpavr_ack_ptr - 1;
+        if (av->dccpav_buf_tail == 0)
+                av->dccpav_buf_tail = DCCP_MAX_ACKVEC_LEN - 1;
+
+        av->dccpav_vec_len -= avr->dccpavr_sent_len;
+
+        /* free records */
+        list_for_each_entry_safe_from(avr, next, &av->dccpav_records,
+                                      dccpavr_node) {
+                list_del_init(&avr->dccpavr_node);
+                dccp_ackvec_record_delete(avr);
+        }
 }
 
 void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
                                  const u64 ackno)
 {
-        /* Check if we actually sent an ACK vector */
-        if (av->dccpav_ack_seqno == DCCP_MAX_SEQNO + 1)
-                return;
+        struct dccp_ackvec_record *avr;
 
-        if (ackno == av->dccpav_ack_seqno) {
+        /*
+         * If we traverse backwards, it should be faster when we have large
+         * windows. We will be receiving ACKs for stuff we sent a while back
+         * -sorbo.
+         */
+        list_for_each_entry_reverse(avr, &av->dccpav_records, dccpavr_node) {
+                if (ackno == avr->dccpavr_ack_seqno) {
 #ifdef CONFIG_IP_DCCP_DEBUG
-                struct dccp_sock *dp = dccp_sk(sk);
-                const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
-                                        "CLIENT rx ack: " : "server rx ack: ";
+                        struct dccp_sock *dp = dccp_sk(sk);
+                        const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
+                                                "CLIENT rx ack: " : "server rx ack: ";
 #endif
-                dccp_pr_debug("%sACK packet 0, len=%d, ack_seqno=%llu, "
-                              "ack_ackno=%llu, ACKED!\n",
-                              debug_prefix, 1,
-                              (unsigned long long)av->dccpav_ack_seqno,
-                              (unsigned long long)av->dccpav_ack_ackno);
-                dccp_ackvec_throw_away_ack_record(av);
-                av->dccpav_ack_seqno = DCCP_MAX_SEQNO + 1;
+                        dccp_pr_debug("%sACK packet 0, len=%d, ack_seqno=%llu, "
+                                      "ack_ackno=%llu, ACKED!\n",
+                                      debug_prefix, 1,
+                                      (unsigned long long)avr->dccpavr_ack_seqno,
+                                      (unsigned long long)avr->dccpavr_ack_ackno);
+                        dccp_ackvec_throw_record(av, avr);
+                        break;
+                }
         }
 }
 
@@ -346,28 +391,20 @@ static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
                                             const unsigned char *vector)
 {
         unsigned char i;
+        struct dccp_ackvec_record *avr;
 
         /* Check if we actually sent an ACK vector */
-        if (av->dccpav_ack_seqno == DCCP_MAX_SEQNO + 1)
+        if (list_empty(&av->dccpav_records))
                 return;
-        /*
-         * We're in the receiver half connection, so if the received an ACK
-         * vector ackno (e.g. 50) before dccpav_ack_seqno (e.g. 52), we're
-         * not interested.
-         *
-         * Extra explanation with example:
-         * 
-         * if we received an ACK vector with ackno 50, it can only be acking
-         * 50, 49, 48, etc, not 52 (the seqno for the ACK vector we sent).
-         */
-        /* dccp_pr_debug("is %llu < %llu? ", ackno, av->dccpav_ack_seqno); */
-        if (before48(ackno, av->dccpav_ack_seqno)) {
-                /* dccp_pr_debug_cat("yes\n"); */
-                return;
-        }
-        /* dccp_pr_debug_cat("no\n"); */
 
         i = len;
+        /*
+         * XXX
+         * I think it might be more efficient to work backwards. See comment on
+         * rcv_ackno. -sorbo.
+         */
+        avr = list_entry(av->dccpav_records.next, struct dccp_ackvec_record,
+                         dccpavr_node);
         while (i--) {
                 const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
                 u64 ackno_end_rl;
@@ -375,14 +412,20 @@ static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
                 dccp_set_seqno(&ackno_end_rl, ackno - rl);
 
                 /*
-                 * dccp_pr_debug("is %llu <= %llu <= %llu? ", ackno_end_rl,
-                 * av->dccpav_ack_seqno, ackno);
+                 * If our AVR sequence number is greater than the ack, go
+                 * forward in the AVR list until it is not so.
                  */
-                if (between48(av->dccpav_ack_seqno, ackno_end_rl, ackno)) {
+                list_for_each_entry_from(avr, &av->dccpav_records,
+                                         dccpavr_node) {
+                        if (!after48(avr->dccpavr_ack_seqno, ackno))
+                                goto found;
+                }
+                /* End of the dccpav_records list, not found, exit */
+                break;
+found:
+                if (between48(avr->dccpavr_ack_seqno, ackno_end_rl, ackno)) {
                         const u8 state = (*vector &
                                           DCCP_ACKVEC_STATE_MASK) >> 6;
-                        /* dccp_pr_debug_cat("yes\n"); */
-
                         if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED) {
 #ifdef CONFIG_IP_DCCP_DEBUG
                                 struct dccp_sock *dp = dccp_sk(sk);
@@ -395,19 +438,16 @@ static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
                                               "ACKED!\n",
                                               debug_prefix, len,
                                               (unsigned long long)
-                                              av->dccpav_ack_seqno,
+                                              avr->dccpavr_ack_seqno,
                                               (unsigned long long)
-                                              av->dccpav_ack_ackno);
-                                dccp_ackvec_throw_away_ack_record(av);
+                                              avr->dccpavr_ack_ackno);
+                                dccp_ackvec_throw_record(av, avr);
                         }
                         /*
-                         * If dccpav_ack_seqno was not received, no problem
-                         * we'll send another ACK vector.
+                         * If it wasn't received, continue scanning... we might
+                         * find another one.
                          */
-                        av->dccpav_ack_seqno = DCCP_MAX_SEQNO + 1;
-                        break;
                 }
-                /* dccp_pr_debug_cat("no\n"); */
 
                 dccp_set_seqno(&ackno, ackno_end_rl - 1);
                 ++vector;
@@ -428,19 +468,31 @@ int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
 }
 
 static char dccp_ackvec_slab_msg[] __initdata =
-        KERN_CRIT "DCCP: Unable to create ack vectors slab cache\n";
+        KERN_CRIT "DCCP: Unable to create ack vectors slab caches\n";
 
 int __init dccp_ackvec_init(void)
 {
         dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
                                              sizeof(struct dccp_ackvec), 0,
                                              SLAB_HWCACHE_ALIGN, NULL, NULL);
-        if (dccp_ackvec_slab == NULL) {
-                printk(dccp_ackvec_slab_msg);
-                return -ENOBUFS;
-        }
+        if (dccp_ackvec_slab == NULL)
+                goto out_err;
+
+        dccp_ackvec_record_slab =
+                        kmem_cache_create("dccp_ackvec_record",
+                                          sizeof(struct dccp_ackvec_record),
+                                          0, SLAB_HWCACHE_ALIGN, NULL, NULL);
+        if (dccp_ackvec_record_slab == NULL)
+                goto out_destroy_slab;
 
         return 0;
+
+out_destroy_slab:
+        kmem_cache_destroy(dccp_ackvec_slab);
+        dccp_ackvec_slab = NULL;
+out_err:
+        printk(dccp_ackvec_slab_msg);
+        return -ENOBUFS;
 }
 
 void dccp_ackvec_exit(void)
@@ -449,4 +501,8 @@ void dccp_ackvec_exit(void)
                 kmem_cache_destroy(dccp_ackvec_slab);
                 dccp_ackvec_slab = NULL;
         }
+        if (dccp_ackvec_record_slab != NULL) {
+                kmem_cache_destroy(dccp_ackvec_record_slab);
+                dccp_ackvec_record_slab = NULL;
+        }
 }
diff --git a/net/dccp/ackvec.h b/net/dccp/ackvec.h
index 470bae8a9d0..ec7a89bb7b3 100644
--- a/net/dccp/ackvec.h
+++ b/net/dccp/ackvec.h
@@ -13,6 +13,7 @@
 
 #include <linux/config.h>
 #include <linux/compiler.h>
+#include <linux/list.h>
 #include <linux/time.h>
 #include <linux/types.h>
 
@@ -42,11 +43,8 @@
  * Ack Vectors it has recently sent. For each packet sent carrying an
  * Ack Vector, it remembers four variables:
  *
- * @dccpav_ack_seqno - the Sequence Number used for the packet
- *                     (HC-Receiver seqno)
  * @dccpav_ack_ptr - the value of buf_head at the time of acknowledgement.
- * @dccpav_ack_ackno - the Acknowledgement Number used for the packet
- *                     (HC-Sender seqno)
+ * @dccpav_records - list of dccp_ackvec_record
  * @dccpav_ack_nonce - the one-bit sum of the ECN Nonces for all State 0.
  *
  * @dccpav_time         - the time in usecs
@@ -54,8 +52,7 @@
  */
 struct dccp_ackvec {
         u64             dccpav_buf_ackno;
-        u64             dccpav_ack_seqno;
-        u64             dccpav_ack_ackno;
+        struct list_head dccpav_records;
         struct timeval  dccpav_time;
         u8              dccpav_buf_head;
         u8              dccpav_buf_tail;
@@ -67,6 +64,28 @@ struct dccp_ackvec {
         u8              dccpav_buf[DCCP_MAX_ACKVEC_LEN];
 };
 
+/** struct dccp_ackvec_record - ack vector record
+ *
+ * ACK vector record as defined in Appendix A of spec.
+ *
+ * The list is sorted by dccpavr_ack_seqno
+ *
+ * @dccpavr_node - node in dccpav_records
+ * @dccpavr_ack_seqno - sequence number of the packet this record was sent on
+ * @dccpavr_ack_ackno - sequence number being acknowledged
+ * @dccpavr_ack_ptr - pointer into dccpav_buf where this record starts
+ * @dccpavr_ack_nonce - dccpav_ack_nonce at the time this record was sent
+ * @dccpavr_sent_len - lenght of the record in dccpav_buf
+ */
+struct dccp_ackvec_record {
+        struct list_head dccpavr_node;
+        u64              dccpavr_ack_seqno;
+        u64              dccpavr_ack_ackno;
+        u8               dccpavr_ack_ptr;
+        u8               dccpavr_ack_nonce;
+        u8               dccpavr_sent_len;
+};
+
 struct sock;
 struct sk_buff;