struct dccp_ackvec *av = kmem_cache_zalloc(dccp_ackvec_slab, priority);
if (av != NULL) {
- av->av_buf_head = DCCPAV_MAX_ACKVEC_LEN - 1;
+ av->av_buf_head = av->av_buf_tail = DCCPAV_MAX_ACKVEC_LEN - 1;
INIT_LIST_HEAD(&av->av_records);
}
return av;
}
}
-static void dccp_ackvec_insert_avr(struct dccp_ackvec *av,
- struct dccp_ackvec_record *avr)
+/**
+ * dccp_ackvec_update_records - Record information about sent Ack Vectors
+ * @av: Ack Vector records to update
+ * @seqno: Sequence number of the packet carrying the Ack Vector just sent
+ * @nonce_sum: The sum of all buffer nonces contained in the Ack Vector
+ */
+int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seqno, u8 nonce_sum)
{
+ struct dccp_ackvec_record *avr;
+
+ avr = kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
+ if (avr == NULL)
+ return -ENOBUFS;
+
+ avr->avr_ack_seqno = seqno;
+ avr->avr_ack_ptr = av->av_buf_head;
+ avr->avr_ack_ackno = av->av_buf_ackno;
+ avr->avr_ack_nonce = nonce_sum;
+ avr->avr_ack_runlen = dccp_ackvec_runlen(av->av_buf + av->av_buf_head);
/*
- * AVRs are sorted by seqno. Since we are sending them in order, we
- * just add the AVR at the head of the list.
- * -sorbo.
+ * When the buffer overflows, we keep no more than one record. This is
+ * the simplest way of disambiguating sender-Acks dating from before the
+ * overflow from sender-Acks which refer to after the overflow; a simple
+ * solution is preferable here since we are handling an exception.
+ */
+ if (av->av_overflow)
+ dccp_ackvec_purge_records(av);
+ /*
+ * Since GSS is incremented for each packet, the list is automatically
+ * arranged in descending order of @ack_seqno.
*/
- if (!list_empty(&av->av_records)) {
- const struct dccp_ackvec_record *head =
- list_entry(av->av_records.next,
- struct dccp_ackvec_record,
- avr_node);
- BUG_ON(before48(avr->avr_ack_seqno, head->avr_ack_seqno));
- }
-
list_add(&avr->avr_node, &av->av_records);
+
+ dccp_pr_debug("Added Vector, ack_seqno=%llu, ack_ackno=%llu (rl=%u)\n",
+ (unsigned long long)avr->avr_ack_seqno,
+ (unsigned long long)avr->avr_ack_ackno,
+ avr->avr_ack_runlen);
+ return 0;
}
-int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
+static struct dccp_ackvec_record *dccp_ackvec_lookup(struct list_head *av_list,
+ const u64 ackno)
{
- struct dccp_sock *dp = dccp_sk(sk);
- struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
- /* Figure out how many options do we need to represent the ackvec */
- const u8 nr_opts = DIV_ROUND_UP(av->av_vec_len, DCCP_SINGLE_OPT_MAXLEN);
- u16 len = av->av_vec_len + 2 * nr_opts;
- u8 i, nonce = 0;
- const unsigned char *tail, *from;
- unsigned char *to;
struct dccp_ackvec_record *avr;
+ /*
+ * Exploit that records are inserted in descending order of sequence
+ * number, start with the oldest record first. If @ackno is `before'
+ * the earliest ack_ackno, the packet is too old to be considered.
+ */
+ list_for_each_entry_reverse(avr, av_list, avr_node) {
+ if (avr->avr_ack_seqno == ackno)
+ return avr;
+ if (before48(ackno, avr->avr_ack_seqno))
+ break;
+ }
+ return NULL;
+}
- if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
- return -1;
+/*
+ * Buffer index and length computation using modulo-buffersize arithmetic.
+ * Note that, as pointers move from right to left, head is `before' tail.
+ */
+static inline u16 __ackvec_idx_add(const u16 a, const u16 b)
+{
+ return (a + b) % DCCPAV_MAX_ACKVEC_LEN;
+}
- avr = kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
- if (avr == NULL)
- return -1;
+static inline u16 __ackvec_idx_sub(const u16 a, const u16 b)
+{
+ return __ackvec_idx_add(a, DCCPAV_MAX_ACKVEC_LEN - b);
+}
+
+u16 dccp_ackvec_buflen(const struct dccp_ackvec *av)
+{
+ if (unlikely(av->av_overflow))
+ return DCCPAV_MAX_ACKVEC_LEN;
+ return __ackvec_idx_sub(av->av_buf_tail, av->av_buf_head);
+}
+
+/**
+ * dccp_ackvec_update_old - Update previous state as per RFC 4340, 11.4.1
+ * @av: non-empty buffer to update
+ * @distance: negative or zero distance of @seqno from buf_ackno downward
+ * @seqno: the (old) sequence number whose record is to be updated
+ * @state: state in which packet carrying @seqno was received
+ */
+static void dccp_ackvec_update_old(struct dccp_ackvec *av, s64 distance,
+ u64 seqno, enum dccp_ackvec_states state)
+{
+ u16 ptr = av->av_buf_head;
+
+ BUG_ON(distance > 0);
+ if (unlikely(dccp_ackvec_is_empty(av)))
+ return;
- DCCP_SKB_CB(skb)->dccpd_opt_len += len;
+ do {
+ u8 runlen = dccp_ackvec_runlen(av->av_buf + ptr);
- to = skb_push(skb, len);
- len = av->av_vec_len;
- from = av->av_buf + av->av_buf_head;
- tail = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;
+ if (distance + runlen >= 0) {
+ /*
+ * Only update the state if packet has not been received
+ * yet. This is OK as per the second table in RFC 4340,
+ * 11.4.1; i.e. here we are using the following table:
+ * RECEIVED
+ * 0 1 3
+ * S +---+---+---+
+ * T 0 | 0 | 0 | 0 |
+ * O +---+---+---+
+ * R 1 | 1 | 1 | 1 |
+ * E +---+---+---+
+ * D 3 | 0 | 1 | 3 |
+ * +---+---+---+
+ * The "Not Received" state was set by reserve_seats().
+ */
+ if (av->av_buf[ptr] == DCCPAV_NOT_RECEIVED)
+ av->av_buf[ptr] = state;
+ else
+ dccp_pr_debug("Not changing %llu state to %u\n",
+ (unsigned long long)seqno, state);
+ break;
+ }
+
+ distance += runlen + 1;
+ ptr = __ackvec_idx_add(ptr, 1);
+
+ } while (ptr != av->av_buf_tail);
+}
+
+/* Mark @num entries after buf_head as "Not yet received". */
+static void dccp_ackvec_reserve_seats(struct dccp_ackvec *av, u16 num)
+{
+ u16 start = __ackvec_idx_add(av->av_buf_head, 1),
+ len = DCCPAV_MAX_ACKVEC_LEN - start;
+
+ /* check for buffer wrap-around */
+ if (num > len) {
+ memset(av->av_buf + start, DCCPAV_NOT_RECEIVED, len);
+ start = 0;
+ num -= len;
+ }
+ if (num)
+ memset(av->av_buf + start, DCCPAV_NOT_RECEIVED, num);
+}
- for (i = 0; i < nr_opts; ++i) {
- int copylen = len;
+/**
+ * dccp_ackvec_add_new - Record one or more new entries in Ack Vector buffer
+ * @av: container of buffer to update (can be empty or non-empty)
+ * @num_packets: number of packets to register (must be >= 1)
+ * @seqno: sequence number of the first packet in @num_packets
+ * @state: state in which packet carrying @seqno was received
+ */
+static void dccp_ackvec_add_new(struct dccp_ackvec *av, u32 num_packets,
+ u64 seqno, enum dccp_ackvec_states state)
+{
+ u32 num_cells = num_packets;
- if (len > DCCP_SINGLE_OPT_MAXLEN)
- copylen = DCCP_SINGLE_OPT_MAXLEN;
+ if (num_packets > DCCPAV_BURST_THRESH) {
+ u32 lost_packets = num_packets - 1;
+ DCCP_WARN("Warning: large burst loss (%u)\n", lost_packets);
/*
- * RFC 4340, 12.2: Encode the Nonce Echo for this Ack Vector via
- * its type; ack_nonce is the sum of all individual buf_nonce's.
+ * We received 1 packet and have a loss of size "num_packets-1"
+ * which we squeeze into num_cells-1 rather than reserving an
+ * entire byte for each lost packet.
+ * The reason is that the vector grows in O(burst_length); when
+ * it grows too large there will no room left for the payload.
+ * This is a trade-off: if a few packets out of the burst show
+ * up later, their state will not be changed; it is simply too
+ * costly to reshuffle/reallocate/copy the buffer each time.
+ * Should such problems persist, we will need to switch to a
+ * different underlying data structure.
*/
- nonce ^= av->av_buf_nonce[i];
-
- *to++ = DCCPO_ACK_VECTOR_0 + av->av_buf_nonce[i];
- *to++ = copylen + 2;
+ for (num_packets = num_cells = 1; lost_packets; ++num_cells) {
+ u8 len = min(lost_packets, (u32)DCCPAV_MAX_RUNLEN);
- /* Check if buf_head wraps */
- if (from + copylen > tail) {
- const u16 tailsize = tail - from;
+ av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, 1);
+ av->av_buf[av->av_buf_head] = DCCPAV_NOT_RECEIVED | len;
- memcpy(to, from, tailsize);
- to += tailsize;
- len -= tailsize;
- copylen -= tailsize;
- from = av->av_buf;
+ lost_packets -= len;
}
+ }
- memcpy(to, from, copylen);
- from += copylen;
- to += copylen;
- len -= copylen;
+ if (num_cells + dccp_ackvec_buflen(av) >= DCCPAV_MAX_ACKVEC_LEN) {
+ DCCP_CRIT("Ack Vector buffer overflow: dropping old entries\n");
+ av->av_overflow = true;
}
- /*
- * Each sent Ack Vector is recorded in the list, as per A.2 of RFC 4340.
- */
- avr->avr_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
- avr->avr_ack_ptr = av->av_buf_head;
- avr->avr_ack_ackno = av->av_buf_ackno;
- avr->avr_ack_nonce = nonce;
- avr->avr_ack_runlen = dccp_ackvec_runlen(av->av_buf + av->av_buf_head);
+ av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, num_packets);
+ if (av->av_overflow)
+ av->av_buf_tail = av->av_buf_head;
- dccp_ackvec_insert_avr(av, avr);
+ av->av_buf[av->av_buf_head] = state;
+ av->av_buf_ackno = seqno;
- dccp_pr_debug("%s ACK Vector 0, len=%d, ack_seqno=%llu, "
- "ack_ackno=%llu\n",
- dccp_role(sk), avr->avr_ack_runlen,
- (unsigned long long)avr->avr_ack_seqno,
- (unsigned long long)avr->avr_ack_ackno);
- return 0;
+ if (num_packets > 1)
+ dccp_ackvec_reserve_seats(av, num_packets - 1);
+}
+
+/**
+ * dccp_ackvec_input - Register incoming packet in the buffer
+ */
+void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb)
+{
+ u64 seqno = DCCP_SKB_CB(skb)->dccpd_seq;
+ enum dccp_ackvec_states state = DCCPAV_RECEIVED;
+
+ if (dccp_ackvec_is_empty(av)) {
+ dccp_ackvec_add_new(av, 1, seqno, state);
+ av->av_tail_ackno = seqno;
+
+ } else {
+ s64 num_packets = dccp_delta_seqno(av->av_buf_ackno, seqno);
+ u8 *current_head = av->av_buf + av->av_buf_head;
+
+ if (num_packets == 1 &&
+ dccp_ackvec_state(current_head) == state &&
+ dccp_ackvec_runlen(current_head) < DCCPAV_MAX_RUNLEN) {
+
+ *current_head += 1;
+ av->av_buf_ackno = seqno;
+
+ } else if (num_packets > 0) {
+ dccp_ackvec_add_new(av, num_packets, seqno, state);
+ } else {
+ dccp_ackvec_update_old(av, num_packets, seqno, state);
+ }
+ }
}
/*
return 0;
}
+/**
+ * dccp_ackvec_clear_state - Perform house-keeping / garbage-collection
+ * This routine is called when the peer acknowledges the receipt of Ack Vectors
+ * up to and including @ackno. While based on on section A.3 of RFC 4340, here
+ * are additional precautions to prevent corrupted buffer state. In particular,
+ * we use tail_ackno to identify outdated records; it always marks the earliest
+ * packet of group (2) in 11.4.2.
+ */
+void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno)
+ {
+ struct dccp_ackvec_record *avr, *next;
+ u8 runlen_now, eff_runlen;
+ s64 delta;
+
+ avr = dccp_ackvec_lookup(&av->av_records, ackno);
+ if (avr == NULL)
+ return;
+ /*
+ * Deal with outdated acknowledgments: this arises when e.g. there are
+ * several old records and the acks from the peer come in slowly. In
+ * that case we may still have records that pre-date tail_ackno.
+ */
+ delta = dccp_delta_seqno(av->av_tail_ackno, avr->avr_ack_ackno);
+ if (delta < 0)
+ goto free_records;
+ /*
+ * Deal with overlapping Ack Vectors: don't subtract more than the
+ * number of packets between tail_ackno and ack_ackno.
+ */
+ eff_runlen = delta < avr->avr_ack_runlen ? delta : avr->avr_ack_runlen;
+
+ runlen_now = dccp_ackvec_runlen(av->av_buf + avr->avr_ack_ptr);
+ /*
+ * The run length of Ack Vector cells does not decrease over time. If
+ * the run length is the same as at the time the Ack Vector was sent, we
+ * free the ack_ptr cell. That cell can however not be freed if the run
+ * length has increased: in this case we need to move the tail pointer
+ * backwards (towards higher indices), to its next-oldest neighbour.
+ */
+ if (runlen_now > eff_runlen) {
+
+ av->av_buf[avr->avr_ack_ptr] -= eff_runlen + 1;
+ av->av_buf_tail = __ackvec_idx_add(avr->avr_ack_ptr, 1);
+
+ /* This move may not have cleared the overflow flag. */
+ if (av->av_overflow)
+ av->av_overflow = (av->av_buf_head == av->av_buf_tail);
+ } else {
+ av->av_buf_tail = avr->avr_ack_ptr;
+ /*
+ * We have made sure that avr points to a valid cell within the
+ * buffer. This cell is either older than head, or equals head
+ * (empty buffer): in both cases we no longer have any overflow.
+ */
+ av->av_overflow = 0;
+ }
+
+ /*
+ * The peer has acknowledged up to and including ack_ackno. Hence the
+ * first packet in group (2) of 11.4.2 is the successor of ack_ackno.
+ */
+ av->av_tail_ackno = ADD48(avr->avr_ack_ackno, 1);
+
+free_records:
+ list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) {
+ list_del(&avr->avr_node);
+ kmem_cache_free(dccp_ackvec_record_slab, avr);
+ }
+}
+
int __init dccp_ackvec_init(void)
{
dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
git://bbs.cooldavid.org / net-next-2.6.git / blobdiff