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;
+
+ do {
+ u8 runlen = dccp_ackvec_runlen(av->av_buf + ptr);
+
+ 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);
+}
+
+/**
+ * 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 (num_packets > DCCPAV_BURST_THRESH) {
+ u32 lost_packets = num_packets - 1;
+
+ DCCP_WARN("Warning: large burst loss (%u)\n", lost_packets);
+ /*
+ * 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.
+ */
+ for (num_packets = num_cells = 1; lost_packets; ++num_cells) {
+ u8 len = min(lost_packets, (u32)DCCPAV_MAX_RUNLEN);
+
+ av->av_buf_head = __ackvec_idx_sub(av->av_buf_head, 1);
+ av->av_buf[av->av_buf_head] = DCCPAV_NOT_RECEIVED | len;
+
+ lost_packets -= len;
+ }
+ }
+
+ 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;
+ }
+
+ 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;
+
+ av->av_buf[av->av_buf_head] = state;
+ av->av_buf_ackno = seqno;
+
+ 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);
+ }
+ }
+}
+
/*
* If several packets are missing, the HC-Receiver may prefer to enter multiple
* bytes with run length 0, rather than a single byte with a larger run length;
projects / GitHub / LineageOS / android_kernel_motorola_exynos9610.git / commitdiff