[DCCP]: Move the ack vector code to net/dccp/ackvec.[ch]

Isolating it, that will be used when we introduce a CCID2 (TCP-Like)
implementation.

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 419 insertions, 0 deletions

diff --git a/net/dccp/ackvec.c b/net/dccp/ackvec.c
new file mode 100644
index 000000000000..6530283eafca
--- /dev/null
+++ b/net/dccp/ackvec.c
@@ -0,0 +1,419 @@
+/*
+ *  net/dccp/ackvec.c
+ *
+ *  An implementation of the DCCP protocol
+ *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
+ *
+ *      This program is free software; you can redistribute it and/or modify it
+ *      under the terms of the GNU General Public License as published by the
+ *      Free Software Foundation; version 2 of the License;
+ */
+
+#include "ackvec.h"
+#include "dccp.h"
+
+#include <linux/dccp.h>
+#include <linux/skbuff.h>
+
+#include <net/sock.h>
+
+int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
+{
+        struct dccp_sock *dp = dccp_sk(sk);
+        struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
+        int len = av->dccpav_vec_len + 2;
+        struct timeval now;
+        u32 elapsed_time;
+        unsigned char *to, *from;
+
+        dccp_timestamp(sk, &now);
+        elapsed_time = timeval_delta(&now, &av->dccpav_time) / 10;
+
+        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);
+        *to++ = DCCPO_ACK_VECTOR_0;
+        *to++ = len;
+
+        len  = av->dccpav_vec_len;
+        from = av->dccpav_buf + av->dccpav_buf_head;
+
+        /* Check if buf_head wraps */
+        if (av->dccpav_buf_head + len > av->dccpav_vec_len) {
+                const u32 tailsize = (av->dccpav_vec_len - av->dccpav_buf_head);
+
+                memcpy(to, from, tailsize);
+                to   += tailsize;
+                len  -= tailsize;
+                from = av->dccpav_buf;
+        }
+
+        memcpy(to, from, len);
+        /*
+         *      From draft-ietf-dccp-spec-11.txt:
+         *
+         *      For each acknowledgement it sends, the HC-Receiver will add an
+         *      acknowledgement record.  ack_seqno will equal the HC-Receiver
+         *      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;
+
+        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;
+}
+
+struct dccp_ackvec *dccp_ackvec_alloc(const unsigned int len,
+                                      const unsigned int __nocast priority)
+{
+        struct dccp_ackvec *av = kmalloc(sizeof(*av) + len, priority);
+
+        if (av != NULL) {
+                av->dccpav_buf_len      = len;
+                av->dccpav_buf_head     =
+                        av->dccpav_buf_tail = av->dccpav_buf_len - 1;
+                av->dccpav_buf_ackno    =
+                        av->dccpav_ack_ackno = av->dccpav_ack_seqno = ~0LLU;
+                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;
+        }
+
+        return av;
+}
+
+void dccp_ackvec_free(struct dccp_ackvec *av)
+{
+        kfree(av);
+}
+
+static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
+                                   const unsigned int index)
+{
+        return av->dccpav_buf[index] & DCCP_ACKVEC_STATE_MASK;
+}
+
+static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
+                                 const unsigned int index)
+{
+        return av->dccpav_buf[index] & DCCP_ACKVEC_LEN_MASK;
+}
+
+/*
+ * 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;
+ * this simplifies table updates if one of the missing packets arrives.
+ */
+static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
+                                                 const unsigned int packets,
+                                                  const unsigned char state)
+{
+        unsigned int gap;
+        signed long new_head;
+
+        if (av->dccpav_vec_len + packets > av->dccpav_buf_len)
+                return -ENOBUFS;
+
+        gap      = packets - 1;
+        new_head = av->dccpav_buf_head - packets;
+
+        if (new_head < 0) {
+                if (gap > 0) {
+                        memset(av->dccpav_buf, DCCP_ACKVEC_STATE_NOT_RECEIVED,
+                               gap + new_head + 1);
+                        gap = -new_head;
+                }
+                new_head += av->dccpav_buf_len;
+        } 
+
+        av->dccpav_buf_head = new_head;
+
+        if (gap > 0)
+                memset(av->dccpav_buf + av->dccpav_buf_head + 1,
+                       DCCP_ACKVEC_STATE_NOT_RECEIVED, gap);
+
+        av->dccpav_buf[av->dccpav_buf_head] = state;
+        av->dccpav_vec_len += packets;
+        return 0;
+}
+
+/*
+ * Implements the draft-ietf-dccp-spec-11.txt Appendix A
+ */
+int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
+                    const u64 ackno, const u8 state)
+{
+        /*
+         * Check at the right places if the buffer is full, if it is, tell the
+         * caller to start dropping packets till the HC-Sender acks our ACK
+         * vectors, when we will free up space in dccpav_buf.
+         *
+         * We may well decide to do buffer compression, etc, but for now lets
+         * just drop.
+         *
+         * From Appendix A:
+         *
+         *      Of course, the circular buffer may overflow, either when the
+         *      HC-Sender is sending data at a very high rate, when the
+         *      HC-Receiver's acknowledgements are not reaching the HC-Sender,
+         *      or when the HC-Sender is forgetting to acknowledge those acks
+         *      (so the HC-Receiver is unable to clean up old state). In this
+         *      case, the HC-Receiver should either compress the buffer (by
+         *      increasing run lengths when possible), transfer its state to
+         *      a larger buffer, or, as a last resort, drop all received
+         *      packets, without processing them whatsoever, until its buffer
+         *      shrinks again.
+         */
+
+        /* See if this is the first ackno being inserted */
+        if (av->dccpav_vec_len == 0) {
+                av->dccpav_buf[av->dccpav_buf_head] = state;
+                av->dccpav_vec_len = 1;
+        } else if (after48(ackno, av->dccpav_buf_ackno)) {
+                const u64 delta = dccp_delta_seqno(av->dccpav_buf_ackno,
+                                                   ackno);
+
+                /*
+                 * Look if the state of this packet is the same as the
+                 * previous ackno and if so if we can bump the head len.
+                 */
+                if (delta == 1 &&
+                    dccp_ackvec_state(av, av->dccpav_buf_head) == state &&
+                    (dccp_ackvec_len(av, av->dccpav_buf_head) <
+                     DCCP_ACKVEC_LEN_MASK))
+                        av->dccpav_buf[av->dccpav_buf_head]++;
+                else if (dccp_ackvec_set_buf_head_state(av, delta, state))
+                        return -ENOBUFS;
+        } else {
+                /*
+                 * A.1.2.  Old Packets
+                 *
+                 *      When a packet with Sequence Number S arrives, and
+                 *      S <= buf_ackno, the HC-Receiver will scan the table
+                 *      for the byte corresponding to S. (Indexing structures
+                 *      could reduce the complexity of this scan.)
+                 */
+                u64 delta = dccp_delta_seqno(ackno, av->dccpav_buf_ackno);
+                unsigned int index = av->dccpav_buf_head;
+
+                while (1) {
+                        const u8 len = dccp_ackvec_len(av, index);
+                        const u8 state = dccp_ackvec_state(av, index);
+                        /*
+                         * valid packets not yet in dccpav_buf have a reserved
+                         * entry, with a len equal to 0.
+                         */
+                        if (state == DCCP_ACKVEC_STATE_NOT_RECEIVED &&
+                            len == 0 && delta == 0) { /* Found our
+                                                         reserved seat! */
+                                dccp_pr_debug("Found %llu reserved seat!\n",
+                                              (unsigned long long)ackno);
+                                av->dccpav_buf[index] = state;
+                                goto out;
+                        }
+                        /* len == 0 means one packet */
+                        if (delta < len + 1)
+                                goto out_duplicate;
+
+                        delta -= len + 1;
+                        if (++index == av->dccpav_buf_len)
+                                index = 0;
+                }
+        }
+
+        av->dccpav_buf_ackno = ackno;
+        dccp_timestamp(sk, &av->dccpav_time);
+out:
+        dccp_pr_debug("");
+        return 0;
+
+out_duplicate:
+        /* Duplicate packet */
+        dccp_pr_debug("Received a dup or already considered lost "
+                      "packet: %llu\n", (unsigned long long)ackno);
+        return -EILSEQ;
+}
+
+#ifdef CONFIG_IP_DCCP_DEBUG
+void dccp_ackvector_print(const u64 ackno, const unsigned char *vector, int len)
+{
+        if (!dccp_debug)
+                return;
+
+        printk("ACK vector len=%d, ackno=%llu |", len,
+               (unsigned long long)ackno);
+
+        while (len--) {
+                const u8 state = (*vector & DCCP_ACKVEC_STATE_MASK) >> 6;
+                const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
+
+                printk("%d,%d|", state, rl);
+                ++vector;
+        }
+
+        printk("\n");
+}
+
+void dccp_ackvec_print(const struct dccp_ackvec *av)
+{
+        dccp_ackvector_print(av->dccpav_buf_ackno,
+                             av->dccpav_buf + av->dccpav_buf_head,
+                             av->dccpav_vec_len);
+}
+#endif
+
+static void dccp_ackvec_trow_away_ack_record(struct dccp_ackvec *av)
+{
+        /*
+         * 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
+        av->dccpav_buf_tail = av->dccpav_ack_ptr + 1;
+        if (av->dccpav_buf_tail >= av->dccpav_vec_len)
+                av->dccpav_buf_tail -= av->dccpav_vec_len;
+#endif
+        av->dccpav_vec_len -= av->dccpav_sent_len;
+}
+
+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;
+
+        if (ackno == av->dccpav_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: ";
+#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_trow_away_ack_record(av);
+                av->dccpav_ack_seqno = DCCP_MAX_SEQNO + 1;
+        }
+}
+
+static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
+                                            struct sock *sk, u64 ackno,
+                                            const unsigned char len,
+                                            const unsigned char *vector)
+{
+        unsigned char i;
+
+        /* Check if we actually sent an ACK vector */
+        if (av->dccpav_ack_seqno == DCCP_MAX_SEQNO + 1)
+                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;
+        while (i--) {
+                const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
+                u64 ackno_end_rl;
+
+                dccp_set_seqno(&ackno_end_rl, ackno - rl);
+
+                /*
+                 * dccp_pr_debug("is %llu <= %llu <= %llu? ", ackno_end_rl,
+                 * av->dccpav_ack_seqno, ackno);
+                 */
+                if (between48(av->dccpav_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);
+                                const char *debug_prefix =
+                                        dp->dccps_role == DCCP_ROLE_CLIENT ?
+                                        "CLIENT rx ack: " : "server rx ack: ";
+#endif
+                                dccp_pr_debug("%sACK vector 0, len=%d, "
+                                              "ack_seqno=%llu, ack_ackno=%llu, "
+                                              "ACKED!\n",
+                                              debug_prefix, len,
+                                              (unsigned long long)
+                                              av->dccpav_ack_seqno,
+                                              (unsigned long long)
+                                              av->dccpav_ack_ackno);
+                                dccp_ackvec_trow_away_ack_record(av);
+                        }
+                        /*
+                         * If dccpav_ack_seqno was not received, no problem
+                         * we'll send another ACK vector.
+                         */
+                        av->dccpav_ack_seqno = DCCP_MAX_SEQNO + 1;
+                        break;
+                }
+                /* dccp_pr_debug_cat("no\n"); */
+
+                dccp_set_seqno(&ackno, ackno_end_rl - 1);
+                ++vector;
+        }
+}
+
+int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
+                      const u8 opt, const u8 *value, const u8 len)
+{
+        if (len > DCCP_MAX_ACKVEC_LEN)
+                return -1;
+
+        /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
+        dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
+                                        DCCP_SKB_CB(skb)->dccpd_ack_seq,
+                                        len, value);
+        return 0;
+}