[DCCP] ackvec: Introduce dccp_ackvec_slab

[linux-2.6/verdex.git] / net / dccp / ackvec.c

/*
 *  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/init.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/slab.h>

#include <net/sock.h>

static kmem_cache_t *dccp_ackvec_slab;

int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
{
        struct dccp_sock *dp = dccp_sk(sk);
#ifdef CONFIG_IP_DCCP_DEBUG
        const char *debug_prefix = dp->dccps_role == DCCP_ROLE_CLIENT ?
                                "CLIENT tx: " : "server tx: ";
#endif
        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 ((int)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 gfp_t priority)
{
        struct dccp_ackvec *av = kmem_cache_alloc(dccp_ackvec_slab, 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_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)
{
        kmem_cache_free(dccp_ackvec_slab, av);
}

static inline u8 dccp_ackvec_state(const struct dccp_ackvec *av,
                                   const u8 index)
{
        return av->dccpav_buf[index] & DCCP_ACKVEC_STATE_MASK;
}

static inline u8 dccp_ackvec_len(const struct dccp_ackvec *av,
                                 const u8 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;
        long new_head;

        if (av->dccpav_vec_len + packets > DCCP_MAX_ACKVEC_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 += DCCP_MAX_ACKVEC_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);
                u8 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 == DCCP_MAX_ACKVEC_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_throw_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
        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;
}

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_throw_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_throw_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;
}

static char dccp_ackvec_slab_msg[] __initdata =
        KERN_CRIT "DCCP: Unable to create ack vectors slab cache\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;
        }

        return 0;
}

void dccp_ackvec_exit(void)
{
        if (dccp_ackvec_slab != NULL) {
                kmem_cache_destroy(dccp_ackvec_slab);
                dccp_ackvec_slab = NULL;
        }
}