sack_filter.c

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/*-
 * Copyright (c) 2017-9 Netflix, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#ifndef _KERNEL
#define _WANT_TCPCB 1
#endif
#include <sys/types.h>
#include <sys/queue.h>
#include <sys/socket.h>
#ifdef _KERNEL
#include <sys/mbuf.h>
#include <sys/sockopt.h>
#endif
#include <netinet/tcp.h>
#include <netinet/tcp_var.h>
#include <netinet/tcp_seq.h>
#ifndef _KERNEL
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <strings.h>
#include <stdlib.h>
#include <limits.h>
#include <getopt.h>
#endif
#include "sack_filter.h"
 
/*
 * Sack filter is used to filter out sacks
 * that have already been processed. The idea
 * is pretty simple really, consider two sacks
 *
 * SACK 1
 *   cum-ack A
 *     sack B - C
 * SACK 2
 *   cum-ack A
 *     sack D - E
 *     sack B - C
 *
 * The previous sack information (B-C) is repeated
 * in SACK 2. If the receiver gets SACK 1 and then
 * SACK 2 then any work associated with B-C as already
 * been completed. This only effects where we may have
 * (as in bbr or rack) cases where we walk a linked list.
 *
 * Now the utility trys to keep everything in a single
 * cache line. This means that its not perfect and
 * it could be that so big of sack's come that a
 * "remembered" processed sack falls off the list and
 * so gets re-processed. Thats ok, it just means we
 * did some extra work. We could of course take more
 * cache line hits by expanding the size of this
 * structure, but then that would cost more.
 */
 
#ifndef _KERNEL
int detailed_dump = 0;
uint64_t cnt_skipped_oldsack = 0;
uint64_t cnt_used_oldsack = 0;
int highest_used=0;
int over_written=0;
int empty_avail=0;
int no_collapse = 0;
FILE *out = NULL;
FILE *in = NULL;
#endif
 
#define sack_blk_used(sf, i) ((1 << i) & sf->sf_bits)
#define sack_blk_set(sf, i) ((1 << i) | sf->sf_bits)
#define sack_blk_clr(sf, i) (~(1 << i) & sf->sf_bits)
 
#ifndef _KERNEL
static
#endif
void
sack_filter_clear(struct sack_filter *sf, tcp_seq seq)
{
        sf->sf_ack = seq;
        sf->sf_bits = 0;
        sf->sf_cur = 0;
        sf->sf_used = 0;
}
/*
 * Given a previous sack filter block, filter out
 * any entries where the cum-ack moves over them
 * fully or partially.
 */
static void
sack_filter_prune(struct sack_filter *sf, tcp_seq th_ack)
{
        int32_t i;
        /* start with the oldest */
        for (i = 0; i < SACK_FILTER_BLOCKS; i++) {
                if (sack_blk_used(sf, i)) {
                        if (SEQ_GT(th_ack, sf->sf_blks[i].end)) {
                                /* This block is consumed */
                                sf->sf_bits = sack_blk_clr(sf, i);
                                sf->sf_used--;
                        } else if (SEQ_GT(th_ack, sf->sf_blks[i].start)) {
                                /* Some of it is acked */
                                sf->sf_blks[i].start = th_ack;
                                /* We could in theory break here, but
                                 * there are some broken implementations
                                 * that send multiple blocks. We want
                                 * to catch them all with similar seq's.
                                 */
                        }
                }
        }
        sf->sf_ack = th_ack;
}
 
/*
 * Return true if you find that
 * the sackblock b is on the score
 * board. Update it along the way
 * if part of it is on the board.
 */
static int32_t
is_sack_on_board(struct sack_filter *sf, struct sackblk *b)
{
        int32_t i, cnt;
 
        for (i = sf->sf_cur, cnt=0; cnt < SACK_FILTER_BLOCKS; cnt++) {
                if (sack_blk_used(sf, i)) {
                        if (SEQ_LT(b->start, sf->sf_ack)) {
                                /* Behind cum-ack update */
                                b->start = sf->sf_ack;
                        }
                        if (SEQ_LT(b->end, sf->sf_ack)) {
                                /* End back behind too */
                                b->end = sf->sf_ack;
                        }
                        if (b->start == b->end) {
                                return(1);
                        }
                        /* Jonathans Rule 1 */
                        if (SEQ_LEQ(sf->sf_blks[i].start, b->start) &&
                            SEQ_GEQ(sf->sf_blks[i].end, b->end)) {
                                return(1);
                        }
                        /* Jonathans Rule 2 */
                        if(SEQ_LT(sf->sf_blks[i].end, b->start)) {
                                goto nxt_blk;
                        }
                        /* Jonathans Rule 3 */
                        if (SEQ_GT(sf->sf_blks[i].start, b->end)) {
                                goto nxt_blk;
                        }
                        if (SEQ_LEQ(sf->sf_blks[i].start, b->start)) {
                                b->start = sf->sf_blks[i].end;
                                sf->sf_blks[i].end = b->end;
                                goto nxt_blk;
                        }
                        if (SEQ_GEQ(sf->sf_blks[i].end, b->end)) {
                                b->end = sf->sf_blks[i].start;
                                sf->sf_blks[i].start = b->start;
                                goto nxt_blk;
                        }
                }
        nxt_blk:
                i++;
                i %= SACK_FILTER_BLOCKS;
        }
        /* Did we totally consume it in pieces? */
        if (b->start != b->end)
                return(0);
        else
                return(1);
}
 
static int32_t
sack_filter_old(struct sack_filter *sf, struct sackblk *in, int  numblks)
{
        int32_t num, i;
        struct sackblk blkboard[TCP_MAX_SACK];
        /*
         * An old sack has arrived. It may contain data
         * we do not have. We might not have it since
         * we could have had a lost ack <or> we might have the
         * entire thing on our current board. We want to prune
         * off anything we have. With this function though we
         * won't add to the board.
         */
        for( i = 0, num = 0; i<numblks; i++ ) {
                if (is_sack_on_board(sf, &in[i])) {
#ifndef _KERNEL
                        cnt_skipped_oldsack++;
#endif
                        continue;
                }
                /* Did not find it (or found only
                 * a piece of it). Copy it to
                 * our outgoing board.
                 */
                memcpy(&blkboard[num], &in[i], sizeof(struct sackblk));
#ifndef _KERNEL
                cnt_used_oldsack++;
#endif
                num++;
        }
        if (num) {
                memcpy(in, blkboard, (num * sizeof(struct sackblk)));
        }
        return (num);
}
 
/*
 * Given idx its used but there is space available
 * move the entry to the next free slot
 */
static void
sack_move_to_empty(struct sack_filter *sf, uint32_t idx)
{
        int32_t i, cnt;
 
        i = (idx + 1) % SACK_FILTER_BLOCKS;
        for (cnt=0; cnt <(SACK_FILTER_BLOCKS-1); cnt++) {
                if (sack_blk_used(sf, i) == 0) {
                        memcpy(&sf->sf_blks[i], &sf->sf_blks[idx], sizeof(struct sackblk));
                        sf->sf_bits = sack_blk_clr(sf, idx);
                        sf->sf_bits = sack_blk_set(sf, i);
                        return;
                }
                i++;
                i %= SACK_FILTER_BLOCKS;
        }
}
 
static int32_t
sack_filter_new(struct sack_filter *sf, struct sackblk *in, int numblks, tcp_seq th_ack)
{
        struct sackblk blkboard[TCP_MAX_SACK];
        int32_t num, i;
        /*
         * First lets trim the old and possibly
         * throw any away we have.
         */
        for(i=0, num=0; i<numblks; i++) {
                if (is_sack_on_board(sf, &in[i]))
                        continue;
                memcpy(&blkboard[num], &in[i], sizeof(struct sackblk));
                num++;
        }
        if (num == 0)
                return(num);
 
        /* Now what we are left with is either
         * completely merged on to the board
         * from the above steps, or is new
         * and need to be added to the board
         * with the last one updated to current.
         *
         * First copy it out, we want to return that
         * to our caller for processing.
         */
        memcpy(in, blkboard, (num * sizeof(struct sackblk)));
        numblks = num;
        /* Now go through and add to our board as needed */
        for(i=(num-1); i>=0; i--) {
                if (is_sack_on_board(sf, &blkboard[i])) {
                        continue;
                }
                /* Add this guy its not listed */
                sf->sf_cur++;
                sf->sf_cur %= SACK_FILTER_BLOCKS;
                if ((sack_blk_used(sf, sf->sf_cur)) &&
                    (sf->sf_used < SACK_FILTER_BLOCKS)) {
                        sack_move_to_empty(sf, sf->sf_cur);
                }
#ifndef _KERNEL
                if (sack_blk_used(sf, sf->sf_cur)) {
                        over_written++;
                        if (sf->sf_used < SACK_FILTER_BLOCKS)
                                empty_avail++;
                }
#endif
                memcpy(&sf->sf_blks[sf->sf_cur], &in[i], sizeof(struct sackblk));
                if (sack_blk_used(sf, sf->sf_cur) == 0) {
                        sf->sf_used++;
#ifndef _KERNEL
                        if (sf->sf_used > highest_used)
                                highest_used = sf->sf_used;
#endif
                        sf->sf_bits = sack_blk_set(sf, sf->sf_cur);
                }
        }
        return(numblks);
}
 
/*
 * Given a sack block on the board (the skip index) see if
 * any other used entries overlap or meet, if so return the index.
 */
static int32_t
sack_blocks_overlap_or_meet(struct sack_filter *sf, struct sackblk *sb, uint32_t skip)
{
        int32_t i;
 
        for(i=0; i<SACK_FILTER_BLOCKS; i++) {
                if (sack_blk_used(sf, i) == 0)
                        continue;
                if (i == skip)
                        continue;
                if (SEQ_GEQ(sf->sf_blks[i].end, sb->start) &&
                    SEQ_LEQ(sf->sf_blks[i].end, sb->end) &&
                    SEQ_LEQ(sf->sf_blks[i].start, sb->start)) {
                        return(i);
                }
                if (SEQ_LEQ(sf->sf_blks[i].start, sb->end) &&
                    SEQ_GEQ(sf->sf_blks[i].start, sb->start) &&
                    SEQ_GEQ(sf->sf_blks[i].end, sb->end)) {
                        return(i);
                }
        }
        return (-1);
}
 
/*
 * Collapse entry src into entry into
 * and free up the src entry afterwards.
 */
static void
sack_collapse(struct sack_filter *sf, int32_t src, int32_t into)
{
        if (SEQ_LT(sf->sf_blks[src].start, sf->sf_blks[into].start)) {
                /* src has a lower starting point */
                sf->sf_blks[into].start = sf->sf_blks[src].start;
        }
        if (SEQ_GT(sf->sf_blks[src].end, sf->sf_blks[into].end)) {
                /* src has a higher ending point */
                sf->sf_blks[into].end = sf->sf_blks[src].end;
        }
        sf->sf_bits = sack_blk_clr(sf, src);
        sf->sf_used--;
}
 
static void
sack_board_collapse(struct sack_filter *sf)
{
        int32_t i, j, i_d, j_d;
 
        for(i=0; i<SACK_FILTER_BLOCKS; i++) {
                if (sack_blk_used(sf, i) == 0)
                        continue;
                /*
                 * Look at all other blocks but this guy
                 * to see if they overlap. If so we collapse
                 * the two blocks together.
                 */
                j = sack_blocks_overlap_or_meet(sf, &sf->sf_blks[i], i);
                if (j == -1) {
                        /* No overlap */
                        continue;
                }
                /*
                 * Ok j and i overlap with each other, collapse the
                 * one out furthest away from the current position.
                 */
                if (sf->sf_cur > i)
                        i_d = sf->sf_cur - i;
                else
                        i_d = i - sf->sf_cur;
                if (sf->sf_cur > j)
                        j_d = sf->sf_cur - j;
                else
                        j_d = j - sf->sf_cur;
                if (j_d > i_d) {
                        sack_collapse(sf, j, i);
                } else
                        sack_collapse(sf, i, j);
        }
}
 
#ifndef _KERNEL
uint64_t saved=0;
uint64_t tot_sack_blks=0;
 
static void
sack_filter_dump(FILE *out, struct sack_filter *sf)
{
        int i;
        fprintf(out, "  sf_ack:%u sf_bits:0x%x c:%d used:%d\n",
                sf->sf_ack, sf->sf_bits,
                sf->sf_cur, sf->sf_used);
 
        for(i=0; i<SACK_FILTER_BLOCKS; i++) {
                if (sack_blk_used(sf, i)) {
                        fprintf(out, "Entry:%d start:%u end:%u\n", i,
                               sf->sf_blks[i].start,
                               sf->sf_blks[i].end);
                }
        }
}
#endif
 
#ifndef _KERNEL
static
#endif
int
sack_filter_blks(struct sack_filter *sf, struct sackblk *in, int numblks,
                 tcp_seq th_ack)
{
        int32_t i, ret;
 
        if (numblks > TCP_MAX_SACK) {
#ifdef _KERNEL
                panic("sf:%p sb:%p Impossible number of sack blocks %d > 4\n",
                      sf, in,
                      numblks);
#endif
                return(numblks);
        }
#ifndef _KERNEL
        if ((sf->sf_used > 1) && (no_collapse == 0))
                sack_board_collapse(sf);
 
#else
        if (sf->sf_used > 1)
                sack_board_collapse(sf);
#endif
        if ((sf->sf_used == 0) && numblks) {
                /*
                 * We are brand new add the blocks in
                 * reverse order. Note we can see more
                 * than one in new, since ack's could be lost.
                 */
                int cnt_added = 0;
 
                sf->sf_ack = th_ack;
                for(i=(numblks-1), sf->sf_cur=0; i >= 0; i--) {
                        memcpy(&sf->sf_blks[sf->sf_cur], &in[i], sizeof(struct sackblk));
                        sf->sf_bits = sack_blk_set(sf, sf->sf_cur);
                        sf->sf_cur++;
                        sf->sf_cur %= SACK_FILTER_BLOCKS;
                        sf->sf_used++;
                        cnt_added++;
#ifndef _KERNEL
                        if (sf->sf_used > highest_used)
                                highest_used = sf->sf_used;
#endif
                }
                if (sf->sf_cur)
                        sf->sf_cur--;
 
                return (cnt_added);
        }
        if (SEQ_GT(th_ack, sf->sf_ack)) {
                sack_filter_prune(sf, th_ack);
        }
        if (numblks) {
                if (SEQ_GEQ(th_ack, sf->sf_ack)) {
                        ret = sack_filter_new(sf, in, numblks, th_ack);
                } else {
                        ret = sack_filter_old(sf, in, numblks);
                }
        } else
                ret = 0;
        return (ret);
}
 
void
sack_filter_reject(struct sack_filter *sf, struct sackblk *in)
{
        /*
         * Given a specified block (that had made
         * it past the sack filter). Reject that
         * block triming it off any sack-filter block
         * that has it. Usually because the block was
         * too small and did not cover a whole send.
         *
         * This function will only "undo" sack-blocks
         * that are fresh and touch the edges of
         * blocks in our filter.
         */
        int i;
 
        for(i=0; i<SACK_FILTER_BLOCKS; i++) {
                if (sack_blk_used(sf, i) == 0)
                        continue;
                /*
                 * Now given the sack-filter block does it touch
                 * with one of the ends
                 */
                if (sf->sf_blks[i].end == in->end) {
                        /* The end moves back to start */
                        if (SEQ_GT(in->start, sf->sf_blks[i].start))
                                /* in-blk       |----| */
                                /* sf-blk  |---------| */
                                sf->sf_blks[i].end = in->start;
                        else {
                                /* It consumes this block */
                                /* in-blk  |---------| */
                                /* sf-blk     |------| */
                                /* <or> */
                                /* sf-blk  |---------| */
                                sf->sf_bits = sack_blk_clr(sf, i);
                                sf->sf_used--;
                        }
                        continue;
                }
                if (sf->sf_blks[i].start == in->start) {
                        if (SEQ_LT(in->end, sf->sf_blks[i].end)) {
                                /* in-blk  |----|      */
                                /* sf-blk  |---------| */
                                sf->sf_blks[i].start = in->end;
                        } else {
                                /* It consumes this block */
                                /* in-blk  |----------|  */
                                /* sf-blk  |-------|     */
                                /* <or> */
                                /* sf-blk  |----------|  */
                                sf->sf_bits = sack_blk_clr(sf, i);
                                sf->sf_used--;
                        }
                        continue;
                }
        }
}
 
#ifndef _KERNEL
 
int
main(int argc, char **argv)
{
        char buffer[512];
        struct sackblk blks[TCP_MAX_SACK];
        FILE *err;
        tcp_seq th_ack, snd_una, snd_max = 0;
        struct sack_filter sf;
        int32_t numblks,i;
        int snd_una_set=0;
        double a, b, c;
        int invalid_sack_print = 0;
        uint32_t chg_remembered=0;
        uint32_t sack_chg=0;
        char line_buf[10][256];
        int line_buf_at=0;
 
        in = stdin;
        out = stdout;
        while ((i = getopt(argc, argv, "ndIi:o:?h")) != -1) {
                switch (i) {
                case 'n':
                        no_collapse = 1;
                        break;
                case 'd':
                        detailed_dump = 1;
                        break;
                case'I':
                        invalid_sack_print = 1;
                        break;
                case 'i':
                        in = fopen(optarg, "r");
                        if (in == NULL) {
                                fprintf(stderr, "Fatal error can't open %s for input\n", optarg);
                                exit(-1);
                        }
                        break;
                case 'o':
                        out = fopen(optarg, "w");
                        if (out == NULL) {
                                fprintf(stderr, "Fatal error can't open %s for output\n", optarg);
                                exit(-1);
                        }
                        break;
                default:
                case '?':
                case 'h':
                        fprintf(stderr, "Use %s [ -i infile -o outfile -I]\n", argv[0]);
                        return(0);
                        break;
                };
        }
        sack_filter_clear(&sf, 0);
        memset(buffer, 0, sizeof(buffer));
        memset(blks, 0, sizeof(blks));
        numblks = 0;
        fprintf(out, "************************************\n");
        while (fgets(buffer, sizeof(buffer), in) != NULL) {
                sprintf(line_buf[line_buf_at], "%s", buffer);
                line_buf_at++;
                if (strncmp(buffer, "QUIT", 4) == 0) {
                        break;
                } else if (strncmp(buffer, "DUMP", 4) == 0) {
                        sack_filter_dump(out, &sf);
                } else if (strncmp(buffer, "MAX:", 4) == 0) {
                        snd_max = strtoul(&buffer[4], NULL, 0);
                } else if (strncmp(buffer, "COMMIT", 6) == 0) {
                        int nn, ii;
                        if (numblks) {
                                uint32_t szof, tot_chg;
                                for(ii=0; ii<line_buf_at; ii++) {
                                        fprintf(out, "%s", line_buf[ii]);
                                }
                                fprintf(out, "------------------------------------\n");
                                nn = sack_filter_blks(&sf, blks, numblks, th_ack);
                                saved += numblks - nn;
                                tot_sack_blks += numblks;
                                fprintf(out, "ACK:%u\n", sf.sf_ack);
                                for(ii=0, tot_chg=0; ii<nn; ii++) {
                                        szof = blks[ii].end - blks[ii].start;
                                        tot_chg += szof;
                                        fprintf(out, "SACK:%u:%u [%u]\n",
                                               blks[ii].start,
                                                blks[ii].end, szof);
                                }
                                fprintf(out,"************************************\n");
                                chg_remembered = tot_chg;
                                if (detailed_dump) {
                                        sack_filter_dump(out, &sf);
                                        fprintf(out,"************************************\n");
                                }
                        }
                        memset(blks, 0, sizeof(blks));
                        memset(line_buf, 0, sizeof(line_buf));
                        line_buf_at=0;
                        numblks = 0;
                } else if (strncmp(buffer, "CHG:", 4) == 0) {
                        sack_chg = strtoul(&buffer[4], NULL, 0);
                        if ((sack_chg != chg_remembered) &&
                            (sack_chg > chg_remembered)){
                                fprintf(out,"***WARNING WILL RODGERS DANGER!! sack_chg:%u last:%u\n",
                                        sack_chg, chg_remembered
                                        );
                        }
                        sack_chg = chg_remembered = 0;
                } else if (strncmp(buffer, "RXT", 3) == 0) {
                        sack_filter_clear(&sf, snd_una);
                } else if (strncmp(buffer, "ACK:", 4) == 0) {
                        th_ack = strtoul(&buffer[4], NULL, 0);
                        if (snd_una_set == 0) {
                                snd_una = th_ack;
                                snd_una_set = 1;
                        } else if (SEQ_GT(th_ack, snd_una)) {
                                snd_una = th_ack;
                        }
                } else if (strncmp(buffer, "EXIT", 4) == 0) {
                        sack_filter_clear(&sf, snd_una);
                        sack_chg = chg_remembered = 0;
                } else if (strncmp(buffer, "SACK:", 5) == 0) {
                        char *end=NULL;
                        uint32_t start;
                        uint32_t endv;
 
                        start = strtoul(&buffer[5], &end, 0);
                        if (end) {
                                endv = strtoul(&end[1], NULL, 0);
                        } else {
                                fprintf(out, "--Sack invalid skip 0 start:%u : ??\n", start);
                                continue;
                        }
                        if (SEQ_GT(endv, snd_max))
                                snd_max = endv;
                        if (SEQ_LT(endv, start)) {
                                fprintf(out, "--Sack invalid skip 1 endv:%u < start:%u\n", endv, start);
                                continue;
                        }
                        if (numblks == TCP_MAX_SACK) {
                                fprintf(out, "--Exceeded max %d\n", numblks);
                                exit(0);
                        }
                        blks[numblks].start = start;
                        blks[numblks].end = endv;
                        numblks++;
                } else if (strncmp(buffer, "REJ:n:n", 4) == 0) {
                        struct sackblk in;
                        char *end=NULL;
 
                        in.start = strtoul(&buffer[4], &end, 0);
                        if (end) {
                                in.end = strtoul(&end[1], NULL, 0);
                                sack_filter_reject(&sf, &in);
                        } else
                                fprintf(out, "Invalid input END:A:B\n");
                } else if (strncmp(buffer, "HELP", 4) == 0) {
                        fprintf(out, "You can input:\n");
                        fprintf(out, "SACK:S:E -- to define a sack block\n");
                        fprintf(out, "RXT -- to clear the filter without changing the remembered\n");
                        fprintf(out, "EXIT -- To clear the sack filter and start all fresh\n");
                        fprintf(out, "ACK:N -- To advance the cum-ack to N\n");
                        fprintf(out, "MAX:N -- To set send-max to N\n");
                        fprintf(out, "COMMIT -- To apply the sack you built to the filter and dump the filter\n");
                        fprintf(out, "DUMP -- To display the current contents of the sack filter\n");
                        fprintf(out, "QUIT -- To exit this program\n");
                } else {
                        fprintf(out, "Command %s unknown\n", buffer);
                }
                memset(buffer, 0, sizeof(buffer));
        }
        if (in != stdin) {
                fclose(in);
        }
        if (out != stdout) {
                fclose(out);
        }
        a = saved * 100.0;
        b = tot_sack_blks * 1.0;
        if (b > 0.0)
                c = a/b;
        else
                c = 0.0;
        if (out != stdout)
                err = stdout;
        else
                err = stderr;
        fprintf(err, "Saved %lu sack blocks out of %lu (%2.3f%%) old_skip:%lu old_usd:%lu high_cnt:%d ow:%d ea:%d\n",
                saved, tot_sack_blks, c, cnt_skipped_oldsack, cnt_used_oldsack, highest_used, over_written, empty_avail);
        return(0);
}
#endif