FreeBSD/Linux Kernel Cross Reference
sys/netinet/tcp_stacks/sack_filter.h

     #ifndef __sack_filter_h__
     #define __sack_filter_h__
     /*-
      * 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.
     *
     * __FBSDID("$FreeBSD$");
     */
    
    /*
     * Seven entry's is carefully choosen to
     * fit in one cache line. We can easily
     * change this to 15 (but it gets very
     * little extra filtering). To change it
     * to be larger than 15 would require either
     * sf_bits becoming a uint32_t and then you
     * could go to 31.. or change it to a full
     * bitstring.. It is really doubtful you
     * will get much benefit beyond 7, in testing
     * there was a small amount but very very small.
     */
    #define SACK_FILTER_BLOCKS 7
    
    struct sack_filter {
            tcp_seq sf_ack;
            uint16_t sf_bits;
            uint8_t sf_cur;
            uint8_t sf_used;
            struct sackblk sf_blks[SACK_FILTER_BLOCKS];
    };
    #ifdef _KERNEL
    void sack_filter_clear(struct sack_filter *sf, tcp_seq seq);
    int sack_filter_blks(struct sack_filter *sf, struct sackblk *in, int numblks,
                         tcp_seq th_ack);
    void sack_filter_reject(struct sack_filter *sf, struct sackblk *in);
    #endif
    #endif

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