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[/] [or1k/] [trunk/] [linux/] [uClibc/] [include/] [net/] [slcompress.h] - Blame information for rev 1771

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1 1325 phoenix
/*
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 * Definitions for tcp compression routines.
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 *
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 * $Id: slcompress.h,v 1.1.1.1 2004-11-12 23:09:52 phoenix Exp $
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 *
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 * Copyright (c) 1989 Regents of the University of California.
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms are permitted
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 * provided that the above copyright notice and this paragraph are
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 * duplicated in all such forms and that any documentation,
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 * advertising materials, and other materials related to such
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 * distribution and use acknowledge that the software was developed
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 * by the University of California, Berkeley.  The name of the
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 * University may not be used to endorse or promote products derived
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 * from this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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 *
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 *      Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
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 *      - Initial distribution.
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 */
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#ifndef _SLCOMPRESS_H_
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#define _SLCOMPRESS_H_
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#define MAX_STATES 16           /* must be > 2 and < 256 */
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#define MAX_HDR MLEN            /* XXX 4bsd-ism: should really be 128 */
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/*
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 * Compressed packet format:
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 *
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 * The first octet contains the packet type (top 3 bits), TCP
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 * 'push' bit, and flags that indicate which of the 4 TCP sequence
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 * numbers have changed (bottom 5 bits).  The next octet is a
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 * conversation number that associates a saved IP/TCP header with
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 * the compressed packet.  The next two octets are the TCP checksum
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 * from the original datagram.  The next 0 to 15 octets are
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 * sequence number changes, one change per bit set in the header
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 * (there may be no changes and there are two special cases where
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 * the receiver implicitly knows what changed -- see below).
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 *
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 * There are 5 numbers which can change (they are always inserted
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 * in the following order): TCP urgent pointer, window,
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 * acknowlegement, sequence number and IP ID.  (The urgent pointer
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 * is different from the others in that its value is sent, not the
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 * change in value.)  Since typical use of SLIP links is biased
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 * toward small packets (see comments on MTU/MSS below), changes
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 * use a variable length coding with one octet for numbers in the
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 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
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 * range 256 - 65535 or 0.  (If the change in sequence number or
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 * ack is more than 65535, an uncompressed packet is sent.)
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 */
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/*
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 * Packet types (must not conflict with IP protocol version)
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 *
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 * The top nibble of the first octet is the packet type.  There are
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 * three possible types: IP (not proto TCP or tcp with one of the
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 * control flags set); uncompressed TCP (a normal IP/TCP packet but
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 * with the 8-bit protocol field replaced by an 8-bit connection id --
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 * this type of packet syncs the sender & receiver); and compressed
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 * TCP (described above).
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 *
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 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
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 * is logically part of the 4-bit "changes" field that follows.  Top
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 * three bits are actual packet type.  For backward compatibility
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 * and in the interest of conserving bits, numbers are chosen so the
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 * IP protocol version number (4) which normally appears in this nibble
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 * means "IP packet".
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 */
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/* packet types */
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#define TYPE_IP 0x40
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#define TYPE_UNCOMPRESSED_TCP 0x70
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#define TYPE_COMPRESSED_TCP 0x80
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#define TYPE_ERROR 0x00
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/* Bits in first octet of compressed packet */
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#define NEW_C   0x40    /* flag bits for what changed in a packet */
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#define NEW_I   0x20
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#define NEW_S   0x08
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#define NEW_A   0x04
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#define NEW_W   0x02
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#define NEW_U   0x01
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/* reserved, special-case values of above */
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#define SPECIAL_I (NEW_S|NEW_W|NEW_U)           /* echoed interactive traffic */
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#define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U)     /* unidirectional data */
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#define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
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#define TCP_PUSH_BIT 0x10
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/*
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 * "state" data for each active tcp conversation on the wire.  This is
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 * basically a copy of the entire IP/TCP header from the last packet
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 * we saw from the conversation together with a small identifier
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 * the transmit & receive ends of the line use to locate saved header.
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 */
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struct cstate {
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        struct cstate *cs_next; /* next most recently used cstate (xmit only) */
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        u_short cs_hlen;        /* size of hdr (receive only) */
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        u_char cs_id;           /* connection # associated with this state */
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        u_char cs_filler;
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        union {
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                char csu_hdr[MAX_HDR];
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                struct ip csu_ip;       /* ip/tcp hdr from most recent packet */
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        } slcs_u;
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};
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#define cs_ip slcs_u.csu_ip
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#define cs_hdr slcs_u.csu_hdr
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/*
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 * all the state data for one serial line (we need one of these
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 * per line).
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 */
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struct slcompress {
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        struct cstate *last_cs; /* most recently used tstate */
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        u_char last_recv;       /* last rcvd conn. id */
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        u_char last_xmit;       /* last sent conn. id */
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        u_short flags;
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#ifndef SL_NO_STATS
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        int sls_packets;        /* outbound packets */
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        int sls_compressed;     /* outbound compressed packets */
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        int sls_searches;       /* searches for connection state */
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        int sls_misses;         /* times couldn't find conn. state */
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        int sls_uncompressedin; /* inbound uncompressed packets */
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        int sls_compressedin;   /* inbound compressed packets */
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        int sls_errorin;        /* inbound unknown type packets */
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        int sls_tossed;         /* inbound packets tossed because of error */
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#endif
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        struct cstate tstate[MAX_STATES];       /* xmit connection states */
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        struct cstate rstate[MAX_STATES];       /* receive connection states */
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};
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/* flag values */
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#define SLF_TOSS 1              /* tossing rcvd frames because of input err */
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void    sl_compress_init __P((struct slcompress *));
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void    sl_compress_setup __P((struct slcompress *, int));
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u_int   sl_compress_tcp __P((struct mbuf *,
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            struct ip *, struct slcompress *, int));
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int     sl_uncompress_tcp __P((u_char **, int, u_int, struct slcompress *));
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int     sl_uncompress_tcp_core __P((u_char *, int, int, u_int,
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            struct slcompress *, u_char **, u_int *));
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#endif /* _SLCOMPRESS_H_ */

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