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generation scheme. Users may now select between the currently used OpenBSD algorithm and the older random positive increment method. While the OpenBSD algorithm is more secure, it also breaks TIME_WAIT handling; this is causing trouble for an increasing number of folks. To switch between generation schemes, one sets the sysctl net.inet.tcp.tcp_seq_genscheme. 0 = random positive increments, 1 = the OpenBSD algorithm. 1 is still the default. Once a secure _and_ compatible algorithm is implemented, this sysctl will be removed. Reviewed by: jlemon Tested by: numerous subscribers of -net
106 lines
4 KiB
C
106 lines
4 KiB
C
/*
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* Copyright (c) 1982, 1986, 1993, 1995
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)tcp_seq.h 8.3 (Berkeley) 6/21/95
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* $FreeBSD$
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*/
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#ifndef _NETINET_TCP_SEQ_H_
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#define _NETINET_TCP_SEQ_H_
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/*
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* TCP sequence numbers are 32 bit integers operated
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* on with modular arithmetic. These macros can be
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* used to compare such integers.
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*/
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#define SEQ_LT(a,b) ((int)((a)-(b)) < 0)
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#define SEQ_LEQ(a,b) ((int)((a)-(b)) <= 0)
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#define SEQ_GT(a,b) ((int)((a)-(b)) > 0)
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#define SEQ_GEQ(a,b) ((int)((a)-(b)) >= 0)
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/* for modulo comparisons of timestamps */
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#define TSTMP_LT(a,b) ((int)((a)-(b)) < 0)
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#define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0)
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/*
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* TCP connection counts are 32 bit integers operated
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* on with modular arithmetic. These macros can be
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* used to compare such integers.
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*/
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#define CC_LT(a,b) ((int)((a)-(b)) < 0)
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#define CC_LEQ(a,b) ((int)((a)-(b)) <= 0)
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#define CC_GT(a,b) ((int)((a)-(b)) > 0)
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#define CC_GEQ(a,b) ((int)((a)-(b)) >= 0)
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/* Macro to increment a CC: skip 0 which has a special meaning */
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#define CC_INC(c) (++(c) == 0 ? ++(c) : (c))
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/*
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* Macros to initialize tcp sequence numbers for
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* send and receive from initial send and receive
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* sequence numbers.
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*/
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#define tcp_rcvseqinit(tp) \
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(tp)->rcv_adv = (tp)->rcv_nxt = (tp)->irs + 1
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#define tcp_sendseqinit(tp) \
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(tp)->snd_una = (tp)->snd_nxt = (tp)->snd_max = (tp)->snd_up = \
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(tp)->iss
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#define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * hz)
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/* timestamp wrap-around time */
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#ifdef _KERNEL
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extern tcp_cc tcp_ccgen; /* global connection count */
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/*
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* Increment for tcp_iss each second.
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* This is designed to increment at the standard 250 KB/s,
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* but with a random component averaging 128 KB.
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* We also increment tcp_iss by a quarter of this amount
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* each time we use the value for a new connection.
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* If defined, the tcp_random18() macro should produce a
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* number in the range [0-0x3ffff] that is hard to predict.
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*
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* The variable tcp_iss and tcp_random18() are only used
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* by sequence number generation scheme 0.
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*/
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#ifndef tcp_random18
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#define tcp_random18() (arc4random() & 0x3ffff)
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#endif
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#define TCP_ISSINCR (122*1024 + tcp_random18())
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extern tcp_seq tcp_iss;
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#else
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#define TCP_ISSINCR (250*1024) /* increment for tcp_iss each second */
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#endif /* _KERNEL */
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#endif /* _NETINET_TCP_SEQ_H_ */
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