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1 | /* |
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2 | * Sequence number / nonce mechanism for udp tunnel |
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3 | * |
4 | * arguments: none |
5 | * |
6 | * encoding: prepend 4 bytes of sequence arithmetic serial number |
7 | * decoding: check increasingness, or ignore |
8 | */ |
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9 | /* |
10 | * Copyright (C) 2000 Ian Jackson |
11 | * |
12 | * This is free software; you can redistribute it and/or modify it |
13 | * under the terms of the GNU General Public License as published by |
14 | * the Free Software Foundation; either version 2 of the License, or |
15 | * (at your option) any later version. |
16 | * |
17 | * This program is distributed in the hope that it will be useful, but |
18 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
20 | * General Public License for more details. |
21 | * |
22 | * You should have received a copy of the GNU General Public License |
23 | * along with userv-utils; if not, write to the Free Software |
24 | * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
25 | */ |
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26 | |
27 | #include <netinet/in.h> |
28 | |
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29 | #include "forwarder.h" |
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30 | |
31 | struct mechdata { |
32 | uint32_t number; |
33 | int anyseen; /* decode only */ |
34 | }; |
35 | |
36 | static void mes_sequence(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) { |
37 | struct mechdata *md; |
38 | |
39 | XMALLOC(md); |
40 | get_random(&md->number,sizeof(md->number)); |
41 | *maxprefix_io += 4; |
42 | *md_r= md; |
43 | } |
44 | |
45 | static void mds_sequence(struct mechdata **md_r) { |
46 | struct mechdata *md; |
47 | XMALLOC(md); |
48 | md->anyseen= 0; |
49 | *md_r= md; |
50 | } |
51 | |
52 | static void menc_sequence(struct mechdata *md, struct buffer *buf) { |
53 | md->number++; |
54 | *(uint32_t*)buf_prepend(buf,4)= htonl(md->number); |
55 | } |
56 | |
57 | static const char *mdec_check(struct mechdata *md, struct buffer *buf) { |
58 | uint32_t *sp, sequence; |
59 | |
60 | BUF_UNPREPEND(sp,buf,4); |
61 | sequence= ntohl(*sp); |
62 | |
63 | if (md->anyseen) |
64 | if (sequence - md->number >= 0x800000UL) return "out of order packet"; |
65 | |
66 | md->number= sequence; |
67 | md->anyseen= 1; |
68 | |
69 | return 0; |
70 | } |
71 | |
72 | static const char *mdec_skip(struct mechdata *md, struct buffer *buf) { |
73 | uint32_t *sp; |
74 | BUF_UNPREPEND(sp,buf,4); |
75 | return 0; |
76 | } |
77 | |
78 | const struct mechanism mechlist_sequence[]= { |
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79 | { "nonce", mes_sequence, mds_sequence, menc_sequence, mdec_skip }, |
80 | { "sequence", mes_sequence, mds_sequence, menc_sequence, mdec_check }, |
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81 | { 0 } |
82 | }; |