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1 | /* |
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2 | * Sequence number / nonce mechanism for udp tunnel |
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3 | * |
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4 | * mechanisms: nonce, sequence |
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5 | * arguments: none |
6 | * |
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7 | * restrictions: none |
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8 | * encoding: prepend 4 bytes of sequence arithmetic serial number |
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9 | * decoding: check increasingness (sequence), or ignore (nonce) |
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10 | */ |
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11 | /* |
12 | * Copyright (C) 2000 Ian Jackson |
13 | * |
14 | * This is free software; you can redistribute it and/or modify it |
15 | * under the terms of the GNU General Public License as published by |
16 | * the Free Software Foundation; either version 2 of the License, or |
17 | * (at your option) any later version. |
18 | * |
19 | * This program is distributed in the hope that it will be useful, but |
20 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
22 | * General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU General Public License |
25 | * along with userv-utils; if not, write to the Free Software |
26 | * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
27 | */ |
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28 | |
29 | #include <netinet/in.h> |
30 | |
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31 | #include "forwarder.h" |
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32 | |
33 | struct mechdata { |
34 | uint32_t number; |
35 | int anyseen; /* decode only */ |
36 | }; |
37 | |
38 | static void mes_sequence(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) { |
39 | struct mechdata *md; |
40 | |
41 | XMALLOC(md); |
42 | get_random(&md->number,sizeof(md->number)); |
43 | *maxprefix_io += 4; |
44 | *md_r= md; |
45 | } |
46 | |
47 | static void mds_sequence(struct mechdata **md_r) { |
48 | struct mechdata *md; |
49 | XMALLOC(md); |
50 | md->anyseen= 0; |
51 | *md_r= md; |
52 | } |
53 | |
54 | static void menc_sequence(struct mechdata *md, struct buffer *buf) { |
55 | md->number++; |
56 | *(uint32_t*)buf_prepend(buf,4)= htonl(md->number); |
57 | } |
58 | |
59 | static const char *mdec_check(struct mechdata *md, struct buffer *buf) { |
60 | uint32_t *sp, sequence; |
61 | |
62 | BUF_UNPREPEND(sp,buf,4); |
63 | sequence= ntohl(*sp); |
64 | |
65 | if (md->anyseen) |
66 | if (sequence - md->number >= 0x800000UL) return "out of order packet"; |
67 | |
68 | md->number= sequence; |
69 | md->anyseen= 1; |
70 | |
71 | return 0; |
72 | } |
73 | |
74 | static const char *mdec_skip(struct mechdata *md, struct buffer *buf) { |
75 | uint32_t *sp; |
76 | BUF_UNPREPEND(sp,buf,4); |
77 | return 0; |
78 | } |
79 | |
80 | const struct mechanism mechlist_sequence[]= { |
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81 | { "nonce", mes_sequence, mds_sequence, menc_sequence, mdec_skip }, |
82 | { "sequence", mes_sequence, mds_sequence, menc_sequence, mdec_check }, |
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83 | { 0 } |
84 | }; |