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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 | /* |
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12 | * Copyright (C) 2000,2003 Ian Jackson |
13 | * This file is part of ipif, part of userv-utils |
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14 | * |
15 | * This is free software; you can redistribute it and/or modify it |
16 | * under the terms of the GNU General Public License as published by |
17 | * the Free Software Foundation; either version 2 of the License, or |
18 | * (at your option) any later version. |
19 | * |
20 | * This program is distributed in the hope that it will be useful, but |
21 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
22 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
23 | * General Public License for more details. |
24 | * |
25 | * You should have received a copy of the GNU General Public License |
26 | * along with userv-utils; if not, write to the Free Software |
27 | * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
28 | */ |
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29 | |
30 | #include <netinet/in.h> |
31 | |
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32 | #include "forwarder.h" |
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33 | |
34 | struct mechdata { |
35 | uint32_t number; |
36 | int anyseen; /* decode only */ |
37 | }; |
38 | |
39 | static void mes_sequence(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) { |
40 | struct mechdata *md; |
41 | |
42 | XMALLOC(md); |
43 | get_random(&md->number,sizeof(md->number)); |
44 | *maxprefix_io += 4; |
45 | *md_r= md; |
46 | } |
47 | |
48 | static void mds_sequence(struct mechdata **md_r) { |
49 | struct mechdata *md; |
50 | XMALLOC(md); |
51 | md->anyseen= 0; |
52 | *md_r= md; |
53 | } |
54 | |
55 | static void menc_sequence(struct mechdata *md, struct buffer *buf) { |
56 | md->number++; |
57 | *(uint32_t*)buf_prepend(buf,4)= htonl(md->number); |
58 | } |
59 | |
60 | static const char *mdec_check(struct mechdata *md, struct buffer *buf) { |
61 | uint32_t *sp, sequence; |
62 | |
63 | BUF_UNPREPEND(sp,buf,4); |
64 | sequence= ntohl(*sp); |
65 | |
66 | if (md->anyseen) |
67 | if (sequence - md->number >= 0x800000UL) return "out of order packet"; |
68 | |
69 | md->number= sequence; |
70 | md->anyseen= 1; |
71 | |
72 | return 0; |
73 | } |
74 | |
75 | static const char *mdec_skip(struct mechdata *md, struct buffer *buf) { |
76 | uint32_t *sp; |
77 | BUF_UNPREPEND(sp,buf,4); |
78 | return 0; |
79 | } |
80 | |
81 | const struct mechanism mechlist_sequence[]= { |
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82 | { "nonce", mes_sequence, mds_sequence, menc_sequence, mdec_skip }, |
83 | { "sequence", mes_sequence, mds_sequence, menc_sequence, mdec_check }, |
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84 | { 0 } |
85 | }; |