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c64d8cd5 MW |
1 | /* -*-c-*- |
2 | * | |
3 | * Report MTU on path to specified host | |
4 | * | |
5 | * (c) 2008 Straylight/Edgeware | |
6 | */ | |
7 | ||
8 | /*----- Licensing notice --------------------------------------------------* | |
9 | * | |
10 | * This file is part of Trivial IP Encryption (TrIPE). | |
11 | * | |
12 | * TrIPE is free software; you can redistribute it and/or modify | |
13 | * it 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 | * TrIPE is distributed in the hope that it will be useful, | |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | * GNU General Public License for more details. | |
21 | * | |
22 | * You should have received a copy of the GNU General Public License | |
23 | * along with TrIPE; if not, write to the Free Software Foundation, | |
24 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
25 | */ | |
26 | ||
27 | /*----- Header files ------------------------------------------------------*/ | |
28 | ||
29 | #include "config.h" | |
30 | ||
31 | #include <errno.h> | |
32 | #include <stdio.h> | |
33 | #include <stdlib.h> | |
34 | #include <string.h> | |
35 | #include <time.h> | |
36 | ||
37 | #include <sys/types.h> | |
38 | #include <sys/time.h> | |
39 | #include <unistd.h> | |
40 | ||
41 | #include <sys/socket.h> | |
42 | #include <netinet/in.h> | |
43 | #include <arpa/inet.h> | |
44 | #include <netdb.h> | |
45 | ||
46 | #include <mLib/dstr.h> | |
47 | #include <mLib/hex.h> | |
48 | #include <mLib/mdwopt.h> | |
49 | #include <mLib/quis.h> | |
50 | #include <mLib/report.h> | |
51 | #include <mLib/tv.h> | |
52 | ||
53 | /*----- Static variables --------------------------------------------------*/ | |
54 | ||
55 | static unsigned char buf[65536]; | |
56 | ||
57 | /*----- Utility functions -------------------------------------------------*/ | |
58 | ||
59 | /* Fill buffer with a constant but pseudorandom string. Uses a simple | |
60 | * LFSR. | |
61 | */ | |
62 | static void fillbuffer(unsigned char *p, size_t sz) | |
63 | { | |
64 | unsigned int y = 0xbc20; | |
65 | const unsigned char *l = p + sz; | |
66 | int i; | |
67 | #define POLY 0x002d | |
68 | ||
69 | while (p < l) { | |
70 | *p++ = y & 0xff; | |
71 | for (i = 0; i < 8; i++) { | |
72 | if (!(y & 0x8000)) y <<= 1; | |
73 | else y = (y << 1) ^ POLY; | |
74 | } | |
75 | } | |
76 | } | |
77 | ||
78 | /*----- Doing the actual job ----------------------------------------------*/ | |
79 | ||
80 | #if defined(linux) | |
81 | ||
82 | #ifndef IP_MTU | |
83 | # define IP_MTU 14 /* Blech! */ | |
84 | #endif | |
85 | ||
86 | static int pathmtu(struct sockaddr_in *sin, double to) | |
87 | { | |
88 | int sk; | |
89 | fd_set fd_in; | |
90 | int mtu; | |
91 | int i; | |
92 | size_t sz; | |
664a5c0e | 93 | struct timeval tv, tvproto; |
c64d8cd5 | 94 | |
664a5c0e | 95 | tvproto.tv_sec = to; tvproto.tv_usec = (to - tvproto.tv_sec) * 1000000; |
c64d8cd5 MW |
96 | if ((sk = socket(PF_INET, SOCK_DGRAM, 0)) < 0) goto fail_0; |
97 | i = IP_PMTUDISC_DO; | |
98 | if (setsockopt(sk, SOL_IP, IP_MTU_DISCOVER, &i, sizeof(i))) | |
99 | goto fail_1; | |
100 | if (connect(sk, (struct sockaddr *)sin, sizeof(*sin))) goto fail_1; | |
101 | for (;;) { | |
102 | sz = sizeof(mtu); | |
103 | if (getsockopt(sk, SOL_IP, IP_MTU, &mtu, &sz)) goto fail_1; | |
104 | if (write(sk, buf, mtu - 28) < 0) goto fail_1; | |
664a5c0e | 105 | FD_SET(sk, &fd_in); tv = tvproto; |
c64d8cd5 MW |
106 | if (select(sk + 1, &fd_in, 0, 0, &tv) < 0) goto fail_1; |
107 | if (!FD_ISSET(sk, &fd_in)) break; | |
108 | if (read(sk, &i, 1) >= 0 || | |
109 | errno == ECONNREFUSED || errno == EHOSTUNREACH) | |
110 | break; | |
111 | if (errno != EMSGSIZE) goto fail_1; | |
112 | } | |
113 | close(sk); | |
114 | return (mtu); | |
115 | ||
116 | fail_1: | |
117 | close(sk); | |
118 | fail_0: | |
119 | return (-1); | |
120 | } | |
121 | ||
122 | #else | |
123 | ||
124 | # error "path MTU discovery not implemented" | |
125 | ||
126 | #endif | |
127 | ||
128 | /*----- Help options ------------------------------------------------------*/ | |
129 | ||
130 | static void version(FILE *fp) | |
131 | { pquis(fp, "$, TrIPE version " VERSION "\n"); } | |
132 | ||
133 | static void usage(FILE *fp) | |
134 | { pquis(fp, "Usage: $ [-t TIMEOUT] [-H HEADER] HOST [PORT]\n"); } | |
135 | ||
136 | static void help(FILE *fp) | |
137 | { | |
138 | version(fp); | |
139 | fputc('\n', fp); | |
140 | usage(fp); | |
141 | fputs("\ | |
142 | \n\ | |
143 | Options in full:\n\ | |
144 | \n\ | |
145 | -h, --help Show this help text.\n\ | |
146 | -v, --version Show version number.\n\ | |
147 | -u, --usage Show brief usage message.\n\ | |
148 | \n\ | |
149 | -t, --timeout=TIMEOUT Time to wait for reply, in seconds.\n\ | |
150 | -H, --header=HEX Packet header, in hexadecimal.\n\ | |
151 | ", fp); | |
152 | } | |
153 | ||
154 | /*----- Main code ---------------------------------------------------------*/ | |
155 | ||
156 | int main(int argc, char *argv[]) | |
157 | { | |
158 | struct sockaddr_in sin; | |
159 | hex_ctx hc; | |
160 | dstr d = DSTR_INIT; | |
161 | size_t sz; | |
162 | int i; | |
163 | unsigned long u; | |
164 | char *q; | |
165 | struct hostent *h; | |
166 | struct servent *s; | |
167 | double to = 5.0; | |
168 | unsigned f = 0; | |
169 | ||
170 | #define f_bogus 1u | |
171 | ||
172 | ego(argv[0]); | |
173 | fillbuffer(buf, sizeof(buf)); | |
174 | sin.sin_port = htons(7); | |
175 | ||
176 | for (;;) { | |
177 | static const struct option opts[] = { | |
178 | { "help", 0, 0, 'h' }, | |
179 | { "version", 0, 0, 'v' }, | |
180 | { "usage", 0, 0, 'u' }, | |
181 | { "header", OPTF_ARGREQ, 0, 'H' }, | |
182 | { "timeout", OPTF_ARGREQ, 0, 't' }, | |
183 | { 0, 0, 0, 0 } | |
184 | }; | |
185 | ||
186 | i = mdwopt(argc, argv, "hvu" "H:", opts, 0, 0, 0); | |
187 | if (i < 0) break; | |
188 | switch (i) { | |
189 | case 'h': help(stdout); exit(0); | |
190 | case 'v': version(stdout); exit(0); | |
191 | case 'u': usage(stdout); exit(0); | |
192 | ||
193 | case 'H': | |
194 | DRESET(&d); | |
195 | hex_init(&hc); | |
196 | hex_decode(&hc, optarg, strlen(optarg), &d); | |
197 | hex_decode(&hc, 0, 0, &d); | |
198 | sz = d.len < sizeof(buf) ? d.len : sizeof(buf); | |
199 | memcpy(buf, d.buf, sz); | |
200 | break; | |
201 | ||
202 | case 't': | |
203 | errno = 0; | |
204 | to = strtod(optarg, &q); | |
205 | if (errno || *q) die(EXIT_FAILURE, "bad timeout"); | |
206 | break; | |
207 | ||
208 | default: | |
209 | f |= f_bogus; | |
210 | break; | |
211 | } | |
212 | } | |
213 | argv += optind; argc -= optind; | |
214 | if ((f & f_bogus) || 1 > argc || argc > 2) { | |
215 | usage(stderr); | |
216 | exit(EXIT_FAILURE); | |
217 | } | |
218 | ||
219 | if ((h = gethostbyname(*argv)) == 0) | |
220 | die(EXIT_FAILURE, "unknown host `%s': %s", *argv, hstrerror(h_errno)); | |
221 | if (h->h_addrtype != AF_INET) | |
222 | die(EXIT_FAILURE, "unsupported address family for host `%s'", *argv); | |
223 | memcpy(&sin.sin_addr, h->h_addr, sizeof(struct in_addr)); | |
224 | argv++; argc--; | |
225 | ||
226 | if (*argv) { | |
227 | errno = 0; | |
228 | u = strtoul(*argv, &q, 0); | |
229 | if (!errno && !*q) | |
230 | sin.sin_port = htons(u); | |
231 | else if ((s = getservbyname(*argv, "udp")) == 0) | |
232 | die(EXIT_FAILURE, "unknown UDP service `%s'", *argv); | |
233 | else | |
234 | sin.sin_port = s->s_port; | |
235 | } | |
236 | ||
237 | sin.sin_family = AF_INET; | |
238 | i = pathmtu(&sin, to); | |
239 | if (i < 0) | |
240 | die(EXIT_FAILURE, "failed to discover MTU: %s", strerror(errno)); | |
241 | printf("%d\n", i); | |
242 | if (ferror(stdout) || fflush(stdout) || fclose(stdout)) | |
243 | die(EXIT_FAILURE, "failed to write result: %s", strerror(errno)); | |
244 | return (0); | |
245 | } | |
246 | ||
247 | /*----- That's all, folks -------------------------------------------------*/ |