3 * Report MTU on path to specified host
5 * (c) 2008 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Trivial IP Encryption (TrIPE).
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.
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.
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.
27 /*----- Header files ------------------------------------------------------*/
37 #include <sys/types.h>
41 #include <sys/socket.h>
42 #include <netinet/in.h>
43 #include <arpa/inet.h>
46 #include <mLib/dstr.h>
48 #include <mLib/mdwopt.h>
49 #include <mLib/quis.h>
50 #include <mLib/report.h>
53 /*----- Static variables --------------------------------------------------*/
55 static unsigned char buf[65536];
57 /*----- Utility functions -------------------------------------------------*/
59 /* Fill buffer with a constant but pseudorandom string. Uses a simple
62 static void fillbuffer(unsigned char *p, size_t sz)
64 unsigned int y = 0xbc20;
65 const unsigned char *l = p + sz;
71 for (i = 0; i < 8; i++) {
72 if (!(y & 0x8000)) y <<= 1;
73 else y = (y << 1) ^ POLY;
78 /*----- Doing the actual job ----------------------------------------------*/
83 # define IP_MTU 14 /* Blech! */
86 static int pathmtu(struct sockaddr_in *sin, double to)
95 tv.tv_sec = to; tv.tv_usec = (to - tv.tv_sec) * 1000000;
96 if ((sk = socket(PF_INET, SOCK_DGRAM, 0)) < 0) goto fail_0;
98 if (setsockopt(sk, SOL_IP, IP_MTU_DISCOVER, &i, sizeof(i)))
100 if (connect(sk, (struct sockaddr *)sin, sizeof(*sin))) goto fail_1;
103 if (getsockopt(sk, SOL_IP, IP_MTU, &mtu, &sz)) goto fail_1;
104 if (write(sk, buf, mtu - 28) < 0) goto fail_1;
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)
111 if (errno != EMSGSIZE) goto fail_1;
124 # error "path MTU discovery not implemented"
128 /*----- Help options ------------------------------------------------------*/
130 static void version(FILE *fp)
131 { pquis(fp, "$, TrIPE version " VERSION "\n"); }
133 static void usage(FILE *fp)
134 { pquis(fp, "Usage: $ [-t TIMEOUT] [-H HEADER] HOST [PORT]\n"); }
136 static void help(FILE *fp)
145 -h, --help Show this help text.\n\
146 -v, --version Show version number.\n\
147 -u, --usage Show brief usage message.\n\
149 -t, --timeout=TIMEOUT Time to wait for reply, in seconds.\n\
150 -H, --header=HEX Packet header, in hexadecimal.\n\
154 /*----- Main code ---------------------------------------------------------*/
156 int main(int argc, char *argv[])
158 struct sockaddr_in sin;
173 fillbuffer(buf, sizeof(buf));
174 sin.sin_port = htons(7);
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' },
186 i = mdwopt(argc, argv, "hvu" "H:", opts, 0, 0, 0);
189 case 'h': help(stdout); exit(0);
190 case 'v': version(stdout); exit(0);
191 case 'u': usage(stdout); exit(0);
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);
204 to = strtod(optarg, &q);
205 if (errno || *q) die(EXIT_FAILURE, "bad timeout");
213 argv += optind; argc -= optind;
214 if ((f & f_bogus) || 1 > argc || argc > 2) {
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));
228 u = strtoul(*argv, &q, 0);
230 sin.sin_port = htons(u);
231 else if ((s = getservbyname(*argv, "udp")) == 0)
232 die(EXIT_FAILURE, "unknown UDP service `%s'", *argv);
234 sin.sin_port = s->s_port;
237 sin.sin_family = AF_INET;
238 i = pathmtu(&sin, to);
240 die(EXIT_FAILURE, "failed to discover MTU: %s", strerror(errno));
242 if (ferror(stdout) || fflush(stdout) || fclose(stdout))
243 die(EXIT_FAILURE, "failed to write result: %s", strerror(errno));
247 /*----- That's all, folks -------------------------------------------------*/