pathmtu/pathmtu.c: Document the `--verbose' option.

[tripe] / pathmtu / pathmtu.c

diff --git a/pathmtu/pathmtu.c b/pathmtu/pathmtu.c
index d347b0dddf20070b938e9301bfba7026c9bde7bf..6d988031c474a520fcc0b7b57f6886fe3854b55b 100644 (file)
--- a/pathmtu/pathmtu.c
+++ b/pathmtu/pathmtu.c
@@ -9,29 +9,25 @@
  *
  * This file is part of Trivial IP Encryption (TrIPE).
  *
- * TrIPE is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
+ * TrIPE is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 3 of the License, or (at your
+ * option) any later version.
  *
- * TrIPE is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
+ * TrIPE is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
  *
  * You should have received a copy of the GNU General Public License
- * along with TrIPE; if not, write to the Free Software Foundation,
- * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ * along with TrIPE.  If not, see <https://www.gnu.org/licenses/>.
  */
 
 /*----- Header files ------------------------------------------------------*/
 
-#if defined(linux)
-#  define _BSD_SOURCE
-#endif
-
 #include "config.h"
 
+#include <assert.h>
 #include <errno.h>
 #include <stddef.h>
 #include <stdio.h>
@@ -238,6 +234,8 @@ static int pathmtu(const struct param *pp)
    * try to hug that initially.
    */
   for (;;) {
+    assert(lo <= mtu && mtu <= hi);
+    if (pp->f & F_VERBOSE) moan("probe: %d <= %d <= %d", lo, mtu, hi);
     rc = probe(&ps, st, mtu);
     switch (rc) {
 
@@ -295,19 +293,36 @@ static int pathmtu(const struct param *pp)
          if (pp->f & F_VERBOSE) moan("probe returned: found correct MTU");
          goto done;
        }
-       if (pp->f & F_VERBOSE) moan("probe returned: guessing higher");
        lo = mtu;
+
+       /* Now we must make a new guess, between lo and hi.  We know that lo
+        * is good; but we're not so sure about hi here.  We know that hi >
+        * lo, so this will find an approximate midpoint, greater than lo and
+        * no more than hi.
+        */
+       if (pp->f & F_VERBOSE) moan("probe returned: guessing higher");
        mtu += (hi - lo + 1)/2;
        break;
 
       case RC_LOWER:
       lower:
-       if (mtu == lo) {
+       /* If this didn't work, and we're already at the bottom of our
+        * possible range, then something has gone horribly wrong.
+        */
+       assert(lo < mtu);
+       hi = mtu - 1;
+       if (lo == hi) {
          if (pp->f & F_VERBOSE) moan("error returned: found correct MTU");
+         mtu = lo;
          goto done;
        }
+
+       /* We must make a new guess, between lo and hi.  We're probably
+        * fairly sure that lo will succeed, since either it's the minimum
+        * MTU or we've tested it already; but we're not quite sure about hi,
+        * so we want to aim high.
+        */
        if (pp->f & F_VERBOSE) moan("error returned: guessing lower");
-       hi = mtu - 1;
        mtu -= (hi - lo + 1)/2;
        break;
 
@@ -383,7 +398,7 @@ struct raw_state {
 static int raw_setup(void *stv, int sk, const struct param *pp)
 {
   struct raw_state *st = stv;
-  size_t sz;
+  socklen_t sz;
   int i, mtu = -1;
   struct ifaddrs *ifa, *ifaa, *ifap;
   struct ifreq ifr;
@@ -597,13 +612,13 @@ static int linux_setup(void *stv, int sk, const struct param *pp)
 {
   struct linux_state *st = stv;
   int i, mtu;
-  size_t sz;
+  socklen_t sz;
 
   /* Snaffle the UDP socket. */
   st->sk = sk;
 
   /* Turn on kernel path-MTU discovery and force DF on. */
-  i = IP_PMTUDISC_DO;
+  i = IP_PMTUDISC_PROBE;
   if (setsockopt(st->sk, IPPROTO_IP, IP_MTU_DISCOVER, &i, sizeof(i)))
     return (-1);
 
@@ -635,7 +650,7 @@ static int linux_selproc(void *stv, fd_set *fd_in, struct probestate *ps)
 {
   struct linux_state *st = stv;
   int mtu;
-  size_t sz;
+  socklen_t sz;
   ssize_t n;
   unsigned char b[65536];
 
@@ -680,7 +695,7 @@ static void version(FILE *fp)
 
 static void usage(FILE *fp)
 {
-  pquis(fp, "Usage: $ [-H HEADER] [-m METHOD]\n\
+  pquis(fp, "Usage: $ [-v] [-H HEADER] [-m METHOD]\n\
         [-r SECS] [-g FACTOR] [-t SECS] HOST [PORT]\n");
 }
 
@@ -696,13 +711,14 @@ static void help(FILE *fp)
 Options in full:\n\
 \n\
 -h, --help             Show this help text.\n\
--v, --version          Show version number.\n\
+-V, --version          Show version number.\n\
 -u, --usage            Show brief usage message.\n\
 \n\
 -g, --growth=FACTOR    Growth factor for retransmit interval.\n\
 -m, --method=METHOD    Use METHOD to probe for MTU.\n\
 -r, --retransmit=SECS  Retransmit if no reply after SEC.\n\
 -t, --timeout=SECS     Give up expecting a reply after SECS.\n\
+-v, --verbose          Write a running commentary to stderr.\n\
 -H, --header=HEX       Packet header, in hexadecimal.\n\
 \n\
 Probe methods:\n\