X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/tripe/blobdiff_plain/88510d86bc0300f9a30ac9904826e75eaa4e791c..22062fb6942187996596bdcde5ee639854c3157c:/pathmtu/pathmtu.c

diff --git a/pathmtu/pathmtu.c b/pathmtu/pathmtu.c
index d347b0dd..8cf7d18a 100644
--- 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>
@@ -109,6 +105,48 @@ static double s2f(const char *s, const char *what)
 static void f2tv(struct timeval *tv, double t)
   { tv->tv_sec = t; tv->tv_usec = (t - tv->tv_sec)*MILLION; }
 
+union addr {
+  struct sockaddr sa;
+  struct sockaddr_in sin;
+  struct sockaddr_in6 sin6;
+};
+
+/* Check whether an address family is even slightly supported. */
+static int addrfamok(int af)
+{
+  switch (af) {
+    case AF_INET: case AF_INET6: return (1);
+    default: return (0);
+  }
+}
+
+/* Return the size of a socket address. */
+static size_t addrsz(const union addr *a)
+{
+  switch (a->sa.sa_family) {
+    case AF_INET: return (sizeof(a->sin));
+    case AF_INET6: return (sizeof(a->sin6));
+    default: abort();
+  }
+}
+
+/* Compare two addresses.  Maybe compare the port numbers too. */
+#define AEF_PORT 1u
+static int addreq(const union addr *a, const union addr *b, unsigned f)
+{
+  switch (a->sa.sa_family) {
+    case AF_INET:
+      return (a->sin.sin_addr.s_addr == b->sin.sin_addr.s_addr &&
+	      (!(f&AEF_PORT) || a->sin.sin_port == b->sin.sin_port));
+    case AF_INET6:
+      return (!memcmp(a->sin6.sin6_addr.s6_addr,
+		      b->sin6.sin6_addr.s6_addr, 16) &&
+	      (!(f&AEF_PORT) || a->sin6.sin6_port == b->sin6.sin6_port));
+    default:
+      abort();
+  }
+}
+
 /*----- Main algorithm skeleton -------------------------------------------*/
 
 struct param {
@@ -119,7 +157,7 @@ struct param {
   double timeout;			/* Retransmission timeout */
   int seqoff;				/* Offset to write sequence number */
   const struct probe_ops *pops;		/* Probe algorithm description */
-  struct sockaddr_in sin;		/* Destination address */
+  union addr a;				/* Destination address */
 };
 
 struct probestate {
@@ -226,18 +264,27 @@ static int pathmtu(const struct param *pp)
   /* Build and connect a UDP socket.  We'll need this to know the local port
    * number to use if nothing else.  Set other stuff up.
    */
-  if ((sk = socket(PF_INET, SOCK_DGRAM, 0)) < 0) goto fail_0;
-  if (connect(sk, (struct sockaddr *)&pp->sin, sizeof(pp->sin))) goto fail_1;
+  if ((sk = socket(pp->a.sa.sa_family, SOCK_DGRAM, IPPROTO_UDP)) < 0)
+    goto fail_0;
+  if (connect(sk, &pp->a.sa, addrsz(&pp->a))) goto fail_1;
   st = xmalloc(pp->pops->statesz);
   if ((mtu = pp->pops->setup(st, sk, pp)) < 0) goto fail_2;
   ps.pp = pp; ps.q = rand() & 0xffff;
-  lo = 576; hi = mtu;
+  switch (pp->a.sa.sa_family) {
+    case AF_INET: lo = 576; break;
+    case AF_INET6: lo = 1280; break;
+    default: abort();
+  }
+  hi = mtu;
+  if (hi < lo) { errno = EMSGSIZE; return (-1); }
 
   /* And now we do a thing which is sort of like a binary search, except that
    * we also take explicit clues as establishing a new upper bound, and we
    * 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 +342,36 @@ 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;
 
@@ -375,7 +439,7 @@ struct phdr {
 };
 
 struct raw_state {
-  struct sockaddr_in me, sin;
+  union addr me, a;
   int sk, rawicmp, rawudp;
   unsigned q;
 };
@@ -383,22 +447,30 @@ 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;
 
-  /* If we couldn't acquire raw sockets, we fail here. */
-  if (rawerr) { errno = rawerr; goto fail_0; }
-  st->rawicmp = rawicmp; st->rawudp = rawudp; st->sk = sk;
+  /* Check that the address is OK, and that we have the necessary raw
+   * sockets.
+   */
+  switch (pp->a.sa.sa_family) {
+    case AF_INET:
+      if (rawerr) { errno = rawerr; goto fail_0; }
+      st->rawicmp = rawicmp; st->rawudp = rawudp; st->sk = sk;
+      break;
+    default:
+      errno = EPFNOSUPPORT; goto fail_0;
+  }
 
   /* Initialize the sequence number. */
   st->q = rand() & 0xffff;
 
   /* Snaffle the local and remote address and port number. */
-  st->sin = pp->sin;
+  st->a = pp->a;
   sz = sizeof(st->me);
-  if (getsockname(sk, (struct sockaddr *)&st->me, &sz))
+  if (getsockname(sk, &st->me.sa, &sz))
     goto fail_0;
 
   /* There isn't a portable way to force the DF flag onto a packet through
@@ -419,10 +491,9 @@ static int raw_setup(void *stv, int sk, const struct param *pp)
   for (i = 0; i < 2; i++) {
     for (ifap = 0, ifa = ifaa; ifa; ifa = ifa->ifa_next) {
       if (!(ifa->ifa_flags & IFF_UP) || !ifa->ifa_addr ||
-	  ifa->ifa_addr->sa_family != AF_INET ||
+	  ifa->ifa_addr->sa_family != st->me.sa.sa_family ||
 	  (i == 0 &&
-	   ((struct sockaddr_in *)ifa->ifa_addr)->sin_addr.s_addr !=
-		st->me.sin_addr.s_addr) ||
+	   !addreq((union addr *)ifa->ifa_addr, &st->me, 0)) ||
 	  (i == 1 && ifap && strcmp(ifap->ifa_name, ifa->ifa_name) == 0) ||
 	  strlen(ifa->ifa_name) >= sizeof(ifr.ifr_name))
 	continue;
@@ -470,13 +541,13 @@ static int raw_xmit(void *stv, int mtu)
   ip->ip_ttl = 64;
   ip->ip_p = IPPROTO_UDP;
   ip->ip_sum = 0;
-  ip->ip_src = st->me.sin_addr;
-  ip->ip_dst = st->sin.sin_addr;
+  ip->ip_src = st->me.sin.sin_addr;
+  ip->ip_dst = st->a.sin.sin_addr;
 
   /* Build a UDP packet in the output buffer. */
   udp = (struct udphdr *)(ip + 1);
-  udp->uh_sport = st->me.sin_port;
-  udp->uh_dport = st->sin.sin_port;
+  udp->uh_sport = st->me.sin.sin_port;
+  udp->uh_dport = st->a.sin.sin_port;
   udp->uh_ulen = htons(mtu - sizeof(*ip));
   udp->uh_sum = 0;
 
@@ -498,8 +569,7 @@ static int raw_xmit(void *stv, int mtu)
   /* Send the whole thing off.  If we're too big for the interface then we
    * might need to trim immediately.
    */
-  if (sendto(st->rawudp, b, mtu, 0,
-	     (struct sockaddr *)&st->sin, sizeof(st->sin)) < 0) {
+  if (sendto(st->rawudp, b, mtu, 0, &st->a.sa, addrsz(&st->a)) < 0) {
     if (errno == EMSGSIZE) return (RC_LOWER);
     else goto fail_0;
   }
@@ -518,6 +588,7 @@ static int raw_selproc(void *stv, fd_set *fd_in, struct probestate *ps)
   struct ip *ip;
   struct icmp *icmp;
   struct udphdr *udp;
+  const unsigned char *payload;
   ssize_t n;
 
   /* An ICMP packet: see what's inside. */
@@ -539,17 +610,20 @@ static int raw_selproc(void *stv, fd_set *fd_in, struct probestate *ps)
     if (n < sizeof(*ip) ||
 	ip->ip_p != IPPROTO_UDP || ip->ip_hl != sizeof(*ip)/4 ||
 	ip->ip_id != htons(st->q) ||
-	ip->ip_src.s_addr != st->me.sin_addr.s_addr ||
-	ip->ip_dst.s_addr != st->sin.sin_addr.s_addr)
+	ip->ip_src.s_addr != st->me.sin.sin_addr.s_addr ||
+	ip->ip_dst.s_addr != st->a.sin.sin_addr.s_addr)
       goto skip_icmp;
     n -= sizeof(*ip);
 
     udp = (struct udphdr *)(ip + 1);
-    if (n < sizeof(udp) || udp->uh_sport != st->me.sin_port ||
-	udp->uh_dport != st->sin.sin_port)
+    if (n < sizeof(udp) || udp->uh_sport != st->me.sin.sin_port ||
+	udp->uh_dport != st->a.sin.sin_port)
       goto skip_icmp;
     n -= sizeof(*udp);
 
+    payload = (const unsigned char *)(udp + 1);
+    if (!mypacketp(ps, payload, n)) goto skip_icmp;
+
     if (icmp->icmp_code == ICMP_UNREACH_PORT) return (RC_HIGHER);
     else if (icmp->icmp_code != ICMP_UNREACH_NEEDFRAG) goto skip_icmp;
     else if (icmp->icmp_nextmtu) return (htons(icmp->icmp_nextmtu));
@@ -597,13 +671,19 @@ 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;
+
+  /* Check that the address is OK. */
+  switch (pp->a.sa.sa_family) {
+    case AF_INET: break;
+    default: errno = EPFNOSUPPORT; return (-1);
+  }
 
   /* 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 +715,7 @@ 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 +760,7 @@ static void version(FILE *fp)
 
 static void usage(FILE *fp)
 {
-  pquis(fp, "Usage: $ [-H HEADER] [-m METHOD]\n\
+  pquis(fp, "Usage: $ [-46v] [-H HEADER] [-m METHOD]\n\
 	 [-r SECS] [-g FACTOR] [-t SECS] HOST [PORT]\n");
 }
 
@@ -696,13 +776,16 @@ 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\
+-4, --ipv4		Restrict to IPv4 only.\n\
+-6, --ipv6		Restrict to IPv6 only.\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\
@@ -719,11 +802,9 @@ int main(int argc, char *argv[])
   hex_ctx hc;
   dstr d = DSTR_INIT;
   size_t sz;
-  int i;
-  unsigned long u;
-  char *q;
-  struct hostent *h;
-  struct servent *s;
+  int i, err;
+  struct addrinfo aihint = { 0 }, *ailist, *ai;
+  const char *host, *svc = "7";
   unsigned f = 0;
 
 #define f_bogus 1u
@@ -736,13 +817,19 @@ int main(int argc, char *argv[])
 
   ego(argv[0]);
   fillbuffer(buf, sizeof(buf));
-  pp.sin.sin_port = htons(7);
+
+  aihint.ai_family = AF_UNSPEC;
+  aihint.ai_protocol = IPPROTO_UDP;
+  aihint.ai_socktype = SOCK_DGRAM;
+  aihint.ai_flags = AI_ADDRCONFIG;
 
   for (;;) {
     static const struct option opts[] = {
       { "help",		0,		0,	'h' },
       { "version",	0,		0,	'V' },
       { "usage",	0,		0,	'u' },
+      { "ipv4",		0,		0,	'4' },
+      { "ipv6",		0,		0,	'6' },
       { "header",	OPTF_ARGREQ,	0,	'H' },
       { "growth",	OPTF_ARGREQ,	0,	'g' },
       { "method",	OPTF_ARGREQ,	0,	'm' },
@@ -752,7 +839,7 @@ int main(int argc, char *argv[])
       { 0,		0,		0,	0 }
     };
 
-    i = mdwopt(argc, argv, "hVu" "H:g:m:r:t:v", opts, 0, 0, 0);
+    i = mdwopt(argc, argv, "hVu" "46H:g:m:r:t:v", opts, 0, 0, 0);
     if (i < 0) break;
     switch (i) {
       case 'h': help(stdout); exit(0);
@@ -769,6 +856,8 @@ int main(int argc, char *argv[])
 	pp.seqoff = sz;
 	break;
 
+      case '4': aihint.ai_family = AF_INET; break;
+      case '6': aihint.ai_family = AF_INET6; break;
       case 'g': pp.regr = s2f(optarg, "retransmit growth factor"); break;
       case 'r': pp.retx = s2f(optarg, "retransmit interval"); break;
       case 't': pp.timeout = s2f(optarg, "timeout"); break;
@@ -793,25 +882,17 @@ int main(int argc, char *argv[])
     exit(EXIT_FAILURE);
   }
 
-  if ((h = gethostbyname(*argv)) == 0)
-    die(EXIT_FAILURE, "unknown host `%s': %s", *argv, hstrerror(h_errno));
-  if (h->h_addrtype != AF_INET)
-    die(EXIT_FAILURE, "unsupported address family for host `%s'", *argv);
-  memcpy(&pp.sin.sin_addr, h->h_addr, sizeof(struct in_addr));
-  argv++; argc--;
-
-  if (*argv) {
-    errno = 0;
-    u = strtoul(*argv, &q, 0);
-    if (!errno && !*q)
-      pp.sin.sin_port = htons(u);
-    else if ((s = getservbyname(*argv, "udp")) == 0)
-      die(EXIT_FAILURE, "unknown UDP service `%s'", *argv);
-    else
-      pp.sin.sin_port = s->s_port;
+  host = argv[0];
+  if (argv[1]) svc = argv[1];
+  if ((err = getaddrinfo(host, svc, &aihint, &ailist)) != 0) {
+    die(EXIT_FAILURE, "unknown host `%s' or service `%s': %s",
+	host, svc, gai_strerror(err));
   }
+  for (ai = ailist; ai && !addrfamok(ai->ai_family); ai = ai->ai_next);
+  if (!ai) die(EXIT_FAILURE, "no supported address families for `%s'", host);
+  assert(ai->ai_addrlen <= sizeof(pp.a));
+  memcpy(&pp.a, ai->ai_addr, ai->ai_addrlen);
 
-  pp.sin.sin_family = AF_INET;
   i = pathmtu(&pp);
   if (i < 0)
     die(EXIT_FAILURE, "failed to discover MTU: %s", strerror(errno));