From c92dd0f9cd0817808db64562c1d0e0a7f592572b Mon Sep 17 00:00:00 2001
From: angelos <angelos@openbsd.org>
Date: Thu, 20 Apr 2000 07:47:11 +0000
Subject: [PATCH] Add a "minimum ttl" option (starting point). Useful for
 skipping over local-ISP routers that don't generate ICMP time exceeded.

---
 usr.sbin/traceroute/traceroute.8 |  8 +++++++-
 usr.sbin/traceroute/traceroute.c | 32 +++++++++++++++++++++-----------
 2 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/usr.sbin/traceroute/traceroute.8 b/usr.sbin/traceroute/traceroute.8
index 7836c105c50..17cdaf22eac 100644
--- a/usr.sbin/traceroute/traceroute.8
+++ b/usr.sbin/traceroute/traceroute.8
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: traceroute.8,v 1.20 2000/04/15 02:15:21 aaron Exp $
+.\"	$OpenBSD: traceroute.8,v 1.21 2000/04/20 07:47:11 angelos Exp $
 .\"	$NetBSD: traceroute.8,v 1.6 1995/10/12 03:05:50 mycroft Exp $
 .\"
 .\" Copyright (c) 1990, 1991, 1993
@@ -45,6 +45,7 @@
 .Nd print the route packets take to network host
 .Sh SYNOPSIS
 .Nm traceroute
+.Op Fl b Ar min_ttl
 .Op Fl c
 .Op Fl d
 .Op Fl D
@@ -83,6 +84,11 @@ name.
 .Pp
 The options are as follows:
 .Bl -tag -width Ds
+.It Fl b Ar min_ttl
+Set the first time-to-live used in outgoing probe packets. The effect is that
+the first min_ttl - 1 hosts will be skipped in the output of
+.Nm
+The default value is 1 (skip no hosts).
 .It Fl d
 Turn on socket-level debugging.
 .It Fl D
diff --git a/usr.sbin/traceroute/traceroute.c b/usr.sbin/traceroute/traceroute.c
index 7d6f4164b1e..9b23d9b2cef 100644
--- a/usr.sbin/traceroute/traceroute.c
+++ b/usr.sbin/traceroute/traceroute.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: traceroute.c,v 1.31 1999/12/23 16:17:05 angelos Exp $	*/
+/*	$OpenBSD: traceroute.c,v 1.32 2000/04/20 07:47:11 angelos Exp $	*/
 /*	$NetBSD: traceroute.c,v 1.10 1995/05/21 15:50:45 mycroft Exp $	*/
 
 /*-
@@ -289,6 +289,7 @@ char *hostname;
 
 int nprobes = 3;
 int max_ttl = IPDEFTTL;
+int min_ttl = 1;
 u_short ident;
 u_short port = 32768+666;	/* start udp dest port # for probe packets */
 u_char	proto = IPPROTO_UDP;
@@ -329,17 +330,19 @@ main(argc, argv)
 	lsrr = 0;
 	on = 1;
 	seq = tos = 0;
-	while ((ch = getopt(argc, argv, "dDIg:m:np:q:rs:t:w:vlP:c")) != -1)
+	while ((ch = getopt(argc, argv, "dDIg:b:m:np:q:rs:t:w:vlP:c")) != -1)
 		switch (ch) {
-		case 'I':
-			proto = IPPROTO_ICMP;
-			break;
-		case 'd':
-			options |= SO_DEBUG;
+		case 'b':
+			min_ttl = atoi(optarg);
+			if (min_ttl < 1 || min_ttl > max_ttl)
+				errx(1, "min ttl must be 1 to %d.", max_ttl);
 			break;
 		case 'c':
 		        incflag = 0;
 		        break;
+		case 'd':
+			options |= SO_DEBUG;
+			break;
 		case 'D':
 			dump = 1;
 			break;
@@ -356,13 +359,17 @@ main(argc, argv)
 				lsrrlen = 4;
 			lsrrlen += 4;
 			break;
+		case 'I':
+			proto = IPPROTO_ICMP;
+			break;
 		case 'l':
 			ttl_flag++;
 			break;
 		case 'm':
 			max_ttl = atoi(optarg);
-			if (max_ttl < 1 || max_ttl > MAXTTL)
-				errx(1, "max ttl must be 1 to %d.", MAXTTL);
+			if (max_ttl < min_ttl || max_ttl > MAXTTL)
+				errx(1, "max ttl must be %d to %d.", min_ttl,
+				     MAXTTL);
 			break;
 		case 'n':
 			nflag++;
@@ -530,7 +537,10 @@ main(argc, argv)
 	Fprintf(stderr, ", %d hops max, %d byte packets\n", max_ttl, datalen);
 	(void) fflush(stderr);
 
-	for (ttl = 1; ttl <= max_ttl; ++ttl) {
+	if (min_ttl > 1)
+		Printf("Skipping %d intermediate hops\n", min_ttl - 1);
+
+	for (ttl = min_ttl; ttl <= max_ttl; ++ttl) {
 		in_addr_t lastaddr = 0;
 		int got_there = 0;
 		int unreachable = 0;
@@ -994,6 +1004,6 @@ usage()
 	(void)fprintf(stderr,
 "usage: traceroute [-dDInrvc] [-g gateway_addr] ... [-m max_ttl] [-p port#]\n\t\
 [-P proto] [-q nqueries] [-s src_addr] [-t tos]\n\t\
-[-w wait] host [data size]\n");
+[-w wait] [-b min_ttl] host [data size]\n");
 	exit(1);
 }
-- 
2.20.1