If -s is not given do a dummy connect to get outgoing ip,

unconditionally try to bind to this ip and get a source port for udp
this way, like traceroute6 is doing.  This means you can no longer
traceroute from IPs not present on the system. (There are probably
better tools if you want to send traffic from spoofed IPs.)
OK benno@

2 files changed, 48 insertions, 14 deletions

diff --git a/usr.sbin/traceroute/traceroute.8 b/usr.sbin/traceroute/traceroute.8
index 9c924b3b516..a5b0b54a0d9 100644
--- a/usr.sbin/traceroute/traceroute.8
+++ b/usr.sbin/traceroute/traceroute.8
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: traceroute.8,v 1.53 2014/03/24 11:11:49 mpi Exp $
+.\"	$OpenBSD: traceroute.8,v 1.54 2014/04/18 16:19:11 florian Exp $
 .\"	$NetBSD: traceroute.8,v 1.6 1995/10/12 03:05:50 mycroft Exp $
 .\"
 .\" Copyright (c) 1990, 1991, 1993
@@ -33,7 +33,7 @@
 .\"
 .\"	@(#)traceroute.8	8.1 (Berkeley) 6/6/93
 .\"
-.Dd $Mdocdate: March 24 2014 $
+.Dd $Mdocdate: April 18 2014 $
 .Dt TRACEROUTE 8
 .Os
 .Sh NAME
@@ -160,9 +160,8 @@ a hostname) as the source address in outgoing probe packets.
 On hosts with more than one IP address, this option can be used to
 force the source address to be something other than the IP address
 of the interface the probe packet is sent on.
-If the IP address
-is not one of this machine's interface addresses and the user is
-not the superuser, an error is returned and nothing is sent.
+If the IP address is not one of this machine's interface addresses an error is
+returned and nothing is sent.
 .It Fl t Ar toskeyword
 Set the
 .Em type-of-service
diff --git a/usr.sbin/traceroute/traceroute.c b/usr.sbin/traceroute/traceroute.c
index cef00f91254..661a6dcc30c 100644
--- a/usr.sbin/traceroute/traceroute.c
+++ b/usr.sbin/traceroute/traceroute.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: traceroute.c,v 1.100 2014/04/18 16:04:39 florian Exp $	*/
+/*	$OpenBSD: traceroute.c,v 1.101 2014/04/18 16:19:11 florian Exp $	*/
 /*	$NetBSD: traceroute.c,v 1.10 1995/05/21 15:50:45 mycroft Exp $	*/
 
 /*-
@@ -234,6 +234,8 @@
 #include <string.h>
 #include <unistd.h>
 
+#define DUMMY_PORT 10010
+
 #define MAX_LSRR		((MAX_IPOPTLEN - 4) / 4)
 
 #define MPLS_LABEL(m)		((m & MPLS_LABEL_MASK) >> MPLS_LABEL_OFFSET)
@@ -288,6 +290,7 @@ char *hostname;
 int nprobes = 3;
 u_int8_t max_ttl = IPDEFTTL;
 u_int8_t first_ttl = 1;
+u_int16_t srcport;
 u_short ident;
 u_int16_t port = 32768+666;	/* start udp dest port # for probe packets */
 u_char	proto = IPPROTO_UDP;
@@ -574,7 +577,7 @@ main(int argc, char *argv[])
 	ip->ip_v = IPVERSION;
 	ip->ip_tos = tos;
 
-	ident = (getpid() & 0xffff) | 0x8000;
+	ident = getpid() & 0xffff;
 	tmprnd = arc4random();
 	sec_perturb = (tmprnd & 0x80000000) ? -(tmprnd & 0x7ff) :
 	    (tmprnd & 0x7ff);
@@ -597,8 +600,8 @@ main(int argc, char *argv[])
 		(void) setsockopt(sndsock, SOL_SOCKET, SO_DEBUG,
 		    (char *)&on, sizeof(on));
 
+	(void) memset(&from, 0, sizeof(struct sockaddr));
 	if (source) {
-		(void) memset(&from, 0, sizeof(struct sockaddr));
 		from.sin_family = AF_INET;
 		if (inet_aton(source, &from.sin_addr) == 0)
 			errx(1, "unknown host %s", source);
@@ -607,12 +610,44 @@ main(int argc, char *argv[])
 		    (ntohl(from.sin_addr.s_addr) & 0xff000000U) == 0x7f000000U &&
 		    (ntohl(to.sin_addr.s_addr) & 0xff000000U) != 0x7f000000U)
 			errx(1, "source is on 127/8, destination is not");
-
-		if (getuid() &&
-		    bind(sndsock, (struct sockaddr *)&from, sizeof(from)) < 0)
-			err(1, "bind");
+	} else {
+		struct sockaddr_in nxt;
+		int dummy;
+		socklen_t len;
+
+		nxt = to;
+		nxt.sin_port = htons(DUMMY_PORT);
+		if ((dummy = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
+			perror("socket");
+			exit(1);
+		}
+		if (connect(dummy, (struct sockaddr *)&nxt, sizeof(nxt)) < 0) {
+			perror("connect");
+			exit(1);
+		}
+		len = sizeof(from);
+		if (getsockname(dummy, (struct sockaddr *)&from, &len) < 0) {
+			perror("getsockname");
+			exit(1);
+		}
+		close(dummy);
 	}
+	from.sin_port = htons(0);
+	if (bind(sndsock, (struct sockaddr *)&from, sizeof(from)) < 0) {
+		perror("bind sndsock");
+		exit(1);
+	}
+
+	{
+		socklen_t len;
 
+		len = sizeof(from);
+		if (getsockname(sndsock, (struct sockaddr *)&from, &len) < 0) {
+			perror("getsockname");
+			exit(1);
+		}
+		srcport = ntohs(from.sin_port);
+	}
 	fprintf(stderr, "traceroute to %s (%s)", hostname,
 		inet_ntoa(to.sin_addr));
 	if (source)
@@ -923,7 +958,7 @@ build_probe4(int seq, u_int8_t ttl, int iflag)
 		op = (struct packetdata *)(icmpp + 1);
 		break;
 	case IPPROTO_UDP:
-		up->uh_sport = htons(ident);
+		up->uh_sport = htons(srcport);
 		if (iflag)
 			up->uh_dport = htons(port+seq);
 		else
@@ -1085,7 +1120,7 @@ packet_ok(struct msghdr *mhdr, int cc,int seq, int iflag)
 		case IPPROTO_UDP:
 			up = (struct udphdr *)((u_char *)hip + hlen);
 			if (hlen + 12 <= cc && hip->ip_p == proto &&
-			    up->uh_sport == htons(ident) &&
+			    up->uh_sport == htons(srcport) &&
 			    ((iflag && up->uh_dport == htons(port + seq)) ||
 			    (!iflag && up->uh_dport == htons(port))))
 				return (type == ICMP_TIMXCEED? -1 : code + 1);