From owner-freebsd-bugs  Sat Aug 26 18:40: 9 2000
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Date: Sun, 27 Aug 2000 03:29:13 +0200 (CEST)
From: volf@oasis.IAEhv.nl
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Subject: kern/20877: ICMP error msg on UDP port unreachable is incorrect 
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>Number:         20877
>Category:       kern
>Synopsis:       ICMP error msg on UDP port unreachable is incorrect
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Aug 26 18:40:01 PDT 2000
>Closed-Date:
>Last-Modified:
>Originator:     Frank Volf
>Release:        FreeBSD 4.1-STABLE i386
>Organization:
/etc/organization
>Environment:
>Description:

When a UDP packet is send to a port that is unreachable (which is a common 
feature used in e.g. traceroute) an ICMP error message is returned (icmp 
port unreachable) which includes (part of) the original IP packet.

The problem is that this (part of) the original IP packet is not completely
correct. The ip_id field is not in network byte order (in ip_input(), ip_id
is translated to host byte order), but this is never reverted before the
IP packet is send to icmp_error for generation of the ICMP error message.
The following patch (relative to 4.1 stable source code) fixes the problem:

Index: udp_usrreq.c
===================================================================
RCS file: /home2/CVS/src/sys/netinet/udp_usrreq.c,v
retrieving revision 1.64.2.3
diff -u -u -r1.64.2.3 udp_usrreq.c
--- udp_usrreq.c	2000/08/03 00:09:36	1.64.2.3
+++ udp_usrreq.c	2000/08/27 01:02:35
@@ -358,8 +358,10 @@
 		if (badport_bandlim(0) < 0)
 			goto bad;
 #endif
-		if (!blackhole)
+		if (!blackhole) {
+			HTONS(ip->ip_id);
 			icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_PORT, 0, 0);
+		}
 		else
 			goto bad;
 		return;


Please commit this patch to the FreeBSD source code repository.

Many thanks,

               Frank


>How-To-Repeat:
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:


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