Date: Thu, 23 May 2002 16:39:27 -0400 (EDT) From: Rob Manchester <rmanches@brown.edu> To: FreeBSD-gnats-submit@FreeBSD.org Subject: kern/38473: src address in ipv4 hdr for multicast packets contain hosts group rather than hosts address Message-ID: <200205232039.g4NKdRLM005572@lester.manchero.org>
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>Number: 38473
>Category: kern
>Synopsis: src address in ipv4 hdr for multicast packets contain hosts group rather than hosts address
>Confidential: no
>Severity: critical
>Priority: high
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Thu May 23 16:50:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: Rob Manchester
>Release: FreeBSD 4.6-RC i386
>Organization:
>Environment:
System: FreeBSD lester 4.6-RC FreeBSD 4.6-RC #21: Sat May 18 17:02:34 EDT 2002 rmanches@lester:/usr/obj/usr/src/sys/LESTER i386
>Description:
according to section 6.2 of rfc1054, the source address in the
ip header should contain the host's address rather than the host's
group address. FreeBSD from at least 4.5->4.6rc sets the source
address to the host group. I don't see a reason for doing this,
and it causes incompatibility with other os's ipv4 mc
implementaion, mainly linux.
>How-To-Repeat:
send out a mc packet using ipv4 and watch the outgoing packets
using tcpdump.
>Fix:
if the src address is a multicast addres, set the address to that of the
outgoing interface.
Index: ip_output.c
===================================================================
RCS file: /home/ncvs/src/sys/netinet/ip_output.c,v
retrieving revision 1.157
diff -u -r1.157 ip_output.c
--- ip_output.c 2002/05/21 18:52:24 1.157
+++ ip_output.c 2002/05/23 01:31:09
@@ -316,10 +316,11 @@
}
}
/*
- * If source address not specified yet, use address
- * of outgoing interface.
+ * If source address not specified yet, or it is a mc
+ * address, use the address of outgoing interface
*/
- if (ip->ip_src.s_addr == INADDR_ANY) {
+ if (ip->ip_src.s_addr == INADDR_ANY ||
+ IN_MULTICAST(ntohl(ip->ip_src.s_addr))) {
/* Interface may have no addresses. */
if (ia != NULL)
ip->ip_src = IA_SIN(ia)->sin_addr;
>Release-Note:
>Audit-Trail:
>Unformatted:
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