997271 – ipcalc does not understand RFC3021

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Bug 997271 - ipcalc does not understand RFC3021

Summary: ipcalc does not understand RFC3021

Keywords:
Status:	CLOSED ERRATA
Alias:	None
Product:	Red Hat Enterprise Linux 6
Classification:	Red Hat
Component:	initscripts
Sub Component:
Version:	6.4
Hardware:	All
OS:	Linux
Priority:	unspecified
Severity:	low
Target Milestone:	rc
Target Release:	---
Assignee:	Lukáš Nykrýn
QA Contact:	Jan Ščotka
Docs Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+	depends on / blocked

Reported:	2013-08-15 06:44 UTC by Telford Tendys
Modified:	2018-10-12 15:24 UTC (History)
CC List:	3 users (show)
Fixed In Version:	initscripts-9.03.47-1.el6
Doc Type:	Bug Fix
Doc Text:	Cause: ipcalc did not know about rfc3021 Consequence: Broadcast address was not computed correctly Fix: We have taught ipcalc that rfc3021 exists. Result: Broadcast address should be now correct.
Clone Of:
Environment:
Last Closed:	2015-07-22 07:18:18 UTC
Target Upstream Version:
Embargoed:

Attachments	(Terms of Use)

Links
System	ID	Private	Priority	Status	Summary	Last Updated
Red Hat Bugzilla	1638834	1	None	None	None	2021-01-20 06:05:38 UTC
Red Hat Product Errata	RHBA-2015:1380	0	normal	SHIPPED_LIVE	initscripts bug fix update	2015-07-20 17:58:24 UTC

Internal Links: 1638834

Description Telford Tendys 2013-08-15 06:44:43 UTC

Description of problem:

Broadcast address is wrong for /31 networks, this will cause misconfiguration of ethernet devices.

Version-Release number of selected component (if applicable):

   initscripts-9.03.38-1.el6.centos.1.i686


How reproducible: Always

Steps to Reproduce:

ipcalc -b 10.10.10.10/31

Actual results:

BROADCAST=10.10.10.11

Expected results:

BROADCAST=255.255.255.255

Additional info:

[root@fmc ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth1
DEVICE="eth1"
BOOTPROTO="static"
HWADDR="00:0C:29:2F:92:7C"
IPV6INIT="no"
MTU="1500"
NM_CONTROLLED="no"
TYPE="Ethernet"
ONBOOT=yes
IPADDR=10.81.81.81
NETMASK=255.255.255.254


Note that "BROADCAST=255.255.255.255" needs to be manually inserted if you want your ethernet configured correctly, actually it should not require that because the correct result is well defined already.

[root@fmc ~]# strace -o /tmp/fff -f  /sbin/ifup  eth1
[root@fmc ~]# fgrep ipcalc /tmp/fff
9100  execve("/bin/ipcalc", ["/bin/ipcalc", "--prefix", "10.81.81.81", "255.255.255.254"], [/* 18 vars */]) = 0
9101  execve("/bin/ipcalc", ["/bin/ipcalc", "--broadcast", "10.81.81.81", "255.255.255.254"], [/* 18 vars */]) = 0
9106  execve("/bin/ipcalc", ["/bin/ipcalc", "--network", "10.81.81.81", "255.255.255.254"], [/* 18 vars */]) = 0


You can see the script depends on ipcalc to get the answer right... and so it should get the answer right.

Comment 1 Telford Tendys 2013-08-15 06:45:54 UTC

http://tools.ietf.org/html/rfc3021

Comment 3 Lukáš Nykrýn 2013-08-26 10:43:48 UTC

Can you please try this patch:
diff --git a/src/ipcalc.c b/src/ipcalc.c
index 7316f05..416180b 100644
--- a/src/ipcalc.c
+++ b/src/ipcalc.c
@@ -141,7 +141,11 @@ struct in_addr calc_broadcast(struct in_addr addr, int prefix)
     struct in_addr broadcast;
 
     memset(&broadcast, 0, sizeof(broadcast));
-    broadcast.s_addr = (addr.s_addr & mask.s_addr) | ~mask.s_addr;
+
+    if (mask.s_addr ==  htonl(0xFFFFFFFE))
+        broadcast.s_addr = htonl(0xFFFFFFFF);
+    else
+        broadcast.s_addr = (addr.s_addr & mask.s_addr) | ~mask.s_addr;
     return broadcast;
 }

Comment 4 Telford Tendys 2013-09-02 05:28:37 UTC

I replied to the Bugzilla email, but does not seem to have updated...

Yes the above patch worked for me (I tested by rebuilding SRPM). May I suggest a one-line comment in the source code mentioning RFC3021 (so people can find a reference explaining why it works that way, also in case anyone in future greps out the code looking for the RFC number) ?

Comment 7 Lukáš Nykrýn 2015-02-04 14:00:59 UTC

https://git.fedorahosted.org/cgit/initscripts.git/commit/?h=rhel6-branch&id=7a7ab0c

Comment 10 errata-xmlrpc 2015-07-22 07:18:18 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-1380.html

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