Date: Thu, 30 Apr 1998 19:20:29 +0300 (EEST) From: Ruslan Ermilov <ru@ucb.crimea.ua> To: FreeBSD-gnats-submit@FreeBSD.ORG Subject: kern/6466: loopback interface has no SIOCSIFFLAGS handler, this causes bugs Message-ID: <199804301620.TAA16249@relay.ucb.crimea.ua>
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>Number: 6466
>Category: kern
>Synopsis: loopback interface has no SIOCSIFFLAGS handler, this causes bugs
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Thu Apr 30 09:30:01 PDT 1998
>Last-Modified:
>Originator: Ruslan Ermilov
>Organization:
United Commercial Bank
>Release: FreeBSD 2.2.6-STABLE i386
>Environment:
-stable and (I guess) -current.
>Description:
Loopback network interface driver (net/if_loop.c) has no
SIOCSIFFLAGS ioctl handler.
This causes bugs.
I noticed this after running tcpdump on lo0.
Once set, IFF_PROMISC flag isn't cleared on lo0.
Searching in the source code (net/if.c, net/if_loop.c, net/bpf.c)
I found the problem:
1. The IFF_PROMISC flag is cleared in ifpromisc(ifp,0).
2. ifpromisc(ifp,0) is called from bpf_detach() only if
(struct bpf_d).bd_promisc is set to non-zero.
3. bd_promisc is set to 1 in bpfioctl() while handling BIOCPROMISC.
It is set to 1 only if ifpromisc(ifp,1) returns 0.
4. ifpromisc(ifp,1) fails on if_ioctl(lo0, SIOCSIFFLAGS)
because if_loop.c has no handler for SIOCSIFFLAGS.
>How-To-Repeat:
1. Run ``ifconfig lo0'':
lo0: flags=8149<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
inet 127.0.0.1 netmask 0xff000000
2. Run ``tcpdump -i lo0''
3. Stop ``tcpdump -i lo0''
4. Run ``ifconfig lo0'' again:
lo0: flags=8149<UP,LOOPBACK,RUNNING,PROMISC,MULTICAST> mtu 16384
^^^^^^^
inet 127.0.0.1 netmask 0xff000000
>Fix:
This patch for RELENG_2_2:
Index: if_loop.c
===================================================================
RCS file: /usr/FreeBSD-CVS/src/sys/net/if_loop.c,v
retrieving revision 1.22
diff -u -r1.22 if_loop.c
--- if_loop.c 1996/06/19 16:24:10 1.22
+++ if_loop.c 1998/04/30 16:09:16
@@ -293,6 +293,9 @@
ifp->if_mtu = ifr->ifr_mtu;
break;
+ case SIOCSIFFLAGS:
+ break;
+
default:
error = EINVAL;
}
>Audit-Trail:
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