Date: Mon, 23 Jul 2001 13:50:13 -0700 (PDT) From: Voradesh Yenbut <yenbut@cs.washington.edu> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/29170: ARP request fails after "bad gateway value" in if_ether.c Message-ID: <200107232050.f6NKoDT42365@freefall.freebsd.org>
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>Number: 29170
>Category: kern
>Synopsis: ARP request fails after "bad gateway value" in if_ether.c
>Confidential: no
>Severity: serious
>Priority: high
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Mon Jul 23 14:00:00 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator: Voradesh Yenbut
>Release: 4.2, 3.4
>Organization:
CSE, U of Washington
>Environment:
FreeBSD bs8.cs.washington.edu 4.2-RELEASE FreeBSD 4.2-RELEASE #2: Mon Jul 23 12:13:29 PDT 2001 root@orion.cs.washington.edu:/usr/src/sys/compile/BS-GENERIC i386
>Description:
We have several FreeBSD systems running DNS servers. For some unknown
reasons, one of the systems serving a subnet where most clients run
Windows 2000, occasionally failed to do arp address resolution.
The kernel logged messages like the followings:
arp_rtrequest: bad gateway value
arplookup 128.95.8.74 failed: could not allocate llinfo
arpresolve: can't allocate llinfo for 128.95.8.74rt
arp_rtrequest: bad gateway value
arplookup 128.95.8.233 failed: could not allocate llinfo
arpresolve: can't allocate llinfo for 128.95.8.233rt
arp_rtrequest: bad gateway value
arplookup 128.95.8.232 failed: could not allocate llinfo
arpresolve: can't allocate llinfo for 128.95.8.232rt
arplookup 128.95.8.233 failed: could not allocate llinfo
arpresolve: can't allocate llinfo for 128.95.8.233rt
arp_rtrequest: bad gateway value
arplookup 128.95.8.230 failed: could not allocate llinfo
arpresolve: can't allocate llinfo for 128.95.8.230rt
arp_rtrequest: bad gateway value
arplookup 128.95.8.160 failed: could not allocate llinfo
arpresolve: can't allocate llinfo for 128.95.8.160rt
ARP requests to the addresses above failed afterward. A system reboot
made ARP requests work again, but sooner or later the same problem
comes back.
As I searched FreeBSD mailing lists for a solution, several reports
of similar problems were found but I did not see a good solution.
>How-To-Repeat:
I don't know how to repeat this, but it can be simulated by making a
condition in arp_rtrequest() of /usr/src/sys/netinet/if_ether.c to
break out of RTM_RESOLVE. For example,
The following code use a static variable:
static int toggle = 1; /* added */
to simulate one fault with bad gateway value condition.
case RTM_RESOLVE:
if (gate->sa_family != AF_LINK ||
toggle || /* added */
gate->sa_len < sizeof(null_sdl)) {
log(LOG_DEBUG, "arp_rtrequest: bad gateway value\n");
if (toggle) toggle = 0; /* added */
break;
}
After a system reboot, the system will generate "rp_rtrequest: bad
gateway value" to the first host it tries to contact which is
is likely to be its default gateway. Even though toggle's value
is 0, subsequent attempts to contact the host generates messages:
arplookup xx.xx.x.xxx failed: could not allocate llinfo
arpresolve: can't allocate llinfo for xx.xx.xx.xxrt
This leads to believe that a good cleanup is not automatically done to
a route if for some reasons it has an error.
>Fix:
I don't completely understand the arp code so may not have an insight
to really correct the problem, but the following patch seems to get
around the problem ("bad gateway value" is still seen but no more messages
about llinfo and arp works with the address causing the message.):
--- if_ether.c 2001/07/23 16:35:07 1.1
+++ if_ether.c 2001/07/23 19:13:24
@@ -199,7 +199,13 @@
case RTM_RESOLVE:
if (gate->sa_family != AF_LINK ||
gate->sa_len < sizeof(null_sdl)) {
- log(LOG_DEBUG, "arp_rtrequest: bad gateway value\n");
+ log(LOG_DEBUG, "arp_rtrequest: %s bad gateway value %s\n",
+ inet_ntoa(SIN(rt_key(rt))->sin_addr),
+ gate->sa_family != AF_LINK? "family": "");
+ rtrequest(RTM_DELETE,
+ (struct sockaddr *)rt_key(rt),
+ rt->rt_gateway,
+ rt_mask(rt), rt->rt_flags, 0);
break;
}
SDL(gate)->sdl_type = rt->rt_ifp->if_type;
>Release-Note:
>Audit-Trail:
>Unformatted:
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