Re: ifconfig carpX a.b.c.d -> arpresolve: route contains no arp information

2017-07-24 Thread Remi Locherer 
On Mon, Jul 24, 2017 at 02:22:33PM +0200, Martin Pieuchot wrote:
> On 21/07/17(Fri) 12:13, Remi Locherer wrote:
> > [...] 
> > Somebody suggested in a private mail to use /32 masks for carp interfaces.
> > This fix/workaround helps indeed!
> 
> Good to know!  However from my developer's chair there's still a bug.
> Nothing should happen to a route attached to vio1 when you modify
> something on carp1.
> 
> Could you repeat the "route monitor" steps with a kernel containing the
> diff below? 

here you go:

gw1# route monitor
got message of size 192 on Mon Jul 24 19:32:43 2017
RTM_DELETE: Delete Route: len 192, priority 3, table 0, ifidx 3, pid: 0, seq 0, 
errno 0
flags:
fmask:
use:0   mtu:0expire:0
locks:  inits:
sockaddrs: 
 10.0.20.10 08:00:27:6b:9a:c1 08:00:27:7e:f3:d5 10.0.20.2
got message of size 192 on Mon Jul 24 19:32:43 2017
RTM_DELETE: Delete Route: len 192, priority 19, table 0, ifidx 7, pid: 0, seq 
0, errno 0
flags:
fmask:
use:0   mtu:0expire:0
locks:  inits:
sockaddrs: 
 10.0.20.0 10.0.20.1 255.255.255.0 00:00:5e:00:01:17 10.0.20.1
got message of size 176 on Mon Jul 24 19:32:43 2017
RTM_DELETE: Delete Route: len 176, priority 1, table 0, ifidx 7, pid: 0, seq 0, 
errno 0
flags:
fmask:
use:0   mtu:0expire:0
locks:  inits:
sockaddrs: 
 10.0.20.255 10.0.20.1 00:00:5e:00:01:17 10.0.20.1
got message of size 192 on Mon Jul 24 19:32:43 2017
RTM_DELETE: Delete Route: len 192, priority 1, table 0, ifidx 7, pid: 0, seq 0, 
errno 0
flags:
fmask:
use:0   mtu:0expire:0
locks:  inits:
sockaddrs: 
 10.0.20.1 00:00:5e:00:01:17 00:00:5e:00:01:17 10.0.20.1
got message of size 96 on Mon Jul 24 19:32:43 2017
RTM_DELADDR: address being removed from iface: len 96, metric 0, flags:
sockaddrs: 
 255.255.255.0 00:00:5e:00:01:17 10.0.20.1 10.0.20.255
got message of size 168 on Mon Jul 24 19:32:43 2017
RTM_IFINFO: iface status change: len 168, if# 7, name: carp2, link: invalid, 
mtu: 1500, flags:
got message of size 104 on Mon Jul 24 19:32:43 2017
RTM_NEWADDR: address being added to iface: len 104, metric 0, flags:
sockaddrs: 
 255.255.255.0 00:00:5e:00:01:17 10.0.20.1 default
got message of size 192 on Mon Jul 24 19:32:43 2017
RTM_ADD: Add Route: len 192, priority 1, table 0, ifidx 7, pid: 0, seq 0, errno 0
flags:
fmask:
use:0   mtu:0expire:0
locks:  inits:
sockaddrs: 
 10.0.20.1 00:00:5e:00:01:17 00:00:5e:00:01:17 10.0.20.1
got message of size 192 on Mon Jul 24 19:32:43 2017
RTM_ADD: Add Route: len 192, priority 147, table 0, ifidx 7, pid: 0, seq 0, 
errno 0
flags:
fmask:
use:0   mtu:0expire:0
locks:  inits:
sockaddrs: 
 10.0.20.0 10.0.20.1 255.255.255.0 00:00:5e:00:01:17 10.0.20.1
got message of size 176 on Mon Jul 24 19:32:43 2017
RTM_ADD: Add Route: len 176, priority 129, table 0, ifidx 7, pid: 0, seq 0, 
errno 0
flags:
fmask:
use:0   mtu:0expire:0
locks:  inits:
sockaddrs: 
 10.0.20.255 10.0.20.1 00:00:5e:00:01:17 10.0.20.1
got message of size 168 on Mon Jul 24 19:32:43 2017
RTM_IFINFO: iface status change: len 168, if# 7, name: carp2, link: backup, 
mtu: 1500, flags:
got message of size 168 on Mon Jul 24 19:32:46 2017
RTM_IFINFO: iface status change: len 168, if# 7, name: carp2, link: master, 
mtu: 1500, flags:

Re: ifconfig carpX a.b.c.d -> arpresolve: route contains no arp information

2017-07-24 Thread Martin Pieuchot 
On 21/07/17(Fri) 12:13, Remi Locherer wrote:
> [...] 
> Somebody suggested in a private mail to use /32 masks for carp interfaces.
> This fix/workaround helps indeed!

Good to know!  However from my developer's chair there's still a bug.
Nothing should happen to a route attached to vio1 when you modify
something on carp1.

Could you repeat the "route monitor" steps with a kernel containing the
diff below? 

Index: net/route.c
===
RCS file: /cvs/src/sys/net/route.c,v
retrieving revision 1.360
diff -u -p -r1.360 route.c
--- net/route.c 24 Jul 2017 09:20:32 -  1.360
+++ net/route.c 24 Jul 2017 12:19:23 -
@@ -627,7 +627,7 @@ rtdeletemsg(struct rtentry *rt, struct i
 {
int error;
struct rt_addrinfo  info;
-   unsigned intifidx;
+   struct sockaddr_rtlabel sa_rl;
struct sockaddr_in6 sa_mask;
 
KASSERT(rt->rt_ifidx == ifp->if_index);
@@ -637,16 +637,18 @@ rtdeletemsg(struct rtentry *rt, struct i
 * deleted.  That will allow the information being reported to
 * be accurate (and consistent with route_output()).
 */
-   bzero((caddr_t)&info, sizeof(info));
+   memset(&info, 0, sizeof(info));
info.rti_info[RTAX_DST] = rt_key(rt);
+   info.rti_info[RTAX_GATEWAY] = rt->rt_gateway;
if (!ISSET(rt->rt_flags, RTF_HOST))
info.rti_info[RTAX_NETMASK] = rt_plen2mask(rt, &sa_mask);
-   info.rti_info[RTAX_GATEWAY] = rt->rt_gateway;
+   info.rti_info[RTAX_LABEL] = rtlabel_id2sa(rt->rt_labelid, &sa_rl);
info.rti_flags = rt->rt_flags;
-   ifidx = rt->rt_ifidx;
+   info.rti_info[RTAX_IFP] = sdltosa(ifp->if_sadl);
+   info.rti_info[RTAX_IFA] = rt->rt_ifa->ifa_addr;
error = rtrequest_delete(&info, rt->rt_priority, ifp, &rt, tableid);
KERNEL_LOCK();
-   rtm_miss(RTM_DELETE, &info, info.rti_flags, rt->rt_priority, ifidx,
+   rtm_miss(RTM_DELETE, &info, rt->rt_flags, rt->rt_priority, rt->rt_ifidx,
error, tableid);
KERNEL_UNLOCK();
if (error == 0)

Re: ifconfig carpX a.b.c.d -> arpresolve: route contains no arp information

2017-07-21 Thread Remi Locherer 

On 2017-07-10 17:52, Remi Locherer wrote:
Synopsis:	ifconfig carpX a.b.c.d -> arpresolve: route contains no arp 
information

Category:   kernel
Environment:

System  : OpenBSD 6.1
	Details : OpenBSD 6.1 (GENERIC.MP) #20: Sat Apr  1 13:45:56 MDT 
2017
			 
dera...@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP


Architecture: OpenBSD.amd64
Machine : amd64


Description:

After reconfiguring an existing carp interface with the same ip the
gateway stops forwarding traffic (forwarding to directly connected
hosts still works).
In /var/log/messages this can be found:

Jul 10 12:54:27 gw1 /bsd: arpresolve: 10.0.20.10: route contains no
arp information



How-To-Repeat:


[...]


I can reproduce this problem with:
- OpenBSD 6.1 -release
- OpenBSD 6.1 -stable (all patches applied with syspatch)
- OpenBSD 6.1 -current (7.7.2017)

With OpenBSD 6.0 3 pings are lost after executing ifconfig and then 
packages

are forwarded again as expected.




Fix:

unknown. Workaround: route change 10.0.200.0/24 10.0.20.10



Somebody suggested in a private mail to use /32 masks for carp 
interfaces.

This fix/workaround helps indeed!

Re: ifconfig carpX a.b.c.d -> arpresolve: route contains no arp information

2017-07-12 Thread Remi Locherer 

On 2017-07-12 11:34, Martin Pieuchot wrote:

On 11/07/17(Tue) 13:55, Remi Locherer wrote:

On 2017-07-11 13:23, Remi Locherer wrote:
> On 2017-07-11 11:32, Martin Pieuchot wrote:
> > Hello and thanks for the detailed bug report.
> >
> > On 10/07/17(Mon) 17:52, Remi Locherer wrote:
> > > >Synopsis:ifconfig carpX a.b.c.d -> arpresolve: route contains no arp 
information
> > > >Category:kernel
> > > >Environment:
> > >  System  : OpenBSD 6.1
> > >  Details : OpenBSD 6.1 (GENERIC.MP) #20: Sat Apr  1 13:45:56
> > > MDT 2017
> > >
> > > dera...@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP
> > >
> > >  Architecture: OpenBSD.amd64
> > >  Machine : amd64
> > >
> > > >Description:
> > >  After reconfiguring an existing carp interface with the same ip
> > > the gateway stops forwarding traffic (forwarding to directly
> > > connected hosts still works).
> > > In /var/log/messages this can be found:
> > >
> > > Jul 10 12:54:27 gw1 /bsd: arpresolve: 10.0.20.10: route contains
> > > no arp information
> >
> > How does the routing table looks like when you see such message?  And
> > the ARP table?


Somehow a route attached to vio2 is removed from the routing table when
you modify carp2.

Could you run 'route monitor' then do 'ifconfig carp2 delete'?  This
should hopefully reproduce the problem and the output of 'route 
monitor'

will give us more infos.


This is the output captured on 6.1-stable:

gw1# route monitor
got message of size 144 on Wed Jul 12 16:02:07 2017
RTM_DELETE: Delete Route: len 144, priority 3, table 0, ifidx 3, pid: 0, 
seq 0, errno 0

flags:
fmask:
use:0   mtu:0expire:0
locks:  inits:
sockaddrs: 
 10.0.20.10 08:00:27:6b:9a:c1
got message of size 192 on Wed Jul 12 16:02:07 2017
RTM_DELETE: Delete Route: len 192, priority 19, table 0, ifidx 7, pid: 
0, seq 0, errno 0

flags:
fmask:
use:0   mtu:0expire:0
locks:  inits:
sockaddrs: 
 10.0.20.0 10.0.20.1 255.255.255.0 00:00:5e:00:01:17 10.0.20.1
got message of size 176 on Wed Jul 12 16:02:07 2017
RTM_DELETE: Delete Route: len 176, priority 1, table 0, ifidx 7, pid: 0, 
seq 0, errno 0

flags:
fmask:
use:0   mtu:0expire:0
locks:  inits:
sockaddrs: 
 10.0.20.255 10.0.20.1 00:00:5e:00:01:17 10.0.20.1
got message of size 192 on Wed Jul 12 16:02:07 2017
RTM_DELETE: Delete Route: len 192, priority 1, table 0, ifidx 7, pid: 0, 
seq 0, errno 0

flags:
fmask:
use:0   mtu:0expire:0
locks:  inits:
sockaddrs: 
 10.0.20.1 00:00:5e:00:01:17 00:00:5e:00:01:17 10.0.20.1
got message of size 96 on Wed Jul 12 16:02:07 2017
RTM_DELADDR: address being removed from iface: len 96, metric 0, flags:
sockaddrs: 
 255.255.255.0 00:00:5e:00:01:17 10.0.20.1 10.0.20.255
got message of size 168 on Wed Jul 12 16:02:08 2017
RTM_IFINFO: iface status change: len 168, if# 7, name: carp2, link: 
invalid, mtu: 1500, flags:

Re: ifconfig carpX a.b.c.d -> arpresolve: route contains no arp information

2017-07-12 Thread Martin Pieuchot 
On 11/07/17(Tue) 13:55, Remi Locherer wrote:
> On 2017-07-11 13:23, Remi Locherer wrote:
> > On 2017-07-11 11:32, Martin Pieuchot wrote:
> > > Hello and thanks for the detailed bug report.
> > > 
> > > On 10/07/17(Mon) 17:52, Remi Locherer wrote:
> > > > >Synopsis:  ifconfig carpX a.b.c.d -> arpresolve: route contains no 
> > > > >arp information
> > > > >Category:  kernel
> > > > >Environment:
> > > > System  : OpenBSD 6.1
> > > > Details : OpenBSD 6.1 (GENERIC.MP) #20: Sat Apr  1 13:45:56
> > > > MDT 2017
> > > > 
> > > > dera...@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP
> > > > 
> > > > Architecture: OpenBSD.amd64
> > > > Machine : amd64
> > > > 
> > > > >Description:
> > > > After reconfiguring an existing carp interface with the same ip
> > > > the gateway stops forwarding traffic (forwarding to directly
> > > > connected hosts still works).
> > > > In /var/log/messages this can be found:
> > > > 
> > > > Jul 10 12:54:27 gw1 /bsd: arpresolve: 10.0.20.10: route contains
> > > > no arp information
> > > 
> > > How does the routing table looks like when you see such message?  And
> > > the ARP table?

Somehow a route attached to vio2 is removed from the routing table when
you modify carp2.

Could you run 'route monitor' then do 'ifconfig carp2 delete'?  This
should hopefully reproduce the problem and the output of 'route monitor'
will give us more infos.

Re: ifconfig carpX a.b.c.d -> arpresolve: route contains no arp information

2017-07-11 Thread Remi Locherer 

On 2017-07-11 13:23, Remi Locherer wrote:

On 2017-07-11 11:32, Martin Pieuchot wrote:

Hello and thanks for the detailed bug report.

On 10/07/17(Mon) 17:52, Remi Locherer wrote:

>Synopsis:   ifconfig carpX a.b.c.d -> arpresolve: route contains no arp 
information
>Category:   kernel
>Environment:
System  : OpenBSD 6.1
	Details : OpenBSD 6.1 (GENERIC.MP) #20: Sat Apr  1 13:45:56 MDT 
2017
			 
dera...@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP


Architecture: OpenBSD.amd64
Machine : amd64

>Description:
	After reconfiguring an existing carp interface with the same ip the 
gateway stops forwarding traffic (forwarding to directly connected 
hosts still works).

In /var/log/messages this can be found:

Jul 10 12:54:27 gw1 /bsd: arpresolve: 10.0.20.10: route contains no 
arp information


How does the routing table looks like when you see such message?  And
the ARP table?


gw1# route -nv show -inet
Routing tables

Internet:
DestinationGatewayFlags   Refs  Use   Mtu
Prio Iface Label
default10.0.2.2   UGS0   22 - 8 
vio0
224/4  127.0.0.1  URS00 32768 8 
lo0
10.0.2/24  10.0.2.15  UCn10 - 4 
vio0
10.0.2.2   52:54:00:12:35:02  UHLch  2   16 - 3 
vio0
10.0.2.15  08:00:27:23:af:65  UHLl   04 - 1 
vio0
10.0.2.255 10.0.2.15  UHb00 - 1 
vio0
10.0.10/24 10.0.10.2  UCn11 - 4 
vio1
10.0.10/24 10.0.10.1  UCn00 -19 
carp1
10.0.10.1  00:00:5e:00:01:17  UHLl   00 - 1 
carp1
10.0.10.2  08:00:27:7d:87:23  UHLl   01 - 1 
vio1
10.0.10.10 08:00:27:1e:30:02  UHLc   0   93 - 3 
vio1
10.0.10.25510.0.10.2  UHb00 - 1 
vio1
10.0.10.25510.0.10.1  UHb00 - 1 
carp1
10.0.20/24 10.0.20.2  UCn02 - 4 
vio2
10.0.20/24 10.0.20.1  UCn00 -19 
carp2
10.0.20.1  00:00:5e:00:01:17  UHLl   00 - 1 
carp2
10.0.20.2  08:00:27:7e:f3:d5  UHLl   01 - 1 
vio2
10.0.20.25510.0.20.2  UHb00 - 1 
vio2
10.0.20.25510.0.20.1  UHb00 - 1 
carp2
10.0.200/2410.0.20.10 UGS0   89 - 8 
vio2
127/8  127.0.0.1  UGRS   00 32768 8 
lo0
127.0.0.1  127.0.0.1  UHhl   12 32768 1 
lo0

gw1# arp -an
Host Ethernet AddressNetif Expire   
 Flags

10.0.2.2 52:54:00:12:35:02vio0 19m32s
10.0.2.1508:00:27:23:af:65vio0 
permanent l
10.0.10.100:00:5e:00:01:17   carp1 
permanent l
10.0.10.208:00:27:7d:87:23vio1 
permanent l

10.0.10.10   08:00:27:1e:30:02vio1 18m31s
10.0.20.100:00:5e:00:01:17   carp2 
permanent l
10.0.20.208:00:27:7e:f3:d5vio2 
permanent l

gw1#


What happen if you destroy carp2 instead of re-adding the same 
address?

Do you see the same problem?


Not 100% the same. My ping also stops and the same message is printed
to /var/log/mesages.
But the gateway does not send "icmp: host 10.0.200.1 unreachable" to 
10.0.10.10.


I missed something here: In my test setup I have only a single gateway. 
After
destroying carp2 the ip 10.0.20.1 is not configured anywhere. But that 
ip is the
defautl gateway of the test client. That is why I do not see icmp 
unreachable

messages sent by the gw1.



The routing and arp table after destroying carp2:

gw1# ifconfig carp2 destroy
gw1# route -nv show -inet
Routing tables

Internet:
DestinationGatewayFlags   Refs  Use   Mtu
Prio Iface Label
default10.0.2.2   UGS0   26 - 8 
vio0
224/4  127.0.0.1  URS00 32768 8 
lo0
10.0.2/24  10.0.2.15  UCn10 - 4 
vio0
10.0.2.2   52:54:00:12:35:02  UHLch  2   20 - 3 
vio0
10.0.2.15  08:00:27:23:af:65  UHLl   04 - 1 
vio0
10.0.2.255 10.0.2.15  UHb00 - 1 
vio0
10.0.10/24 10.0.10.2  UCn11 - 4 
vio1
10.0.10/24 10.0.10.1  UCn00 -19 
carp1
10.0.10.1  00:00:5e:00:01:17  UHLl   00 - 1 
carp1
10.0.10.2  08:00:27:7d:87:23  UHLl   01 - 1 
vio1
10.0.10.10 08:00:27:1e:30:02

Re: ifconfig carpX a.b.c.d -> arpresolve: route contains no arp information

2017-07-11 Thread Remi Locherer 

On 2017-07-11 11:32, Martin Pieuchot wrote:

Hello and thanks for the detailed bug report.

On 10/07/17(Mon) 17:52, Remi Locherer wrote:

>Synopsis:   ifconfig carpX a.b.c.d -> arpresolve: route contains no arp 
information
>Category:   kernel
>Environment:
System  : OpenBSD 6.1
	Details : OpenBSD 6.1 (GENERIC.MP) #20: Sat Apr  1 13:45:56 MDT 
2017
			 
dera...@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP


Architecture: OpenBSD.amd64
Machine : amd64

>Description:
	After reconfiguring an existing carp interface with the same ip the 
gateway stops forwarding traffic (forwarding to directly connected 
hosts still works).

In /var/log/messages this can be found:

Jul 10 12:54:27 gw1 /bsd: arpresolve: 10.0.20.10: route contains no 
arp information


How does the routing table looks like when you see such message?  And
the ARP table?


gw1# route -nv show -inet
Routing tables

Internet:
DestinationGatewayFlags   Refs  Use   Mtu  Prio 
Iface Label
default10.0.2.2   UGS0   22 - 8 
vio0
224/4  127.0.0.1  URS00 32768 8 
lo0
10.0.2/24  10.0.2.15  UCn10 - 4 
vio0
10.0.2.2   52:54:00:12:35:02  UHLch  2   16 - 3 
vio0
10.0.2.15  08:00:27:23:af:65  UHLl   04 - 1 
vio0
10.0.2.255 10.0.2.15  UHb00 - 1 
vio0
10.0.10/24 10.0.10.2  UCn11 - 4 
vio1
10.0.10/24 10.0.10.1  UCn00 -19 
carp1
10.0.10.1  00:00:5e:00:01:17  UHLl   00 - 1 
carp1
10.0.10.2  08:00:27:7d:87:23  UHLl   01 - 1 
vio1
10.0.10.10 08:00:27:1e:30:02  UHLc   0   93 - 3 
vio1
10.0.10.25510.0.10.2  UHb00 - 1 
vio1
10.0.10.25510.0.10.1  UHb00 - 1 
carp1
10.0.20/24 10.0.20.2  UCn02 - 4 
vio2
10.0.20/24 10.0.20.1  UCn00 -19 
carp2
10.0.20.1  00:00:5e:00:01:17  UHLl   00 - 1 
carp2
10.0.20.2  08:00:27:7e:f3:d5  UHLl   01 - 1 
vio2
10.0.20.25510.0.20.2  UHb00 - 1 
vio2
10.0.20.25510.0.20.1  UHb00 - 1 
carp2
10.0.200/2410.0.20.10 UGS0   89 - 8 
vio2
127/8  127.0.0.1  UGRS   00 32768 8 
lo0
127.0.0.1  127.0.0.1  UHhl   12 32768 1 
lo0

gw1# arp -an
Host Ethernet AddressNetif Expire
Flags

10.0.2.2 52:54:00:12:35:02vio0 19m32s
10.0.2.1508:00:27:23:af:65vio0 permanent 
l
10.0.10.100:00:5e:00:01:17   carp1 permanent 
l
10.0.10.208:00:27:7d:87:23vio1 permanent 
l

10.0.10.10   08:00:27:1e:30:02vio1 18m31s
10.0.20.100:00:5e:00:01:17   carp2 permanent 
l
10.0.20.208:00:27:7e:f3:d5vio2 permanent 
l

gw1#



What happen if you destroy carp2 instead of re-adding the same address?
Do you see the same problem?


Not 100% the same. My ping also stops and the same message is printed to 
/var/log/mesages.
But the gateway does not send "icmp: host 10.0.200.1 unreachable" to 
10.0.10.10.


The routing and arp table after destroying carp2:

gw1# ifconfig carp2 destroy
gw1# route -nv show -inet
Routing tables

Internet:
DestinationGatewayFlags   Refs  Use   Mtu  Prio 
Iface Label
default10.0.2.2   UGS0   26 - 8 
vio0
224/4  127.0.0.1  URS00 32768 8 
lo0
10.0.2/24  10.0.2.15  UCn10 - 4 
vio0
10.0.2.2   52:54:00:12:35:02  UHLch  2   20 - 3 
vio0
10.0.2.15  08:00:27:23:af:65  UHLl   04 - 1 
vio0
10.0.2.255 10.0.2.15  UHb00 - 1 
vio0
10.0.10/24 10.0.10.2  UCn11 - 4 
vio1
10.0.10/24 10.0.10.1  UCn00 -19 
carp1
10.0.10.1  00:00:5e:00:01:17  UHLl   00 - 1 
carp1
10.0.10.2  08:00:27:7d:87:23  UHLl   01 - 1 
vio1
10.0.10.10 08:00:27:1e:30:02  UHLc   0  247 - 3 
vio1
10.0.10.25510.0.10.2  UHb00 - 1 
vio1
10.0.10.25510.0.10.1  UHb00 - 1 
carp1
10.0.20/24 10.0.20.2  UCn08 - 4 
vio2
10.0.20.2  08:00:27:7e:f

Re: ifconfig carpX a.b.c.d -> arpresolve: route contains no arp information

2017-07-11 Thread Martin Pieuchot 
Hello and thanks for the detailed bug report.

On 10/07/17(Mon) 17:52, Remi Locherer wrote:
> >Synopsis:ifconfig carpX a.b.c.d -> arpresolve: route contains no arp 
> >information
> >Category:kernel
> >Environment:
>   System  : OpenBSD 6.1
>   Details : OpenBSD 6.1 (GENERIC.MP) #20: Sat Apr  1 13:45:56 MDT 2017
>
> dera...@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP
> 
>   Architecture: OpenBSD.amd64
>   Machine : amd64
> 
> >Description:
>   After reconfiguring an existing carp interface with the same ip the 
> gateway stops forwarding traffic (forwarding to directly connected hosts 
> still works).
> In /var/log/messages this can be found:
> 
> Jul 10 12:54:27 gw1 /bsd: arpresolve: 10.0.20.10: route contains no arp 
> information

How does the routing table looks like when you see such message?  And
the ARP table?

What happen if you destroy carp2 instead of re-adding the same address?
Do you see the same problem?