Re: kern/52077: "route add" installs unreachable gateway

[Ryota Ozaki <ozaki-r%netbsd.org@localhost>]

On Wed, Mar 15, 2017 at 6:05 PM,  <s-yamaguchi%iij.ad.jp@localhost> wrote:
>>Number:         52077
>>Category:       kern
>>Synopsis:       "route add" installs unreachable gateway
>>Confidential:   no
>>Severity:       non-critical
>>Priority:       low
>>Responsible:    kern-bug-people
>>State:          open
>>Class:          sw-bug
>>Submitter-Id:   net
>>Arrival-Date:   Wed Mar 15 09:05:00 +0000 2017
>>Originator:     Shoichi Yamaguchi
>>Release:        -current
>>Organization:
> Internet Initiative Japan Inc.
>>Environment:
> NetBSD netbsd 7.99.66 NetBSD 7.99.66 (GENERIC) #4: Wed Mar 15 15:04:08 JST 2017  root@deskfd:(hidden) amd64
>>Description:
> the "route add" command install wrong route whose gateway is unreachable if the destination is reachable. And the route whose gateway is directly connected cannot be installed.
> I do not know whether this is bug, or not. But, OpenBSD fixed this behavior at the following commit.And, FreeBSD is same behavior as OpenBSD too
>  - https://bitbucket.org/braindamaged/openbsd-src/commits/097d8d9ded40b4c7832d2e7e486a7876832445fc
>
>>How-To-Repeat:
> netbsd# route show -inet
> Routing tables
>
> Internet:
> Destination        Gateway            Flags    Refs      Use    Mtu Interface
> default            192.168.95.1       UG          -        -      -  wm1
> 127/8              localhost          UGR         -        -  33624  lo0
> localhost          lo0                UHl         -        -  33624  lo0
> 192.168.56/24      link#2             U           -        -      -  wm0
> 192.168.56.68      link#2             UHl         -        -      -  lo0
> 192.168.95/24      link#3             U           -        -      -  wm1
> 192.168.95.105     link#3             UHl         -        -      -  lo0
> netbsd# route add -net 192.168.56.192/26 10.0.0.1
> add net 192.168.56.192: gateway 10.0.0.1
> netbsd# route show -inet
> Routing tables
>
> Internet:
> Destination        Gateway            Flags    Refs      Use    Mtu Interface
> default            192.168.95.1       UG          -        -      -  wm1
> 127/8              localhost          UGR         -        -  33624  lo0
> localhost          lo0                UHl         -        -  33624  lo0
> 192.168.56/24      link#2             U           -        -      -  wm0
> 192.168.56.68      link#2             UHl         -        -      -  lo0
> 192.168.56.192/26  10.0.0.1           UG          -        -      -  wm0
> 192.168.95/24      link#3             U           -        -      -  wm1
> 192.168.95.105     link#3             UHl         -        -      -  lo0
> netbsd# route get 192.168.56.193
>    route to: 192.168.56.193
> destination: 192.168.56.192
>        mask: 255.255.255.192
>     gateway: 10.0.0.1
>  local addr: 192.168.56.68
>   interface: wm0
>       flags: <UP,GATEWAY,DONE,STATIC>
>  recvpipe  sendpipe  ssthresh  rtt,msec    rttvar  hopcount      mtu     expire
>        0         0         0         0         0         0         0         0
>>Fix:
> diff --git a/sys/net/route.c b/sys/net/route.c
> index 1411f54..c99fc6e 100644
> --- a/sys/net/route.c
> +++ b/sys/net/route.c
> @@ -1026,11 +1026,15 @@ ifa_ifwithroute_psref(int flags, const struct sockaddr *dst,
>
>                 /* XXX we cannot call rtalloc1 if holding the rt lock */
>                 if (RT_LOCKED())
> -                       rt = rtalloc1_locked(dst, 0, true);
> +                       rt = rtalloc1_locked(gateway, 0, true);
>                 else
> -                       rt = rtalloc1(dst, 0);
> +                       rt = rtalloc1(gateway, 0);
>                 if (rt == NULL)
>                         return NULL;
> +               if (rt->rt_flags & RTF_GATEWAY) {
> +                       rt_unref(rt);
> +                       return NULL;
> +               }
>                 /*
>                  * Just in case. May not need to do this workaround.
>                  * Revisit when working on rtentry MP-ification.
>
>
> ----------------------------------------------------------------
> Added the RTF_GATEWAY check by looking at the following commit:
>  - https://bitbucket.org/braindamaged/openbsd-src/commits/78ba7cb9777cd1540f703219bd6463521f1f138b
>

The patch breaks an ATF test, t_route#route_default_reject;
"route change -inet6 default -reject" in the test begins failing.

It seems that we need to skip route checks if a gateway isn't specified,
which exist in FreeBSD and OpenBSD: http://www.netbsd.org/~ozaki-r/pr52077.diff

  ozaki-r