[BUG][iproute2][5.0] ip route show table default: "Error: ipv4: FIB table does not exist."

[BUG][iproute2][5.0] ip route show table default: "Error: ipv4: FIB table does not exist."

[emersonbernier]

After upgrading iproute2 from 4.20 to 5.0 the following error occurs:

$ ip route show table default
Error: ipv4: FIB table does not exist.
Dump terminated

The command works for all tables other than 'default' one. It seems related to this commit[1]

I also saw "Error: ipv4: MR table does not exist." message in logs related to this commit[2] but don't know exact command to reproduce it. I've seen some fixups[3] for mentioned commits and wonder it they weren't complete.

I reproduced it on Linux 4.20.17 and 5.0.3.

[1] https://github.com/torvalds/linux/commit/18a8021a7be3207686851208f91a2f105b2d4703#diff-04a14e4f51765994f87e7e5e7681d0e1R861 <https://github.com/torvalds/linux/commit/18a8021a7be3207686851208f91a2f105b2d4703#diff-04a14e4f51765994f87e7e5e7681d0e1R861>

[2] https://github.com/torvalds/linux/commit/cb167893f41e21e6bd283d78e53489289dc0592d#diff-9900db808ce5e5dd24a7341cd8ed1609R2545 <https://github.com/torvalds/linux/commit/cb167893f41e21e6bd283d78e53489289dc0592d#diff-9900db808ce5e5dd24a7341cd8ed1609R2545>

[3] https://github.com/torvalds/linux/commit/73155879b3c1ac3ace35208a54a3a160ec520bef

Re: [BUG][iproute2][5.0] ip route show table default: "Error: ipv4: FIB table does not exist."

[David Ahern]

On 3/23/19 7:00 AM, emersonbernier@tutanota.com wrote:
> After upgrading iproute2 from 4.20 to 5.0 the following error occurs:
> 
> $ ip route show table default
> Error: ipv4: FIB table does not exist.
> Dump terminated
> 
> The command works for all tables other than 'default' one. It seems related to this commit[1]


'default' maps to table 253, and the table has not been created in the
kernel. Local (255) and main (254) do exist.

Re: [BUG][iproute2][5.0] ip route show table default: "Error: ipv4: FIB table does not exist."

[emersonbernier]

Mar 24, 2019, 2:17 PM by dsahern@gmail.com:

> On 3/23/19 7:00 AM, > emersonbernier@tutanota.com <mailto:emersonbernier@tutanota.com>>  wrote:
>
>> After upgrading iproute2 from 4.20 to 5.0 the following error occurs:
>>
>> $ ip route show table default
>> Error: ipv4: FIB table does not exist.
>> Dump terminated
>>
>> The command works for all tables other than 'default' one. It seems related to this commit[1]
>>
>
>
> 'default' maps to table 253, and the table has not been created in the
> kernel. Local (255) and main (254) do exist.
>
Ok but previous versions of iproute2 didn't treat this as error and didn't exited with non-zero status. Is non existing default route a system error which needs fixing?

Re: [BUG][iproute2][5.0] ip route show table default: "Error: ipv4: FIB table does not exist."

[David Ahern]

On 3/24/19 11:02 AM, emersonbernier@tutanota.com wrote:
> Ok but previous versions of iproute2 didn't treat this as error and didn't exited with non-zero status. Is non existing default route a system error which needs fixing?

The kernel is returning that error, not iproute2.

It is the default *table*, not a default route.

Re: [BUG][iproute2][5.0] ip route show table default: "Error: ipv4: FIB table does not exist."

[emersonbernier]

Mar 24, 2019, 5:20 PM by dsahern@gmail.com:

> On 3/24/19 11:02 AM, > emersonbernier@tutanota.com <mailto:emersonbernier@tutanota.com>>  wrote:
>
>> Ok but previous versions of iproute2 didn't treat this as error and didn't exited with non-zero status. Is non existing default route a system error which needs fixing?
>>
>
> The kernel is returning that error, not iproute2.
>
I mean that with older versions of iproute2 this error isn't shown for userspace.
> It is the default *table*, not a default route.
>
True. Still the question remains: is non existing default table a system error which needs fixing?

Re: [BUG][iproute2][5.0] ip route show table default: "Error: ipv4: FIB table does not exist."

[David Ahern]

On 3/24/19 11:34 AM, emersonbernier@tutanota.com wrote:
> Mar 24, 2019, 5:20 PM by dsahern@gmail.com:
> 
>> On 3/24/19 11:02 AM, > emersonbernier@tutanota.com <mailto:emersonbernier@tutanota.com>>  wrote:
>>
>>> Ok but previous versions of iproute2 didn't treat this as error and didn't exited with non-zero status. Is non existing default route a system error which needs fixing?
>>>
>>
>> The kernel is returning that error, not iproute2.
>>
> I mean that with older versions of iproute2 this error isn't shown for userspace.
>> It is the default *table*, not a default route.
>>
> True. Still the question remains: is non existing default table a system error which needs fixing?
> 

no, there is no system error. The kernel is telling iproute2 the
requested table does not exist. Arguably iproute2 can catch a request to
dump the 'default' table and not throw an error.

Re: [BUG][iproute2][5.0] ip route show table default: "Error: ipv4: FIB table does not exist."

[Michal Kubecek]

On Sun, Mar 24, 2019 at 11:20:33AM -0600, David Ahern wrote:
> On 3/24/19 11:02 AM, emersonbernier@tutanota.com wrote:
> > Ok but previous versions of iproute2 didn't treat this as error and didn't exited with non-zero status. Is non existing default route a system error which needs fixing?
> 
> The kernel is returning that error, not iproute2.
> 
> It is the default *table*, not a default route.

Something did change on iproute2 side between 4.20 and 5.0, though:

lion:~ # rpm -q iproute2
iproute2-4.20-0.x86_64
lion:~ # ip route show table default ; echo $?
0
lion:~ # ip route show table 123 ; echo $?
0
...
lion:~ # rpm -q iproute2
iproute2-5.0.0-0.x86_64
lion:~ # ip route show table default ; echo $?
Error: ipv4: FIB table does not exist.
Dump terminated
2
lion:~ # ip route show table 123 ; echo $?
Error: ipv4: FIB table does not exist.
Dump terminated
2

All I did was updating iproute2 package, the same kernel was running for
both (I tried 5.0.3 and 5.1-rc1).

Michal

Re: [BUG][iproute2][5.0] ip route show table default: "Error: ipv4: FIB table does not exist."

[Michal Kubecek]

On Sun, Mar 24, 2019 at 07:29:08PM +0100, Michal Kubecek wrote:
> On Sun, Mar 24, 2019 at 11:20:33AM -0600, David Ahern wrote:
> > On 3/24/19 11:02 AM, emersonbernier@tutanota.com wrote:
> > > Ok but previous versions of iproute2 didn't treat this as error and didn't exited with non-zero status. Is non existing default route a system error which needs fixing?
> > 
> > The kernel is returning that error, not iproute2.
> > 
> > It is the default *table*, not a default route.
> 
> Something did change on iproute2 side between 4.20 and 5.0, though:
> 
> lion:~ # rpm -q iproute2
> iproute2-4.20-0.x86_64
> lion:~ # ip route show table default ; echo $?
> 0
> lion:~ # ip route show table 123 ; echo $?
> 0
> ...
> lion:~ # rpm -q iproute2
> iproute2-5.0.0-0.x86_64
> lion:~ # ip route show table default ; echo $?
> Error: ipv4: FIB table does not exist.
> Dump terminated
> 2
> lion:~ # ip route show table 123 ; echo $?
> Error: ipv4: FIB table does not exist.
> Dump terminated
> 2
> 
> All I did was updating iproute2 package, the same kernel was running for
> both (I tried 5.0.3 and 5.1-rc1).

Commit c7e6371bc4af ("ip route: Add protocol, table id and device to
dump request") seems to be an obvious candidate. Before it, no matching
rules in the dump used to be presented as an empty table but now ip gets
a kernel error which it displays to the user.

Michal

Re: [BUG][iproute2][5.0] ip route show table default: "Error: ipv4: FIB table does not exist."

[David Ahern]

On 3/24/19 12:36 PM, Michal Kubecek wrote:
> On Sun, Mar 24, 2019 at 07:29:08PM +0100, Michal Kubecek wrote:
>> On Sun, Mar 24, 2019 at 11:20:33AM -0600, David Ahern wrote:
>>> On 3/24/19 11:02 AM, emersonbernier@tutanota.com wrote:
>>>> Ok but previous versions of iproute2 didn't treat this as error and didn't exited with non-zero status. Is non existing default route a system error which needs fixing?
>>>
>>> The kernel is returning that error, not iproute2.
>>>
>>> It is the default *table*, not a default route.
>>
>> Something did change on iproute2 side between 4.20 and 5.0, though:
>>
>> lion:~ # rpm -q iproute2
>> iproute2-4.20-0.x86_64
>> lion:~ # ip route show table default ; echo $?
>> 0
>> lion:~ # ip route show table 123 ; echo $?
>> 0
>> ...
>> lion:~ # rpm -q iproute2
>> iproute2-5.0.0-0.x86_64
>> lion:~ # ip route show table default ; echo $?
>> Error: ipv4: FIB table does not exist.
>> Dump terminated
>> 2
>> lion:~ # ip route show table 123 ; echo $?
>> Error: ipv4: FIB table does not exist.
>> Dump terminated
>> 2
>>
>> All I did was updating iproute2 package, the same kernel was running for
>> both (I tried 5.0.3 and 5.1-rc1).
> 
> Commit c7e6371bc4af ("ip route: Add protocol, table id and device to
> dump request") seems to be an obvious candidate. Before it, no matching
> rules in the dump used to be presented as an empty table but now ip gets
> a kernel error which it displays to the user.
> 

It's the commit that enables strict checking. Kernel side has been
changed to better inform the user of what happens on a request when
strict checking is enabled. iproute2 has been updated to use this.

Essentially, ip asks for a dump of table 253. In the past there is no
data, so nothing to return. The strict checking tells you explicitly
"that table does not exist" versus the old method where nothing is
returned and the user has to guess "the table exists but is empty or
there is a bug dumping the table?"

Given the legacy of table 253/default, iproute2 can easily catch this
error and just do nothing for backwards compatibility.

Re: [BUG][iproute2][5.0] ip route show table default: "Error: ipv4: FIB table does not exist."

[emersonbernier]

Mar 24, 2019, 10:09 PM by dsahern@gmail.com:

> On 3/24/19 12:36 PM, Michal Kubecek wrote:
>
>> On Sun, Mar 24, 2019 at 07:29:08PM +0100, Michal Kubecek wrote:
>>
>>> On Sun, Mar 24, 2019 at 11:20:33AM -0600, David Ahern wrote:
>>>
>>>> On 3/24/19 11:02 AM, >>>> emersonbernier@tutanota.com <mailto:emersonbernier@tutanota.com>>>>>  wrote:
>>>>
>>>>> Ok but previous versions of iproute2 didn't treat this as error and didn't exited with non-zero status. Is non existing default route a system error which needs fixing?
>>>>>
>>>>
>>>> The kernel is returning that error, not iproute2.
>>>>
>>>> It is the default *table*, not a default route.
>>>>
>>>
>>> Something did change on iproute2 side between 4.20 and 5.0, though:
>>>
>>> lion:~ # rpm -q iproute2
>>> iproute2-4.20-0.x86_64
>>> lion:~ # ip route show table default ; echo $?
>>> 0
>>> lion:~ # ip route show table 123 ; echo $?
>>> 0
>>> ...
>>> lion:~ # rpm -q iproute2
>>> iproute2-5.0.0-0.x86_64
>>> lion:~ # ip route show table default ; echo $?
>>> Error: ipv4: FIB table does not exist.
>>> Dump terminated
>>> 2
>>> lion:~ # ip route show table 123 ; echo $?
>>> Error: ipv4: FIB table does not exist.
>>> Dump terminated
>>> 2
>>>
>>> All I did was updating iproute2 package, the same kernel was running for
>>> both (I tried 5.0.3 and 5.1-rc1).
>>>
>>
>> Commit c7e6371bc4af ("ip route: Add protocol, table id and device to
>> dump request") seems to be an obvious candidate. Before it, no matching
>> rules in the dump used to be presented as an empty table but now ip gets
>> a kernel error which it displays to the user.
>>
>
> It's the commit that enables strict checking. Kernel side has been
> changed to better inform the user of what happens on a request when
> strict checking is enabled. iproute2 has been updated to use this.
>
> Essentially, ip asks for a dump of table 253. In the past there is no
> data, so nothing to return. The strict checking tells you explicitly
> "that table does not exist" versus the old method where nothing is
> returned and the user has to guess "the table exists but is empty or
> there is a bug dumping the table?"
>
> Given the legacy of table 253/default, iproute2 can easily catch this
> error and just do nothing for backwards compatibility.
>
Hi, 

are those changes planned then? I don't see anything in repo
https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/log/

Re: [BUG][iproute2][5.0] ip route show table default: "Error: ipv4: FIB table does not exist."

[David Ahern]

On 5/2/19 7:17 AM, emersonbernier@tutanota.com wrote:
> Hi, 
> 
> are those changes planned then? I don't see anything in repo
> https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/log/
> 

I have not taken the time yet. Feel free to submit a patch.

5.1 `ip route get addr/cidr` regression

[Jason A. Donenfeld]

Hi,

I'm back now and catching up with a lot of things. A few people have
mentioned to me that wg-quick(8), a bash script that makes a bunch of
iproute2 invocations, appears to be broken on 5.1. I've distilled the
behavior change down to the following.

Behavior on 5.0:

+ ip link add wg0 type dummy
+ ip address add 192.168.50.2/24 dev wg0
+ ip link set mtu 1420 up dev wg0
+ ip route get 192.168.50.0/24
broadcast 192.168.50.0 dev wg0 src 192.168.50.2 uid 0
   cache <local,brd>

Behavior on 5.1:

+ ip link add wg0 type dummy
+ ip address add 192.168.50.2/24 dev wg0
+ ip link set mtu 1420 up dev wg0
+ ip route get 192.168.50.0/24
RTNETLINK answers: Invalid argument

Upon investigating, I'm not sure that `ip route get` was ever suitable
for getting details on a particular route. So I'll adjust the
wg-quick(8) code accordingly. But FYI, this is unexpected userspace
breakage.

Jason

On Sat, Mar 23, 2019 at 2:00 PM <emersonbernier@tutanota.com> wrote:
>
> After upgrading iproute2 from 4.20 to 5.0 the following error occurs:
>
> $ ip route show table default
> Error: ipv4: FIB table does not exist.
> Dump terminated
>
> The command works for all tables other than 'default' one. It seems related to this commit[1]
>
> I also saw "Error: ipv4: MR table does not exist." message in logs related to this commit[2] but don't know exact command to reproduce it. I've seen some fixups[3] for mentioned commits and wonder it they weren't complete.
>
> I reproduced it on Linux 4.20.17 and 5.0.3.
>
> [1] https://github.com/torvalds/linux/commit/18a8021a7be3207686851208f91a2f105b2d4703#diff-04a14e4f51765994f87e7e5e7681d0e1R861 <https://github.com/torvalds/linux/commit/18a8021a7be3207686851208f91a2f105b2d4703#diff-04a14e4f51765994f87e7e5e7681d0e1R861>
>
> [2] https://github.com/torvalds/linux/commit/cb167893f41e21e6bd283d78e53489289dc0592d#diff-9900db808ce5e5dd24a7341cd8ed1609R2545 <https://github.com/torvalds/linux/commit/cb167893f41e21e6bd283d78e53489289dc0592d#diff-9900db808ce5e5dd24a7341cd8ed1609R2545>
>
> [3] https://github.com/torvalds/linux/commit/73155879b3c1ac3ace35208a54a3a160ec520bef

Re: 5.1 `ip route get addr/cidr` regression

[Michal Kubecek]

On Fri, May 17, 2019 at 12:22:41PM +0200, Jason A. Donenfeld wrote:
> Hi,
> 
> I'm back now and catching up with a lot of things. A few people have
> mentioned to me that wg-quick(8), a bash script that makes a bunch of
> iproute2 invocations, appears to be broken on 5.1. I've distilled the
> behavior change down to the following.
> 
> Behavior on 5.0:
> 
> + ip link add wg0 type dummy
> + ip address add 192.168.50.2/24 dev wg0
> + ip link set mtu 1420 up dev wg0
> + ip route get 192.168.50.0/24
> broadcast 192.168.50.0 dev wg0 src 192.168.50.2 uid 0
>    cache <local,brd>
> 
> Behavior on 5.1:
> 
> + ip link add wg0 type dummy
> + ip address add 192.168.50.2/24 dev wg0
> + ip link set mtu 1420 up dev wg0
> + ip route get 192.168.50.0/24
> RTNETLINK answers: Invalid argument

With recent kernel and iproute2 5.1, I get

  alaris:~ # ip route get 172.17.1.2/24
  Error: ipv4: Invalid values in header for route get request.

This message comes from kernel commit a00302b60777 ("net: ipv4: route:
perform strict checks also for doit handlers") which only considers the
range valid if the prefix is /32 (a single address).

But these checks are only performed when userspace requests strict
validation which iproute2 does since (iproute2) commit aea41afcfd6d ("ip
bridge: Set NETLINK_GET_STRICT_CHK on socket"). So I would say the
change is a result of the combination of kernel (5.1) commit
a00302b60777 and iproute2 (5.0) commit aea41afcfd6d.

> Upon investigating, I'm not sure that `ip route get` was ever suitable
> for getting details on a particular route. So I'll adjust the
> wg-quick(8) code accordingly. But FYI, this is unexpected userspace
> breakage.

AFAIK the purpose of 'ip route get' always was to let the user check
the result of a route lookup, i.e. "what route would be used if I sent
a packet to an address". To be honest I would have to check how exactly
was "ip route get <addr>/<prefixlen>" implemented before.

Michal Kubecek

Re: 5.1 `ip route get addr/cidr` regression

[David Ahern]

On 5/17/19 4:22 AM, Jason A. Donenfeld wrote:
> Hi,
> 
> I'm back now and catching up with a lot of things. A few people have
> mentioned to me that wg-quick(8), a bash script that makes a bunch of
> iproute2 invocations, appears to be broken on 5.1. I've distilled the
> behavior change down to the following.
> 
> Behavior on 5.0:
> 
> + ip link add wg0 type dummy
> + ip address add 192.168.50.2/24 dev wg0
> + ip link set mtu 1420 up dev wg0
> + ip route get 192.168.50.0/24
> broadcast 192.168.50.0 dev wg0 src 192.168.50.2 uid 0
>    cache <local,brd>
> 
> Behavior on 5.1:
> 
> + ip link add wg0 type dummy
> + ip address add 192.168.50.2/24 dev wg0
> + ip link set mtu 1420 up dev wg0
> + ip route get 192.168.50.0/24
> RTNETLINK answers: Invalid argument

This is a 5.1 change.
a00302b607770 ("net: ipv4: route: perform strict checks also for doit
handlers")

Basically, the /24 is unexpected. I'll send a patch.

> 
> Upon investigating, I'm not sure that `ip route get` was ever suitable
> for getting details on a particular route. So I'll adjust the

'ip route get <prefix> fibmatch' will show the fib entry.

Re: 5.1 `ip route get addr/cidr` regression

[David Ahern]

On 5/17/19 8:17 AM, Michal Kubecek wrote:
> AFAIK the purpose of 'ip route get' always was to let the user check
> the result of a route lookup, i.e. "what route would be used if I sent
> a packet to an address". To be honest I would have to check how exactly
> was "ip route get <addr>/<prefixlen>" implemented before.
> 

The prefixlen was always silently ignored. We are trying to clean up
this 'silent ignoring' just hitting a few speed bumps.

Re: 5.1 `ip route get addr/cidr` regression

[Jason A. Donenfeld]

On Fri, May 17, 2019 at 5:21 PM David Ahern <dsahern@gmail.com> wrote:
>
> On 5/17/19 8:17 AM, Michal Kubecek wrote:
> > AFAIK the purpose of 'ip route get' always was to let the user check
> > the result of a route lookup, i.e. "what route would be used if I sent
> > a packet to an address". To be honest I would have to check how exactly
> > was "ip route get <addr>/<prefixlen>" implemented before.
> >
>
> The prefixlen was always silently ignored. We are trying to clean up
> this 'silent ignoring' just hitting a few speed bumps.

Indeed what we were after has always been, `ip route show dev <dev>
match <addr>/<prefixlen>`, and the old positive return value from `ip
route get` wasn't always correct for what we were using it for. So
mostly the breakage exposed another bug here.

Re: 5.1 `ip route get addr/cidr` regression

[Stephen Hemminger]

On Fri, 17 May 2019 09:17:51 -0600
David Ahern <dsahern@gmail.com> wrote:

> On 5/17/19 4:22 AM, Jason A. Donenfeld wrote:
> > Hi,
> > 
> > I'm back now and catching up with a lot of things. A few people have
> > mentioned to me that wg-quick(8), a bash script that makes a bunch of
> > iproute2 invocations, appears to be broken on 5.1. I've distilled the
> > behavior change down to the following.
> > 
> > Behavior on 5.0:
> > 
> > + ip link add wg0 type dummy
> > + ip address add 192.168.50.2/24 dev wg0
> > + ip link set mtu 1420 up dev wg0
> > + ip route get 192.168.50.0/24
> > broadcast 192.168.50.0 dev wg0 src 192.168.50.2 uid 0
> >    cache <local,brd>
> > 
> > Behavior on 5.1:
> > 
> > + ip link add wg0 type dummy
> > + ip address add 192.168.50.2/24 dev wg0
> > + ip link set mtu 1420 up dev wg0
> > + ip route get 192.168.50.0/24
> > RTNETLINK answers: Invalid argument  
> 
> This is a 5.1 change.
> a00302b607770 ("net: ipv4: route: perform strict checks also for doit
> handlers")
> 
> Basically, the /24 is unexpected. I'll send a patch.
> 
> > 
> > Upon investigating, I'm not sure that `ip route get` was ever suitable
> > for getting details on a particular route. So I'll adjust the  
> 
> 'ip route get <prefix> fibmatch' will show the fib entry.
> 

If you want to keep the error, the kernel should send additional
extack as to reason. EINVAL is not user friendly...

Re: 5.1 `ip route get addr/cidr` regression

[David Ahern]

On 5/17/19 11:35 AM, Stephen Hemminger wrote:
> On Fri, 17 May 2019 09:17:51 -0600
> David Ahern <dsahern@gmail.com> wrote:
> 
>> On 5/17/19 4:22 AM, Jason A. Donenfeld wrote:
>>> Hi,
>>>
>>> I'm back now and catching up with a lot of things. A few people have
>>> mentioned to me that wg-quick(8), a bash script that makes a bunch of
>>> iproute2 invocations, appears to be broken on 5.1. I've distilled the
>>> behavior change down to the following.
>>>
>>> Behavior on 5.0:
>>>
>>> + ip link add wg0 type dummy
>>> + ip address add 192.168.50.2/24 dev wg0
>>> + ip link set mtu 1420 up dev wg0
>>> + ip route get 192.168.50.0/24
>>> broadcast 192.168.50.0 dev wg0 src 192.168.50.2 uid 0
>>>    cache <local,brd>
>>>
>>> Behavior on 5.1:
>>>
>>> + ip link add wg0 type dummy
>>> + ip address add 192.168.50.2/24 dev wg0
>>> + ip link set mtu 1420 up dev wg0
>>> + ip route get 192.168.50.0/24
>>> RTNETLINK answers: Invalid argument  
>>
>> This is a 5.1 change.
>> a00302b607770 ("net: ipv4: route: perform strict checks also for doit
>> handlers")
>>
>> Basically, the /24 is unexpected. I'll send a patch.
>>
>>>
>>> Upon investigating, I'm not sure that `ip route get` was ever suitable
>>> for getting details on a particular route. So I'll adjust the  
>>
>> 'ip route get <prefix> fibmatch' will show the fib entry.
>>
> 
> If you want to keep the error, the kernel should send additional
> extack as to reason. EINVAL is not user friendly...
> 

The kernel does set an extack for all EINVAL in this code path.

Not sure why Jason is not seeing that. Really odd that he hits the error
AND does not get a message back since it requires an updated ip command
to set the strict checking flag and that command understands extack.
Perhaps no libmnl?

Re: 5.1 `ip route get addr/cidr` regression

[David Ahern]

On 5/17/19 11:35 AM, Stephen Hemminger wrote:
> On Fri, 17 May 2019 09:17:51 -0600
> David Ahern <dsahern@gmail.com> wrote:
> 
>> On 5/17/19 4:22 AM, Jason A. Donenfeld wrote:
>>> Hi,
>>>
>>> I'm back now and catching up with a lot of things. A few people have
>>> mentioned to me that wg-quick(8), a bash script that makes a bunch of
>>> iproute2 invocations, appears to be broken on 5.1. I've distilled the
>>> behavior change down to the following.
>>>
>>> Behavior on 5.0:
>>>
>>> + ip link add wg0 type dummy
>>> + ip address add 192.168.50.2/24 dev wg0
>>> + ip link set mtu 1420 up dev wg0
>>> + ip route get 192.168.50.0/24
>>> broadcast 192.168.50.0 dev wg0 src 192.168.50.2 uid 0
>>>    cache <local,brd>
>>>
>>> Behavior on 5.1:
>>>
>>> + ip link add wg0 type dummy
>>> + ip address add 192.168.50.2/24 dev wg0
>>> + ip link set mtu 1420 up dev wg0
>>> + ip route get 192.168.50.0/24
>>> RTNETLINK answers: Invalid argument  
>>
>> This is a 5.1 change.
>> a00302b607770 ("net: ipv4: route: perform strict checks also for doit
>> handlers")
>>
>> Basically, the /24 is unexpected. I'll send a patch.

oh, and I think changing iproute2 to ignore the /24 and always set to 32
is better than changing the kernel to allow a prefix length that is ignored.

Re: 5.1 `ip route get addr/cidr` regression

[Jason A. Donenfeld]

On Fri, May 17, 2019 at 7:39 PM David Ahern <dsahern@gmail.com> wrote:
> Not sure why Jason is not seeing that. Really odd that he hits the error
> AND does not get a message back since it requires an updated ip command
> to set the strict checking flag and that command understands extack.
> Perhaps no libmnl?

Right, no libmnl. This is coming out of the iproute2 compiled for the
tests at https://www.wireguard.com/build-status/ which are pretty
minimal. Extact support would be kind of useful for diagnostics, and
wg(8) already uses it, so I can probably put that in my build system.

Re: 5.1 `ip route get addr/cidr` regression

[Jason A. Donenfeld]

On Fri, May 17, 2019 at 10:19 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> On Fri, May 17, 2019 at 7:39 PM David Ahern <dsahern@gmail.com> wrote:
> > Not sure why Jason is not seeing that. Really odd that he hits the error
> > AND does not get a message back since it requires an updated ip command
> > to set the strict checking flag and that command understands extack.
> > Perhaps no libmnl?
>
> Right, no libmnl. This is coming out of the iproute2 compiled for the
> tests at https://www.wireguard.com/build-status/ which are pretty
> minimal. Extact support would be kind of useful for diagnostics, and
> wg(8) already uses it, so I can probably put that in my build system.

Voila, extack:

+ ip link add wg0 type dummy
+ ip addr add 192.168.4.2/24 dev wg0
+ ip link set wg0 up
+ ip route get 192.168.4.0/24
Error: ipv4: Invalid values in header for route