Hi Ed,

When creating an adjacency for the first time we send out a probe packet 
(ARP/ND) to see if the peer will resolve it.

/neale

From: Ed Warnicke <hagb...@gmail.com>
Date: Friday, 20 August 2021 at 16:54
To: Neale Ranns <ne...@graphiant.com>
Cc: zsta...@gmail.com <zsta...@gmail.com>, Artem Glazychev 
<artem.glazyc...@xored.com>, vpp-dev <vpp-dev@lists.fd.io>
Subject: Re: [vpp-dev] Adding new route via ipv6 link-local
Neale,

Question... looking at the trace it looks like we are having an issue with 
fib_sas6_get ... could you help me understand why we are calling fib_sas6_get 
in this situation?

Ed

On Fri, Aug 20, 2021 at 9:49 AM Neale Ranns 
<ne...@graphiant.com<mailto:ne...@graphiant.com>> wrote:

Hi Ed,

It does. But in this case the command is adding a route through an interface, 
which is not the same as configuring a prefix on an interface (nor ip6 enabling 
it).

/neale

From: Ed Warnicke <hagb...@gmail.com<mailto:hagb...@gmail.com>>
Date: Friday, 20 August 2021 at 16:40
To: Neale Ranns <ne...@graphiant.com<mailto:ne...@graphiant.com>>
Cc: zsta...@gmail.com<mailto:zsta...@gmail.com> 
<zsta...@gmail.com<mailto:zsta...@gmail.com>>, Artem Glazychev 
<artem.glazyc...@xored.com<mailto:artem.glazyc...@xored.com>>, vpp-dev 
<vpp-dev@lists.fd.io<mailto:vpp-dev@lists.fd.io>>
Subject: Re: [vpp-dev] Adding new route via ipv6 link-local
Neale,

I'm a bit confused... I had previously thought that *adding* an IPv6 address to 
a link *did* IPv6 enable it...

Ed

On Fri, Aug 20, 2021 at 9:20 AM Neale Ranns 
<ne...@graphiant.com<mailto:ne...@graphiant.com>> wrote:
Hi Artem, Stanislav,

I agree graceful handling is needed, return false if there is no link local.

If you enabled ip6 on the link first, this wouldn’t be a problem. The link will 
need to be ip6 enabled if you want something to reply.

/neale


From: vpp-dev@lists.fd.io<mailto:vpp-dev@lists.fd.io> 
<vpp-dev@lists.fd.io<mailto:vpp-dev@lists.fd.io>> on behalf of Stanislav Zaikin 
via lists.fd.io<http://lists.fd.io> 
<zstaseg=gmail....@lists.fd.io<mailto:gmail....@lists.fd.io>>
Date: Friday, 20 August 2021 at 16:10
To: Artem Glazychev 
<artem.glazyc...@xored.com<mailto:artem.glazyc...@xored.com>>
Cc: vpp-dev <vpp-dev@lists.fd.io<mailto:vpp-dev@lists.fd.io>>
Subject: Re: [vpp-dev] Adding new route via ipv6 link-local
Hello Artem,

Looks like we need (at least) to add a check for nullptr.

DBGvpp# create tap
tap0
DBGvpp# set interface state tap0 up
DBGvpp# ip route add fa::1/120 via fe80::1 tap0

Thread 1 "vpp_main" received signal SIGSEGV, Segmentation fault.
0x00007ffff774ba90 in ip6_address_copy (dst=0x7fffaf487aa0, src=0x0) at 
/home/zstas/vpp/src/vnet/ip/ip6_packet.h:129
129  dst->as_u64[0] = src->as_u64[0];
(gdb) bt
#0  0x00007ffff774ba90 in ip6_address_copy (dst=0x7fffaf487aa0, src=0x0) at 
/home/zstas/vpp/src/vnet/ip/ip6_packet.h:129
#1  0x00007ffff774b892 in fib_sas6_get (sw_if_index=1, dst=0x7fffb91b4e50, 
src=0x7fffaf487aa0) at /home/zstas/vpp/src/vnet/fib/fib_sas.c:105

On Fri, 20 Aug 2021 at 15:20, Artem Glazychev 
<artem.glazyc...@xored.com<mailto:artem.glazyc...@xored.com>> wrote:

Hello,

Found a crash: if we add the route via fe80:: after the interface upping - vpp 
crashes.

For example:

DBGvpp# create tap

tap0

DBGvpp# set int state tap0 up

DBGvpp# ip route add fa::1/120 via fe80::1 tap0

make: *** [Makefile:537: run] Aborted



If we swap set ... up and ip route ... - no crashes.

Could you please explain me if such a situation is possible at all?
In any case, I believe that vpp should not crash.

Thanks.



--
Best regards
Stanislav Zaikin


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