netdev - Re: IPv6 source based policy routing query

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Date:   Mon, 8 Jan 2018 16:17:41 +0530
From:   sundeep subbaraya <sundeep.lkml@...il.com>
To:     linux-net@...r.kernel.org, netdev@...r.kernel.org,
        David Miller <davem@...emloft.net>
Subject: Re: IPv6 source based policy routing query

Hi David,

Please let me know any other mailing list or persons I need to add.

Thanks,
Sundeep

On Fri, Jan 5, 2018 at 12:07 PM, sundeep subbaraya
<sundeep.lkml@...il.com> wrote:
> Hi,
>
> I am quite new to IPv6.
> I ran to one problem hope you guys can help me.
> I have multiple ethernet port box which runs by Altera's Cyclone 5.
> I am using source based policy routing for ipv6.
> The problem is when there is "default via <gateway>" entry in per interface
> routing table then ping to a link local address of directly connected PC from
> that interface fails.
>
> # ip -6 rule
> 0:      from all lookup local
> 16383:  from all oif eth2 lookup eth2
> 16383:  from 2001::200 lookup eth2
> 32766:  from all lookup main
>
> # ip -6 route show table eth2
> 2001::/64 dev eth2  src 2001::200  metric 1024  pref medium
> default via 2001::5 dev eth2  metric 1024  pref medium
>
> # ping6 fe80::21b:cdff:fe03:1357 -I eth2
> PING fe80::21b:cdff:fe03:1357(fe80::21b:cdff:fe03:1357) from
> fe80::2b0:aeff:fe03:7c1c eth2: 56 data bytes
> From fe80::2b0:aeff:fe03:7c1c icmp_seq=1 Destination unreachable:
> Address unreachable
> From fe80::2b0:aeff:fe03:7c1c icmp_seq=2 Destination unreachable:
> Address unreachable
> From fe80::2b0:aeff:fe03:7c1c icmp_seq=3 Destination unreachable:
> Address unreachable
> ^C
> --- fe80::21b:cdff:fe03:1357 ping statistics ---
> 5 packets transmitted, 0 received, +3 errors, 100% packet loss, time 4007ms
>
> # ip -6 route del default dev eth2 table eth2
> # ping6 fe80::21b:cdff:fe03:1357 -I eth2
> PING fe80::21b:cdff:fe03:1357(fe80::21b:cdff:fe03:1357) from
> fe80::2b0:aeff:fe03:7c1c eth2: 56 data bytes
> 64 bytes from fe80::21b:cdff:fe03:1357: icmp_seq=1 ttl=64 time=0.285 ms
> 64 bytes from fe80::21b:cdff:fe03:1357: icmp_seq=2 ttl=64 time=1.73 ms
> 64 bytes from fe80::21b:cdff:fe03:1357: icmp_seq=3 ttl=64 time=1.75 ms
> ^C
> --- fe80::21b:cdff:fe03:1357 ping statistics ---
> 3 packets transmitted, 3 received, 0% packet loss, time 2001ms
> rtt min/avg/max/mdev = 0.285/1.258/1.755/0.688 ms
>
> From Wireshark captures, though I ping link local first Neighbor
> solicitation for default
> gateway ip 2001::5 goes on wire. Since that gateway is not present
> ping does not work.
> If gateway is present and reply with Neighbor Advertisement then echo
> request and replies with
> link local happens properly after that.
> Why does Neighbor Solicitation for default gateway happens though we
> ping link local address ?
> I assume link local ping should work despite of unavailable default gateway.
> Please correct me if am wrong. Also let me know how to change this behavior.
>
> I am using 4.1.22-ltsi kernel.
>
> Thanks,
> Sundeep