netdev - Re: [PATCH net] ipv6: fix neighbour resolution with raw socket

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Date:   Thu, 20 Jun 2019 09:12:04 -0600
From:   David Ahern <dsahern@...il.com>
To:     Nicolas Dichtel <nicolas.dichtel@...nd.com>, davem@...emloft.net
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net] ipv6: fix neighbour resolution with raw socket

On 6/20/19 6:34 AM, Nicolas Dichtel wrote:
> The scenario is the following: the user uses a raw socket to send an ipv6
> packet, destinated to a not-connected network, and specify a connected nh.
> Here is the corresponding python script to reproduce this scenario:
> 
>  import socket
>  IPPROTO_RAW = 255
>  send_s = socket.socket(socket.AF_INET6, socket.SOCK_RAW, IPPROTO_RAW)
>  # scapy
>  # p = IPv6(src='fd00:100::1', dst='fd00:200::fa')/ICMPv6EchoRequest()
>  # str(p)
>  req = b'`\x00\x00\x00\x00\x08:@\xfd\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xfd\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xfa\x80\x00\x81\xc0\x00\x00\x00\x00'
>  send_s.sendto(req, ('fd00:175::2', 0, 0, 0))
> 
> fd00:175::/64 is a connected route and fd00:200::fa is not a connected
> host.
> 
> With this scenario, the kernel starts by sending a NS to resolve
> fd00:175::2. When it receives the NA, it flushes its queue and try to send
> the initial packet. But instead of sending it, it sends another NS to
> resolve fd00:200::fa, which obvioulsy fails, thus the packet is dropped. If
> the user sends again the packet, it now uses the right nh (fd00:175::2).
> 

what's the local address and route setup? You reference fd00:100::1 and
fd00:200::fa with connected route fd00:175::/64.