Le 20/06/2019 à 17:12, David Ahern a écrit :
> 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.
>
The test in done on the dut:
+-----+ +------+ +------+ +-----+
| tnl | | dut |.1 .2|router| | tnr |
| | | 2+-------------+2 | | |
| |.1 .2| |fd00:125::/64| |.2 .1| |
| 1+-------------+1 | | 1+-------------+1 |
| |fd00:100::/64| | | |fd00:200::/64| |
| | | |.1 .2| | | |
| | | 3+-------------+3 | | |
| | | |fd00:175::/64| | | |
+-----+ +------+ +------+ +-----+
On dut:
ip address add fd00:100::2/64 dev ntfp1
ip address add fd00:125::1/64 dev ntfp2
ip address add fd00:175::1/64 dev ntfp3
ip route add fd00:200::/64 via fd00:125::2
ip route add fd00:200::/120 nexthop via fd00:125::2 nexthop via fd00:175::2
Note that fd00:200::fa is not reachable but we expect to see the packet on the
host 'router'.
