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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💯: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). The problem is that ip6_dst_lookup_neigh() uses the rt6i_gateway, which is :: because the associated route is a connected route, thus it uses the dst addr of the packet. Let's use rt6_nexthop() to choose the right nh. Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.