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Martin KaFai Lau
456add4c9b
[ Upstream commit7ece54a60e] If a sk_v6_rcv_saddr is !IPV6_ADDR_ANY and !IPV6_ADDR_MAPPED, it implicitly implies it is an ipv6only socket. However, in inet6_bind(), this addr_type checking and setting sk->sk_ipv6only to 1 are only done after sk->sk_prot->get_port(sk, snum) has been completed successfully. This inconsistency between sk_v6_rcv_saddr and sk_ipv6only confuses the 'get_port()'. In particular, when binding SO_REUSEPORT UDP sockets, udp_reuseport_add_sock(sk,...) is called. udp_reuseport_add_sock() checks "ipv6_only_sock(sk2) == ipv6_only_sock(sk)" before adding sk to sk2->sk_reuseport_cb. In this case, ipv6_only_sock(sk2) could be 1 while ipv6_only_sock(sk) is still 0 here. The end result is, reuseport_alloc(sk) is called instead of adding sk to the existing sk2->sk_reuseport_cb. It can be reproduced by binding two SO_REUSEPORT UDP sockets on an IPv6 address (!ANY and !MAPPED). Only one of the socket will receive packet. The fix is to set the implicit sk_ipv6only before calling get_port(). The original sk_ipv6only has to be saved such that it can be restored in case get_port() failed. The situation is similar to the inet_reset_saddr(sk) after get_port() has failed. Thanks to Calvin Owens <calvinowens@fb.com> who created an easy reproduction which leads to a fix. Fixes:e32ea7e747("soreuseport: fast reuseport UDP socket selection") Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.