From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xin Long Date: Tue, 23 Jun 2020 10:13:30 +0000 Subject: Re: Strange problem with SCTP+IPv6 Message-Id: List-Id: References: <20200621155604.GA23135@minyard.net> <20200622165759.GA3235@minyard.net> <4B68D06C-00F4-42C3-804A-B5531AABCE21@lurchi.franken.de> <20200622183253.GQ2491@localhost.localdomain> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Michael Tuexen Cc: Marcelo Ricardo Leitner , minyard@acm.org, Vlad Yasevich , Neil Horman , linux-sctp@vger.kernel.org, LKML On Tue, Jun 23, 2020 at 2:34 AM Michael Tuexen wrote: > > > On 22. Jun 2020, at 20:32, Marcelo Ricardo Leitner wrote: > > > > On Mon, Jun 22, 2020 at 08:01:24PM +0200, Michael Tuexen wrote: > >>> On 22. Jun 2020, at 18:57, Corey Minyard wrote: > >>> > >>> On Mon, Jun 22, 2020 at 08:01:23PM +0800, Xin Long wrote: > >>>> On Sun, Jun 21, 2020 at 11:56 PM Corey Minyard wrote: > >>>>> > >>>>> I've stumbled upon a strange problem with SCTP and IPv6. If I create an > >>>>> sctp listening socket on :: and set the IPV6_V6ONLY socket option on it, > >>>>> then I make a connection to it using ::1, the connection will drop after > >>>>> 2.5 seconds with an ECONNRESET error. > >>>>> > >>>>> It only happens on SCTP, it doesn't have the issue if you connect to a > >>>>> full IPv6 address instead of ::1, and it doesn't happen if you don't > >>>>> set IPV6_V6ONLY. I have verified current end of tree kernel.org. > >>>>> I tried on an ARM system and x86_64. > >>>>> > >>>>> I haven't dug into the kernel to see if I could find anything yet, but I > >>>>> thought I would go ahead and report it. I am attaching a reproducer. > >>>>> Basically, compile the following code: > >>>> The code only set IPV6_V6ONLY on server side, so the client side will > >>>> still bind all the local ipv4 addresses (as you didn't call bind() to > >>>> bind any specific addresses ). Then after the connection is created, > >>>> the client will send HB on the v4 paths to the server. The server > >>>> will abort the connection, as it can't support v4. > >>>> > >>>> So you can work around it by either: > >>>> > >>>> - set IPV6_V6ONLY on client side. > >>>> > >>>> or > >>>> > >>>> - bind to the specific v6 addresses on the client side. > >>>> > >>>> I don't see RFC said something about this. > >>>> So it may not be a good idea to change the current behaviour > >>>> to not establish the connection in this case, which may cause regression. > >>> > >>> Ok, I understand this. It's a little strange, but I see why it works > >>> this way. > >> I don't. I would expect it to work as I described in my email. > >> Could someone explain me how and why it is behaving different from > >> my expectation? > > > > It looks like a bug to me. Testing with this test app here, I can see > > the INIT_ACK being sent with a bunch of ipv4 addresses in it and > > that's unexpected for a v6only socket. As is, it's the server saying > > "I'm available at these other addresses too, but not." > I agree. Then we need a fix in sctp_bind_addrs_to_raw(): @@ -238,6 +240,9 @@ union sctp_params sctp_bind_addrs_to_raw(const struct sctp_bind_addr *bp, addrparms = retval; list_for_each_entry(addr, &bp->address_list, list) { + if ((PF_INET6 = sk->sk_family) && inet_v6_ipv6only(sk) && + (AF_INET = addr->a.sa.sa_family)) + continue; af = sctp_get_af_specific(addr->a.v4.sin_family); len = af->to_addr_param(&addr->a, &rawaddr); memcpy(addrparms.v, &rawaddr, len); > > Best regards > Michael > > > > Thanks, > > Marcelo > > > >> > >> Best regards > >> Michael > >>> > >>> Thanks, > >>> > >>> -corey > >>> > >>>> > >>>>> > >>>>> gcc -g -o sctptest -Wall sctptest.c > >>>>> > >>>>> and run it in one window as a server: > >>>>> > >>>>> ./sctptest a > >>>>> > >>>>> (Pass in any option to be the server) and run the following in another > >>>>> window as the client: > >>>>> > >>>>> ./sctptest > >>>>> > >>>>> It disconnects after about 2.5 seconds. If it works, it should just sit > >>>>> there forever. > >>>>> > >>>>> -corey > >>>>> > >>>>> > >>>>> #include > >>>>> #include > >>>>> #include > >>>>> #include > >>>>> #include > >>>>> #include > >>>>> #include > >>>>> #include > >>>>> #include > >>>>> #include > >>>>> #include > >>>>> > >>>>> static int > >>>>> getaddr(const char *addr, const char *port, bool listen, > >>>>> struct addrinfo **rai) > >>>>> { > >>>>> struct addrinfo *ai, hints; > >>>>> > >>>>> memset(&hints, 0, sizeof(hints)); > >>>>> hints.ai_flags = AI_ADDRCONFIG; > >>>>> if (listen) > >>>>> hints.ai_flags |= AI_PASSIVE; > >>>>> hints.ai_family = AF_UNSPEC; > >>>>> hints.ai_socktype = SOCK_STREAM; > >>>>> hints.ai_protocol = IPPROTO_SCTP; > >>>>> if (getaddrinfo(addr, port, &hints, &ai)) { > >>>>> perror("getaddrinfo"); > >>>>> return -1; > >>>>> } > >>>>> > >>>>> *rai = ai; > >>>>> return 0; > >>>>> } > >>>>> > >>>>> static int > >>>>> waitread(int s) > >>>>> { > >>>>> char data[1]; > >>>>> ssize_t rv; > >>>>> > >>>>> rv = read(s, data, sizeof(data)); > >>>>> if (rv = -1) { > >>>>> perror("read"); > >>>>> return -1; > >>>>> } > >>>>> printf("Read %d bytes\n", (int) rv); > >>>>> return 0; > >>>>> } > >>>>> > >>>>> static int > >>>>> do_server(void) > >>>>> { > >>>>> int err, ls, s, optval; > >>>>> struct addrinfo *ai; > >>>>> > >>>>> printf("Server\n"); > >>>>> > >>>>> err = getaddr("::", "3023", true, &ai); > >>>>> if (err) > >>>>> return err; > >>>>> > >>>>> ls = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); > >>>>> if (ls = -1) { > >>>>> perror("socket"); > >>>>> return -1; > >>>>> } > >>>>> > >>>>> optval = 1; > >>>>> if (setsockopt(ls, SOL_SOCKET, SO_REUSEADDR, > >>>>> (void *)&optval, sizeof(optval)) = -1) { > >>>>> perror("setsockopt reuseaddr"); > >>>>> return -1; > >>>>> } > >>>>> > >>>>> /* Comment this out and it will work. */ > >>>>> if (setsockopt(ls, IPPROTO_IPV6, IPV6_V6ONLY, &optval, > >>>>> sizeof(optval)) = -1) { > >>>>> perror("setsockopt ipv6 only"); > >>>>> return -1; > >>>>> } > >>>>> > >>>>> err = bind(ls, ai->ai_addr, ai->ai_addrlen); > >>>>> if (err = -1) { > >>>>> perror("bind"); > >>>>> return -1; > >>>>> } > >>>>> > >>>>> err = listen(ls, 5); > >>>>> if (err = -1) { > >>>>> perror("listen"); > >>>>> return -1; > >>>>> } > >>>>> > >>>>> s = accept(ls, NULL, NULL); > >>>>> if (s = -1) { > >>>>> perror("accept"); > >>>>> return -1; > >>>>> } > >>>>> > >>>>> close(ls); > >>>>> > >>>>> err = waitread(s); > >>>>> close(s); > >>>>> return err; > >>>>> } > >>>>> > >>>>> static int > >>>>> do_client(void) > >>>>> { > >>>>> int err, s; > >>>>> struct addrinfo *ai; > >>>>> > >>>>> printf("Client\n"); > >>>>> > >>>>> err = getaddr("::1", "3023", false, &ai); > >>>>> if (err) > >>>>> return err; > >>>>> > >>>>> s = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); > >>>>> if (s = -1) { > >>>>> perror("socket"); > >>>>> return -1; > >>>>> } > >>>>> > >>>>> err = connect(s, ai->ai_addr, ai->ai_addrlen); > >>>>> if (err = -1) { > >>>>> perror("connect"); > >>>>> return -1; > >>>>> } > >>>>> > >>>>> err = waitread(s); > >>>>> close(s); > >>>>> return err; > >>>>> } > >>>>> > >>>>> int > >>>>> main(int argc, char *argv[]) > >>>>> { > >>>>> int err; > >>>>> > >>>>> if (argc > 1) > >>>>> err = do_server(); > >>>>> else > >>>>> err = do_client(); > >>>>> return !!err; > >>>>> } > >>>>> > >> >