From: "Chuck Lever" Subject: Re: [PATCH 04/14] text-based mount command: get_client_address support for IPv6 Date: Thu, 10 Jul 2008 16:35:57 -0400 Message-ID: <76bd70e30807101335y54f8b479v39953a772e08e88c@mail.gmail.com> References: <20080710001725.6137.83845.stgit@tarkus.1015granger.net> <20080710003723.6137.51761.stgit@tarkus.1015granger.net> <20080710193008.GA27734@fieldses.org> <5E74A13F-4A79-4356-8BBE-7B535F00EA66@oracle.com> <20080710194310.GC27734@fieldses.org> Reply-To: chucklever@gmail.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: steved@redhat.com, linux-nfs@vger.kernel.org To: "J. Bruce Fields" Return-path: Received: from mu-out-0910.google.com ([209.85.134.184]:30058 "EHLO mu-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757192AbYGJUgA (ORCPT ); Thu, 10 Jul 2008 16:36:00 -0400 Received: by mu-out-0910.google.com with SMTP id w8so1118572mue.1 for ; Thu, 10 Jul 2008 13:35:57 -0700 (PDT) In-Reply-To: <20080710194310.GC27734@fieldses.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, Jul 10, 2008 at 3:43 PM, J. Bruce Fields wrote: > On Thu, Jul 10, 2008 at 03:36:21PM -0400, Chuck Lever wrote: >> On Jul 10, 2008, at 3:30 PM, J. Bruce Fields wrote: >>> On Wed, Jul 09, 2008 at 08:37:24PM -0400, Chuck Lever wrote: >>>> Introduce IPv6-enabled version of get_client_address. The legacy >>>> mount >>>> command could use this eventually as well. >>>> >>>> I don't remember how to tell an NFSv4 server to disable the callback >>>> channel: whether an ANY address is passed with SETCLIENTID, or a >>>> loopback address is passed. The patch allows either to be used with >>>> a >>>> compile-time switch. >>> >>> I would have thought INADDR_ANY. But in any case we should just pick >>> one.... >> >> Well, yes, but we should pick the "correct" one. :-) The patch does it >> this way just to make a note of this issue so we can make a decision >> before committing this upstream. >> >> Does RFC 3530 have any recommendation about this? > > Not that I can find on a quick skim. Is it clarified in the NFSv4.1 draft? > I don't see why the spec would forbid running over loopback, though, in > which case a loopback callback address would make sense. And I assume > INADDR_ANY is always meaningless as a destination address, so is a > logical way to tell the server it can't call back to you. Yep, I agree. I recall a few years back at a CITI bake-a-thon there was a certain server vendor who had trouble with loopback callback addresses, probably because their implementation was server-only, so an NFSv4 callback from loopback would make no sense for them. The client in this case was sending a loopback callback address because it hadn't implemented a callback service and wanted to prevent the server from calling it back. Do we have a high degree of certainty that sending an ANY address is appropriate if the client can't determine a reasonable callback address to send with SETCLIENTID? Is it at least OK for Linux's NFSv4 server? If we think this might be a problem, I can change all this back to simply failing the mount request when the mount.nfs command can't figure out a valid callback address. >>>> >>>> Signed-off-by: Chuck Lever >>>> --- >>>> >>>> utils/mount/network.c | 122 +++++++++++++++++++++++++++++++++++++++ >>>> ++++++++++ >>>> utils/mount/network.h | 2 + >>>> 2 files changed, 124 insertions(+), 0 deletions(-) >>>> >>>> diff --git a/utils/mount/network.c b/utils/mount/network.c >>>> index 3f2721b..128d7f7 100644 >>>> --- a/utils/mount/network.c >>>> +++ b/utils/mount/network.c >>>> @@ -918,3 +918,125 @@ int get_client_address(struct sockaddr_in >>>> *saddr, struct sockaddr_in *caddr) >>>> } >>>> return 1; >>>> } >>>> + >>>> +/* >>>> + * Try a getsockname() on a connected datagram socket. >>>> + * >>>> + * Returns 1 and fills in @buf if successful; otherwise, zero. >>>> + * >>>> + * A connected datagram socket prevents leaving a socket in >>>> TIME_WAIT. >>>> + * This conserves the ephemeral port number space, helping reduce >>>> failed >>>> + * socket binds during mount storms. >>>> + */ >>>> +static int nfs_ca_sockname(const struct sockaddr *sap, const >>>> socklen_t salen, >>>> + struct sockaddr *buf, socklen_t *buflen) >>>> +{ >>>> + struct sockaddr_in sin = { >>>> + .sin_family = AF_INET, >>>> + .sin_addr.s_addr = htonl(INADDR_ANY), >>>> + }; >>>> + struct sockaddr_in6 sin6 = { >>>> + .sin6_family = AF_INET6, >>>> + .sin6_addr = IN6ADDR_ANY_INIT, >>>> + }; >>>> + int sock; >>>> + >>>> + sock = socket(sap->sa_family, SOCK_DGRAM, IPPROTO_UDP); >>>> + if (sock < 0) >>>> + return 0; >>>> + >>>> + switch (sap->sa_family) { >>>> + case AF_INET: >>>> + if (bind(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0) { >>>> + close(sock); >>>> + return 0; >>>> + } >>>> + break; >>>> + case AF_INET6: >>>> + if (bind(sock, (struct sockaddr *)&sin6, sizeof(sin6)) < 0) { >>>> + close(sock); >>>> + return 0; >>>> + } >>>> + break; >>>> + default: >>>> + errno = EAFNOSUPPORT; >>>> + return 0; >>>> + } >>>> + >>>> + if (connect(sock, sap, salen) < 0) { >>>> + close(sock); >>>> + return 0; >>>> + } >>>> + >>>> + return !getsockname(sock, buf, buflen); >>>> +} >>>> + >>>> +/* >>>> + * Try to generate an address that prevents the server from calling >>>> us. >>>> + * >>>> + * Returns 1 and fills in @buf if successful; otherwise, zero. >>>> + */ >>>> +static int nfs_ca_gai(const struct sockaddr *sap, const socklen_t >>>> salen, >>>> + struct sockaddr *buf, socklen_t *buflen) >>>> +{ >>>> + struct addrinfo *gai_results; >>>> + struct addrinfo gai_hint = { >>>> + .ai_family = sap->sa_family, >>>> +#ifdef GENERATE_LOOPBACK_ADDRESS >>>> + .ai_flags = 0, /* loopback */ >>>> +#else >>>> + .ai_flags = AI_PASSIVE, /* ANYADDR */ >>>> +#endif >>>> + }; >>>> + >>>> + if (getaddrinfo(NULL, "", &gai_hint, &gai_results)) >>>> + return 0; >>>> + >>>> + *buflen = gai_results->ai_addrlen; >>>> + memcpy(buf, gai_results->ai_addr, *buflen); >>>> + >>>> + freeaddrinfo(gai_results); >>>> + >>>> + return 1; >>>> +} >>>> + >>>> +/** >>>> + * nfs_callback_address - acquire our local network address >>>> + * @sap: pointer to address of remote >>>> + * @sap_len: length of address >>>> + * @buf: pointer to buffer to be filled in with local network >>>> address >>>> + * @buflen: IN: length of buffer to fill in; OUT: length of filled- >>>> in address >>>> + * >>>> + * Discover a network address that an NFSv4 server can use to call >>>> us back. >>>> + * On multi-homed clients, this address depends on which NIC we use >>>> to >>>> + * route requests to the server. >>>> + * >>>> + * Returns 1 and fills in @buf if an unambiguous local address is >>>> + * available; returns 1 and fills in an appropriate ANYADDR address >>>> + * if a local address isn't available; otherwise, returns zero. >>>> + */ >>>> +int nfs_callback_address(const struct sockaddr *sap, const >>>> socklen_t salen, >>>> + struct sockaddr *buf, socklen_t *buflen) >>>> +{ >>>> + struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)buf; >>>> + >>>> + if (nfs_ca_sockname(sap, salen, buf, buflen) == 0) >>>> + if (nfs_ca_gai(sap, salen, buf, buflen) == 0) >>>> + goto out_failed; >>>> + >>>> + /* >>>> + * The server can't use an interface ID that was generated >>>> + * here on the client, so always clear sin6_scope_id. >>>> + */ >>>> + if (sin6->sin6_family == AF_INET6) >>>> + sin6->sin6_scope_id = 0; >>>> + >>>> + return 1; >>>> + >>>> +out_failed: >>>> + *buflen = 0; >>>> + if (verbose) >>>> + nfs_error(_("%s: failed to construct callback address")); >>>> + return 0; >>>> + >>>> +} >>>> diff --git a/utils/mount/network.h b/utils/mount/network.h >>>> index 8da7e20..2f4ff3a 100644 >>>> --- a/utils/mount/network.h >>>> +++ b/utils/mount/network.h >>>> @@ -58,6 +58,8 @@ int nfs_string_to_sockaddr(const char *, const >>>> size_t, >>>> int nfs_present_sockaddr(const struct sockaddr *, >>>> const socklen_t, char *, const size_t); >>>> int get_client_address(struct sockaddr_in *, struct sockaddr_in *); >>>> +int nfs_callback_address(const struct sockaddr *, const socklen_t, >>>> + struct sockaddr *, socklen_t *); >>>> int nfs_call_umount(clnt_addr_t *, dirpath *); >>>> int clnt_ping(struct sockaddr_in *, const unsigned long, >>>> const unsigned long, const unsigned int, >>>> -- Chuck Lever