From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:47666 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727358AbeIMVTN (ORCPT ); Thu, 13 Sep 2018 17:19:13 -0400 Subject: [PATCH 1/6] dns: Allow the dns resolver to retrieve a server set From: David Howells To: viro@zeniv.linux.org.uk Cc: dhowells@redhat.com, linux-afs@lists.infradead.org, keyrings@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 13 Sep 2018 17:09:01 +0100 Message-ID: <153685494161.16086.536892492442787707.stgit@warthog.procyon.org.uk> In-Reply-To: <153685493441.16086.3483582787020297039.stgit@warthog.procyon.org.uk> References: <153685493441.16086.3483582787020297039.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Allow the DNS resolver to retrieve a set of servers and their associated addresses, ports, preference and weight ratings. In terms of communication with userspace, "srv=1" is added to the callout string (the '1' indicating the maximum data version supported by the kernel) to ask the userspace side for this. If the userspace side doesn't recognise it, it will ignore the option and return the usual text address list. If the userspace side does recognise it, it will return some binary data that begins with a zero byte that would cause the string parsers to give an error. The second byte contains the version of the data in the blob (this may be between 1 and the version specified in the callout data). The remainder of the payload is version-specific. In version 1, the payload looks like (note that this is packed): u8 Non-string marker (ie. 0) u8 Content (0 => Server list) u8 Version (ie. 1) u8 Number of servers foreach-server { u16 Name length (LE) u16 Priority (as per SRV record) (LE) u16 Weight (as per SRV record) (LE) u16 Port (LE) u8 Protocol (IPPROTO_*) u8 Number of addresses char[] Name (not NUL-terminated) foreach-address { u8 Family (AF_INET{,6}) union { u8[4] ipv4_addr u8[16] ipv6_addr } } } This can then be used to fetch a whole cell's configuration for AFS, for example. Signed-off-by: David Howells --- net/dns_resolver/dns_key.c | 61 ++++++++++++++++++++++++++++++++++++++++-- net/dns_resolver/dns_query.c | 5 +-- 2 files changed, 59 insertions(+), 7 deletions(-) diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c index 7f4534828f6c..ac3c9aa75727 100644 --- a/net/dns_resolver/dns_key.c +++ b/net/dns_resolver/dns_key.c @@ -48,14 +48,40 @@ const struct cred *dns_resolver_cache; /* * Preparse instantiation data for a dns_resolver key. * - * The data must be a NUL-terminated string, with the NUL char accounted in - * datalen. + * For normal hostname lookups, the data must be a NUL-terminated string, with + * the NUL char accounted in datalen. * * If the data contains a '#' characters, then we take the clause after each * one to be an option of the form 'key=value'. The actual data of interest is * the string leading up to the first '#'. For instance: * * "ip1,ip2,...#foo=bar" + * + * For server list requests, the data must begin with a NUL char and be + * followed by a byte indicating the version of the data format. Version 1 + * looks something like (note this is packed): + * + * u8 Non-string marker (ie. 0) + * u8 Content (0 is server list) + * u8 Version (ie. 1) + * u8 Number of servers + * foreach-server { + * u16 Name length (LE) + * u16 Priority (as per SRV record, low first) (LE) + * u16 Weight (as per SRV record, higher first) (LE) + * u16 Port (LE) + * u8 Protocol (IPPROTO_*) + * u8 Number of addresses + * char[] Name (not NUL-terminated) + * foreach-address { + * u8 Family (AF_INET{,6}) + * union { + * u8[4] ipv4_addr + * u8[16] ipv6_addr + * } + * } + * } + * */ static int dns_resolver_preparse(struct key_preparsed_payload *prep) @@ -66,9 +92,37 @@ dns_resolver_preparse(struct key_preparsed_payload *prep) int datalen = prep->datalen, result_len = 0; const char *data = prep->data, *end, *opt; + if (datalen <= 1 || !data) + return -EINVAL; + + if (data[0] == 0) { + /* It may be a server list. */ + if (datalen <= 3) + return -EINVAL; + + data++; + kenter("[%u,%u],%u", data[0], data[1], datalen); + if (data[0] != 0) { + pr_warn_ratelimited( + "dns_resolver: Unsupported result type (%u)\n", + (unsigned char)data[0]); + return -EINVAL; + } + + if (data[1] != 1) { + pr_warn_ratelimited( + "dns_resolver: Unsupported server list version (%u)\n", + (unsigned char)data[1]); + return -EINVAL; + } + + result_len = datalen - 1; + goto store_result; + } + kenter("'%*.*s',%u", datalen, datalen, data, datalen); - if (datalen <= 1 || !data || data[datalen - 1] != '\0') + if (!data || data[datalen - 1] != '\0') return -EINVAL; datalen--; @@ -144,6 +198,7 @@ dns_resolver_preparse(struct key_preparsed_payload *prep) return 0; } +store_result: kdebug("store result"); prep->quotalen = result_len; diff --git a/net/dns_resolver/dns_query.c b/net/dns_resolver/dns_query.c index 49da67034f29..76338c38738a 100644 --- a/net/dns_resolver/dns_query.c +++ b/net/dns_resolver/dns_query.c @@ -148,12 +148,9 @@ int dns_query(const char *type, const char *name, size_t namelen, if (_result) { ret = -ENOMEM; - *_result = kmalloc(len + 1, GFP_KERNEL); + *_result = kmemdup_nul(upayload->data, len, GFP_KERNEL); if (!*_result) goto put; - - memcpy(*_result, upayload->data, len); - (*_result)[len] = '\0'; } if (_expiry)