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authorDavid Howells <dhowells@redhat.com>2018-10-04 14:27:55 +0100
committerDavid S. Miller <davem@davemloft.net>2018-10-04 09:40:52 -0700
commitbbb4c4323a4d9cb5ca04db904aa3050a7586839a (patch)
tree7737c6f82a31650e7d282f94a227cdea167599dc /net/dns_resolver
parent0aa63eb9a904d50527cc5eadb061d16e607dd4c6 (diff)
dns: Allow the dns resolver to retrieve a server set
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 Source (eg. DNS_RECORD_FROM_DNS_SRV) u8 Status (eg. DNS_LOOKUP_GOOD) 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 Source (eg. DNS_RECORD_FROM_NSS) u8 Status (eg. DNS_LOOKUP_GOT_NOT_FOUND) u8 Protocol (eg. DNS_SERVER_PROTOCOL_UDP) 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 VL-server configuration for AFS, for example. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/dns_resolver')
-rw-r--r--net/dns_resolver/dns_key.c67
-rw-r--r--net/dns_resolver/dns_query.c5
2 files changed, 65 insertions, 7 deletions
diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 7f4534828f6c..a65d553e730d 100644
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -29,6 +29,7 @@
#include <linux/keyctl.h>
#include <linux/err.h>
#include <linux/seq_file.h>
+#include <linux/dns_resolver.h>
#include <keys/dns_resolver-type.h>
#include <keys/user-type.h>
#include "internal.h"
@@ -48,27 +49,86 @@ 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 (DNS_PAYLOAD_IS_*)
+ * u8 Version (e.g. 1)
+ * u8 Source of server list
+ * u8 Lookup status of server list
+ * u8 Number of servers
+ * foreach-server {
+ * __le16 Name length
+ * __le16 Priority (as per SRV record, low first)
+ * __le16 Weight (as per SRV record, higher first)
+ * __le16 Port
+ * u8 Source of address list
+ * u8 Lookup status of address list
+ * u8 Protocol (DNS_SERVER_PROTOCOL_*)
+ * u8 Number of addresses
+ * char[] Name (not NUL-terminated)
+ * foreach-address {
+ * u8 Family (DNS_ADDRESS_IS_*)
+ * union {
+ * u8[4] ipv4_addr
+ * u8[16] ipv6_addr
+ * }
+ * }
+ * }
+ *
*/
static int
dns_resolver_preparse(struct key_preparsed_payload *prep)
{
+ const struct dns_payload_header *bin;
struct user_key_payload *upayload;
unsigned long derrno;
int ret;
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 <= sizeof(*bin))
+ return -EINVAL;
+
+ bin = (const struct dns_payload_header *)data;
+ kenter("[%u,%u],%u", bin->content, bin->version, datalen);
+ if (bin->content != DNS_PAYLOAD_IS_SERVER_LIST) {
+ pr_warn_ratelimited(
+ "dns_resolver: Unsupported content type (%u)\n",
+ bin->content);
+ return -EINVAL;
+ }
+
+ if (bin->version != 1) {
+ pr_warn_ratelimited(
+ "dns_resolver: Unsupported server list version (%u)\n",
+ bin->version);
+ return -EINVAL;
+ }
+
+ result_len = datalen;
+ 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 +204,7 @@ 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)