dns: Allow the dns resolver to retrieve a server set

[linux-2.6-block.git] / net / dns_resolver / dns_key.c

diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 7f4534828f6c96c0b0fe99d54add4ce9be0c1877..a65d553e730d9130d0fe26d896aa2cffcc5aaae1 100644 (file)
--- 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;