[CIFS] Adds to dns_resolver checking if the server name is an IP addr and skipping upcall in this case.

Signed-off-by: Igor Mammedov <niallain@gmail.com>
Signed-off-by: sfrench@us.ibm.com

1 files changed, 52 insertions, 10 deletions

diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
index 7cc86c418182..939e256f8497 100644
--- a/fs/cifs/dns_resolve.c
+++ b/fs/cifs/dns_resolve.c
@@ -55,6 +55,32 @@ struct key_type key_type_dns_resolver = {
         .match       = user_match,
 };
 
+/* Checks if supplied name is IP address
+ * returns:
+ *              1 - name is IP
+ *              0 - name is not IP
+ */
+static int is_ip(const char *name)
+{
+        int rc;
+        struct sockaddr_in sin_server;
+        struct sockaddr_in6 sin_server6;
+
+        rc = cifs_inet_pton(AF_INET, name,
+                        &sin_server.sin_addr.s_addr);
+
+        if (rc <= 0) {
+                /* not ipv4 address, try ipv6 */
+                rc = cifs_inet_pton(AF_INET6, name,
+                                &sin_server6.sin6_addr.in6_u);
+                if (rc > 0)
+                        return 1;
+        } else {
+                return 1;
+        }
+        /* we failed translating address */
+        return 0;
+}
 
 /* Resolves server name to ip address.
  * input:
@@ -67,8 +93,9 @@ int
 dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
 {
         int rc = -EAGAIN;
-        struct key *rkey;
+        struct key *rkey = ERR_PTR(-EAGAIN);
         char *name;
+        char *data = NULL;
         int len;
 
         if (!ip_addr || !unc)
@@ -97,26 +124,41 @@ dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
         memcpy(name, unc+2, len);
         name[len] = 0;
 
+        if (is_ip(name)) {
+                cFYI(1, ("%s: it is IP, skipping dns upcall: %s",
+                                        __func__, name));
+                data = name;
+                goto skip_upcall;
+        }
+
         rkey = request_key(&key_type_dns_resolver, name, "");
         if (!IS_ERR(rkey)) {
-                len = strlen(rkey->payload.data);
-                *ip_addr = kmalloc(len+1, GFP_KERNEL);
-                if (*ip_addr) {
-                        memcpy(*ip_addr, rkey->payload.data, len);
-                        (*ip_addr)[len] = '\0';
-                        cFYI(1, ("%s: resolved: %s to %s", __func__,
+                data = rkey->payload.data;
+                cFYI(1, ("%s: resolved: %s to %s", __func__,
                                         rkey->description,
                                         *ip_addr
                                 ));
+        } else {
+                cERROR(1, ("%s: unable to resolve: %s", __func__, name));
+                goto out;
+        }
+
+skip_upcall:
+        if (data) {
+                len = strlen(data);
+                *ip_addr = kmalloc(len+1, GFP_KERNEL);
+                if (*ip_addr) {
+                        memcpy(*ip_addr, data, len);
+                        (*ip_addr)[len] = '\0';
                         rc = 0;
                 } else {
                         rc = -ENOMEM;
                 }
-                key_put(rkey);
-        } else {
-                cERROR(1, ("%s: unable to resolve: %s", __func__, name));
+                if (!IS_ERR(rkey))
+                        key_put(rkey);
         }
 
+out:
         kfree(name);
         return rc;
 }