libsmb: reuse connections derived from DFS referrals

[MS-DFSC] 3.2.1.1 and 3.2.1.2 states that DFS targets with the same site
location or relative cost are placed in random order in a DFS referral
response.

libsmbclient currently resolves DFS referrals on every API call, always
using the first entry in the referral response. With random ordering,
libsmbclient may open a new server connection, rather than reuse an
existing (cached) connection established in a previous DFS referred API
call.

This change sees libsmbclient check the connection cache for any of the
DFS referral response entries before creating a new connection.

This change is based on a patch by Har Gagan Sahai
<SHarGagan@novell.com>.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=10123

Signed-off-by: David Disseldorp <ddiss@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
(cherry picked from commit 7b7d4f740fe5017107d3100041cc8c7982f0eac7)
[ddiss@samba.org: 4.0 rebase without smbXcli_tcon context]

diff --git a/source3/libsmb/clidfs.c b/source3/libsmb/clidfs.c
index b2e2e9ec2b085d85318a29815b39e0e6940c6fd4..93c964a4d02f37ef990a0ec5d4b3242da9ca1646 100644 (file)
--- a/source3/libsmb/clidfs.c
+++ b/source3/libsmb/clidfs.c
@@ -776,6 +776,11 @@ NTSTATUS cli_dfs_get_referral(TALLOC_CTX *ctx,
 
 /********************************************************************
 ********************************************************************/
+struct cli_dfs_path_split {
+       char *server;
+       char *share;
+       char *extrapath;
+};
 
 NTSTATUS cli_resolve_path(TALLOC_CTX *ctx,
                          const char *mountpt,
@@ -793,15 +798,16 @@ NTSTATUS cli_resolve_path(TALLOC_CTX *ctx,
        char *cleanpath = NULL;
        char *extrapath = NULL;
        int pathlen;
-       char *server = NULL;
-       char *share = NULL;
        struct cli_state *newcli = NULL;
+       struct cli_state *ccli = NULL;
+       int count = 0;
        char *newpath = NULL;
        char *newmount = NULL;
        char *ppath = NULL;
        SMB_STRUCT_STAT sbuf;
        uint32 attributes;
        NTSTATUS status;
+       struct cli_dfs_path_split *dfs_refs = NULL;
 
        if ( !rootcli || !path || !targetcli ) {
                return NT_STATUS_INVALID_PARAMETER;
@@ -885,26 +891,83 @@ NTSTATUS cli_resolve_path(TALLOC_CTX *ctx,
                return status;
        }
 
-       /* Just store the first referral for now. */
-
        if (!refs[0].dfspath) {
                return NT_STATUS_NOT_FOUND;
        }
-       if (!split_dfs_path(ctx, refs[0].dfspath, &server, &share,
-                           &extrapath)) {
-               return NT_STATUS_NOT_FOUND;
+
+       /*
+        * Bug#10123 - DFS referal entries can be provided in a random order,
+        * so check the connection cache for each item to avoid unnecessary
+        * reconnections.
+        */
+       dfs_refs = talloc_array(ctx, struct cli_dfs_path_split, num_refs);
+       if (dfs_refs == NULL) {
+               return NT_STATUS_NO_MEMORY;
+       }
+
+       for (count = 0; count < num_refs; count++) {
+               if (!split_dfs_path(dfs_refs, refs[count].dfspath,
+                                   &dfs_refs[count].server,
+                                   &dfs_refs[count].share,
+                                   &dfs_refs[count].extrapath)) {
+                       TALLOC_FREE(dfs_refs);
+                       return NT_STATUS_NOT_FOUND;
+               }
+
+               ccli = cli_cm_find(rootcli, dfs_refs[count].server,
+                                  dfs_refs[count].share);
+               if (ccli != NULL) {
+                       extrapath = dfs_refs[count].extrapath;
+                       *targetcli = ccli;
+                       break;
+               }
+       }
+
+       /*
+        * If no cached connection was found, then connect to the first live
+        * referral server in the list.
+        */
+       for (count = 0; (ccli == NULL) && (count < num_refs); count++) {
+               /* Connect to the target server & share */
+               status = cli_cm_connect(ctx, rootcli,
+                               dfs_refs[count].server,
+                               dfs_refs[count].share,
+                               dfs_auth_info,
+                               false,
+                               smb1cli_conn_encryption_on(rootcli->conn),
+                               smbXcli_conn_protocol(rootcli->conn),
+                               0,
+                               0x20,
+                               targetcli);
+               if (!NT_STATUS_IS_OK(status)) {
+                       d_printf("Unable to follow dfs referral [\\%s\\%s]\n",
+                                dfs_refs[count].server,
+                                dfs_refs[count].share);
+                       continue;
+               } else {
+                       extrapath = dfs_refs[count].extrapath;
+                       break;
+               }
+       }
+
+       /* No available referral server for the connection */
+       if (*targetcli == NULL) {
+               TALLOC_FREE(dfs_refs);
+               return status;
        }
 
        /* Make sure to recreate the original string including any wildcards. */
 
        dfs_path = cli_dfs_make_full_path(ctx, rootcli, path);
        if (!dfs_path) {
+               TALLOC_FREE(dfs_refs);
                return NT_STATUS_NO_MEMORY;
        }
        pathlen = strlen(dfs_path);
        consumed = MIN(pathlen, consumed);
        *pp_targetpath = talloc_strdup(ctx, &dfs_path[consumed]);
        if (!*pp_targetpath) {
+               TALLOC_FREE(dfs_refs);
                return NT_STATUS_NO_MEMORY;
        }
        dfs_path[consumed] = '\0';
@@ -915,23 +978,6 @@ NTSTATUS cli_resolve_path(TALLOC_CTX *ctx,
         * (in \server\share\path format).
         */
 
-       /* Open the connection to the target server & share */
-       status = cli_cm_open(ctx, rootcli,
-                            server,
-                            share,
-                            dfs_auth_info,
-                            false,
-                            smb1cli_conn_encryption_on(rootcli->conn),
-                            smbXcli_conn_protocol(rootcli->conn),
-                            0,
-                            0x20,
-                            targetcli);
-       if (!NT_STATUS_IS_OK(status)) {
-               d_printf("Unable to follow dfs referral [\\%s\\%s]\n",
-                       server, share );
-               return status;
-       }
-
        if (extrapath && strlen(extrapath) > 0) {
                /* EMC Celerra NAS version 5.6.50 (at least) doesn't appear to */
                /* put the trailing \ on the path, so to be save we put one in if needed */
@@ -947,6 +993,7 @@ NTSTATUS cli_resolve_path(TALLOC_CTX *ctx,
                                                  *pp_targetpath);
                }
                if (!*pp_targetpath) {
+                       TALLOC_FREE(dfs_refs);
                        return NT_STATUS_NO_MEMORY;
                }
        }
@@ -960,18 +1007,21 @@ NTSTATUS cli_resolve_path(TALLOC_CTX *ctx,
                d_printf("cli_resolve_path: "
                        "dfs_path (%s) not in correct format.\n",
                        dfs_path );
+               TALLOC_FREE(dfs_refs);
                return NT_STATUS_NOT_FOUND;
        }
 
        ppath++; /* Now pointing at start of server name. */
 
        if ((ppath = strchr_m( dfs_path, '\\' )) == NULL) {
+               TALLOC_FREE(dfs_refs);
                return NT_STATUS_NOT_FOUND;
        }
 
        ppath++; /* Now pointing at start of share name. */
 
        if ((ppath = strchr_m( ppath+1, '\\' )) == NULL) {
+               TALLOC_FREE(dfs_refs);
                return NT_STATUS_NOT_FOUND;
        }
 
@@ -979,6 +1029,7 @@ NTSTATUS cli_resolve_path(TALLOC_CTX *ctx,
 
        newmount = talloc_asprintf(ctx, "%s\\%s", mountpt, ppath );
        if (!newmount) {
+               TALLOC_FREE(dfs_refs);
                return NT_STATUS_NOT_FOUND;
        }
 
@@ -1003,6 +1054,7 @@ NTSTATUS cli_resolve_path(TALLOC_CTX *ctx,
                         */
                        *targetcli = newcli;
                        *pp_targetpath = newpath;
+                       TALLOC_FREE(dfs_refs);
                        return status;
                }
        }
@@ -1013,14 +1065,17 @@ NTSTATUS cli_resolve_path(TALLOC_CTX *ctx,
        if ((*targetcli)->dfsroot) {
                dfs_path = talloc_strdup(ctx, *pp_targetpath);
                if (!dfs_path) {
+                       TALLOC_FREE(dfs_refs);
                        return NT_STATUS_NO_MEMORY;
                }
                *pp_targetpath = cli_dfs_make_full_path(ctx, *targetcli, dfs_path);
                if (*pp_targetpath == NULL) {
+                       TALLOC_FREE(dfs_refs);
                        return NT_STATUS_NO_MEMORY;
                }
        }
 
+       TALLOC_FREE(dfs_refs);
        return NT_STATUS_OK;
 }