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]

1 files changed, 79 insertions, 24 deletions

diff --git a/source3/libsmb/clidfs.c b/source3/libsmb/clidfs.c
index b2e2e9ec2b0..93c964a4d02 100644
--- 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;
 }