cifs: Allow to disable or force initialization of NetBIOS session

Currently SMB client always tries to initialize NetBIOS session when the
server port is 139. This is useful for default cases, but nowadays when
using non-standard routing or testing between VMs, it is common that
servers are listening on non-standard ports.

So add a new mount option -o nbsessinit and -o nonbsessinit which either
forces initialization or disables initialization regardless of server port
number.

This allows Linux SMB client to connect to older SMB1 server listening on
non-standard port, which requires initialization of NetBIOS session, by
using additional mount options -o port= and -o nbsessinit.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: pali

fs/smb/client/cifsglob.h

@@ -714,6 +714,7 @@ struct TCP_Server_Info {
 	spinlock_t srv_lock;  /* protect anything here that is not protected */
 	__u64 conn_id; /* connection identifier (useful for debugging) */
 	int srv_count; /* reference counter */
+	int rfc1001_sessinit; /* whether to estasblish netbios session */
 	/* 15 character server name + 0x20 16th byte indicating type = srv */
 	char server_RFC1001_name[RFC1001_NAME_LEN_WITH_NULL];
 	struct smb_version_operations	*ops;

fs/smb/client/connect.c

@@ -1701,6 +1701,7 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx,
 		ctx->source_rfc1001_name, RFC1001_NAME_LEN_WITH_NULL);
 	memcpy(tcp_ses->server_RFC1001_name,
 		ctx->target_rfc1001_name, RFC1001_NAME_LEN_WITH_NULL);
+	tcp_ses->rfc1001_sessinit = ctx->rfc1001_sessinit;
 	tcp_ses->session_estab = false;
 	tcp_ses->sequence_number = 0;
 	tcp_ses->channel_sequence_num = 0; /* only tracked for primary channel */
@@ -3328,7 +3329,15 @@ generic_ip_connect(struct TCP_Server_Info *server)
 		return rc;
 	}
 	trace_smb3_connect_done(server->hostname, server->conn_id, &server->dstaddr);
-	if (sport == htons(RFC1001_PORT))
+
+	/*
+	 * Establish RFC1001 NetBIOS session when it was explicitly requested
+	 * by mount option -o nbsessinit, or when connecting to default RFC1001
+	 * server port (139) and it was not explicitly disabled by mount option
+	 * -o nonbsessinit.
+	 */
+	if (server->rfc1001_sessinit == 1 ||
+	    (server->rfc1001_sessinit == -1 && sport == htons(RFC1001_PORT)))
 		rc = ip_rfc1001_connect(server);
 
 	return rc;

fs/smb/client/fs_context.c

@@ -135,6 +135,7 @@ const struct fs_parameter_spec smb3_fs_parameters[] = {
 	fsparam_flag("witness", Opt_witness),
 	fsparam_flag_no("nativesocket", Opt_nativesocket),
 	fsparam_flag_no("unicode", Opt_unicode),
+	fsparam_flag_no("nbsessinit", Opt_nbsessinit),
 
 	/* Mount options which take uid or gid */
 	fsparam_uid("backupuid", Opt_backupuid),
@@ -968,6 +969,10 @@ static int smb3_verify_reconfigure_ctx(struct fs_context *fc,
 		cifs_errorf(fc, "can not change unicode during remount\n");
 		return -EINVAL;
 	}
+	if (new_ctx->rfc1001_sessinit != old_ctx->rfc1001_sessinit) {
+		cifs_errorf(fc, "can not change nbsessinit during remount\n");
+		return -EINVAL;
+	}
 
 	return 0;
 }
@@ -1609,6 +1614,10 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 		if (i == RFC1001_NAME_LEN && param->string[i] != 0)
 			pr_warn("server netbiosname longer than 15 truncated\n");
 		break;
+	case Opt_nbsessinit:
+		ctx->rfc1001_sessinit = !result.negated;
+		cifs_dbg(FYI, "rfc1001_sessinit set to %d\n", ctx->rfc1001_sessinit);
+		break;
 	case Opt_ver:
 		/* version of mount userspace tools, not dialect */
 		/* If interface changes in mount.cifs bump to new ver */
@@ -1896,13 +1905,16 @@ int smb3_init_fs_context(struct fs_context *fc)
 	memset(ctx->source_rfc1001_name, 0x20, RFC1001_NAME_LEN);
 	for (i = 0; i < strnlen(nodename, RFC1001_NAME_LEN); i++)
 		ctx->source_rfc1001_name[i] = toupper(nodename[i]);
-
 	ctx->source_rfc1001_name[RFC1001_NAME_LEN] = 0;
+
 	/*
 	 * null target name indicates to use *SMBSERVR default called name
 	 *  if we end up sending RFC1001 session initialize
 	 */
 	ctx->target_rfc1001_name[0] = 0;
+
+	ctx->rfc1001_sessinit = -1; /* autodetect based on port number */
+
 	ctx->cred_uid = current_uid();
 	ctx->linux_uid = current_uid();
 	ctx->linux_gid = current_gid();

fs/smb/client/fs_context.h

@@ -174,6 +174,7 @@ enum cifs_param {
 	Opt_iocharset,
 	Opt_netbiosname,
 	Opt_servern,
+	Opt_nbsessinit,
 	Opt_ver,
 	Opt_vers,
 	Opt_sec,
@@ -216,6 +217,7 @@ struct smb3_fs_context {
 	char *iocharset;  /* local code page for mapping to and from Unicode */
 	char source_rfc1001_name[RFC1001_NAME_LEN_WITH_NULL]; /* clnt nb name */
 	char target_rfc1001_name[RFC1001_NAME_LEN_WITH_NULL]; /* srvr nb name */
+	int rfc1001_sessinit;
 	kuid_t cred_uid;
 	kuid_t linux_uid;
 	kgid_t linux_gid;