[PATCH 1/6] cifs: Allow to disable or force initialization of NetBIOS session

["Pali Rohár" <pali@kernel.org>]

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>
---
 fs/smb/client/cifsglob.h   |  1 +
 fs/smb/client/connect.c    | 11 ++++++++++-
 fs/smb/client/fs_context.c | 14 +++++++++++++-
 fs/smb/client/fs_context.h |  2 ++
 4 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index d4c60d85d7a4..bea4b8a8b30e 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -716,6 +716,7 @@ 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;
diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index 20b8bb957468..9cbfdc31cdda 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -1738,6 +1738,7 @@ 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 */
@@ -3206,7 +3207,15 @@ 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;
diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index e2ae9819b5ba..3774f02f45c9 100644
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -134,6 +134,7 @@ const struct fs_parameter_spec smb3_fs_parameters[] = {
 	fsparam_flag("compress", Opt_compress),
 	fsparam_flag("witness", Opt_witness),
 	fsparam_flag_no("unicode", Opt_unicode),
+	fsparam_flag_no("nbsessinit", Opt_nbsessinit),
 
 	/* Mount options which take uid or gid */
 	fsparam_uid("backupuid", Opt_backupuid),
@@ -965,6 +966,10 @@ 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;
 }
@@ -1585,6 +1590,10 @@ 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 */
@@ -1872,13 +1881,16 @@ 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();
diff --git a/fs/smb/client/fs_context.h b/fs/smb/client/fs_context.h
index af2d94022a30..e6b22a5fbd0f 100644
--- a/fs/smb/client/fs_context.h
+++ b/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;
-- 
2.20.1