1 files changed, 76 insertions, 0 deletions
diff --git a/fs/cifs/dfs.c b/fs/cifs/dfs.c
new file mode 100644
index 000000000000..0b15d7e9f818
--- /dev/null
+++ b/fs/cifs/dfs.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2022 Paulo Alcantara <palcantara@suse.de>
+ */
+
+#include "cifsproto.h"
+#include "cifs_debug.h"
+#include "dns_resolve.h"
+#include "fs_context.h"
+#include "dfs.h"
+
+/* Resolve UNC server name and set destination ip address in fs context */
+static int resolve_unc(const char *path, struct smb3_fs_context *ctx)
+{
+	int rc;
+	char *ip = NULL;
+
+	rc = dns_resolve_server_name_to_ip(path, &ip, NULL);
+	if (rc < 0) {
+		cifs_dbg(FYI, "%s: failed to resolve UNC server name: %d\n", __func__, rc);
+		return rc;
+	}
+
+	if (!cifs_convert_address((struct sockaddr *)&ctx->dstaddr, ip, strlen(ip))) {
+		cifs_dbg(VFS, "%s: could not determinate destination address\n", __func__);
+		rc = -EHOSTUNREACH;
+	} else
+		rc = 0;
+
+	kfree(ip);
+	return rc;
+}
+
+/**
+ * dfs_parse_target_referral - set fs context for dfs target referral
+ *
+ * @full_path: full path in UNC format.
+ * @ref: dfs referral pointer.
+ * @ctx: smb3 fs context pointer.
+ *
+ * Return zero if dfs referral was parsed correctly, otherwise non-zero.
+ */
+int dfs_parse_target_referral(const char *full_path, const struct dfs_info3_param *ref,
+			      struct smb3_fs_context *ctx)
+{
+	int rc;
+	const char *prepath = NULL;
+	char *path;
+
+	if (!full_path || !*full_path || !ref || !ctx)
+		return -EINVAL;
+
+	if (WARN_ON_ONCE(!ref->node_name || ref->path_consumed < 0))
+		return -EINVAL;
+
+	if (strlen(full_path) - ref->path_consumed) {
+		prepath = full_path + ref->path_consumed;
+		/* skip initial delimiter */
+		if (*prepath == '/' || *prepath == '\\')
+			prepath++;
+	}
+
+	path = cifs_build_devname(ref->node_name, prepath);
+	if (IS_ERR(path))
+		return PTR_ERR(path);
+
+	rc = smb3_parse_devname(path, ctx);
+	if (rc)
+		goto out;
+
+	rc = resolve_unc(path, ctx);
+
+out:
+	kfree(path);
+	return rc;
+}