[PATCH v2 08/12] fsmonitor: determine if filesystem is local or remote

["Eric DeCosta via GitGitGadget" <gitgitgadget@gmail.com>]

From: Eric DeCosta <edecosta@mathworks.com>

Compare the given path to the mounted filesystems. Find the mount that is
the longest prefix of the path (if any) and determine if that mount is on a
local or remote filesystem.

Signed-off-by: Eric DeCosta <edecosta@mathworks.com>
---
 compat/fsmonitor/fsm-path-utils-linux.c | 169 ++++++++++++++++++++++++
 1 file changed, 169 insertions(+)
 create mode 100644 compat/fsmonitor/fsm-path-utils-linux.c

diff --git a/compat/fsmonitor/fsm-path-utils-linux.c b/compat/fsmonitor/fsm-path-utils-linux.c
new file mode 100644
index 00000000000..039f044b670
--- /dev/null
+++ b/compat/fsmonitor/fsm-path-utils-linux.c
@@ -0,0 +1,169 @@
+#include "fsmonitor.h"
+#include "fsmonitor-path-utils.h"
+#include <errno.h>
+#include <mntent.h>
+#include <sys/mount.h>
+#include <sys/statvfs.h>
+
+/*
+ * https://github.com/coreutils/gnulib/blob/master/lib/mountlist.c
+ */
+#ifndef ME_REMOTE
+/* A file system is "remote" if its Fs_name contains a ':'
+   or if (it is of type (smbfs or cifs) and its Fs_name starts with '//')
+   or if it is of any other of the listed types
+   or Fs_name is equal to "-hosts" (used by autofs to mount remote fs).
+   "VM" file systems like prl_fs or vboxsf are not considered remote here. */
+# define ME_REMOTE(Fs_name, Fs_type)            \
+	(strchr (Fs_name, ':') != NULL              \
+	 || ((Fs_name)[0] == '/'                    \
+		 && (Fs_name)[1] == '/'                 \
+		 && (strcmp (Fs_type, "smbfs") == 0     \
+			 || strcmp (Fs_type, "smb3") == 0   \
+			 || strcmp (Fs_type, "cifs") == 0)) \
+	 || strcmp (Fs_type, "acfs") == 0           \
+	 || strcmp (Fs_type, "afs") == 0            \
+	 || strcmp (Fs_type, "coda") == 0           \
+	 || strcmp (Fs_type, "auristorfs") == 0     \
+	 || strcmp (Fs_type, "fhgfs") == 0          \
+	 || strcmp (Fs_type, "gpfs") == 0           \
+	 || strcmp (Fs_type, "ibrix") == 0          \
+	 || strcmp (Fs_type, "ocfs2") == 0          \
+	 || strcmp (Fs_type, "vxfs") == 0           \
+	 || strcmp ("-hosts", Fs_name) == 0)
+#endif
+
+static int find_mount(const char *path, const struct statvfs *fs,
+	struct mntent *ent)
+{
+	const char *const mounts = "/proc/mounts";
+	const char *rp = real_pathdup(path, 1);
+	struct mntent *ment = NULL;
+	struct statvfs mntfs;
+	FILE *fp;
+	int found = 0;
+	int dlen, plen, flen = 0;
+
+	ent->mnt_fsname = NULL;
+	ent->mnt_dir = NULL;
+	ent->mnt_type = NULL;
+
+	fp = setmntent(mounts, "r");
+	if (!fp) {
+		error_errno(_("setmntent('%s') failed"), mounts);
+		return -1;
+	}
+
+	plen = strlen(rp);
+
+	/* read all the mount information and compare to path */
+	while ((ment = getmntent(fp)) != NULL) {
+		if (statvfs(ment->mnt_dir, &mntfs)) {
+			switch (errno) {
+			case EPERM:
+			case ESRCH:
+			case EACCES:
+				continue;
+			default:
+				error_errno(_("statvfs('%s') failed"), ment->mnt_dir);
+				endmntent(fp);
+				return -1;
+			}
+		}
+
+		/* is mount on the same filesystem and is a prefix of the path */
+		if ((fs->f_fsid == mntfs.f_fsid) &&
+			!strncmp(ment->mnt_dir, rp, strlen(ment->mnt_dir))) {
+			dlen = strlen(ment->mnt_dir);
+			if (dlen > plen)
+				continue;
+			/*
+			 * root is always a potential match; otherwise look for
+			 * directory prefix
+			 */
+			if ((dlen == 1 && ment->mnt_dir[0] == '/') ||
+				(dlen > flen && (!rp[dlen] || rp[dlen] == '/'))) {
+				flen = dlen;
+				/*
+				 * https://man7.org/linux/man-pages/man3/getmntent.3.html
+				 *
+				 * The pointer points to a static area of memory which is
+				 * overwritten by subsequent calls to getmntent().
+				 */
+				found = 1;
+				free(ent->mnt_fsname);
+				free(ent->mnt_dir);
+				free(ent->mnt_type);
+				ent->mnt_fsname = xstrdup(ment->mnt_fsname);
+				ent->mnt_dir = xstrdup(ment->mnt_dir);
+				ent->mnt_type = xstrdup(ment->mnt_type);
+			}
+		}
+	}
+	endmntent(fp);
+
+	if (!found)
+		return -1;
+
+	return 0;
+}
+
+int fsmonitor__get_fs_info(const char *path, struct fs_info *fs_info)
+{
+	struct mntent ment;
+	struct statvfs fs;
+
+	if (statvfs(path, &fs))
+		return error_errno(_("statvfs('%s') failed"), path);
+
+
+	if (find_mount(path, &fs, &ment) < 0) {
+		free(ment.mnt_fsname);
+		free(ment.mnt_dir);
+		free(ment.mnt_type);
+		return -1;
+	}
+
+	trace_printf_key(&trace_fsmonitor,
+			 "statvfs('%s') [flags 0x%08lx] '%s' '%s'",
+			 path, fs.f_flag, ment.mnt_type, ment.mnt_fsname);
+
+	fs_info->is_remote = ME_REMOTE(ment.mnt_fsname, ment.mnt_type);
+	fs_info->typename = ment.mnt_fsname;
+	free(ment.mnt_dir);
+	free(ment.mnt_type);
+
+	trace_printf_key(&trace_fsmonitor,
+				"'%s' is_remote: %d",
+				path, fs_info->is_remote);
+	return 0;
+}
+
+int fsmonitor__is_fs_remote(const char *path)
+{
+	struct fs_info fs;
+
+	if (fsmonitor__get_fs_info(path, &fs))
+		return -1;
+
+	free(fs.typename);
+
+	return fs.is_remote;
+}
+
+/*
+ * No-op for now.
+ */
+int fsmonitor__get_alias(const char *path, struct alias_info *info)
+{
+	return 0;
+}
+
+/*
+ * No-op for now.
+ */
+char *fsmonitor__resolve_alias(const char *path,
+	const struct alias_info *info)
+{
+	return NULL;
+}
-- 
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