1 files changed, 366 insertions, 0 deletions
diff --git a/lib/fs.c b/lib/fs.c
new file mode 100644
index 0000000..622f28b
--- /dev/null
+++ b/lib/fs.c
@@ -0,0 +1,366 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * fs.c         filesystem APIs
+ *
+ * Authors:	David Ahern <dsa@cumulusnetworks.com>
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/socket.h>
+#include <sys/mount.h>
+#include <ctype.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <limits.h>
+
+#include "utils.h"
+
+#ifndef HAVE_HANDLE_AT
+# include <sys/syscall.h>
+#endif
+
+#define CGROUP2_FS_NAME "cgroup2"
+
+/* if not already mounted cgroup2 is mounted here for iproute2's use */
+#define MNT_CGRP2_PATH  "/var/run/cgroup2"
+
+
+#ifndef HAVE_HANDLE_AT
+struct file_handle {
+	unsigned handle_bytes;
+	int handle_type;
+	unsigned char f_handle[];
+};
+
+static int name_to_handle_at(int dirfd, const char *pathname,
+	struct file_handle *handle, int *mount_id, int flags)
+{
+	return syscall(__NR_name_to_handle_at, dirfd, pathname, handle,
+		       mount_id, flags);
+}
+
+static int open_by_handle_at(int mount_fd, struct file_handle *handle, int flags)
+{
+	return syscall(__NR_open_by_handle_at, mount_fd, handle, flags);
+}
+#endif
+
+/* return mount path of first occurrence of given fstype */
+static char *find_fs_mount(const char *fs_to_find)
+{
+	char path[4096];
+	char fstype[128];    /* max length of any filesystem name */
+	char *mnt = NULL;
+	FILE *fp;
+
+	fp = fopen("/proc/mounts", "r");
+	if (!fp) {
+		fprintf(stderr,
+			"Failed to open mounts file: %s\n", strerror(errno));
+		return NULL;
+	}
+
+	while (fscanf(fp, "%*s %4095s %127s %*s %*d %*d\n",
+		      path, fstype) == 2) {
+		if (strcmp(fstype, fs_to_find) == 0) {
+			mnt = strdup(path);
+			break;
+		}
+	}
+
+	fclose(fp);
+
+	return mnt;
+}
+
+/* caller needs to free string returned */
+char *find_cgroup2_mount(bool do_mount)
+{
+	char *mnt = find_fs_mount(CGROUP2_FS_NAME);
+
+	if (mnt)
+		return mnt;
+
+	if (!do_mount) {
+		fprintf(stderr, "Failed to find cgroup2 mount\n");
+		return NULL;
+	}
+
+	mnt = strdup(MNT_CGRP2_PATH);
+	if (!mnt) {
+		fprintf(stderr, "Failed to allocate memory for cgroup2 path\n");
+		return NULL;
+
+	}
+
+	if (make_path(mnt, 0755)) {
+		fprintf(stderr, "Failed to setup cgroup2 directory\n");
+		free(mnt);
+		return NULL;
+	}
+
+	if (mount("none", mnt, CGROUP2_FS_NAME, 0, NULL)) {
+		/* EBUSY means already mounted */
+		if (errno == EBUSY)
+			goto out;
+
+		if (errno == ENODEV) {
+			fprintf(stderr,
+				"Failed to mount cgroup2. Are CGROUPS enabled in your kernel?\n");
+		} else {
+			fprintf(stderr,
+				"Failed to mount cgroup2: %s\n",
+				strerror(errno));
+		}
+		free(mnt);
+		return NULL;
+	}
+out:
+	return mnt;
+}
+
+__u64 get_cgroup2_id(const char *path)
+{
+	char fh_buf[sizeof(struct file_handle) + sizeof(__u64)] = { 0 };
+	struct file_handle *fhp = (struct file_handle *)fh_buf;
+	union {
+		__u64 id;
+		unsigned char bytes[sizeof(__u64)];
+	} cg_id = { .id = 0 };
+	char *mnt = NULL;
+	int mnt_fd = -1;
+	int mnt_id;
+
+	if (!path) {
+		fprintf(stderr, "Invalid cgroup2 path\n");
+		return 0;
+	}
+
+	fhp->handle_bytes = sizeof(__u64);
+	if (name_to_handle_at(AT_FDCWD, path, fhp, &mnt_id, 0) < 0) {
+		/* try at cgroup2 mount */
+
+		while (*path == '/')
+			path++;
+		if (*path == '\0') {
+			fprintf(stderr, "Invalid cgroup2 path\n");
+			goto out;
+		}
+
+		mnt = find_cgroup2_mount(false);
+		if (!mnt)
+			goto out;
+
+		mnt_fd = open(mnt, O_RDONLY);
+		if (mnt_fd < 0) {
+			fprintf(stderr, "Failed to open cgroup2 mount\n");
+			goto out;
+		}
+
+		fhp->handle_bytes = sizeof(__u64);
+		if (name_to_handle_at(mnt_fd, path, fhp, &mnt_id, 0) < 0) {
+			fprintf(stderr, "Failed to get cgroup2 ID: %s\n",
+					strerror(errno));
+			goto out;
+		}
+	}
+	if (fhp->handle_bytes != sizeof(__u64)) {
+		fprintf(stderr, "Invalid size of cgroup2 ID\n");
+		goto out;
+	}
+
+	memcpy(cg_id.bytes, fhp->f_handle, sizeof(__u64));
+
+out:
+	if (mnt_fd >= 0)
+		close(mnt_fd);
+	free(mnt);
+
+	return cg_id.id;
+}
+
+#define FILEID_INO32_GEN 1
+
+/* caller needs to free string returned */
+char *get_cgroup2_path(__u64 id, bool full)
+{
+	char fh_buf[sizeof(struct file_handle) + sizeof(__u64)] = { 0 };
+	struct file_handle *fhp = (struct file_handle *)fh_buf;
+	union {
+		__u64 id;
+		unsigned char bytes[sizeof(__u64)];
+	} cg_id = { .id = id };
+	int mnt_fd = -1, fd = -1;
+	char link_buf[PATH_MAX];
+	char *path = NULL;
+	char fd_path[64];
+	int link_len;
+	char *mnt = NULL;
+
+	if (!id) {
+		fprintf(stderr, "Invalid cgroup2 ID\n");
+		goto out;
+	}
+
+	mnt = find_cgroup2_mount(false);
+	if (!mnt)
+		goto out;
+
+	mnt_fd = open(mnt, O_RDONLY);
+	if (mnt_fd < 0) {
+		fprintf(stderr, "Failed to open cgroup2 mount\n");
+		goto out;
+	}
+
+	fhp->handle_bytes = sizeof(__u64);
+	fhp->handle_type = FILEID_INO32_GEN;
+	memcpy(fhp->f_handle, cg_id.bytes, sizeof(__u64));
+
+	fd = open_by_handle_at(mnt_fd, fhp, 0);
+	if (fd < 0) {
+		fprintf(stderr, "Failed to open cgroup2 by ID\n");
+		goto out;
+	}
+
+	snprintf(fd_path, sizeof(fd_path), "/proc/self/fd/%d", fd);
+	link_len = readlink(fd_path, link_buf, sizeof(link_buf) - 1);
+	if (link_len < 0) {
+		fprintf(stderr,
+			"Failed to read value of symbolic link %s\n",
+			fd_path);
+		goto out;
+	}
+	link_buf[link_len] = '\0';
+
+	if (full)
+		path = strdup(link_buf);
+	else
+		path = strdup(link_buf + strlen(mnt));
+	if (!path)
+		fprintf(stderr,
+			"Failed to allocate memory for cgroup2 path\n");
+
+out:
+	if (fd >= 0)
+		close(fd);
+	if (mnt_fd >= 0)
+		close(mnt_fd);
+	free(mnt);
+
+	return path;
+}
+
+int make_path(const char *path, mode_t mode)
+{
+	char *dir, *delim;
+	int rc = -1;
+
+	delim = dir = strdup(path);
+	if (dir == NULL) {
+		fprintf(stderr, "strdup failed copying path");
+		return -1;
+	}
+
+	/* skip '/' -- it had better exist */
+	if (*delim == '/')
+		delim++;
+
+	while (1) {
+		delim = strchr(delim, '/');
+		if (delim)
+			*delim = '\0';
+
+		rc = mkdir(dir, mode);
+		if (rc && errno != EEXIST) {
+			fprintf(stderr, "mkdir failed for %s: %s\n",
+				dir, strerror(errno));
+			goto out;
+		}
+
+		if (delim == NULL)
+			break;
+
+		*delim = '/';
+		delim++;
+		if (*delim == '\0')
+			break;
+	}
+	rc = 0;
+out:
+	free(dir);
+
+	return rc;
+}
+
+int get_command_name(const char *pid, char *comm, size_t len)
+{
+	char path[PATH_MAX];
+	char line[128];
+	FILE *fp;
+
+	if (snprintf(path, sizeof(path),
+		     "/proc/%s/status", pid) >= sizeof(path)) {
+		return -1;
+	}
+
+	fp = fopen(path, "r");
+	if (!fp)
+		return -1;
+
+	comm[0] = '\0';
+	while (fgets(line, sizeof(line), fp)) {
+		char *nl, *name;
+
+		name = strstr(line, "Name:");
+		if (!name)
+			continue;
+
+		name += 5;
+		while (isspace(*name))
+			name++;
+
+		nl = strchr(name, '\n');
+		if (nl)
+			*nl = '\0';
+
+		strlcpy(comm, name, len);
+		break;
+	}
+
+	fclose(fp);
+
+	return 0;
+}
+
+int get_task_name(pid_t pid, char *name, size_t len)
+{
+	char path[PATH_MAX];
+	FILE *f;
+
+	if (!pid)
+		return -1;
+
+	if (snprintf(path, sizeof(path), "/proc/%d/comm", pid) >= sizeof(path))
+		return -1;
+
+	f = fopen(path, "r");
+	if (!f)
+		return -1;
+
+	if (!fgets(name, len, f)) {
+		fclose(f);
+		return -1;
+	}
+
+	/* comm ends in \n, get rid of it */
+	name[strcspn(name, "\n")] = '\0';
+
+	fclose(f);
+
+	return 0;
+}