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-rw-r--r--src/basic/fd-util.c321
1 files changed, 321 insertions, 0 deletions
diff --git a/src/basic/fd-util.c b/src/basic/fd-util.c
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+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+ This file is part of systemd.
+
+ Copyright 2010 Lennart Poettering
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "fd-util.h"
+#include "util.h"
+
+int close_nointr(int fd) {
+ assert(fd >= 0);
+
+ if (close(fd) >= 0)
+ return 0;
+
+ /*
+ * Just ignore EINTR; a retry loop is the wrong thing to do on
+ * Linux.
+ *
+ * http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html
+ * https://bugzilla.gnome.org/show_bug.cgi?id=682819
+ * http://utcc.utoronto.ca/~cks/space/blog/unix/CloseEINTR
+ * https://sites.google.com/site/michaelsafyan/software-engineering/checkforeintrwheninvokingclosethinkagain
+ */
+ if (errno == EINTR)
+ return 0;
+
+ return -errno;
+}
+
+int safe_close(int fd) {
+
+ /*
+ * Like close_nointr() but cannot fail. Guarantees errno is
+ * unchanged. Is a NOP with negative fds passed, and returns
+ * -1, so that it can be used in this syntax:
+ *
+ * fd = safe_close(fd);
+ */
+
+ if (fd >= 0) {
+ PROTECT_ERRNO;
+
+ /* The kernel might return pretty much any error code
+ * via close(), but the fd will be closed anyway. The
+ * only condition we want to check for here is whether
+ * the fd was invalid at all... */
+
+ assert_se(close_nointr(fd) != -EBADF);
+ }
+
+ return -1;
+}
+
+void safe_close_pair(int p[]) {
+ assert(p);
+
+ if (p[0] == p[1]) {
+ /* Special case pairs which use the same fd in both
+ * directions... */
+ p[0] = p[1] = safe_close(p[0]);
+ return;
+ }
+
+ p[0] = safe_close(p[0]);
+ p[1] = safe_close(p[1]);
+}
+
+void close_many(const int fds[], unsigned n_fd) {
+ unsigned i;
+
+ assert(fds || n_fd <= 0);
+
+ for (i = 0; i < n_fd; i++)
+ safe_close(fds[i]);
+}
+
+int fclose_nointr(FILE *f) {
+ assert(f);
+
+ /* Same as close_nointr(), but for fclose() */
+
+ if (fclose(f) == 0)
+ return 0;
+
+ if (errno == EINTR)
+ return 0;
+
+ return -errno;
+}
+
+FILE* safe_fclose(FILE *f) {
+
+ /* Same as safe_close(), but for fclose() */
+
+ if (f) {
+ PROTECT_ERRNO;
+
+ assert_se(fclose_nointr(f) != EBADF);
+ }
+
+ return NULL;
+}
+
+DIR* safe_closedir(DIR *d) {
+
+ if (d) {
+ PROTECT_ERRNO;
+
+ assert_se(closedir(d) >= 0 || errno != EBADF);
+ }
+
+ return NULL;
+}
+
+int fd_nonblock(int fd, bool nonblock) {
+ int flags, nflags;
+
+ assert(fd >= 0);
+
+ flags = fcntl(fd, F_GETFL, 0);
+ if (flags < 0)
+ return -errno;
+
+ if (nonblock)
+ nflags = flags | O_NONBLOCK;
+ else
+ nflags = flags & ~O_NONBLOCK;
+
+ if (nflags == flags)
+ return 0;
+
+ if (fcntl(fd, F_SETFL, nflags) < 0)
+ return -errno;
+
+ return 0;
+}
+
+int fd_cloexec(int fd, bool cloexec) {
+ int flags, nflags;
+
+ assert(fd >= 0);
+
+ flags = fcntl(fd, F_GETFD, 0);
+ if (flags < 0)
+ return -errno;
+
+ if (cloexec)
+ nflags = flags | FD_CLOEXEC;
+ else
+ nflags = flags & ~FD_CLOEXEC;
+
+ if (nflags == flags)
+ return 0;
+
+ if (fcntl(fd, F_SETFD, nflags) < 0)
+ return -errno;
+
+ return 0;
+}
+
+_pure_ static bool fd_in_set(int fd, const int fdset[], unsigned n_fdset) {
+ unsigned i;
+
+ assert(n_fdset == 0 || fdset);
+
+ for (i = 0; i < n_fdset; i++)
+ if (fdset[i] == fd)
+ return true;
+
+ return false;
+}
+
+int close_all_fds(const int except[], unsigned n_except) {
+ _cleanup_closedir_ DIR *d = NULL;
+ struct dirent *de;
+ int r = 0;
+
+ assert(n_except == 0 || except);
+
+ d = opendir("/proc/self/fd");
+ if (!d) {
+ int fd;
+ struct rlimit rl;
+
+ /* When /proc isn't available (for example in chroots)
+ * the fallback is brute forcing through the fd
+ * table */
+
+ assert_se(getrlimit(RLIMIT_NOFILE, &rl) >= 0);
+ for (fd = 3; fd < (int) rl.rlim_max; fd ++) {
+
+ if (fd_in_set(fd, except, n_except))
+ continue;
+
+ if (close_nointr(fd) < 0)
+ if (errno != EBADF && r == 0)
+ r = -errno;
+ }
+
+ return r;
+ }
+
+ while ((de = readdir(d))) {
+ int fd = -1;
+
+ if (hidden_file(de->d_name))
+ continue;
+
+ if (safe_atoi(de->d_name, &fd) < 0)
+ /* Let's better ignore this, just in case */
+ continue;
+
+ if (fd < 3)
+ continue;
+
+ if (fd == dirfd(d))
+ continue;
+
+ if (fd_in_set(fd, except, n_except))
+ continue;
+
+ if (close_nointr(fd) < 0) {
+ /* Valgrind has its own FD and doesn't want to have it closed */
+ if (errno != EBADF && r == 0)
+ r = -errno;
+ }
+ }
+
+ return r;
+}
+
+int same_fd(int a, int b) {
+ struct stat sta, stb;
+ pid_t pid;
+ int r, fa, fb;
+
+ assert(a >= 0);
+ assert(b >= 0);
+
+ /* Compares two file descriptors. Note that semantics are
+ * quite different depending on whether we have kcmp() or we
+ * don't. If we have kcmp() this will only return true for
+ * dup()ed file descriptors, but not otherwise. If we don't
+ * have kcmp() this will also return true for two fds of the same
+ * file, created by separate open() calls. Since we use this
+ * call mostly for filtering out duplicates in the fd store
+ * this difference hopefully doesn't matter too much. */
+
+ if (a == b)
+ return true;
+
+ /* Try to use kcmp() if we have it. */
+ pid = getpid();
+ r = kcmp(pid, pid, KCMP_FILE, a, b);
+ if (r == 0)
+ return true;
+ if (r > 0)
+ return false;
+ if (errno != ENOSYS)
+ return -errno;
+
+ /* We don't have kcmp(), use fstat() instead. */
+ if (fstat(a, &sta) < 0)
+ return -errno;
+
+ if (fstat(b, &stb) < 0)
+ return -errno;
+
+ if ((sta.st_mode & S_IFMT) != (stb.st_mode & S_IFMT))
+ return false;
+
+ /* We consider all device fds different, since two device fds
+ * might refer to quite different device contexts even though
+ * they share the same inode and backing dev_t. */
+
+ if (S_ISCHR(sta.st_mode) || S_ISBLK(sta.st_mode))
+ return false;
+
+ if (sta.st_dev != stb.st_dev || sta.st_ino != stb.st_ino)
+ return false;
+
+ /* The fds refer to the same inode on disk, let's also check
+ * if they have the same fd flags. This is useful to
+ * distinguish the read and write side of a pipe created with
+ * pipe(). */
+ fa = fcntl(a, F_GETFL);
+ if (fa < 0)
+ return -errno;
+
+ fb = fcntl(b, F_GETFL);
+ if (fb < 0)
+ return -errno;
+
+ return fa == fb;
+}
+
+void cmsg_close_all(struct msghdr *mh) {
+ struct cmsghdr *cmsg;
+
+ assert(mh);
+
+ CMSG_FOREACH(cmsg, mh)
+ if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS)
+ close_many((int*) CMSG_DATA(cmsg), (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int));
+}
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