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author | Lennart Poettering <lennart@poettering.net> | 2015-10-25 13:14:12 +0100 |
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committer | Lennart Poettering <lennart@poettering.net> | 2015-10-25 13:19:18 +0100 |
commit | 3ffd4af22052963e7a29431721ee204e634bea75 (patch) | |
tree | fe60142dfddd37cfc02b7a135542107e772b36c3 /src/basic/fd-util.c | |
parent | 04c0136989b7eb896bfb0fb176e11233d69e1453 (diff) | |
download | systemd-3ffd4af22052963e7a29431721ee204e634bea75.tar.gz |
util-lib: split out fd-related operations into fd-util.[ch]
There are more than enough to deserve their own .c file, hence move them
over.
Diffstat (limited to 'src/basic/fd-util.c')
-rw-r--r-- | src/basic/fd-util.c | 321 |
1 files changed, 321 insertions, 0 deletions
diff --git a/src/basic/fd-util.c b/src/basic/fd-util.c new file mode 100644 index 0000000000..e54c104597 --- /dev/null +++ b/src/basic/fd-util.c @@ -0,0 +1,321 @@ +/*-*- 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)); +} |