// The utility library for universal variables. Used both by the client library and by the daemon.
#include "config.h" // IWYU pragma: keep
#include <arpa/inet.h> // IWYU pragma: keep
#include <errno.h>
#include <fcntl.h>
// We need the sys/file.h for the flock() declaration on Linux but not OS X.
#include <sys/file.h> // IWYU pragma: keep
// We need the ioctl.h header so we can check if SIOCGIFHWADDR is defined by it so we know if we're
// on a Linux system.
#include <limits.h>
#include <netinet/in.h> // IWYU pragma: keep
#include <sys/ioctl.h> // IWYU pragma: keep
#if !defined(__APPLE__) && !defined(__CYGWIN__)
#include <pwd.h>
#endif
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <cstring>
#ifdef __CYGWIN__
#include <sys/mman.h>
#endif
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h> // IWYU pragma: keep
#endif
#include <signal.h>
#include <sys/stat.h>
#include <sys/time.h> // IWYU pragma: keep
#include <sys/types.h> // IWYU pragma: keep
#include <unistd.h>
#include <atomic>
#include <cwchar>
#include <map>
#include <string>
#include <type_traits>
#include <utility>
#include "common.h"
#include "env.h"
#include "env_universal_common.h"
#include "fallback.h" // IWYU pragma: keep
#include "flog.h"
#include "path.h"
#include "signal.h"
#include "utf8.h"
#include "util.h" // IWYU pragma: keep
#include "wcstringutil.h"
#include "wutil.h"
#ifdef __APPLE__
#define FISH_NOTIFYD_AVAILABLE
#include <notify.h>
#endif
#ifdef __HAIKU__
#define _BSD_SOURCE
#include <bsd/ifaddrs.h>
#endif // Haiku
/// Error message.
#define PARSE_ERR L"Unable to parse universal variable message: '%ls'"
/// Small note about not editing ~/.fishd manually. Inserted at the top of all .fishd files.
#define SAVE_MSG "# This file contains fish universal variable definitions.\n"
/// Version for fish 3.0
#define UVARS_VERSION_3_0 "3.0"
// Maximum file size we'll read.
static constexpr size_t k_max_read_size = 16 * 1024 * 1024;
// Fields used in fish 2.x uvars.
namespace fish2x_uvars {
namespace {
constexpr const char *SET = "SET";
constexpr const char *SET_EXPORT = "SET_EXPORT";
} // namespace
} // namespace fish2x_uvars
// Fields used in fish 3.0 uvars
namespace fish3_uvars {
namespace {
constexpr const char *SETUVAR = "SETUVAR";
constexpr const char *EXPORT = "--export";
constexpr const char *PATH = "--path";
} // namespace
} // namespace fish3_uvars
/// The different types of messages found in the fishd file.
enum class uvar_message_type_t { set, set_export };
static wcstring get_machine_identifier();
/// return a list of paths where the uvars file has been historically stored.
static wcstring_list_t get_legacy_paths(const wcstring &wdir) {
wcstring_list_t result;
// A path used during fish 3.0 development.
result.push_back(wdir + L"/fish_universal_variables");
// Paths used in 2.x.
result.push_back(wdir + L"/fishd." + get_machine_identifier());
wcstring hostname_id;
if (get_hostname_identifier(hostname_id)) {
result.push_back(wdir + L'/' + hostname_id);
}
return result;
}
static maybe_t<wcstring> default_vars_path_directory() {
wcstring path;
if (!path_get_config(path)) return none();
return path;
}
static maybe_t<wcstring> default_vars_path() {
if (auto path = default_vars_path_directory()) {
path->append(L"/fish_variables");
return path;
}
return none();
}
/// Test if the message msg contains the command cmd.
/// On success, updates the cursor to just past the command.
static bool match(const wchar_t **inout_cursor, const char *cmd) {
const wchar_t *cursor = *inout_cursor;
size_t len = std::strlen(cmd);
if (!std::equal(cmd, cmd + len, cursor)) {
return false;
}
if (cursor[len] && cursor[len] != L' ' && cursor[len] != L'\t') return false;
*inout_cursor = cursor + len;
return true;
}
/// The universal variable format has some funny escaping requirements; here we try to be safe.
static bool is_universal_safe_to_encode_directly(wchar_t c) {
if (c < 32 || c > 128) return false;
return iswalnum(c) || std::wcschr(L"/_", c);
}
/// Escape specified string.
static wcstring full_escape(const wcstring &in) {
wcstring out;
for (wchar_t c : in) {
if (is_universal_safe_to_encode_directly(c)) {
out.push_back(c);
} else if (c <= static_cast<wchar_t>(ASCII_MAX)) {
// See #1225 for discussion of use of ASCII_MAX here.
append_format(out, L"\\x%.2x", c);
} else if (c < 65536) {
append_format(out, L"\\u%.4x", c);
} else {
append_format(out, L"\\U%.8x", c);
}
}
return out;
}
/// Converts input to UTF-8 and appends it to receiver, using storage as temp storage.
static bool append_utf8(const wcstring &input, std::string *receiver, std::string *storage) {
bool result = false;
if (wchar_to_utf8_string(input, storage)) {
receiver->append(*storage);
result = true;
}
return result;
}
/// Creates a file entry like "SET fish_color_cwd:FF0". Appends the result to *result (as UTF8).
/// Returns true on success. storage may be used for temporary storage, to avoid allocations.
static bool append_file_entry(env_var_t::env_var_flags_t flags, const wcstring &key_in,
const wcstring &val_in, std::string *result, std::string *storage) {
namespace f3 = fish3_uvars;
assert(storage != nullptr);
assert(result != nullptr);
// Record the length on entry, in case we need to back up.
bool success = true;
const size_t result_length_on_entry = result->size();
// Append SETVAR header.
result->append(f3::SETUVAR);
result->push_back(' ');
// Append flags.
if (flags & env_var_t::flag_export) {
result->append(f3::EXPORT);
result->push_back(' ');
}
if (flags & env_var_t::flag_pathvar) {
result->append(f3::PATH);
result->push_back(' ');
}
// Append variable name like "fish_color_cwd".
if (!valid_var_name(key_in)) {
FLOGF(error, L"Illegal variable name: '%ls'", key_in.c_str());
success = false;
}
if (success && !append_utf8(key_in, result, storage)) {
FLOGF(error, L"Could not convert %ls to narrow character string", key_in.c_str());
success = false;
}
// Append ":".
if (success) {
result->push_back(':');
}
// Append value.
if (success && !append_utf8(full_escape(val_in), result, storage)) {
FLOGF(error, L"Could not convert %ls to narrow character string", val_in.c_str());
success = false;
}
// Append newline.
if (success) {
result->push_back('\n');
}
// Don't modify result on failure. It's sufficient to simply resize it since all we ever did was
// append to it.
if (!success) {
result->resize(result_length_on_entry);
}
return success;
}
/// Encoding of a null string.
static const wchar_t *const ENV_NULL = L"\x1d";
/// Character used to separate arrays in universal variables file.
/// This is 30, the ASCII record separator.
static const wchar_t UVAR_ARRAY_SEP = 0x1e;
/// Decode a serialized universal variable value into a list.
static wcstring_list_t decode_serialized(const wcstring &val) {
if (val == ENV_NULL) return {};
return split_string(val, UVAR_ARRAY_SEP);
}
/// Decode a a list into a serialized universal variable value.
static wcstring encode_serialized(const wcstring_list_t &vals) {
if (vals.empty()) return ENV_NULL;
return join_strings(vals, UVAR_ARRAY_SEP);
}
env_universal_t::env_universal_t(wcstring path)
: narrow_vars_path(wcs2string(path)), explicit_vars_path(std::move(path)) {}
maybe_t<env_var_t> env_universal_t::get(const wcstring &name) const {
auto where = vars.find(name);
if (where != vars.end()) return where->second;
return none();
}
maybe_t<env_var_t::env_var_flags_t> env_universal_t::get_flags(const wcstring &name) const {
auto where = vars.find(name);
if (where != vars.end()) {
return where->second.get_flags();
}
return none();
}
void env_universal_t::set_internal(const wcstring &key, const env_var_t &var) {
ASSERT_IS_LOCKED(lock);
bool new_entry = vars.count(key) == 0;
env_var_t &entry = vars[key];
if (new_entry || entry != var) {
entry = var;
this->modified.insert(key);
if (entry.exports()) export_generation += 1;
}
}
void env_universal_t::set(const wcstring &key, const env_var_t &var) {
scoped_lock locker(lock);
this->set_internal(key, var);
}
bool env_universal_t::remove_internal(const wcstring &key) {
ASSERT_IS_LOCKED(lock);
auto iter = this->vars.find(key);
if (iter != this->vars.end()) {
if (iter->second.exports()) export_generation += 1;
this->vars.erase(iter);
this->modified.insert(key);
return true;
}
return false;
}
bool env_universal_t::remove(const wcstring &key) {
scoped_lock locker(lock);
return this->remove_internal(key);
}
wcstring_list_t env_universal_t::get_names(bool show_exported, bool show_unexported) const {
wcstring_list_t result;
scoped_lock locker(lock);
for (const auto &kv : vars) {
const wcstring &key = kv.first;
const env_var_t &var = kv.second;
if ((var.exports() && show_exported) || (!var.exports() && show_unexported)) {
result.push_back(key);
}
}
return result;
}
// Given a variable table, generate callbacks representing the difference between our vars and the
// new vars. Update our exports generation.
void env_universal_t::generate_callbacks_and_update_exports(const var_table_t &new_vars,
callback_data_list_t &callbacks) {
// Construct callbacks for erased values.
for (const auto &kv : this->vars) {
const wcstring &key = kv.first;
// Skip modified values.
if (this->modified.count(key)) {
continue;
}
// If the value is not present in new_vars, it has been erased.
if (new_vars.count(key) == 0) {
callbacks.push_back(callback_data_t(key, none()));
if (kv.second.exports()) export_generation += 1;
}
}
// Construct callbacks for newly inserted or changed values.
for (const auto &kv : new_vars) {
const wcstring &key = kv.first;
// Skip modified values.
if (this->modified.find(key) != this->modified.end()) {
continue;
}
// See if the value has changed.
const env_var_t &new_entry = kv.second;
var_table_t::const_iterator existing = this->vars.find(key);
bool old_exports = (existing != this->vars.end() && existing->second.exports());
bool export_changed = (old_exports != new_entry.exports());
bool value_changed = existing != this->vars.end() && existing->second != new_entry;
if (export_changed || value_changed) {
export_generation += 1;
}
if (existing == this->vars.end() || export_changed || value_changed) {
// Value is set for the first time, or has changed.
callbacks.push_back(callback_data_t(key, new_entry.as_string()));
}
}
}
void env_universal_t::acquire_variables(var_table_t &vars_to_acquire) {
// Copy modified values from existing vars to vars_to_acquire.
for (const auto &key : this->modified) {
auto src_iter = this->vars.find(key);
if (src_iter == this->vars.end()) {
/* The value has been deleted. */
vars_to_acquire.erase(key);
} else {
// The value has been modified. Copy it over. Note we can destructively modify the
// source entry in vars since we are about to get rid of this->vars entirely.
env_var_t &src = src_iter->second;
env_var_t &dst = vars_to_acquire[key];
dst = src;
}
}
// We have constructed all the callbacks and updated vars_to_acquire. Acquire it!
this->vars = std::move(vars_to_acquire);
}
void env_universal_t::load_from_fd(int fd, callback_data_list_t &callbacks) {
ASSERT_IS_LOCKED(lock);
assert(fd >= 0);
// Get the dev / inode.
const file_id_t current_file = file_id_for_fd(fd);
if (current_file == last_read_file) {
FLOGF(uvar_file, L"universal log sync elided based on fstat()");
} else {
// Read a variables table from the file.
var_table_t new_vars;
uvar_format_t format = this->read_message_internal(fd, &new_vars);
// Hacky: if the read format is in the future, avoid overwriting the file: never try to
// save.
if (format == uvar_format_t::future) {
ok_to_save = false;
}
// Announce changes and update our exports generation.
this->generate_callbacks_and_update_exports(new_vars, callbacks);
// Acquire the new variables.
this->acquire_variables(new_vars);
last_read_file = current_file;
}
}
bool env_universal_t::load_from_path(const std::string &path, callback_data_list_t &callbacks) {
ASSERT_IS_LOCKED(lock);
// Check to see if the file is unchanged. We do this again in load_from_fd, but this avoids
// opening the file unnecessarily.
if (last_read_file != kInvalidFileID && file_id_for_path(path) == last_read_file) {
FLOGF(uvar_file, L"universal log sync elided based on fast stat()");
return true;
}
bool result = false;
autoclose_fd_t fd{open_cloexec(path.c_str(), O_RDONLY)};
if (fd.valid()) {
FLOGF(uvar_file, L"universal log reading from file");
this->load_from_fd(fd.fd(), callbacks);
result = true;
}
return result;
}
bool env_universal_t::load_from_path(const wcstring &path, callback_data_list_t &callbacks) {
std::string tmp = wcs2string(path);
return load_from_path(tmp, callbacks);
}
uint64_t env_universal_t::get_export_generation() const {
scoped_lock locker(lock);
return export_generation;
}
/// Serialize the contents to a string.
std::string env_universal_t::serialize_with_vars(const var_table_t &vars) {
std::string storage;
std::string contents;
contents.append(SAVE_MSG);
contents.append("# VERSION: " UVARS_VERSION_3_0 "\n");
// Preserve legacy behavior by sorting the values first
using env_pair_t =
std::pair<std::reference_wrapper<const wcstring>, std::reference_wrapper<const env_var_t>>;
std::vector<env_pair_t> cloned(vars.begin(), vars.end());
std::sort(cloned.begin(), cloned.end(), [](const env_pair_t &p1, const env_pair_t &p2) {
return p1.first.get() < p2.first.get();
});
for (const auto &kv : cloned) {
// Append the entry. Note that append_file_entry may fail, but that only affects one
// variable; soldier on.
const wcstring &key = kv.first;
const env_var_t &var = kv.second;
append_file_entry(var.get_flags(), key, encode_serialized(var.as_list()), &contents,
&storage);
}
return contents;
}
/// Writes our state to the fd. path is provided only for error reporting.
bool env_universal_t::write_to_fd(int fd, const wcstring &path) {
ASSERT_IS_LOCKED(lock);
assert(fd >= 0);
bool success = true;
std::string contents = serialize_with_vars(vars);
if (write_loop(fd, contents.data(), contents.size()) < 0) {
const char *error = std::strerror(errno);
FLOGF(error, _(L"Unable to write to universal variables file '%ls': %s"), path.c_str(),
error);
success = false;
}
// Since we just wrote out this file, it matches our internal state; pretend we read from it.
this->last_read_file = file_id_for_fd(fd);
// We don't close the file.
return success;
}
bool env_universal_t::move_new_vars_file_into_place(const wcstring &src, const wcstring &dst) {
int ret = wrename(src, dst);
if (ret != 0) {
const char *error = std::strerror(errno);
FLOGF(error, _(L"Unable to rename file from '%ls' to '%ls': %s"), src.c_str(), dst.c_str(),
error);
}
return ret == 0;
}
bool env_universal_t::initialize(callback_data_list_t &callbacks) {
scoped_lock locker(lock);
if (!explicit_vars_path.empty()) {
return load_from_path(narrow_vars_path, callbacks);
}
// Get the variables path; if there is none (e.g. HOME is bogus) it's hopeless.
auto vars_path = default_vars_path();
if (!vars_path) return false;
bool success = load_from_path(*vars_path, callbacks);
if (!success && errno == ENOENT) {
// We failed to load, because the file was not found. Attempt to load from our legacy paths.
if (auto dir = default_vars_path_directory()) {
for (const wcstring &path : get_legacy_paths(*dir)) {
if (load_from_path(path, callbacks)) {
// Mark every variable as modified.
// This tells the uvars to write out the values loaded from the legacy path;
// otherwise it will conclude that the values have been deleted since they
// aren't present.
for (const auto &kv : vars) {
modified.insert(kv.first);
}
success = true;
break;
}
}
}
}
// If we succeeded, we store the *default path*, not the legacy one.
if (success) {
explicit_vars_path = *vars_path;
narrow_vars_path = wcs2string(*vars_path);
}
return success;
}
autoclose_fd_t env_universal_t::open_temporary_file(const wcstring &directory, wcstring *out_path) {
// Create and open a temporary file for writing within the given directory. Try to create a
// temporary file, up to 10 times. We don't use mkstemps because we want to open it CLO_EXEC.
// This should almost always succeed on the first try.
assert(!string_suffixes_string(L"/", directory)); //!OCLINT(multiple unary operator)
int saved_errno = 0;
const wcstring tmp_name_template = directory + L"/fishd.tmp.XXXXXX";
autoclose_fd_t result;
std::string narrow_str;
for (size_t attempt = 0; attempt < 10 && !result.valid(); attempt++) {
narrow_str = wcs2string(tmp_name_template);
result.reset(fish_mkstemp_cloexec(&narrow_str[0]));
saved_errno = errno;
}
*out_path = str2wcstring(narrow_str);
if (!result.valid()) {
const char *error = std::strerror(saved_errno);
FLOGF(error, _(L"Unable to open temporary file '%ls': %s"), out_path->c_str(), error);
}
return result;
}
/// Check how long the operation took and print a message if it took too long.
/// Returns false if it took too long else true.
static bool check_duration(double start_time) {
double duration = timef() - start_time;
if (duration > 0.25) {
FLOGF(warning, _(L"Locking the universal var file took too long (%.3f seconds)."),
duration);
return false;
}
return true;
}
/// Try locking the file. Return true if we succeeded else false. This is safe in terms of the
/// fallback function implemented in terms of fcntl: only ever run on the main thread, and protected
/// by the universal variable lock.
static bool lock_uvar_file(int fd) {
double start_time = timef();
while (flock(fd, LOCK_EX) == -1) {
if (errno != EINTR) return false; // do nothing per issue #2149
}
return check_duration(start_time);
}
bool env_universal_t::open_and_acquire_lock(const std::string &path, autoclose_fd_t *out_fd) {
// Attempt to open the file for reading at the given path, atomically acquiring a lock. On BSD,
// we can use O_EXLOCK. On Linux, we open the file, take a lock, and then compare fstat() to
// stat(); if they match, it means that the file was not replaced before we acquired the lock.
//
// We pass O_RDONLY with O_CREAT; this creates a potentially empty file. We do this so that we
// have something to lock on.
static std::atomic<bool> do_locking(true);
bool needs_lock = true;
int flags = O_RDWR | O_CREAT;
#ifdef O_EXLOCK
if (do_locking) {
flags |= O_EXLOCK;
needs_lock = false;
}
#endif
autoclose_fd_t fd{};
while (!fd.valid()) {
double start_time = timef();
fd = autoclose_fd_t{open_cloexec(path, flags, 0644)};
if (!fd.valid()) {
if (errno == EINTR) continue; // signaled; try again
#ifdef O_EXLOCK
if (do_locking && (errno == ENOTSUP || errno == EOPNOTSUPP)) {
// Filesystem probably does not support locking. Clear the flag and try again. Note
// that we try taking the lock via flock anyways. Note that on Linux the two errno
// symbols have the same value but on BSD they're different.
flags &= ~O_EXLOCK;
needs_lock = true;
continue;
}
#endif
const char *error = std::strerror(errno);
FLOGF(error, _(L"Unable to open universal variable file '%s': %s"), path.c_str(),
error);
break;
}
assert(fd.valid() && "Should have a valid fd here");
if (!needs_lock && do_locking) {
do_locking = check_duration(start_time);
}
// Try taking the lock, if necessary. If we failed, we may be on lockless NFS, etc.; in that
// case we pretend we succeeded. See the comment in save_to_path for the rationale.
if (needs_lock && do_locking) {
do_locking = lock_uvar_file(fd.fd());
}
// Hopefully we got the lock. However, it's possible the file changed out from under us
// while we were waiting for the lock. Make sure that didn't happen.
if (file_id_for_fd(fd.fd()) != file_id_for_path(path)) {
// Oops, it changed! Try again.
fd.close();
}
}
*out_fd = std::move(fd);
return out_fd->valid();
}
// Returns true if modified variables were written, false if not. (There may still be variable
// changes due to other processes on a false return).
bool env_universal_t::sync(callback_data_list_t &callbacks) {
FLOGF(uvar_file, L"universal log sync");
scoped_lock locker(lock);
// Our saving strategy:
//
// 1. Open the file, producing an fd.
// 2. Lock the file (may be combined with step 1 on systems with O_EXLOCK)
// 3. After taking the lock, check if the file at the given path is different from what we
// opened. If so, start over.
// 4. Read from the file. This can be elided if its dev/inode is unchanged since the last read
// 5. Open an adjacent temporary file
// 6. Write our changes to an adjacent file
// 7. Move the adjacent file into place via rename. This is assumed to be atomic.
// 8. Release the lock and close the file
//
// Consider what happens if Process 1 and 2 both do this simultaneously. Can there be data loss?
// Process 1 opens the file and then attempts to take the lock. Now, either process 1 will see
// the original file, or process 2's new file. If it sees the new file, we're OK: it's going to
// read from the new file, and so there's no data loss. If it sees the old file, then process 2
// must have locked it (if process 1 locks it, switch their roles). The lock will block until
// process 2 reaches step 7; at that point process 1 will reach step 2, notice that the file has
// changed, and then start over.
//
// It's possible that the underlying filesystem does not support locks (lockless NFS). In this
// case, we risk data loss if two shells try to write their universal variables simultaneously.
// In practice this is unlikely, since uvars are usually written interactively.
//
// Prior versions of fish used a hard link scheme to support file locking on lockless NFS. The
// risk here is that if the process crashes or is killed while holding the lock, future
// instances of fish will not be able to obtain it. This seems to be a greater risk than that of
// data loss on lockless NFS. Users who put their home directory on lockless NFS are playing
// with fire anyways.
if (explicit_vars_path.empty()) {
// Initialize the vars path from the default one.
// In some cases we don't "initialize()" before, so we're doing that now.
// This should only happen once.
// FIXME: Why don't we initialize()?
auto def_vars_path = default_vars_path();
if (!def_vars_path) {
FLOG(uvar_file, L"No universal variable path available");
return false;
}
explicit_vars_path = *def_vars_path;
narrow_vars_path = wcs2string(explicit_vars_path);
}
// If we have no changes, just load.
if (modified.empty()) {
this->load_from_path(narrow_vars_path, callbacks);
FLOGF(uvar_file, L"universal log no modifications");
return false;
}
const wcstring directory = wdirname(explicit_vars_path);
bool success = true;
autoclose_fd_t vars_fd{};
FLOGF(uvar_file, L"universal log performing full sync");
// Open the file.
if (success) {
success = this->open_and_acquire_lock(narrow_vars_path, &vars_fd);
if (!success) FLOGF(uvar_file, L"universal log open_and_acquire_lock() failed");
}
// Read from it.
if (success) {
assert(vars_fd.valid());
this->load_from_fd(vars_fd.fd(), callbacks);
}
if (success && ok_to_save) {
success = this->save(directory, explicit_vars_path);
}
return success;
}
// Write our file contents.
// \return true on success, false on failure.
bool env_universal_t::save(const wcstring &directory, const wcstring &vars_path) {
assert(ok_to_save && "It's not OK to save");
wcstring private_file_path;
// Open adjacent temporary file.
autoclose_fd_t private_fd = this->open_temporary_file(directory, &private_file_path);
bool success = private_fd.valid();
if (!success) FLOGF(uvar_file, L"universal log open_temporary_file() failed");
// Write to it.
if (success) {
assert(private_fd.valid());
success = this->write_to_fd(private_fd.fd(), private_file_path);
if (!success) FLOGF(uvar_file, L"universal log write_to_fd() failed");
}
if (success) {
wcstring real_path;
if (auto maybe_real_path = wrealpath(vars_path)) {
real_path = *maybe_real_path;
} else {
real_path = vars_path;
}
// Ensure we maintain ownership and permissions (#2176).
struct stat sbuf;
if (wstat(real_path, &sbuf) >= 0) {
if (fchown(private_fd.fd(), sbuf.st_uid, sbuf.st_gid) == -1)
FLOGF(uvar_file, L"universal log fchown() failed");
if (fchmod(private_fd.fd(), sbuf.st_mode) == -1)
FLOGF(uvar_file, L"universal log fchmod() failed");
}
// Linux by default stores the mtime with low precision, low enough that updates that occur
// in quick succession may result in the same mtime (even the nanoseconds field). So
// manually set the mtime of the new file to a high-precision clock. Note that this is only
// necessary because Linux aggressively reuses inodes, causing the ABA problem; on other
// platforms we tend to notice the file has changed due to a different inode (or file size!)
//
// It's probably worth finding a simpler solution to this. The tests ran into this, but it's
// unlikely to affect users.
#if HAVE_CLOCK_GETTIME && HAVE_FUTIMENS
struct timespec times[2] = {};
times[0].tv_nsec = UTIME_OMIT; // don't change ctime
if (0 == clock_gettime(CLOCK_REALTIME, ×[1])) {
futimens(private_fd.fd(), times);
}
#endif
// Apply new file.
success = this->move_new_vars_file_into_place(private_file_path, real_path);
if (!success) FLOGF(uvar_file, L"universal log move_new_vars_file_into_place() failed");
}
if (success) {
// Since we moved the new file into place, clear the path so we don't try to unlink it.
private_file_path.clear();
}
// Clean up.
if (!private_file_path.empty()) {
wunlink(private_file_path);
}
if (success) {
// All of our modified variables have now been written out.
modified.clear();
}
return success;
}
uvar_format_t env_universal_t::read_message_internal(int fd, var_table_t *vars) {
// Read everything from the fd. Put a sane limit on it.
std::string contents;
while (contents.size() < k_max_read_size) {
char buffer[4096];
ssize_t amt = read_loop(fd, buffer, sizeof buffer);
if (amt <= 0) {
break;
}
contents.append(buffer, amt);
}
// Handle overlong files.
if (contents.size() >= k_max_read_size) {
contents.resize(k_max_read_size);
// Back up to a newline.
size_t newline = contents.rfind('\n');
contents.resize(newline == wcstring::npos ? 0 : newline);
}
return populate_variables(contents, vars);
}
/// \return the format corresponding to file contents \p s.
uvar_format_t env_universal_t::format_for_contents(const std::string &s) {
// Walk over leading comments, looking for one like '# version'
line_iterator_t<std::string> iter{s};
while (iter.next()) {
const std::string &line = iter.line();
if (line.empty()) continue;
if (line.front() != L'#') {
// Exhausted leading comments.
break;
}
// Note scanf %s is max characters to write; add 1 for null terminator.
char versionbuf[64 + 1];
if (sscanf(line.c_str(), "# VERSION: %64s", versionbuf) != 1) continue;
// Try reading the version.
if (!std::strcmp(versionbuf, UVARS_VERSION_3_0)) {
return uvar_format_t::fish_3_0;
} else {
// Unknown future version.
return uvar_format_t::future;
}
}
// No version found, assume 2.x
return uvar_format_t::fish_2_x;
}
uvar_format_t env_universal_t::populate_variables(const std::string &s, var_table_t *out_vars) {
// Decide on the format.
const uvar_format_t format = format_for_contents(s);
line_iterator_t<std::string> iter{s};
wcstring wide_line;
wcstring storage;
while (iter.next()) {
const std::string &line = iter.line();
// Skip empties and constants.
if (line.empty() || line.front() == L'#') continue;
// Convert to UTF8.
wide_line.clear();
if (!utf8_to_wchar(line.data(), line.size(), &wide_line, 0)) continue;
switch (format) {
case uvar_format_t::fish_2_x:
env_universal_t::parse_message_2x_internal(wide_line, out_vars, &storage);
break;
case uvar_format_t::fish_3_0:
// For future formats, just try with the most recent one.
case uvar_format_t::future:
env_universal_t::parse_message_30_internal(wide_line, out_vars, &storage);
break;
}
}
return format;
}
static const wchar_t *skip_spaces(const wchar_t *str) {
while (*str == L' ' || *str == L'\t') str++;
return str;
}
bool env_universal_t::populate_1_variable(const wchar_t *input, env_var_t::env_var_flags_t flags,
var_table_t *vars, wcstring *storage) {
const wchar_t *str = skip_spaces(input);
const wchar_t *colon = std::wcschr(str, L':');
if (!colon) return false;
// Parse out the value into storage, and decode it into a variable.
storage->clear();
if (!unescape_string(colon + 1, storage, 0)) {
return false;
}
env_var_t var{decode_serialized(*storage), flags};
// Parse out the key and write into the map.
storage->assign(str, colon - str);
const wcstring &key = *storage;
(*vars)[key] = std::move(var);
return true;
}
/// Parse message msg per fish 3.0 format.
void env_universal_t::parse_message_30_internal(const wcstring &msgstr, var_table_t *vars,
wcstring *storage) {
namespace f3 = fish3_uvars;
const wchar_t *const msg = msgstr.c_str();
if (msg[0] == L'#') return;
const wchar_t *cursor = msg;
if (!match(&cursor, f3::SETUVAR)) {
FLOGF(warning, PARSE_ERR, msg);
return;
}
// Parse out flags.
env_var_t::env_var_flags_t flags = 0;
for (;;) {
cursor = skip_spaces(cursor);
if (*cursor != L'-') break;
if (match(&cursor, f3::EXPORT)) {
flags |= env_var_t::flag_export;
} else if (match(&cursor, f3::PATH)) {
flags |= env_var_t::flag_pathvar;
} else {
// Skip this unknown flag, for future proofing.
while (*cursor && *cursor != L' ' && *cursor != L'\t') cursor++;
}
}
// Populate the variable with these flags.
if (!populate_1_variable(cursor, flags, vars, storage)) {
FLOGF(warning, PARSE_ERR, msg);
}
}
/// Parse message msg per fish 2.x format.
void env_universal_t::parse_message_2x_internal(const wcstring &msgstr, var_table_t *vars,
wcstring *storage) {
namespace f2x = fish2x_uvars;
const wchar_t *const msg = msgstr.c_str();
const wchar_t *cursor = msg;
if (cursor[0] == L'#') return;
env_var_t::env_var_flags_t flags = 0;
if (match(&cursor, f2x::SET_EXPORT)) {
flags |= env_var_t::flag_export;
} else if (match(&cursor, f2x::SET)) {
flags |= 0;
} else {
FLOGF(warning, PARSE_ERR, msg);
return;
}
if (!populate_1_variable(cursor, flags, vars, storage)) {
FLOGF(warning, PARSE_ERR, msg);
}
}
/// Maximum length of hostname. Longer hostnames are truncated.
#define HOSTNAME_LEN 255
/// Length of a MAC address.
#define MAC_ADDRESS_MAX_LEN 6
// Thanks to Jan Brittenson, http://lists.apple.com/archives/xcode-users/2009/May/msg00062.html
#ifdef SIOCGIFHWADDR
// Linux
#include <net/if.h>
#include <sys/socket.h>
static bool get_mac_address(unsigned char macaddr[MAC_ADDRESS_MAX_LEN],
const char *interface = "eth0") {
bool result = false;
const int dummy = socket(AF_INET, SOCK_STREAM, 0);
if (dummy >= 0) {
struct ifreq r;
strncpy(const_cast<char *>(r.ifr_name), interface, sizeof r.ifr_name - 1);
r.ifr_name[sizeof r.ifr_name - 1] = 0;
if (ioctl(dummy, SIOCGIFHWADDR, &r) >= 0) {
std::memcpy(macaddr, r.ifr_hwaddr.sa_data, MAC_ADDRESS_MAX_LEN);
result = true;
}
close(dummy);
}
return result;
}
#elif defined(HAVE_GETIFADDRS)
// OS X and BSD
#include <ifaddrs.h>
#include <net/if_dl.h>
#include <sys/socket.h>
static bool get_mac_address(unsigned char macaddr[MAC_ADDRESS_MAX_LEN],
const char *interface = "en0") {
// BSD, Mac OS X
struct ifaddrs *ifap;
bool ok = false;
if (getifaddrs(&ifap) != 0) {
return ok;
}
for (const ifaddrs *p = ifap; p; p = p->ifa_next) {
bool is_af_link = p->ifa_addr && p->ifa_addr->sa_family == AF_LINK;
if (is_af_link && p->ifa_name && p->ifa_name[0] &&
!strcmp((const char *)p->ifa_name, interface)) {
const sockaddr_dl &sdl = *reinterpret_cast<sockaddr_dl *>(p->ifa_addr);
size_t alen = sdl.sdl_alen;
if (alen > MAC_ADDRESS_MAX_LEN) alen = MAC_ADDRESS_MAX_LEN;
std::memcpy(macaddr, sdl.sdl_data + sdl.sdl_nlen, alen);
ok = true;
break;
}
}
freeifaddrs(ifap);
return ok;
}
#else
// Unsupported
static bool get_mac_address(unsigned char macaddr[MAC_ADDRESS_MAX_LEN]) { return false; }
#endif
/// Function to get an identifier based on the hostname.
bool get_hostname_identifier(wcstring &result) {
// The behavior of gethostname if the buffer size is insufficient differs by implementation and
// libc version Work around this by using a "guaranteed" sufficient buffer size then truncating
// the result.
bool success = false;
char hostname[256] = {};
if (gethostname(hostname, sizeof(hostname)) == 0) {
result.assign(str2wcstring(hostname));
result.assign(truncate(result, HOSTNAME_LEN));
success = true;
}
return success;
}
/// Get a sort of unique machine identifier. Prefer the MAC address; if that fails, fall back to the
/// hostname; if that fails, pick something.
static wcstring get_machine_identifier() {
wcstring result;
unsigned char mac_addr[MAC_ADDRESS_MAX_LEN] = {};
if (get_mac_address(mac_addr)) {
result.reserve(2 * MAC_ADDRESS_MAX_LEN);
for (auto i : mac_addr) {
append_format(result, L"%02x", i);
}
} else if (!get_hostname_identifier(result)) {
result.assign(L"nohost"); // fallback to a dummy value
}
return result;
}
class universal_notifier_shmem_poller_t final : public universal_notifier_t {
#ifdef __CYGWIN__
// This is what our shared memory looks like. Everything here is stored in network byte order
// (big-endian).
struct universal_notifier_shmem_t {
uint32_t magic;
uint32_t version;
uint32_t universal_variable_seed;
};
#define SHMEM_MAGIC_NUMBER 0xF154
#define SHMEM_VERSION_CURRENT 1000
private:
long long last_change_time{0};
uint32_t last_seed{0};
volatile universal_notifier_shmem_t *region{nullptr};
void open_shmem() {
assert(region == nullptr);
// Use a path based on our uid to avoid collisions.
char path[NAME_MAX];
snprintf(path, sizeof path, "/%ls_shmem_%d", program_name ? program_name : L"fish",
getuid());
autoclose_fd_t fd{shm_open(path, O_RDWR | O_CREAT, 0600)};
if (!fd.valid()) {
const char *error = std::strerror(errno);
FLOGF(error, _(L"Unable to open shared memory with path '%s': %s"), path, error);
return;
}
// Get the size.
off_t size = 0;
struct stat buf = {};
if (fstat(fd.fd(), &buf) < 0) {
const char *error = std::strerror(errno);
FLOGF(error, _(L"Unable to fstat shared memory object with path '%s': %s"), path,
error);
return;
}
size = buf.st_size;
// Set the size, if it's too small.
if (size < (off_t)sizeof(universal_notifier_shmem_t)) {
if (ftruncate(fd.fd(), sizeof(universal_notifier_shmem_t)) < 0) {
const char *error = std::strerror(errno);
FLOGF(error, _(L"Unable to truncate shared memory object with path '%s': %s"), path,
error);
return;
}
}
// Memory map the region.
void *addr = mmap(nullptr, sizeof(universal_notifier_shmem_t), PROT_READ | PROT_WRITE,
MAP_SHARED, fd.fd(), 0);
if (addr == MAP_FAILED) {
const char *error = std::strerror(errno);
FLOGF(error, _(L"Unable to memory map shared memory object with path '%s': %s"), path,
error);
this->region = nullptr;
return;
}
this->region = static_cast<universal_notifier_shmem_t *>(addr);
// Read the current seed.
this->poll();
}
public:
// Our notification involves changing the value in our shared memory. In practice, all clients
// will be in separate processes, so it suffices to set the value to a pid. For testing
// purposes, however, it's useful to keep them in the same process, so we increment the value.
// This isn't "safe" in the sense that multiple simultaneous increments may result in one being
// lost, but it should always result in the value being changed, which is sufficient.
void post_notification() override {
if (region != nullptr) {
/* Read off the seed */
uint32_t seed = ntohl(region->universal_variable_seed); //!OCLINT(constant cond op)
// Increment it. Don't let it wrap to zero.
do {
seed++;
} while (seed == 0);
last_seed = seed;
// Write out our data.
region->magic = htonl(SHMEM_MAGIC_NUMBER); //!OCLINT(constant cond op)
region->version = htonl(SHMEM_VERSION_CURRENT); //!OCLINT(constant cond op)
region->universal_variable_seed = htonl(seed); //!OCLINT(constant cond op)
}
}
universal_notifier_shmem_poller_t() { open_shmem(); }
~universal_notifier_shmem_poller_t() {
if (region != nullptr) {
void *address = const_cast<void *>(static_cast<volatile void *>(region));
if (munmap(address, sizeof(universal_notifier_shmem_t)) < 0) {
wperror(L"munmap");
}
}
}
bool poll() override {
bool result = false;
if (region != nullptr) {
uint32_t seed = ntohl(region->universal_variable_seed); //!OCLINT(constant cond op)
if (seed != last_seed) {
result = true;
last_seed = seed;
last_change_time = get_time();
}
}
return result;
}
unsigned long usec_delay_between_polls() const override {
// If it's been less than five seconds since the last change, we poll quickly Otherwise we
// poll more slowly. Note that a poll is a very cheap shmem read. The bad part about making
// this high is the process scheduling/wakeups it produces.
long long usec_per_sec = 1000000;
if (get_time() - last_change_time < 5LL * usec_per_sec) {
return usec_per_sec / 10; // 10 times a second
}
return usec_per_sec / 3; // 3 times a second
}
#else // this class isn't valid on this system
public:
[[noreturn]] universal_notifier_shmem_poller_t() {
DIE("universal_notifier_shmem_poller_t cannot be used on this system");
}
#endif
};
/// A notifyd-based notifier. Very straightforward.
class universal_notifier_notifyd_t final : public universal_notifier_t {
#ifdef FISH_NOTIFYD_AVAILABLE
// Note that we should not use autoclose_fd_t, as notify_cancel() takes responsibility for
// closing it.
int notify_fd{-1};
int token{-1}; // NOTIFY_TOKEN_INVALID
std::string name{};
void setup_notifyd() {
// Per notify(3), the user.uid.%d style is only accessible to processes with that uid.
char local_name[256];
snprintf(local_name, sizeof local_name, "user.uid.%d.%ls.uvars", getuid(),
program_name ? program_name : L"fish");
name.assign(local_name);
uint32_t status =
notify_register_file_descriptor(name.c_str(), &this->notify_fd, 0, &this->token);
if (status != NOTIFY_STATUS_OK) {
FLOGF(warning, "notify_register_file_descriptor() failed with status %u.", status);
FLOGF(warning, "Universal variable notifications may not be received.");
}
if (notify_fd >= 0) {
// Mark us for non-blocking reads, and CLO_EXEC.
int flags = fcntl(notify_fd, F_GETFL, 0);
if (flags >= 0 && !(flags & O_NONBLOCK)) {
fcntl(notify_fd, F_SETFL, flags | O_NONBLOCK);
}
(void)set_cloexec(notify_fd);
// Serious hack: notify_fd is likely the read end of a pipe. The other end is owned by
// libnotify, which does not mark it as CLO_EXEC (it should!). The next fd is probably
// notify_fd + 1. Do it ourselves. If the implementation changes and some other FD gets
// marked as CLO_EXEC, that's probably a good thing.
(void)set_cloexec(notify_fd + 1);
}
}
public:
universal_notifier_notifyd_t() { setup_notifyd(); }
~universal_notifier_notifyd_t() {
if (token != -1 /* NOTIFY_TOKEN_INVALID */) {
// Note this closes notify_fd.
notify_cancel(token);
}
}
int notification_fd() const override { return notify_fd; }
bool notification_fd_became_readable(int fd) override {
// notifyd notifications come in as 32 bit values. We don't care about the value. We set
// ourselves as non-blocking, so just read until we can't read any more.
assert(fd == notify_fd);
bool read_something = false;
unsigned char buff[64];
ssize_t amt_read;
do {
amt_read = read(notify_fd, buff, sizeof buff);
read_something = (read_something || amt_read > 0);
} while (amt_read == sizeof buff);
return read_something;
}
void post_notification() override {
uint32_t status = notify_post(name.c_str());
if (status != NOTIFY_STATUS_OK) {
FLOGF(warning,
"notify_post() failed with status %u. Uvar notifications may not be sent.",
status);
}
}
#else // this class isn't valid on this system
public:
[[noreturn]] universal_notifier_notifyd_t() {
DIE("universal_notifier_notifyd_t cannot be used on this system");
}
#endif
};
/// Returns a "variables" file in the appropriate runtime directory. This is called infrequently and
/// so does not need to be cached.
static wcstring default_named_pipe_path() {
wcstring result = env_get_runtime_path();
if (!result.empty()) {
result.append(L"/fish_universal_variables");
}
return result;
}
/// Create a fifo (named pipe) at \p test_path if non-null, or a default runtime path if null.
/// Open the fifo for both reading and writing, in non-blocking mode.
/// \return the fifo, or an invalid fd on failure.
static autoclose_fd_t make_fifo(const wchar_t *test_path, const wchar_t *suffix) {
wcstring vars_path = test_path ? wcstring(test_path) : default_named_pipe_path();
vars_path.append(suffix);
const std::string narrow_path = wcs2string(vars_path);
int mkfifo_status = mkfifo(narrow_path.c_str(), 0600);
if (mkfifo_status == -1 && errno != EEXIST) {
const char *error = std::strerror(errno);
const wchar_t *errmsg = _(L"Unable to make a pipe for universal variables using '%ls': %s");
FLOGF(error, errmsg, vars_path.c_str(), error);
return autoclose_fd_t{};
}
autoclose_fd_t res{wopen_cloexec(vars_path, O_RDWR | O_NONBLOCK, 0600)};
if (!res.valid()) {
const char *error = std::strerror(errno);
const wchar_t *errmsg = _(L"Unable to open a pipe for universal variables using '%ls': %s");
FLOGF(error, errmsg, vars_path.c_str(), error);
}
return res;
}
// Named-pipe based notifier. All clients open the same named pipe for reading and writing. The
// pipe's readability status is a trigger to enter polling mode.
//
// To post a notification, write some data to the pipe, wait a little while, and then read it back.
//
// To receive a notification, watch for the pipe to become readable. When it does, enter a polling
// mode until the pipe is no longer readable. To guard against the possibility of a shell exiting
// when there is data remaining in the pipe, if the pipe is kept readable too long, clients will
// attempt to read data out of it (to render it no longer readable).
class universal_notifier_named_pipe_t final : public universal_notifier_t {
#if !defined(__CYGWIN__)
autoclose_fd_t pipe_fd;
long long readback_time_usec{0};
size_t readback_amount{0};
// We "flash" the pipe to make it briefly readable, for this many usec.
static constexpr long long k_flash_duration_usec = 1e5;
// If the pipe remains readable for this many usec, we drain it.
static constexpr long long k_readable_too_long_duration_usec = 5e6;
bool polling_due_to_readable_fd{false};
long long drain_if_still_readable_time_usec{0};
void drain_excessive_data() const {
// The pipe seems to have data on it, that won't go away. Read a big chunk out of it. We
// don't read until it's exhausted, because if someone were to pipe say /dev/null, that
// would cause us to hang!
char buff[512];
ignore_result(read(pipe_fd.fd(), buff, sizeof buff));
}
public:
explicit universal_notifier_named_pipe_t(const wchar_t *test_path)
: pipe_fd(make_fifo(test_path, L".notifier")) {}
~universal_notifier_named_pipe_t() override = default;
int notification_fd() const override {
if (polling_due_to_readable_fd) {
// We are in polling mode because we think our fd is readable. This means that, if we
// return it to be select()'d on, we'll be called back immediately. So don't return it.
return -1;
}
// We are not in polling mode. Return the fd so it can be watched.
return pipe_fd.fd();
}
bool notification_fd_became_readable(int fd) override {
// Our fd is readable. We deliberately do not read anything out of it: if we did, other
// sessions may miss the notification. Instead, we go into "polling mode:" we do not
// select() on our fd for a while, and sync periodically until the fd is no longer readable.
// However, if we are the one who posted the notification, we don't sync (until we clean
// up!)
UNUSED(fd);
bool should_sync = false;
if (readback_time_usec == 0) {
polling_due_to_readable_fd = true;
drain_if_still_readable_time_usec = get_time() + k_readable_too_long_duration_usec;
should_sync = true;
}
return should_sync;
}
void post_notification() override {
if (!pipe_fd.valid()) return;
// We need to write some data (any data) to the pipe, then wait for a while, then read
// it back. Nobody is expected to read it except us.
char c[1] = {'\0'};
ssize_t amt_written = write(pipe_fd.fd(), c, sizeof c);
if (amt_written < 0 && (errno == EWOULDBLOCK || errno == EAGAIN)) {
// Very unsual: the pipe is full!
drain_excessive_data();
}
// Now schedule a read for some time in the future.
this->readback_time_usec = get_time() + k_flash_duration_usec;
this->readback_amount += sizeof c;
}
unsigned long usec_delay_between_polls() const override {
unsigned long readback_delay = ULONG_MAX;
if (this->readback_time_usec > 0) {
// How long until the readback?
long long now = get_time();
if (now >= this->readback_time_usec) {
// Oops, it already passed! Return something tiny.
readback_delay = 1000;
} else {
readback_delay = static_cast<unsigned long>(this->readback_time_usec - now);
}
}
unsigned long polling_delay = ULONG_MAX;
if (polling_due_to_readable_fd) {
// We're in polling mode. Don't return a value less than our polling interval.
polling_delay = k_flash_duration_usec;
}
// Now return the smaller of the two values. If we get ULONG_MAX, it means there's no more
// need to poll; in that case return 0.
unsigned long result = std::min(readback_delay, polling_delay);
if (result == ULONG_MAX) {
result = 0;
}
return result;
}
bool poll() override {
if (!pipe_fd.valid()) return false;
// Check if we are past the readback time.
if (this->readback_time_usec > 0 && get_time() >= this->readback_time_usec) {
// Read back what we wrote. We do nothing with the value.
while (this->readback_amount > 0) {
char buff[64];
size_t amt_to_read = std::min(this->readback_amount, sizeof(buff));
ignore_result(read(this->pipe_fd.fd(), buff, amt_to_read));
this->readback_amount -= amt_to_read;
}
assert(this->readback_amount == 0);
this->readback_time_usec = 0;
}
// Check to see if we are doing readability polling.
if (!polling_due_to_readable_fd) {
return false;
}
// We are polling, so we are definitely going to sync.
// See if this is still readable.
fd_set fds;
FD_ZERO(&fds);
FD_SET(pipe_fd.fd(), &fds);
struct timeval timeout = {};
select(pipe_fd.fd() + 1, &fds, nullptr, nullptr, &timeout);
if (!FD_ISSET(pipe_fd.fd(), &fds)) {
// No longer readable, no longer polling.
polling_due_to_readable_fd = false;
drain_if_still_readable_time_usec = 0;
} else {
// Still readable. If it's been readable for a long time, there is probably
// lingering data on the pipe.
if (get_time() >= drain_if_still_readable_time_usec) {
drain_excessive_data();
}
}
return true;
}
#else // this class isn't valid on this system
public:
universal_notifier_named_pipe_t(const wchar_t *test_path) {
static_cast<void>(test_path);
DIE("universal_notifier_named_pipe_t cannot be used on this system");
}
#endif
};
universal_notifier_t::notifier_strategy_t universal_notifier_t::resolve_default_strategy() {
#ifdef FISH_NOTIFYD_AVAILABLE
return strategy_notifyd;
#elif defined(__CYGWIN__)
return strategy_shmem_polling;
#else
return strategy_named_pipe;
#endif
}
universal_notifier_t &universal_notifier_t::default_notifier() {
static std::unique_ptr<universal_notifier_t> result =
new_notifier_for_strategy(universal_notifier_t::resolve_default_strategy());
return *result;
}
std::unique_ptr<universal_notifier_t> universal_notifier_t::new_notifier_for_strategy(
universal_notifier_t::notifier_strategy_t strat, const wchar_t *test_path) {
switch (strat) {
case strategy_notifyd: {
return make_unique<universal_notifier_notifyd_t>();
}
case strategy_shmem_polling: {
return make_unique<universal_notifier_shmem_poller_t>();
}
case strategy_named_pipe: {
return make_unique<universal_notifier_named_pipe_t>(test_path);
}
}
DIE("should never reach this statement");
return nullptr;
}
// Default implementations.
universal_notifier_t::universal_notifier_t() = default;
universal_notifier_t::~universal_notifier_t() = default;
int universal_notifier_t::notification_fd() const { return -1; }
bool universal_notifier_t::poll() { return false; }
void universal_notifier_t::post_notification() {}
unsigned long universal_notifier_t::usec_delay_between_polls() const { return 0; }
bool universal_notifier_t::notification_fd_became_readable(int fd) {
UNUSED(fd);
return false;
}