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fde74d489c
fish-shell/src/env_universal_common.cpp
David Adam fde74d489c Fix build on Linux 
Broken in dc250e0c29
2018-09-19 10:55:36 +08:00

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// 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 <string.h>
#ifdef __CYGWIN__
#include <sys/mman.h>
#endif
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h> // IWYU pragma: keep
#endif
#include <sys/stat.h>
#include <sys/time.h> // IWYU pragma: keep
#include <sys/types.h> // IWYU pragma: keep
#include <unistd.h>
#include <wchar.h>
#include <atomic>
#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 "path.h"
#include "utf8.h"
#include "util.h" // IWYU pragma: keep
#include "wutil.h"
#include "wcstringutil.h"
#if __APPLE__
#define FISH_NOTIFYD_AVAILABLE 1
#include <notify.h>
#endif
#ifdef __HAIKU__
#define _BSD_SOURCE
#include <bsd/ifaddrs.h>
#endif // Haiku
/// The set command.
#define SET_STR L"SET"
/// The set_export command.
#define SET_EXPORT_STR L"SET_EXPORT"
/// Non-wide version of the set command.
#define SET_MBS "SET"
/// Non-wide version of the set_export command.
#define SET_EXPORT_MBS "SET_EXPORT"
/// 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"
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;
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_universal_variables");
return path;
}
return none();
}
#if !defined(__APPLE__) && !defined(__CYGWIN__)
/// Check, and create if necessary, a secure runtime path. Derived from tmux.c in tmux
/// (http://tmux.sourceforge.net/).
static int check_runtime_path(const char *path) {
// Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
//
// Permission to use, copy, modify, and distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
// IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
// OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
struct stat statpath;
uid_t uid = geteuid();
if (mkdir(path, S_IRWXU) != 0 && errno != EEXIST) return errno;
if (lstat(path, &statpath) != 0) return errno;
if (!S_ISDIR(statpath.st_mode) || statpath.st_uid != uid ||
(statpath.st_mode & (S_IRWXG | S_IRWXO)) != 0)
return EACCES;
return 0;
}
/// Return the path of an appropriate runtime data directory.
static wcstring get_runtime_path() {
wcstring result;
const char *dir = getenv("XDG_RUNTIME_DIR");
// Check that the path is actually usable. Technically this is guaranteed by the fdo spec but in
// practice it is not always the case: see #1828 and #2222.
int mode = R_OK | W_OK | X_OK;
if (dir != NULL && access(dir, mode) == 0 && check_runtime_path(dir) == 0) {
result = str2wcstring(dir);
} else {
// Don't rely on $USER being set, as setup_user() has not yet been called.
// See https://github.com/fish-shell/fish-shell/issues/5180
const char *uname = getpwuid(geteuid())->pw_name;
// /tmp/fish.user
std::string tmpdir = "/tmp/fish.";
tmpdir.append(uname);
if (check_runtime_path(tmpdir.c_str()) != 0) {
debug(0, L"Runtime path not available.");
debug(0, L"Try deleting the directory %s and restarting fish.", tmpdir.c_str());
} else {
result = str2wcstring(tmpdir);
}
}
return result;
}
/// 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 = get_runtime_path();
if (!result.empty()) {
result.append(L"/fish_universal_variables");
}
return result;
}
#endif
/// Test if the message msg contains the command cmd.
static bool match(const wchar_t *msg, const wchar_t *cmd) {
size_t len = wcslen(cmd);
if (wcsncasecmp(msg, cmd, len) != 0) return false;
if (msg[len] && msg[len] != L' ' && msg[len] != L'\t') return false;
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) || wcschr(L"/_", c);
}
/// Escape specified string.
static wcstring full_escape(const wchar_t *in) {
wcstring out;
for (; *in; in++) {
wchar_t c = *in;
if (is_universal_safe_to_encode_directly(c)) {
out.push_back(c);
} else if (c <= (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(fish_message_type_t type, const wcstring &key_in,
const wcstring &val_in, std::string *result, std::string *storage) {
assert(storage != NULL);
assert(result != NULL);
// 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 header like "SET "
result->append(type == SET ? SET_MBS : SET_EXPORT_MBS);
result->push_back(' ');
// Append variable name like "fish_color_cwd".
if (!valid_var_name(key_in)) {
debug(0, L"Illegal variable name: '%ls'", key_in.c_str());
success = false;
}
if (success && !append_utf8(key_in, result, storage)) {
debug(0, 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.c_str()), result, storage)) {
debug(0, 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 *ENV_NULL = L"\x1d";
/// 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, 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, ARRAY_SEP);
}
env_universal_t::env_universal_t(wcstring path) : explicit_vars_path(std::move(path)) {}
maybe_t<env_var_t> env_universal_t::get(const wcstring &name) const {
var_table_t::const_iterator where = vars.find(name);
if (where != vars.end()) return where->second;
return none();
}
bool env_universal_t::get_export(const wcstring &name) const {
bool result = false;
var_table_t::const_iterator where = vars.find(name);
if (where != vars.end()) {
result = where->second.exports();
}
return result;
}
void env_universal_t::set_internal(const wcstring &key, wcstring_list_t vals, bool exportv,
bool overwrite) {
ASSERT_IS_LOCKED(lock);
if (!overwrite && this->modified.find(key) != this->modified.end()) {
// This value has been modified and we're not overwriting it. Skip it.
return;
}
env_var_t &entry = vars[key];
if (entry.exports() != exportv || entry.as_list() != vals) {
entry.set_vals(std::move(vals));
entry.set_exports(exportv);
// If we are overwriting, then this is now modified.
if (overwrite) {
this->modified.insert(key);
}
}
}
void env_universal_t::set(const wcstring &key, wcstring_list_t vals, bool exportv) {
scoped_lock locker(lock);
this->set_internal(key, std::move(vals), exportv, true /* overwrite */);
}
bool env_universal_t::remove_internal(const wcstring &key) {
ASSERT_IS_LOCKED(lock);
size_t erased = this->vars.erase(key);
if (erased > 0) {
this->modified.insert(key);
}
return erased > 0;
}
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);
var_table_t::const_iterator iter;
for (iter = vars.begin(); iter != vars.end(); ++iter) {
const wcstring &key = iter->first;
const env_var_t &var = iter->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.
void env_universal_t::generate_callbacks(const var_table_t &new_vars,
callback_data_list_t &callbacks) const {
// Construct callbacks for erased values.
for (var_table_t::const_iterator iter = this->vars.begin(); iter != this->vars.end(); ++iter) {
const wcstring &key = iter->first;
// Skip modified values.
if (this->modified.find(key) != this->modified.end()) {
continue;
}
// If the value is not present in new_vars, it has been erased.
if (new_vars.find(key) == new_vars.end()) {
callbacks.push_back(callback_data_t(ERASE, key, L""));
}
}
// Construct callbacks for newly inserted or changed values.
for (var_table_t::const_iterator iter = new_vars.begin(); iter != new_vars.end(); ++iter) {
const wcstring &key = iter->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 = iter->second;
var_table_t::const_iterator existing = this->vars.find(key);
if (existing == this->vars.end() || existing->second.exports() != new_entry.exports() ||
existing->second != new_entry) {
// Value has changed.
callbacks.push_back(callback_data_t(new_entry.exports() ? SET_EXPORT : SET, 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) {
var_table_t::iterator 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) {
debug(5, L"universal log sync elided based on fstat()");
} else {
// Read a variables table from the file.
var_table_t new_vars = this->read_message_internal(fd);
// Announce changes.
this->generate_callbacks(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 wcstring &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) {
debug(5, L"universal log sync elided based on fast stat()");
return true;
}
bool result = false;
int fd = wopen_cloexec(path, O_RDONLY);
if (fd >= 0) {
debug(5, L"universal log reading from file");
this->load_from_fd(fd, callbacks);
close(fd);
result = true;
}
return result;
}
/// 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;
// Stuff we output to fd.
std::string contents;
// Temporary storage.
std::string storage;
// Write the save message. If this fails, we don't bother complaining.
write_loop(fd, SAVE_MSG, strlen(SAVE_MSG));
var_table_t::const_iterator iter = vars.begin();
while (iter != vars.end()) {
// Append the entry. Note that append_file_entry may fail, but that only affects one
// variable; soldier on.
const wcstring &key = iter->first;
const env_var_t &var = iter->second;
append_file_entry(var.exports() ? SET_EXPORT : SET, key, encode_serialized(var.as_list()),
&contents, &storage);
// Go to next.
++iter;
// Flush if this is the last iteration or we exceed a page.
if (iter == vars.end() || contents.size() >= 4096) {
if (write_loop(fd, contents.data(), contents.size()) < 0) {
const char *error = strerror(errno);
debug(0, _(L"Unable to write to universal variables file '%ls': %s"), path.c_str(),
error);
success = false;
break;
}
contents.clear();
}
}
// 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 = strerror(errno);
debug(0, _(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(explicit_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;
}
}
}
}
return success;
}
bool env_universal_t::open_temporary_file(const wcstring &directory, wcstring *out_path,
int *out_fd) {
// 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)
bool success = false;
int saved_errno;
const wcstring tmp_name_template = directory + L"/fishd.tmp.XXXXXX";
for (size_t attempt = 0; attempt < 10 && !success; attempt++) {
char *narrow_str = wcs2str(tmp_name_template);
int result_fd = fish_mkstemp_cloexec(narrow_str);
saved_errno = errno;
success = result_fd != -1;
*out_fd = result_fd;
*out_path = str2wcstring(narrow_str);
free(narrow_str);
}
if (!success) {
const char *error = strerror(saved_errno);
debug(0, _(L"Unable to open temporary file '%ls': %s"), out_path->c_str(), error);
}
return success;
}
/// 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) {
debug(1, _(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 wcstring &path, int *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
int fd = -1;
while (fd == -1) {
double start_time = timef();
fd = wopen_cloexec(path, flags, 0644);
if (fd == -1) {
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 = strerror(errno);
debug(0, _(L"Unable to open universal variable file '%ls': %s"), path.c_str(), error);
break;
}
assert(fd >= 0); // if we get here, we must have a valid fd
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);
}
// 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) != file_id_for_path(path)) {
// Oops, it changed! Try again.
close(fd);
fd = -1;
}
}
*out_fd = fd;
return fd >= 0;
}
// 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) {
debug(5, 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.
wcstring vars_path = explicit_vars_path;
if (vars_path.empty()) {
if (auto default_path = default_vars_path()) {
vars_path = default_path.acquire();
}
}
if (vars_path.empty()) {
debug(2, L"No universal variable path available");
return false;
}
// If we have no changes, just load.
if (modified.empty()) {
this->load_from_path(vars_path, callbacks);
debug(5, L"universal log no modifications");
return false;
}
const wcstring directory = wdirname(vars_path);
bool success = true;
int vars_fd = -1;
int private_fd = -1;
wcstring private_file_path;
debug(5, L"universal log performing full sync");
// Open the file.
if (success) {
success = this->open_and_acquire_lock(vars_path, &vars_fd);
if (!success) debug(5, L"universal log open_and_acquire_lock() failed");
}
// Read from it.
if (success) {
assert(vars_fd >= 0);
this->load_from_fd(vars_fd, callbacks);
}
// Open adjacent temporary file.
if (success) {
success = this->open_temporary_file(directory, &private_file_path, &private_fd);
if (!success) debug(5, L"universal log open_temporary_file() failed");
}
// Write to it.
if (success) {
assert(private_fd >= 0);
success = this->write_to_fd(private_fd, private_file_path);
if (!success) debug(5, L"universal log write_to_fd() failed");
}
if (success) {
// Ensure we maintain ownership and permissions (#2176).
struct stat sbuf;
if (wstat(vars_path, &sbuf) >= 0) {
if (fchown(private_fd, sbuf.st_uid, sbuf.st_gid) == -1)
debug(5, L"universal log fchown() failed");
if (fchmod(private_fd, sbuf.st_mode) == -1) debug(5, 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, &times[1])) {
futimens(private_fd, times);
}
#endif
// Apply new file.
success = this->move_new_vars_file_into_place(private_file_path, vars_path);
if (!success) debug(5, 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 (vars_fd >= 0) {
close(vars_fd);
}
if (private_fd >= 0) {
close(private_fd);
}
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;
}
var_table_t env_universal_t::read_message_internal(int fd) {
var_table_t result;
// Temp value used to avoid repeated allocations.
wcstring storage;
// The line we construct (and then parse).
std::string line;
wcstring wide_line;
for (;;) {
// Read into a buffer. Note this is NOT null-terminated!
char buffer[1024];
ssize_t amt = read_loop(fd, buffer, sizeof buffer);
if (amt <= 0) {
break;
}
const size_t bufflen = (size_t)amt;
// Walk over it by lines. The contents of an unterminated line will be left in 'line' for
// the next iteration.
ssize_t line_start = 0;
while (line_start < amt) {
// Run until we hit a newline.
size_t cursor = line_start;
while (cursor < bufflen && buffer[cursor] != '\n') {
cursor++;
}
// Copy over what we read.
line.append(buffer + line_start, cursor - line_start);
// Process it if it's a newline (which is true if we are before the end of the buffer).
if (cursor < bufflen && !line.empty()) {
if (utf8_to_wchar(line.data(), line.size(), &wide_line, 0)) {
env_universal_t::parse_message_internal(wide_line, &result, &storage);
}
line.clear();
}
// Skip over the newline (or skip past the end).
line_start = cursor + 1;
}
}
// We make no effort to handle an unterminated last line.
return result;
}
/// Parse message msg/
void env_universal_t::parse_message_internal(const wcstring &msgstr, var_table_t *vars,
wcstring *storage) {
const wchar_t *msg = msgstr.c_str();
// debug(3, L"parse_message( %ls );", msg);
if (msg[0] == L'#') return;
bool is_set_export = match(msg, SET_EXPORT_STR);
bool is_set = !is_set_export && match(msg, SET_STR);
if (is_set || is_set_export) {
const wchar_t *name, *tmp;
const bool exportv = is_set_export;
name = msg + (exportv ? wcslen(SET_EXPORT_STR) : wcslen(SET_STR));
while (name[0] == L'\t' || name[0] == L' ') name++;
tmp = wcschr(name, L':');
if (tmp) {
// Use 'storage' to hold our key to avoid allocations.
storage->assign(name, tmp - name);
const wcstring &key = *storage;
wcstring val;
if (unescape_string(tmp + 1, &val, 0)) {
env_var_t &entry = (*vars)[key];
entry.set_exports(exportv);
entry.set_vals(decode_serialized(val));
}
} else {
debug(1, PARSE_ERR, msg);
}
} else {
debug(1, PARSE_ERR, msg);
}
}
/// Maximum length of hostname. Longer hostnames are truncated.
#define HOSTNAME_LEN 32
/// 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((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) {
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;
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 (size_t i = 0; i < MAC_ADDRESS_MAX_LEN; i++) {
append_format(result, L"%02x", mac_addr[i]);
}
} else if (!get_hostname_identifier(result)) {
result.assign(L"nohost"); // fallback to a dummy value
}
return result;
}
class universal_notifier_shmem_poller_t : 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;
uint32_t last_seed;
volatile universal_notifier_shmem_t *region;
void open_shmem() {
assert(region == NULL);
// 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());
bool errored = false;
int fd = shm_open(path, O_RDWR | O_CREAT, 0600);
if (fd < 0) {
const char *error = strerror(errno);
debug(0, _(L"Unable to open shared memory with path '%s': %s"), path, error);
errored = true;
}
// Get the size.
off_t size = 0;
if (!errored) {
struct stat buf = {};
if (fstat(fd, &buf) < 0) {
const char *error = strerror(errno);
debug(0, _(L"Unable to fstat shared memory object with path '%s': %s"), path,
error);
errored = true;
}
size = buf.st_size;
}
// Set the size, if it's too small.
bool set_size = !errored && size < (off_t)sizeof(universal_notifier_shmem_t);
if (set_size && ftruncate(fd, sizeof(universal_notifier_shmem_t)) < 0) {
const char *error = strerror(errno);
debug(0, _(L"Unable to truncate shared memory object with path '%s': %s"), path, error);
errored = true;
}
// Memory map the region.
if (!errored) {
void *addr = mmap(NULL, sizeof(universal_notifier_shmem_t), PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0);
if (addr == MAP_FAILED) {
const char *error = strerror(errno);
debug(0, _(L"Unable to memory map shared memory object with path '%s': %s"), path,
error);
this->region = NULL;
} else {
this->region = static_cast<universal_notifier_shmem_t *>(addr);
}
}
// Close the fd, even if the mapping succeeded.
if (fd >= 0) {
close(fd);
}
// 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() {
if (region != NULL) {
/* 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() : last_change_time(0), last_seed(0), region(NULL) {
open_shmem();
}
~universal_notifier_shmem_poller_t() {
if (region != NULL) {
// Behold: C++ in all its glory!
void *address = const_cast<void *>(static_cast<volatile void *>(region));
if (munmap(address, sizeof(universal_notifier_shmem_t)) < 0) {
wperror(L"munmap");
}
}
}
bool poll() {
bool result = false;
if (region != NULL) {
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 {
// 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:
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 : public universal_notifier_t {
#if FISH_NOTIFYD_AVAILABLE
int notify_fd;
int token;
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) {
debug(1, "notify_register_file_descriptor() failed with status %u.", status);
debug(1, "Universal variable notifications may not be received.");
}
if (this->notify_fd >= 0) {
// Mark us for non-blocking reads, and CLO_EXEC.
int flags = fcntl(this->notify_fd, F_GETFL, 0);
if (flags >= 0 && !(flags & O_NONBLOCK)) {
fcntl(this->notify_fd, F_SETFL, flags | O_NONBLOCK);
}
set_cloexec(this->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.
set_cloexec(this->notify_fd + 1);
}
}
public:
universal_notifier_notifyd_t() : notify_fd(-1), token(-1 /* NOTIFY_TOKEN_INVALID */) {
setup_notifyd();
}
~universal_notifier_notifyd_t() {
if (token != -1 /* NOTIFY_TOKEN_INVALID */) {
notify_cancel(token);
}
}
int notification_fd() const { return notify_fd; }
bool notification_fd_became_readable(int fd) {
// 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() {
uint32_t status = notify_post(name.c_str());
if (status != NOTIFY_STATUS_OK) {
debug(1, "notify_post() failed with status %u. Uvar notifications may not be sent.",
status);
}
}
#else // this class isn't valid on this system
public:
universal_notifier_notifyd_t() {
DIE("universal_notifier_notifyd_t cannot be used on this system");
}
#endif
};
#if !defined(__APPLE__) && !defined(__CYGWIN__)
#define NAMED_PIPE_FLASH_DURATION_USEC (1e5)
#define SUSTAINED_READABILITY_CLEANUP_DURATION_USEC (5 * 1e6)
#endif
// 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 : public universal_notifier_t {
#if !defined(__APPLE__) && !defined(__CYGWIN__)
int pipe_fd;
long long readback_time_usec;
size_t readback_amount;
bool polling_due_to_readable_fd;
long long drain_if_still_readable_time_usec;
void make_pipe(const wchar_t *test_path);
void drain_excessive_data() {
// 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!
size_t read_amt = 64 * 1024;
void *buff = malloc(read_amt);
ignore_result(read(this->pipe_fd, buff, read_amt));
free(buff);
}
public:
universal_notifier_named_pipe_t(const wchar_t *test_path)
: pipe_fd(-1),
readback_time_usec(0),
readback_amount(0),
polling_due_to_readable_fd(false),
drain_if_still_readable_time_usec(0) {
make_pipe(test_path);
}
~universal_notifier_named_pipe_t() override {
if (pipe_fd >= 0) {
close(pipe_fd);
}
}
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;
}
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() + SUSTAINED_READABILITY_CLEANUP_DURATION_USEC;
should_sync = true;
}
return should_sync;
}
void post_notification() override {
if (pipe_fd >= 0) {
// 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.
int pid_nbo = htonl(getpid()); //!OCLINT(constant cond op)
ssize_t amt_written = write(this->pipe_fd, &pid_nbo, sizeof pid_nbo);
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() + NAMED_PIPE_FLASH_DURATION_USEC;
this->readback_amount += sizeof pid_nbo;
}
}
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 = (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 = NAMED_PIPE_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 = mini(readback_delay, polling_delay);
if (result == ULONG_MAX) {
result = 0;
}
return result;
}
bool poll() override {
// 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 = mini(this->readback_amount, sizeof buff);
ignore_result(read(this->pipe_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 || pipe_fd < 0) {
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(this->pipe_fd, &fds);
struct timeval timeout = {};
select(this->pipe_fd + 1, &fds, NULL, NULL, &timeout);
if (!FD_ISSET(this->pipe_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() {
#if 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 NULL;
}
// 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; }
void universal_notifier_t::post_notification() {}
bool universal_notifier_t::poll() { return false; }
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;
}
#if !defined(__APPLE__) && !defined(__CYGWIN__)
void universal_notifier_named_pipe_t::make_pipe(const wchar_t *test_path) {
wcstring vars_path = test_path ? wcstring(test_path) : default_named_pipe_path();
vars_path.append(L".notifier");
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 = strerror(errno);
const wchar_t *errmsg = _(L"Unable to make a pipe for universal variables using '%ls': %s");
debug(0, errmsg, vars_path.c_str(), error);
pipe_fd = -1;
return;
}
int fd = wopen_cloexec(vars_path, O_RDWR | O_NONBLOCK, 0600);
if (fd < 0) {
const char *error = strerror(errno);
const wchar_t *errmsg = _(L"Unable to open a pipe for universal variables using '%ls': %s");
debug(0, errmsg, vars_path.c_str(), error);
pipe_fd = -1;
return;
}
pipe_fd = fd;
}
#endif
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