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mirror of https://git.FreeBSD.org/src.git synced 2024-12-05 09:14:03 +00:00
freebsd/contrib/ntp/libntp/work_fork.c
Xin LI 4e1ef62a36 MFV r338092: ntp 4.2.8p12.
Relnotes:	yes
2018-08-21 02:38:07 +00:00

614 lines
13 KiB
C

/*
* work_fork.c - fork implementation for blocking worker child.
*/
#include <config.h>
#include "ntp_workimpl.h"
#ifdef WORK_FORK
#include <stdio.h>
#include <ctype.h>
#include <signal.h>
#include <sys/wait.h>
#include "iosignal.h"
#include "ntp_stdlib.h"
#include "ntp_malloc.h"
#include "ntp_syslog.h"
#include "ntpd.h"
#include "ntp_io.h"
#include "ntp_assert.h"
#include "ntp_unixtime.h"
#include "ntp_worker.h"
/* === variables === */
int worker_process;
addremove_io_fd_func addremove_io_fd;
static volatile int worker_sighup_received;
int saved_argc = 0;
char **saved_argv;
/* === function prototypes === */
static void fork_blocking_child(blocking_child *);
static RETSIGTYPE worker_sighup(int);
static void send_worker_home_atexit(void);
static void cleanup_after_child(blocking_child *);
/* === I/O helpers === */
/* Since we have signals enabled, there's a good chance that blocking IO
* via pipe suffers from EINTR -- and this goes for both directions.
* The next two wrappers will loop until either all the data is written
* or read, plus handling the EOF condition on read. They may return
* zero if no data was transferred at all, and effectively every return
* value that differs from the given transfer length signifies an error
* condition.
*/
static size_t
netread(
int fd,
void * vb,
size_t l
)
{
char * b = vb;
ssize_t r;
while (l) {
r = read(fd, b, l);
if (r > 0) {
l -= r;
b += r;
} else if (r == 0 || errno != EINTR) {
l = 0;
}
}
return (size_t)(b - (char *)vb);
}
static size_t
netwrite(
int fd,
const void * vb,
size_t l
)
{
const char * b = vb;
ssize_t w;
while (l) {
w = write(fd, b, l);
if (w > 0) {
l -= w;
b += w;
} else if (errno != EINTR) {
l = 0;
}
}
return (size_t)(b - (const char *)vb);
}
int set_user_group_ids(void);
/* === functions === */
/*
* exit_worker()
*
* On some systems _exit() is preferred to exit() for forked children.
* For example, http://netbsd.gw.com/cgi-bin/man-cgi?fork++NetBSD-5.0
* recommends _exit() to avoid double-flushing C runtime stream buffers
* and also to avoid calling the parent's atexit() routines in the
* child. On those systems WORKER_CHILD_EXIT is _exit. Since _exit
* bypasses CRT cleanup, fflush() files we know might have output
* buffered.
*/
void
exit_worker(
int exitcode
)
{
if (syslog_file != NULL)
fflush(syslog_file);
fflush(stdout);
fflush(stderr);
WORKER_CHILD_EXIT (exitcode); /* space before ( required */
}
static RETSIGTYPE
worker_sighup(
int sig
)
{
if (SIGHUP == sig)
worker_sighup_received = 1;
}
int
worker_sleep(
blocking_child * c,
time_t seconds
)
{
u_int sleep_remain;
sleep_remain = (u_int)seconds;
do {
if (!worker_sighup_received)
sleep_remain = sleep(sleep_remain);
if (worker_sighup_received) {
TRACE(1, ("worker SIGHUP with %us left to sleep",
sleep_remain));
worker_sighup_received = 0;
return -1;
}
} while (sleep_remain);
return 0;
}
void
interrupt_worker_sleep(void)
{
u_int idx;
blocking_child * c;
int rc;
for (idx = 0; idx < blocking_children_alloc; idx++) {
c = blocking_children[idx];
if (NULL == c || c->reusable == TRUE)
continue;
rc = kill(c->pid, SIGHUP);
if (rc < 0)
msyslog(LOG_ERR,
"Unable to signal HUP to wake child pid %d: %m",
c->pid);
}
}
/*
* harvest_child_status() runs in the parent.
*
* Note the error handling -- this is an interaction with SIGCHLD.
* SIG_IGN on SIGCHLD on some OSes means do not wait but reap
* automatically. Since we're not really interested in the result code,
* we simply ignore the error.
*/
static void
harvest_child_status(
blocking_child * c
)
{
if (c->pid) {
/* Wait on the child so it can finish terminating */
if (waitpid(c->pid, NULL, 0) == c->pid)
TRACE(4, ("harvested child %d\n", c->pid));
else if (errno != ECHILD)
msyslog(LOG_ERR, "error waiting on child %d: %m", c->pid);
c->pid = 0;
}
}
/*
* req_child_exit() runs in the parent.
*/
int
req_child_exit(
blocking_child * c
)
{
if (-1 != c->req_write_pipe) {
close(c->req_write_pipe);
c->req_write_pipe = -1;
return 0;
}
/* Closing the pipe forces the child to exit */
harvest_child_status(c);
return -1;
}
/*
* cleanup_after_child() runs in parent.
*/
static void
cleanup_after_child(
blocking_child * c
)
{
harvest_child_status(c);
if (-1 != c->resp_read_pipe) {
(*addremove_io_fd)(c->resp_read_pipe, c->ispipe, TRUE);
close(c->resp_read_pipe);
c->resp_read_pipe = -1;
}
c->resp_read_ctx = NULL;
DEBUG_INSIST(-1 == c->req_read_pipe);
DEBUG_INSIST(-1 == c->resp_write_pipe);
c->reusable = TRUE;
}
static void
send_worker_home_atexit(void)
{
u_int idx;
blocking_child * c;
if (worker_process)
return;
for (idx = 0; idx < blocking_children_alloc; idx++) {
c = blocking_children[idx];
if (NULL == c)
continue;
req_child_exit(c);
}
}
int
send_blocking_req_internal(
blocking_child * c,
blocking_pipe_header * hdr,
void * data
)
{
size_t octets;
size_t rc;
DEBUG_REQUIRE(hdr != NULL);
DEBUG_REQUIRE(data != NULL);
DEBUG_REQUIRE(BLOCKING_REQ_MAGIC == hdr->magic_sig);
if (-1 == c->req_write_pipe) {
fork_blocking_child(c);
DEBUG_INSIST(-1 != c->req_write_pipe);
}
octets = sizeof(*hdr);
rc = netwrite(c->req_write_pipe, hdr, octets);
if (rc == octets) {
octets = hdr->octets - sizeof(*hdr);
rc = netwrite(c->req_write_pipe, data, octets);
if (rc == octets)
return 0;
}
msyslog(LOG_ERR,
"send_blocking_req_internal: short write (%zu of %zu), %m",
rc, octets);
/* Fatal error. Clean up the child process. */
req_child_exit(c);
exit(1); /* otherwise would be return -1 */
}
blocking_pipe_header *
receive_blocking_req_internal(
blocking_child * c
)
{
blocking_pipe_header hdr;
blocking_pipe_header * req;
size_t rc;
size_t octets;
DEBUG_REQUIRE(-1 != c->req_read_pipe);
req = NULL;
rc = netread(c->req_read_pipe, &hdr, sizeof(hdr));
if (0 == rc) {
TRACE(4, ("parent closed request pipe, child %d terminating\n",
c->pid));
} else if (rc != sizeof(hdr)) {
msyslog(LOG_ERR,
"receive_blocking_req_internal: short header read (%zu of %zu), %m",
rc, sizeof(hdr));
} else {
INSIST(sizeof(hdr) < hdr.octets && hdr.octets < 4 * 1024);
req = emalloc(hdr.octets);
memcpy(req, &hdr, sizeof(*req));
octets = hdr.octets - sizeof(hdr);
rc = netread(c->req_read_pipe, (char *)(req + 1),
octets);
if (rc != octets)
msyslog(LOG_ERR,
"receive_blocking_req_internal: short read (%zu of %zu), %m",
rc, octets);
else if (BLOCKING_REQ_MAGIC != req->magic_sig)
msyslog(LOG_ERR,
"receive_blocking_req_internal: packet header mismatch (0x%x)",
req->magic_sig);
else
return req;
}
if (req != NULL)
free(req);
return NULL;
}
int
send_blocking_resp_internal(
blocking_child * c,
blocking_pipe_header * resp
)
{
size_t octets;
size_t rc;
DEBUG_REQUIRE(-1 != c->resp_write_pipe);
octets = resp->octets;
rc = netwrite(c->resp_write_pipe, resp, octets);
free(resp);
if (octets == rc)
return 0;
TRACE(1, ("send_blocking_resp_internal: short write (%zu of %zu), %m\n",
rc, octets));
return -1;
}
blocking_pipe_header *
receive_blocking_resp_internal(
blocking_child * c
)
{
blocking_pipe_header hdr;
blocking_pipe_header * resp;
size_t rc;
size_t octets;
DEBUG_REQUIRE(c->resp_read_pipe != -1);
resp = NULL;
rc = netread(c->resp_read_pipe, &hdr, sizeof(hdr));
if (0 == rc) {
/* this is the normal child exited indication */
} else if (rc != sizeof(hdr)) {
TRACE(1, ("receive_blocking_resp_internal: short header read (%zu of %zu), %m\n",
rc, sizeof(hdr)));
} else if (BLOCKING_RESP_MAGIC != hdr.magic_sig) {
TRACE(1, ("receive_blocking_resp_internal: header mismatch (0x%x)\n",
hdr.magic_sig));
} else {
INSIST(sizeof(hdr) < hdr.octets &&
hdr.octets < 16 * 1024);
resp = emalloc(hdr.octets);
memcpy(resp, &hdr, sizeof(*resp));
octets = hdr.octets - sizeof(hdr);
rc = netread(c->resp_read_pipe, (char *)(resp + 1),
octets);
if (rc != octets)
TRACE(1, ("receive_blocking_resp_internal: short read (%zu of %zu), %m\n",
rc, octets));
else
return resp;
}
cleanup_after_child(c);
if (resp != NULL)
free(resp);
return NULL;
}
#if defined(HAVE_DROPROOT) && defined(WORK_FORK)
void
fork_deferred_worker(void)
{
u_int idx;
blocking_child * c;
REQUIRE(droproot && root_dropped);
for (idx = 0; idx < blocking_children_alloc; idx++) {
c = blocking_children[idx];
if (NULL == c)
continue;
if (-1 != c->req_write_pipe && 0 == c->pid)
fork_blocking_child(c);
}
}
#endif
static void
fork_blocking_child(
blocking_child * c
)
{
static int atexit_installed;
static int blocking_pipes[4] = { -1, -1, -1, -1 };
int rc;
int was_pipe;
int is_pipe;
int saved_errno = 0;
int childpid;
int keep_fd;
int fd;
/*
* parent and child communicate via a pair of pipes.
*
* 0 child read request
* 1 parent write request
* 2 parent read response
* 3 child write response
*/
if (-1 == c->req_write_pipe) {
rc = pipe_socketpair(&blocking_pipes[0], &was_pipe);
if (0 != rc) {
saved_errno = errno;
} else {
rc = pipe_socketpair(&blocking_pipes[2], &is_pipe);
if (0 != rc) {
saved_errno = errno;
close(blocking_pipes[0]);
close(blocking_pipes[1]);
} else {
INSIST(was_pipe == is_pipe);
}
}
if (0 != rc) {
errno = saved_errno;
msyslog(LOG_ERR, "unable to create worker pipes: %m");
exit(1);
}
/*
* Move the descriptors the parent will keep open out of the
* low descriptors preferred by C runtime buffered FILE *.
*/
c->req_write_pipe = move_fd(blocking_pipes[1]);
c->resp_read_pipe = move_fd(blocking_pipes[2]);
/*
* wake any worker child on orderly shutdown of the
* daemon so that it can notice the broken pipes and
* go away promptly.
*/
if (!atexit_installed) {
atexit(&send_worker_home_atexit);
atexit_installed = TRUE;
}
}
#if defined(HAVE_DROPROOT) && !defined(NEED_EARLY_FORK)
/* defer the fork until after root is dropped */
if (droproot && !root_dropped)
return;
#endif
if (syslog_file != NULL)
fflush(syslog_file);
fflush(stdout);
fflush(stderr);
/* [BUG 3050] setting SIGCHLD to SIG_IGN likely causes unwanted
* or undefined effects. We don't do it and leave SIGCHLD alone.
*/
/* signal_no_reset(SIGCHLD, SIG_IGN); */
childpid = fork();
if (-1 == childpid) {
msyslog(LOG_ERR, "unable to fork worker: %m");
exit(1);
}
if (childpid) {
/* this is the parent */
TRACE(1, ("forked worker child (pid %d)\n", childpid));
c->pid = childpid;
c->ispipe = is_pipe;
/* close the child's pipe descriptors. */
close(blocking_pipes[0]);
close(blocking_pipes[3]);
memset(blocking_pipes, -1, sizeof(blocking_pipes));
/* wire into I/O loop */
(*addremove_io_fd)(c->resp_read_pipe, is_pipe, FALSE);
return; /* parent returns */
}
/*
* The parent gets the child pid as the return value of fork().
* The child must work for it.
*/
c->pid = getpid();
worker_process = TRUE;
/*
* Change the process name of the child to avoid confusion
* about ntpd trunning twice.
*/
if (saved_argc != 0) {
int argcc;
int argvlen = 0;
/* Clear argv */
for (argcc = 0; argcc < saved_argc; argcc++) {
int l = strlen(saved_argv[argcc]);
argvlen += l + 1;
memset(saved_argv[argcc], 0, l);
}
strlcpy(saved_argv[0], "ntpd: asynchronous dns resolver", argvlen);
}
/*
* In the child, close all files except stdin, stdout, stderr,
* and the two child ends of the pipes.
*/
DEBUG_INSIST(-1 == c->req_read_pipe);
DEBUG_INSIST(-1 == c->resp_write_pipe);
c->req_read_pipe = blocking_pipes[0];
c->resp_write_pipe = blocking_pipes[3];
kill_asyncio(0);
closelog();
if (syslog_file != NULL) {
fclose(syslog_file);
syslog_file = NULL;
syslogit = TRUE;
}
keep_fd = max(c->req_read_pipe, c->resp_write_pipe);
for (fd = 3; fd < keep_fd; fd++)
if (fd != c->req_read_pipe &&
fd != c->resp_write_pipe)
close(fd);
close_all_beyond(keep_fd);
/*
* We get signals from refclock serial I/O on NetBSD in the
* worker if we do not reset SIGIO's handler to the default.
* It is not conditionalized for NetBSD alone because on
* systems where it is not needed, it is harmless, and that
* allows us to handle unknown others with NetBSD behavior.
* [Bug 1386]
*/
#if defined(USE_SIGIO)
signal_no_reset(SIGIO, SIG_DFL);
#elif defined(USE_SIGPOLL)
signal_no_reset(SIGPOLL, SIG_DFL);
#endif
signal_no_reset(SIGHUP, worker_sighup);
init_logging("ntp_intres", 0, FALSE);
setup_logfile(NULL);
(void) set_user_group_ids();
/*
* And now back to the portable code
*/
exit_worker(blocking_child_common(c));
}
void worker_global_lock(int inOrOut)
{
(void)inOrOut;
}
#else /* !WORK_FORK follows */
char work_fork_nonempty_compilation_unit;
#endif