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libwebsockets/lib/plat/unix/unix-spawn.c

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/*
* libwebsockets - small server side websockets and web server implementation
*
* Copyright (C) 2010 - 2020 Andy Green <andy@warmcat.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#if !defined(_GNU_SOURCE)
#define _GNU_SOURCE
#endif
#include "private-lib-core.h"
#include <unistd.h>
#if defined(__OpenBSD__) || defined(__NetBSD__)
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#include <sys/resource.h>
#include <sys/wait.h>
#endif
void
lws_spawn_timeout(struct lws_sorted_usec_list *sul)
{
struct lws_spawn_piped *lsp = lws_container_of(sul,
struct lws_spawn_piped, sul);
lwsl_warn("%s: spawn exceeded timeout, killing\n", __func__);
lws_spawn_piped_kill_child_process(lsp);
}
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void
lws_spawn_sul_reap(struct lws_sorted_usec_list *sul)
{
struct lws_spawn_piped *lsp = lws_container_of(sul,
struct lws_spawn_piped, sul_reap);
lwsl_notice("%s: reaping spawn after last stdpipe, tries left %d\n",
__func__, lsp->reap_retry_budget);
if (!lws_spawn_reap(lsp) && !lsp->pipes_alive) {
if (--lsp->reap_retry_budget) {
lws_sul_schedule(lsp->info.vh->context, lsp->info.tsi,
&lsp->sul_reap, lws_spawn_sul_reap,
250 * LWS_US_PER_MS);
} else {
lwsl_err("%s: Unable to reap lsp %p, killing\n",
__func__, lsp);
lsp->reap_retry_budget = 20;
lws_spawn_piped_kill_child_process(lsp);
}
}
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}
static struct lws *
lws_create_stdwsi(struct lws_context *context, int tsi,
const struct lws_role_ops *ops)
{
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struct lws_context_per_thread *pt = &context->pt[tsi];
struct lws *new_wsi;
if (!context->vhost_list)
return NULL;
if ((unsigned int)pt->fds_count == context->fd_limit_per_thread - 1) {
lwsl_err("no space for new conn\n");
return NULL;
}
lws_context_lock(context, __func__);
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new_wsi = __lws_wsi_create_with_role(context, tsi, ops, NULL);
lws_context_unlock(context);
if (new_wsi == NULL) {
lwsl_err("Out of memory for new connection\n");
return NULL;
}
new_wsi->rxflow_change_to = LWS_RXFLOW_ALLOW;
/* initialize the instance struct */
lws_role_transition(new_wsi, 0, LRS_ESTABLISHED, ops);
new_wsi->hdr_parsing_completed = 0;
/*
* these can only be set once the protocol is known
* we set an unestablished connection's protocol pointer
* to the start of the defauly vhost supported list, so it can look
* for matching ones during the handshake
*/
new_wsi->user_space = NULL;
return new_wsi;
}
void
lws_spawn_piped_destroy(struct lws_spawn_piped **_lsp)
{
struct lws_spawn_piped *lsp = *_lsp;
int n;
if (!lsp)
return;
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lws_dll2_remove(&lsp->dll);
lws_sul_cancel(&lsp->sul);
lws_sul_cancel(&lsp->sul_reap);
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for (n = 0; n < 3; n++) {
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#if 0
if (lsp->pipe_fds[n][!!(n == 0)] == 0)
lwsl_err("ZERO FD IN CGI CLOSE");
if (lsp->pipe_fds[n][!!(n == 0)] >= 0) {
close(lsp->pipe_fds[n][!!(n == 0)]);
lsp->pipe_fds[n][!!(n == 0)] = LWS_SOCK_INVALID;
}
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#endif
if (lsp->stdwsi[n]) {
lws_set_timeout(lsp->stdwsi[n], 1, LWS_TO_KILL_ASYNC);
lsp->stdwsi[n] = NULL;
}
}
lws_free_set_NULL((*_lsp));
}
int
lws_spawn_reap(struct lws_spawn_piped *lsp)
{
long hz = sysconf(_SC_CLK_TCK); /* accounting Hz */
void *opaque = lsp->info.opaque;
lsp_cb_t cb = lsp->info.reap_cb;
struct lws_spawn_piped temp;
struct tms tms;
#if defined(__OpenBSD__) || defined(__NetBSD__)
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struct rusage rusa;
int status;
#endif
int n;
if (lsp->child_pid < 1)
return 0;
/* check if exited, do not reap yet */
memset(&lsp->si, 0, sizeof(lsp->si));
#if defined(__OpenBSD__) || defined(__NetBSD__)
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n = wait4(lsp->child_pid, &status, WNOHANG, &rusa);
if (!n)
return 0;
lsp->si.si_code = WIFEXITED(status);
#else
n = waitid(P_PID, (id_t)lsp->child_pid, &lsp->si, WEXITED | WNOHANG | WNOWAIT);
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#endif
if (n < 0) {
lwsl_info("%s: child %d still running\n", __func__, lsp->child_pid);
return 0;
}
if (!lsp->si.si_code)
return 0;
/* his process has exited... */
if (!lsp->reaped) {
/* mark the earliest time we knew he had gone */
lsp->reaped = lws_now_usecs();
/*
* Switch the timeout to restrict the amount of grace time
* to drain stdwsi
*/
lws_sul_schedule(lsp->info.vh->context, lsp->info.tsi,
&lsp->sul, lws_spawn_timeout,
5 * LWS_US_PER_SEC);
}
/*
* Stage finalizing our reaction to the process going down until the
* stdwsi flushed whatever is in flight and all noticed they were
* closed. For that reason, each stdwsi close must call lws_spawn_reap
* to check if that was the last one and we can proceed with the reap.
*/
if (!lsp->ungraceful && lsp->pipes_alive) {
lwsl_info("%s: %d stdwsi alive, not reaping\n", __func__,
lsp->pipes_alive);
return 0;
}
/* we reached the reap point, no need for timeout wait */
lws_sul_cancel(&lsp->sul);
/*
* All the stdwsi went down, nothing more is coming... it's over
* Collect the final information and then reap the dead process
*/
if (times(&tms) != (clock_t) -1) {
/*
* Cpu accounting in us
*/
lsp->accounting[0] = (lws_usec_t)((uint64_t)tms.tms_cstime * 1000000) / hz;
lsp->accounting[1] = (lws_usec_t)((uint64_t)tms.tms_cutime * 1000000) / hz;
lsp->accounting[2] = (lws_usec_t)((uint64_t)tms.tms_stime * 1000000) / hz;
lsp->accounting[3] = (lws_usec_t)((uint64_t)tms.tms_utime * 1000000) / hz;
}
temp = *lsp;
#if defined(__OpenBSD__) || defined(__NetBSD__)
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n = wait4(lsp->child_pid, &status, WNOHANG, &rusa);
if (!n)
return 0;
lsp->si.si_code = WIFEXITED(status);
if (lsp->si.si_code == CLD_EXITED)
temp.si.si_code = CLD_EXITED;
temp.si.si_status = WEXITSTATUS(status);
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#else
n = waitid(P_PID, (id_t)lsp->child_pid, &temp.si, WEXITED | WNOHANG);
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#endif
temp.si.si_status &= 0xff; /* we use b8 + for flags */
lwsl_info("%s: waitd says %d, process exit %d\n",
__func__, n, temp.si.si_status);
lsp->child_pid = -1;
/* destroy the lsp itself first (it's freed and plsp set NULL */
if (lsp->info.plsp)
lws_spawn_piped_destroy(lsp->info.plsp);
/* then do the parent callback informing it's destroyed */
if (cb)
cb(opaque, temp.accounting, &temp.si,
temp.we_killed_him_timeout |
(temp.we_killed_him_spew << 1));
return 1; /* was reaped */
}
int
lws_spawn_piped_kill_child_process(struct lws_spawn_piped *lsp)
{
int status, n;
if (lsp->child_pid <= 0)
return 1;
lsp->ungraceful = 1; /* don't wait for flushing, just kill it */
if (lws_spawn_reap(lsp))
/* that may have invalidated lsp */
return 0;
/* kill the process group */
n = kill(-lsp->child_pid, SIGTERM);
lwsl_debug("%s: SIGTERM child PID %d says %d (errno %d)\n", __func__,
lsp->child_pid, n, errno);
if (n < 0) {
/*
* hum seen errno=3 when process is listed in ps,
* it seems we don't always retain process grouping
*
* Direct these fallback attempt to the exact child
*/
n = kill(lsp->child_pid, SIGTERM);
if (n < 0) {
n = kill(lsp->child_pid, SIGPIPE);
if (n < 0) {
n = kill(lsp->child_pid, SIGKILL);
if (n < 0)
lwsl_info("%s: SIGKILL PID %d "
"failed errno %d "
"(maybe zombie)\n", __func__,
lsp->child_pid, errno);
}
}
}
/* He could be unkillable because he's a zombie */
n = 1;
while (n > 0) {
n = waitpid(-lsp->child_pid, &status, WNOHANG);
if (n > 0)
lwsl_debug("%s: reaped PID %d\n", __func__, n);
if (n <= 0) {
n = waitpid(lsp->child_pid, &status, WNOHANG);
if (n > 0)
lwsl_debug("%s: reaped PID %d\n", __func__, n);
}
}
lws_spawn_reap(lsp);
/* that may have invalidated lsp */
return 0;
}
/*
* Deals with spawning a subprocess and executing it securely with stdin/out/err
* diverted into pipes
*/
struct lws_spawn_piped *
lws_spawn_piped(const struct lws_spawn_piped_info *i)
{
const struct lws_protocols *pcol = i->vh->context->vhost_list->protocols;
struct lws_context *context = i->vh->context;
struct lws_spawn_piped *lsp;
const char *wd;
int n, m;
if (i->protocol_name)
pcol = lws_vhost_name_to_protocol(i->vh, i->protocol_name);
if (!pcol) {
lwsl_err("%s: unknown protocol %s\n", __func__,
i->protocol_name ? i->protocol_name : "default");
return NULL;
}
lsp = lws_zalloc(sizeof(*lsp), __func__);
if (!lsp)
return NULL;
/* wholesale take a copy of info */
lsp->info = *i;
lsp->reap_retry_budget = 20;
/*
* Prepare the stdin / out / err pipes
*/
for (n = 0; n < 3; n++) {
lsp->pipe_fds[n][0] = -1;
lsp->pipe_fds[n][1] = -1;
}
/* create pipes for [stdin|stdout] and [stderr] */
for (n = 0; n < 3; n++) {
if (pipe(lsp->pipe_fds[n]) == -1)
goto bail1;
lws_plat_apply_FD_CLOEXEC(lsp->pipe_fds[n][n == 0]);
}
/*
* At this point, we have 6 pipe fds open on lws side and no wsis
* bound to them
*/
/* create wsis for each stdin/out/err fd */
for (n = 0; n < 3; n++) {
lsp->stdwsi[n] = lws_create_stdwsi(i->vh->context, i->tsi,
i->ops ? i->ops : &role_ops_raw_file);
if (!lsp->stdwsi[n]) {
lwsl_err("%s: unable to create lsp stdwsi\n", __func__);
goto bail2;
}
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__lws_lc_tag(i->vh->context, &i->vh->context->lcg[LWSLCG_WSI],
&lsp->stdwsi[n]->lc, "nspawn-stdwsi-%d", n);
lsp->stdwsi[n]->lsp_channel = (uint8_t)n;
lws_vhost_bind_wsi(i->vh, lsp->stdwsi[n]);
fakewsi: replace with smaller substructure Currently we always reserve a fakewsi per pt so events that don't have a related actual wsi, like vhost-protocol-init or vhost cert init via protocol callback can make callbacks that look reasonable to user protocol handler code expecting a valid wsi every time. This patch splits out stuff that user callbacks often unconditionally expect to be in a wsi, like context pointer, vhost pointer etc into a substructure, which is composed into struct lws at the top of it. Internal references (struct lws is opaque, so there are only internal references) are all updated to go via the substructre, the compiler should make that a NOP. Helpers are added when fakewsi is used and referenced. If not PLAT_FREERTOS, we continue to provide a full fakewsi in the pt as before, although the helpers improve consistency by zeroing down the substructure. There is a huge amount of user code out there over the last 10 years that did not always have the minimal examples to follow, some of it does some unexpected things. If it is PLAT_FREERTOS, that is a newer thing in lws and users have the benefit of being able to follow the minimal examples' approach. For PLAT_FREERTOS we don't reserve the fakewsi in the pt any more, saving around 800 bytes. The helpers then create a struct lws_a (the substructure) on the stack, zero it down (but it is only like 4 pointers) and prepare it with whatever we know like the context. Then we cast it to a struct lws * and use it in the user protocol handler call. In this case, the remainder of the struct lws is undefined. However the amount of old protocol handlers that might touch things outside of the substructure in PLAT_FREERTOS is very limited compared to legacy lws user code and the saving is significant on constrained devices. User handlers should not be touching everything in a wsi every time anyway, there are several cases where there is no valid wsi to do the call with. Dereference of things outside the substructure should only happen when the callback reason shows there is a valid wsi bound to the activity (as in all the minimal examples).
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lsp->stdwsi[n]->a.protocol = pcol;
lsp->stdwsi[n]->a.opaque_user_data = i->opaque;
lwsl_debug("%s: lsp stdwsi %p: pipe idx %d -> fd %d / %d\n", __func__,
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lsp->stdwsi[n], n, lsp->pipe_fds[n][n == 0],
lsp->pipe_fds[n][n != 0]);
/* read side is 0, stdin we want the write side, others read */
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lsp->stdwsi[n]->desc.sockfd = lsp->pipe_fds[n][n == 0];
if (fcntl(lsp->pipe_fds[n][n == 0], F_SETFL, O_NONBLOCK) < 0) {
lwsl_err("%s: setting NONBLOCK failed\n", __func__);
goto bail2;
}
/*
* We have bound 3 x pipe fds to wsis, wr side of stdin and rd
* side of stdout / stderr... those are marked CLOEXEC so they
* won't go through the fork
*
* rd side of stdin and wr side of stdout / stderr are open but
* not bound to anything on lws side.
*/
}
/*
* Stitch the wsi fd into the poll wait
*/
for (n = 0; n < 3; n++) {
if (context->event_loop_ops->sock_accept)
if (context->event_loop_ops->sock_accept(lsp->stdwsi[n]))
goto bail3;
if (__insert_wsi_socket_into_fds(context, lsp->stdwsi[n]))
goto bail3;
if (i->opt_parent) {
lsp->stdwsi[n]->parent = i->opt_parent;
lsp->stdwsi[n]->sibling_list = i->opt_parent->child_list;
i->opt_parent->child_list = lsp->stdwsi[n];
}
}
if (lws_change_pollfd(lsp->stdwsi[LWS_STDIN], LWS_POLLIN, LWS_POLLOUT))
goto bail3;
if (lws_change_pollfd(lsp->stdwsi[LWS_STDOUT], LWS_POLLOUT, LWS_POLLIN))
goto bail3;
if (lws_change_pollfd(lsp->stdwsi[LWS_STDERR], LWS_POLLOUT, LWS_POLLIN))
goto bail3;
lwsl_info("%s: fds in %d, out %d, err %d\n", __func__,
lsp->stdwsi[LWS_STDIN]->desc.sockfd,
lsp->stdwsi[LWS_STDOUT]->desc.sockfd,
lsp->stdwsi[LWS_STDERR]->desc.sockfd);
/* we are ready with the redirection pipes... do the (v)fork */
#if defined(__sun) || !defined(LWS_HAVE_VFORK) || !defined(LWS_HAVE_EXECVPE)
lsp->child_pid = fork();
#else
lsp->child_pid = vfork();
#endif
if (lsp->child_pid < 0) {
lwsl_err("%s: fork failed, errno %d", __func__, errno);
goto bail3;
}
#if defined(__linux__)
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if (!lsp->child_pid)
prctl(PR_SET_PDEATHSIG, SIGTERM);
#endif
if (lsp->info.disable_ctrlc)
/* stops non-daemonized main processess getting SIGINT
* from TTY */
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#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__)
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setpgid(0, 0);
#else
setpgrp();
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#endif
if (lsp->child_pid) {
/*
* We are the parent process. We can close our copy of the
* "other" side of the pipe fds, ie, rd for stdin and wr for
* stdout / stderr.
*/
for (n = 0; n < 3; n++)
/* these guys didn't have any wsi footprint */
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close(lsp->pipe_fds[n][n != 0]);
lsp->pipes_alive = 3;
lsp->created = lws_now_usecs();
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lwsl_info("%s: lsp %p spawned PID %d\n", __func__, lsp,
lsp->child_pid);
lws_sul_schedule(context, i->tsi, &lsp->sul, lws_spawn_timeout,
i->timeout_us ? i->timeout_us :
300 * LWS_US_PER_SEC);
if (i->owner)
lws_dll2_add_head(&lsp->dll, i->owner);
if (i->timeout_us)
lws_sul_schedule(context, i->tsi, &lsp->sul,
lws_spawn_timeout, i->timeout_us);
return lsp;
}
/*
* We are the forked process, redirect and kill inherited things.
*
* Because of vfork(), we cannot do anything that changes pages in
* the parent environment. Stuff that changes kernel state for the
* process is OK. Stuff that happens after the execvpe() is OK.
*/
if (i->chroot_path && chroot(i->chroot_path)) {
lwsl_err("%s: child chroot %s failed, errno %d\n",
__func__, i->chroot_path, errno);
exit(2);
}
/* cwd: somewhere we can at least read things and enter it */
wd = i->wd;
if (!wd)
wd = "/tmp";
if (chdir(wd))
lwsl_notice("%s: Failed to cd to %s\n", __func__, wd);
/*
* Bind the child's stdin / out / err to its side of our pipes
*/
for (m = 0; m < 3; m++) {
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if (dup2(lsp->pipe_fds[m][m != 0], m) < 0) {
lwsl_err("%s: stdin dup2 failed\n", __func__);
goto bail3;
}
/*
* CLOEXEC on the lws-side of the pipe fds should have already
* dealt with closing those for the child perspective.
*
* Now it has done the dup, the child should close its original
* copies of its side of the pipes.
*/
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close(lsp->pipe_fds[m][m != 0]);
}
#if defined(__sun) || !defined(LWS_HAVE_VFORK) || !defined(LWS_HAVE_EXECVPE)
#if defined(__linux__) || defined(__APPLE__) || defined(__sun)
m = 0;
while (i->env_array[m]){
const char *p = strchr(i->env_array[m], '=');
int naml = lws_ptr_diff(p, i->env_array[m]);
char enam[32];
if (p) {
lws_strnncpy(enam, i->env_array[m], naml, sizeof(enam));
setenv(enam, p + 1, 1);
}
m++;
}
#endif
execvp(i->exec_array[0], (char * const *)&i->exec_array[0]);
#else
execvpe(i->exec_array[0], (char * const *)&i->exec_array[0],
(char **)&i->env_array[0]);
#endif
lwsl_err("%s: child exec of %s failed %d\n", __func__, i->exec_array[0],
LWS_ERRNO);
_exit(1);
bail3:
while (--n >= 0)
__remove_wsi_socket_from_fds(lsp->stdwsi[n]);
bail2:
for (n = 0; n < 3; n++)
if (lsp->stdwsi[n])
__lws_free_wsi(lsp->stdwsi[n]);
bail1:
for (n = 0; n < 3; n++) {
if (lsp->pipe_fds[n][0] >= 0)
close(lsp->pipe_fds[n][0]);
if (lsp->pipe_fds[n][1] >= 0)
close(lsp->pipe_fds[n][1]);
}
lws_free(lsp);
lwsl_err("%s: failed\n", __func__);
return NULL;
}
void
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lws_spawn_stdwsi_closed(struct lws_spawn_piped *lsp, struct lws *wsi)
{
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int n;
assert(lsp);
lsp->pipes_alive--;
lwsl_debug("%s: pipes alive %d\n", __func__, lsp->pipes_alive);
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if (!lsp->pipes_alive)
lws_sul_schedule(lsp->info.vh->context, lsp->info.tsi,
&lsp->sul_reap, lws_spawn_sul_reap, 1);
for (n = 0; n < 3; n++)
if (lsp->stdwsi[n] == wsi)
lsp->stdwsi[n] = NULL;
}
int
lws_spawn_get_stdfd(struct lws *wsi)
{
return wsi->lsp_channel;
}