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Survive bereaving (updated) #218

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Survive bereaving (updated) #218

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7527a65
initial patch from fkluknav
odoucet Mar 26, 2021
b10b736
modifications requested in merge request
odoucet Mar 26, 2021
fdb7d78
fix unit tests
odoucet Mar 29, 2021
2545cb6
fix test bis
odoucet Mar 29, 2021
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104 changes: 86 additions & 18 deletions dumb-init.c
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,8 @@
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <dirent.h>
#include <ctype.h>
#include "VERSION.h"

#define PRINTERR(...) do { \
Expand All @@ -45,6 +47,7 @@ char signal_temporary_ignores[MAXSIG + 1] = {[0 ... MAXSIG] = 0};
pid_t child_pid = -1;
char debug = 0;
char use_setsid = 1;
static char survive_bereaving = 0;

int translate_signal(int signum) {
if (signum <= 0 || signum > MAXSIG) {
Expand All @@ -70,6 +73,42 @@ void forward_signal(int signum) {
}
}

/*
* Read /proc and see if there are processes except init(PIDs)
*/
signed int is_only_process_running() {
DIR *dp;
struct dirent *ep;
char nonnumber;
signed int count = 0;

dp = opendir ("/proc");
if (dp != NULL) {
while ((ep = readdir (dp)) != NULL) {
nonnumber = 0;
for (int i = 0; ep->d_name[i] != '\0'; ++i) {
if (!isdigit(ep->d_name[i])) {
nonnumber = 1;
break;
}
}
if (!nonnumber) {
DEBUG("/proc/%s is a process\n", ep->d_name);
++count;
if (count > 1) {
closedir(dp);
return 2; //2 is enough, do not count further
}
}
}
closedir(dp);
} else {
PRINTERR("Could not open /proc.\n");
return -1;
}
return count;
}

/*
* The dumb-init signal handler.
*
Expand All @@ -91,13 +130,14 @@ void forward_signal(int signum) {
*
*/
void handle_signal(int signum) {
static char bereaved = 0;
DEBUG("Received signal %d.\n", signum);

if (signal_temporary_ignores[signum] == 1) {
DEBUG("Ignoring tty hand-off signal %d.\n", signum);
signal_temporary_ignores[signum] = 0;
} else if (signum == SIGCHLD) {
int status, exit_status;
int status, exit_status = 0;
pid_t killed_pid;
while ((killed_pid = waitpid(-1, &status, WNOHANG)) > 0) {
if (WIFEXITED(status)) {
Expand All @@ -110,11 +150,26 @@ void handle_signal(int signum) {
}

if (killed_pid == child_pid) {
forward_signal(SIGTERM); // send SIGTERM to any remaining children
DEBUG("Child exited with status %d. Goodbye.\n", exit_status);
bereaved = 1;
if (!survive_bereaving) {
forward_signal(SIGTERM); // send SIGTERM to any remaining children
DEBUG("Child exited with status %d. Goodbye.\n", exit_status);
exit(exit_status);
} else {
DEBUG("Child exited with status %d. Stay alive for your grandchildren.\n", exit_status);
}
}
}

if ((bereaved == 1) && survive_bereaving) {
signed int pc = is_only_process_running();
DEBUG("Process count: %d\n", pc);
if (pc <= 1) {
DEBUG("No process left, exiting.\n");
exit(exit_status);
}
}

} else {
forward_signal(signum);
if (signum == SIGTSTP || signum == SIGTTOU || signum == SIGTTIN) {
Expand All @@ -133,15 +188,19 @@ void print_help(char *argv[]) {
"It is designed to run as PID1 in minimal container environments.\n"
"\n"
"Optional arguments:\n"
" -c, --single-child Run in single-child mode.\n"
" In this mode, signals are only proxied to the\n"
" direct child and not any of its descendants.\n"
" -r, --rewrite s:r Rewrite received signal s to new signal r before proxying.\n"
" To ignore (not proxy) a signal, rewrite it to 0.\n"
" This option can be specified multiple times.\n"
" -v, --verbose Print debugging information to stderr.\n"
" -h, --help Print this help message and exit.\n"
" -V, --version Print the current version and exit.\n"
" -c, --single-child Run in single-child mode.\n"
" In this mode, signals are only proxied to the\n"
" direct child and not any of its descendants.\n"
" -b, --survive-bereaving Do not quit when the direct child dies.\n"
" In this mode, dumb-init will quit when there are no\n"
" other processes running on the host.\n"
" This mode requires dumb-init to be running as PID 1.\n"
" -r, --rewrite s:r Rewrite received signal s to new signal r before proxying.\n"
" To ignore (not proxy) a signal, rewrite it to 0.\n"
" This option can be specified multiple times.\n"
" -v, --verbose Print debugging information to stderr.\n"
" -h, --help Print this help message and exit.\n"
" -V, --version Print the current version and exit.\n"
"\n"
"Full help is available online at https://github.com/Yelp/dumb-init\n",
VERSION_len, VERSION,
Expand Down Expand Up @@ -183,14 +242,15 @@ void set_rewrite_to_sigstop_if_not_defined(int signum) {
char **parse_command(int argc, char *argv[]) {
int opt;
struct option long_options[] = {
{"help", no_argument, NULL, 'h'},
{"single-child", no_argument, NULL, 'c'},
{"rewrite", required_argument, NULL, 'r'},
{"verbose", no_argument, NULL, 'v'},
{"version", no_argument, NULL, 'V'},
{"help", no_argument, NULL, 'h'},
{"single-child", no_argument, NULL, 'c'},
{"rewrite", required_argument, NULL, 'r'},
{"verbose", no_argument, NULL, 'v'},
{"version", no_argument, NULL, 'V'},
{"survive-bereaving",no_argument, NULL, 'b'},
{NULL, 0, NULL, 0},
};
while ((opt = getopt_long(argc, argv, "+hvVcr:", long_options, NULL)) != -1) {
while ((opt = getopt_long(argc, argv, "+hvVcbr:", long_options, NULL)) != -1) {
switch (opt) {
case 'h':
print_help(argv);
Expand All @@ -207,6 +267,9 @@ char **parse_command(int argc, char *argv[]) {
case 'r':
parse_rewrite_signum(optarg);
break;
case 'b':
survive_bereaving = 1;
break;
default:
exit(1);
}
Expand All @@ -222,6 +285,11 @@ char **parse_command(int argc, char *argv[]) {
exit(1);
}

if (survive_bereaving && getpid() != 1) {
PRINTERR("--survive-bereaving is only valid when dumb-init is running as PID 1.\n");
exit(1);
}

char *debug_env = getenv("DUMB_INIT_DEBUG");
if (debug_env && strcmp(debug_env, "1") == 0) {
debug = 1;
Expand Down
22 changes: 13 additions & 9 deletions tests/cli_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -51,15 +51,19 @@ def test_help_message(flag, current_version):
b'It is designed to run as PID1 in minimal container environments.\n'
b'\n'
b'Optional arguments:\n'
b' -c, --single-child Run in single-child mode.\n'
b' In this mode, signals are only proxied to the\n'
b' direct child and not any of its descendants.\n'
b' -r, --rewrite s:r Rewrite received signal s to new signal r before proxying.\n'
b' To ignore (not proxy) a signal, rewrite it to 0.\n'
b' This option can be specified multiple times.\n'
b' -v, --verbose Print debugging information to stderr.\n'
b' -h, --help Print this help message and exit.\n'
b' -V, --version Print the current version and exit.\n'
b' -c, --single-child Run in single-child mode.\n'
b' In this mode, signals are only proxied to the\n'
b' direct child and not any of its descendants.\n'
b' -b, --survive-bereaving Do not quit when the direct child dies.\n'
b' In this mode, dumb-init will quit when there are no\n'
b' other processes running on the host.\n'
b' This mode requires dumb-init to be running as PID 1.\n'
b' -r, --rewrite s:r Rewrite received signal s to new signal r before proxying.\n'
b' To ignore (not proxy) a signal, rewrite it to 0.\n'
b' This option can be specified multiple times.\n'
b' -v, --verbose Print debugging information to stderr.\n'
b' -h, --help Print this help message and exit.\n'
b' -V, --version Print the current version and exit.\n'
b'\n'
b'Full help is available online at https://github.com/Yelp/dumb-init\n'
)
Expand Down