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Improve server signal handling

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Use sigaction(2) instead of deprecated signal(2), allowing SEGV et al to be
received in handler and therefore in re-spawned server.

Receive SIGSEGV et al in a separate handler function which kills the server
with the same signal if it does not re-spawn.

Log a GDB backtrace on SEGV et al before exiting or respawning.

Rename config option "serval.respawn_on_signal" to "server.respawn_on_crash".
This commit is contained in:
Andrew Bettison 2012-07-26 18:31:23 +09:30
parent 99ead3b9b1
commit a6a81a0f64
2 changed files with 63 additions and 33 deletions
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1
serval.h
View File

@ -814,6 +814,7 @@ int dump(char *name, unsigned char *addr, size_t len);
int log_backtrace(const char *file, unsigned int line, const char *function);
char *toprint(char *dstStr, ssize_t dstStrLen, const char *srcBuf, size_t srcBytes);
size_t toprint_strlen(ssize_t dstStrLen, const char *srcBuf, size_t srcBytes);
ssize_t get_self_executable_path(char *buf, size_t len);
#define alloca_toprint(dstlen,buf,len) toprint((char *)alloca(toprint_strlen((dstlen), (buf), (len)) + 1), (dstlen), (buf), (len))

95
server.c
View File

@ -17,6 +17,7 @@ along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <signal.h>
#include <time.h>
#include <unistd.h>
#include <sys/socket.h>
@ -35,7 +36,7 @@ char *exec_args[EXEC_NARGS + 1];
int exec_argc = 0;
int serverMode=0;
int serverRespawnOnSignal = 0;
int serverRespawnOnCrash = 0;
int servalShutdown = 0;
static int server_getpid = 0;
@ -49,6 +50,7 @@ struct in_addr client_addr;
int client_port;
void signal_handler(int signal);
void crash_handler(int signal);
int getKeyring(char *s);
int createServerSocket();
@ -176,20 +178,29 @@ int server(char *backing_file)
}
serverMode = 1;
serverRespawnOnSignal = confValueGetBoolean("server.respawn_on_signal", 0);
serverRespawnOnCrash = confValueGetBoolean("server.respawn_on_crash", 0);
/* Catch sigsegv and other crash signals so that we can relaunch ourselves */
if (serverRespawnOnSignal) {
signal(SIGSEGV, signal_handler);
signal(SIGFPE, signal_handler);
signal(SIGILL, signal_handler);
signal(SIGBUS, signal_handler);
signal(SIGABRT, signal_handler);
}
/* Catch SIGHUP etc so that we can respond to requests to do things */
signal(SIGHUP, signal_handler);
signal(SIGINT, signal_handler);
signal(SIGQUIT, signal_handler);
/* Catch crash signals so that we can log a backtrace before expiring. */
struct sigaction sig;
sig.sa_handler = crash_handler;
sigemptyset(&sig.sa_mask); // Don't block any signals during handler
sig.sa_flags = SA_NODEFER | SA_RESETHAND; // So the signal handler can kill the process by re-sending the same signal to itself
sigaction(SIGSEGV, &sig, NULL);
sigaction(SIGFPE, &sig, NULL);
sigaction(SIGILL, &sig, NULL);
sigaction(SIGBUS, &sig, NULL);
sigaction(SIGABRT, &sig, NULL);
/* Catch SIGHUP etc so that we can respond to requests to do things, eg, shut down. */
sig.sa_handler = signal_handler;
sigemptyset(&sig.sa_mask); // Block the same signals during handler
sigaddset(&sig.sa_mask, SIGHUP);
sigaddset(&sig.sa_mask, SIGINT);
sigaddset(&sig.sa_mask, SIGQUIT);
sig.sa_flags = 0;
sigaction(SIGHUP, &sig, NULL);
sigaction(SIGINT, &sig, NULL);
sigaction(SIGQUIT, &sig, NULL);
if (!overlayMode)
{
@ -424,11 +435,7 @@ void signal_handler(int signal)
char buf[80];
signame(buf, sizeof(buf), signal);
INFOF("Caught %s", buf);
dump_stack();
switch (signal) {
case SIGQUIT:
serverCleanUp();
exit(0);
case SIGHUP:
case SIGINT:
/* Terminate the server process. The shutting down should be done from the main-line code
@ -439,21 +446,43 @@ void signal_handler(int signal)
servalShutdown = 1;
return;
}
/* oops - caught a bad signal -- exec() ourselves fresh */
if (sock>-1)
close(sock);
int i;
for(i=0;i<overlay_interface_count;i++)
if (overlay_interfaces[i].alarm.poll.fd>-1)
close(overlay_interfaces[i].alarm.poll.fd);
strbuf b = strbuf_alloca(1024);
for (i = 0; i < exec_argc; ++i)
strbuf_append_shell_quotemeta(strbuf_puts(b, i ? " " : ""), exec_args[i]);
INFOF("Respawning %s", strbuf_str(b));
execv(exec_args[0], exec_args);
/* Quit if the exec() fails */
WHY_perror("execv");
exit(-3);
serverCleanUp();
exit(0);
}
void crash_handler(int signal)
{
char buf[80];
signame(buf, sizeof(buf), signal);
WHYF("Caught %s", buf);
dump_stack();
BACKTRACE;
if (serverRespawnOnCrash) {
if (sock>-1)
close(sock);
int i;
for(i=0;i<overlay_interface_count;i++)
if (overlay_interfaces[i].alarm.poll.fd>-1)
close(overlay_interfaces[i].alarm.poll.fd);
char execpath[160];
if (get_self_executable_path(execpath, sizeof execpath) != -1) {
strbuf b = strbuf_alloca(1024);
for (i = 0; i < exec_argc; ++i)
strbuf_append_shell_quotemeta(strbuf_puts(b, i ? " " : ""), exec_args[i]);
INFOF("Respawning %s as %s", execpath, strbuf_str(b));
execv(execpath, exec_args);
/* Quit if the exec() fails */
WHY_perror("execv");
} else {
WHY("Cannot respawn");
}
}
// Now die of the same signal, so that our exit status reflects the cause.
INFOF("Re-sending signal %d to self", signal);
kill(getpid(), signal);
// If that didn't work, then die normally.
INFOF("exit(%d)", -signal);
exit(-signal);
}
int getKeyring(char *backing_file)