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GUACAMOLE-533: Wait at most 5 seconds for connection processes to terminate following disconnect.

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This commit is contained in:
Michael Jumper 2018-03-13 17:00:10 -07:00
parent 3516704b82
commit d6a5695f8a
2 changed files with 207 additions and 10 deletions
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209
src/guacd/proc.c
View File

@ -33,11 +33,15 @@
#include <guacamole/user.h>
#include <errno.h>
#include <pthread.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
/**
* Parameters for the user thread.
@ -138,6 +142,151 @@ static void guacd_proc_add_user(guacd_proc* proc, int fd, int owner) {
}
/**
* Forcibly kills all processes within the current process group, including the
* current process and all child processes. This function is only safe to call
* if the process group ID has been correctly set. Calling this function within
* a process which does not have a PGID separate from the main guacd process
* can result in guacd itself being terminated.
*/
static void guacd_kill_current_proc_group() {
/* Forcibly kill all children within process group */
if (kill(0, SIGKILL))
guacd_log(GUAC_LOG_WARNING, "Unable to forcibly terminate "
"client process: %s ", strerror(errno));
}
/**
* The current status of a background attempt to free a guac_client instance.
*/
typedef struct guacd_client_free {
/**
* The guac_client instance being freed.
*/
guac_client* client;
/**
* The condition which is signalled whenever changes are made to the
* completed flag. The completed flag only changes from zero (not yet
* freed) to non-zero (successfully freed).
*/
pthread_cond_t completed_cond;
/**
* Mutex which must be acquired before any changes are made to the
* completed flag.
*/
pthread_mutex_t completed_mutex;
/**
* Whether the guac_client has been successfully freed. Initially, this
* will be zero, indicating that the free operation has not yet been
* attempted. If the client is eventually successfully freed, this will be
* set to a non-zero value. Changes to this flag are signalled through
* the completed_cond condition.
*/
int completed;
} guacd_client_free;
/**
* Thread which frees a given guac_client instance in the background. If the
* free operation succeeds, a flag is set on the provided structure, and the
* change in that flag is signalled with a pthread condition.
*
* At the time this function is provided to a pthread_create() call, the
* completed flag of the associated guacd_client_free structure MUST be
* initialized to zero, the pthread mutex and condition MUST both be
* initialized, and the client pointer must point to the guac_client being
* freed.
*
* @param data
* A pointer to a guacd_client_free structure describing the free
* operation.
*
* @return
* Always NULL.
*/
static void* guacd_client_free_thread(void* data) {
guacd_client_free* free_operation = (guacd_client_free*) data;
/* Attempt to free client (this may never return if the client is
* malfunctioning) */
guac_client_free(free_operation->client);
/* Signal that the client was successfully freed */
pthread_mutex_lock(&free_operation->completed_mutex);
free_operation->completed = 1;
pthread_cond_broadcast(&free_operation->completed_cond);
pthread_mutex_unlock(&free_operation->completed_mutex);
return NULL;
}
/**
* Attempts to free the given guac_client, restricting the time taken by the
* free handler of the guac_client to a finite number of seconds. If the free
* handler does not complete within the time alotted, this function returns
* and the intended free operation is left in an undefined state.
*
* @param client
* The guac_client instance to free.
*
* @param timeout
* The maximum amount of time to wait for the guac_client to be freed,
* in seconds.
*
* @return
* Zero if the guac_client was successfully freed within the time alotted,
* non-zero otherwise.
*/
static int guacd_timed_client_free(guac_client* client, int timeout) {
pthread_t client_free_thread;
guacd_client_free free_operation = {
.client = client,
.completed_cond = PTHREAD_COND_INITIALIZER,
.completed_mutex = PTHREAD_MUTEX_INITIALIZER,
.completed = 0
};
/* Get current time */
struct timeval current_time;
if (gettimeofday(&current_time, NULL))
return 1;
/* Calculate exact time that the free operation MUST complete by */
struct timespec deadline = {
.tv_sec = current_time.tv_sec + timeout,
.tv_nsec = current_time.tv_usec * 1000
};
/* Free the client in a separate thread, so we can time the free operation */
if (pthread_create(&client_free_thread, NULL,
guacd_client_free_thread, &free_operation))
return 1;
/* The mutex associated with the pthread conditional and flag MUST be
* acquired before attempting to wait for the condition */
if (pthread_mutex_lock(&free_operation.completed_mutex))
return 1;
/* Wait a finite amount of time for the free operation to finish */
if (pthread_cond_timedwait(&free_operation.completed_cond,
&free_operation.completed_mutex, &deadline))
return 1;
/* Return status of free operation */
return !free_operation.completed;
}
/**
* Starts protocol-specific handling on the given process by loading the client
* plugin for that protocol. This function does NOT return. It initializes the
@ -154,8 +303,18 @@ static void guacd_proc_add_user(guacd_proc* proc, int fd, int owner) {
*/
static void guacd_exec_proc(guacd_proc* proc, const char* protocol) {
int result = 1;
/* Set process group ID to match PID */
if (setpgid(0, 0)) {
guacd_log(GUAC_LOG_ERROR, "Cannot set PGID for connection process: %s",
strerror(errno));
goto cleanup_process;
}
/* Init client for selected protocol */
if (guac_client_load_plugin(proc->client, protocol)) {
guac_client* client = proc->client;
if (guac_client_load_plugin(client, protocol)) {
/* Log error */
if (guac_error == GUAC_STATUS_NOT_FOUND)
@ -165,10 +324,7 @@ static void guacd_exec_proc(guacd_proc* proc, const char* protocol) {
guacd_log_guac_error(GUAC_LOG_ERROR,
"Unable to load client plugin");
guac_client_free(proc->client);
close(proc->fd_socket);
free(proc);
exit(1);
goto cleanup_client;
}
/* The first file descriptor is the owner */
@ -185,14 +341,47 @@ static void guacd_exec_proc(guacd_proc* proc, const char* protocol) {
}
/* Stop and free client */
guac_client_stop(proc->client);
guac_client_free(proc->client);
cleanup_client:
/* Child is finished */
/* Request client to stop/disconnect */
guac_client_stop(client);
/* Attempt to free client cleanly */
guacd_log(GUAC_LOG_DEBUG, "Requesting termination of client...");
result = guacd_timed_client_free(client, GUACD_CLIENT_FREE_TIMEOUT);
/* If client was unable to be freed, warn and forcibly kill */
if (result) {
guacd_log(GUAC_LOG_WARNING, "Client did not terminate in a timely "
"manner. Forcibly terminating client and any child "
"processes.");
guacd_kill_current_proc_group();
}
else
guacd_log(GUAC_LOG_DEBUG, "Client terminated successfully.");
/* Verify whether children were all properly reaped */
pid_t child_pid;
while ((child_pid = waitpid(0, NULL, WNOHANG)) > 0) {
guacd_log(GUAC_LOG_DEBUG, "Automatically reaped unreaped "
"(zombie) child process with PID %i.", child_pid);
}
/* If running children remain, warn and forcibly kill */
if (child_pid == 0) {
guacd_log(GUAC_LOG_WARNING, "Client reported successful termination, "
"but child processes remain. Forcibly terminating client and "
"child processes.");
guacd_kill_current_proc_group();
}
cleanup_process:
/* Free up all internal resources outside the client */
close(proc->fd_socket);
free(proc);
exit(0);
exit(result);
}

8
src/guacd/proc.h
View File

@ -40,6 +40,14 @@
*/
#define GUACD_USEC_TIMEOUT (GUACD_TIMEOUT*1000)
/**
* The number of seconds to wait for any particular guac_client instance
* to be freed following disconnect. If the free operation does not complete
* within this period of time, the associated process will be forcibly
* terminated.
*/
#define GUACD_CLIENT_FREE_TIMEOUT 5
/**
* Process information of the internal remote desktop client.
*/