Add Linux kernel event handling code

This is a simple handler for uevents send by the Linux
kernel.

CMakeLists.txt

@@ -7,6 +7,9 @@ option( ENABLE_EXAMPLES "Install additional tin2rc examples" ON )
 option( ENABLE_RSVG "Rsvg support (launcher only)" ON )
 option( ENABLE_SN "Startup notification support" ON )
 option( ENABLE_ASAN "Build tint2 with AddressSanitizer" OFF )
+if( CMAKE_SYSTEM_NAME STREQUAL "Linux" )
+  option( ENABLE_UEVENT "Kernel event handling support" ON )
+endif( CMAKE_SYSTEM_NAME STREQUAL "Linux" )
 
 include( FindPkgConfig )
 include( CheckLibraryExists )
@@ -111,6 +114,11 @@ if( ENABLE_SN )
   endif( SN_FOUND )
 endif( ENABLE_SN)
 
+if( ENABLE_UEVENT )
+  add_definitions( -DENABLE_UEVENT )
+  set( SOURCES ${SOURCES} src/util/uevent.c)
+endif( ENABLE_UEVENT )
+
 if( ENABLE_TINT2CONF )
   add_definitions( -DHAVE_VERSION_H )
   add_subdirectory( src/tint2conf )

src/tint.c

@@ -49,6 +49,7 @@
 #include "tooltip.h"
 #include "timer.h"
 #include "xsettings-client.h"
+#include "uevent.h"
 
 // Drag and Drop state variables
 Window dnd_source_window;
@@ -340,6 +341,8 @@ void cleanup()
 		}
 	}
 #endif
+
+	uevent_cleanup();
 }
 
 
@@ -1201,6 +1204,8 @@ start:
 	dnd_sent_request = 0;
 	dnd_launcher_exec = 0;
 
+	int ufd = uevent_init();
+
 	//	sigset_t empty_mask;
 	//	sigemptyset(&empty_mask);
 
@@ -1243,6 +1248,10 @@ start:
 			FD_SET (sn_pipe[0], &fdset);
 			maxfd = maxfd < sn_pipe[0] ? sn_pipe[0] : maxfd;
 		}
+		if (ufd > 0) {
+			FD_SET (ufd, &fdset);
+			maxfd = maxfd < ufd ? ufd : maxfd;
+		}
 		update_next_timeout();
 		if (next_timeout.tv_sec >= 0 && next_timeout.tv_usec >= 0)
 			select_timeout = &next_timeout;
@@ -1251,6 +1260,8 @@ start:
 
 		// Wait for X Event or a Timer
 		if (XPending(server.dsp) > 0 || select(maxfd+1, &fdset, 0, 0, select_timeout) >= 0) {
+			uevent_handler();
+
 			if (sn_pipe_valid) {
 				char buffer[1];
 				while (read(sn_pipe[0], buffer, sizeof(buffer)) > 0) {

src/util/uevent.c

@@ -0,0 +1,204 @@
+/**************************************************************************
+*
+* Linux Kernel uevent handler
+*
+* Copyright (C) 2015 Sebastian Reichel <sre@ring0.de>
+*
+* This program is free software; you can redistribute it and/or
+* modify it under the terms of the GNU General Public License version 2
+* or any later version as published by the Free Software Foundation.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+* You should have received a copy of the GNU General Public License
+* along with this program; if not, write to the Free Software
+* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+**************************************************************************/
+
+#ifdef ENABLE_UEVENT
+
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <sys/socket.h>
+#include <sys/types.h>
+
+#include <linux/types.h>
+#include <linux/netlink.h>
+
+#include "common.h"
+#include "uevent.h"
+
+static int ueventfd = -1;
+static struct sockaddr_nl nls;
+static GList *notifiers = NULL;
+
+static const char* has_prefix(const char *str, const char *end, const char *prefix, size_t prefixlen) {
+	if ((end-str) < prefixlen)
+		return NULL;
+
+	if (!memcmp(str, prefix, prefixlen))
+		return str + prefixlen;
+
+	return NULL;
+}
+
+#define HAS_CONST_PREFIX(str,end,prefix)  has_prefix((str),end,prefix,sizeof(prefix)-1)
+
+static void uevent_param_free(gpointer data) {
+	struct uevent_parameter *param = data;
+	free(param->key);
+	free(param->val);
+	free(param);
+}
+
+static void uevent_free(struct uevent *ev) {
+	free(ev->path);
+	free(ev->subsystem);
+	g_list_free_full(ev->params, uevent_param_free);
+	free(ev);
+}
+
+static struct uevent *uevent_new(char *buffer, int size) {
+	struct uevent *ev;
+	const char* s = buffer;
+	const char* end = s + size;
+	gboolean first = TRUE;
+
+	if (size == 0)
+		return NULL;
+
+	ev = calloc(1, sizeof(*ev));
+	if (!ev)
+		return NULL;
+
+	/* ensure nul termination required by strlen() */
+	buffer[size-1] = '\0';
+
+	for (; s < end; s += strlen(s) + 1) {
+		if (first) {
+			const char *p;
+			for (p = s; *p != '@'; p++) {
+				if (!*p) {
+					/* error: kernel events contain @ */
+					/* triggered by udev events, though */
+					free(ev);
+					return NULL;
+				}
+			}
+			ev->path = strdup(p+1);
+			first = FALSE;
+		} else {
+			const char* val;
+			if ((val = HAS_CONST_PREFIX(s, end, "ACTION=")) != NULL) {
+				if (!strcmp(val, "add"))
+					ev->action = UEVENT_ADD;
+				else if (!strcmp(val, "remove"))
+					ev->action = UEVENT_REMOVE;
+				else if (!strcmp(val, "change"))
+					ev->action = UEVENT_CHANGE;
+				else
+					ev->action = UEVENT_UNKNOWN;
+			} else if ((val = HAS_CONST_PREFIX(s, end, "SEQNUM=")) != NULL) {
+				ev->sequence = atoi(val);
+			} else if ((val = HAS_CONST_PREFIX(s, end, "SUBSYSTEM=")) != NULL) {
+				ev->subsystem = strdup(val);
+			} else {
+				val = strchr(s, '=');
+				if (val) {
+					struct uevent_parameter *param = malloc(sizeof(*param));
+					if(param) {
+						param->key = strndup(s, val-s);
+						param->val = strdup(val+1);
+						ev->params = g_list_append(ev->params, param);
+					}
+				}
+			}
+		}
+	}
+
+	return ev;
+}
+
+void uevent_register_notifier(struct uevent_notify *nb) {
+	notifiers = g_list_append(notifiers, nb);
+}
+
+void uevent_unregister_notifier(struct uevent_notify *nb) {
+	GList *l = notifiers;
+
+	while (l != NULL) {
+		GList *next = l->next;
+		struct uevent_notify *lnb = l->data;
+
+		if(memcmp(nb, lnb, sizeof(struct uevent_notify)) == 0)
+			notifiers = g_list_delete_link(notifiers, l);
+
+		l = next;
+	}
+}
+
+void uevent_handler() {
+	struct uevent *ev;
+	char buf[512];
+	GList *l;
+
+	if (ueventfd < 0)
+		return;
+
+	int len = recv(ueventfd, buf, sizeof(buf), MSG_DONTWAIT);
+	if (len < 0)
+		return;
+
+	ev = uevent_new(buf, len);
+	if(ev) {
+		for (l = notifiers; l != NULL; l = l->next) {
+			struct uevent_notify *nb = l->data;
+
+			if (!(ev->action & nb->action))
+				continue;
+
+			if (nb->subsystem && strcmp(ev->subsystem, nb->subsystem))
+				continue;
+
+			nb->cb(ev, nb->userdata);
+		}
+
+		uevent_free(ev);
+	}
+}
+
+int uevent_init() {
+	/* Open hotplug event netlink socket */
+	memset(&nls,0,sizeof(struct sockaddr_nl));
+	nls.nl_family = AF_NETLINK;
+	nls.nl_pid = getpid();
+	nls.nl_groups = -1;
+
+	/* open socket */
+	ueventfd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
+	if (ueventfd < 0) {
+		fprintf(stderr, "Error: socket open failed\n");
+		return -1;
+	}
+
+	/* Listen to netlink socket */
+	if (bind(ueventfd, (void *)&nls, sizeof(struct sockaddr_nl))) {
+		fprintf(stderr, "Bind failed\n");
+		return -1;
+	}
+
+	printf("Kernel uevent interface initialized...\n");
+
+	return ueventfd;
+}
+
+void uevent_cleanup() {
+	if (ueventfd >= 0)
+		close(ueventfd);
+}
+
+#endif

src/util/uevent.h

@@ -0,0 +1,70 @@
+/**************************************************************************
+*
+* Linux Kernel uevent handler
+*
+* Copyright (C) 2015 Sebastian Reichel <sre@ring0.de>
+*
+* This program is free software; you can redistribute it and/or
+* modify it under the terms of the GNU General Public License version 2
+* or any later version as published by the Free Software Foundation.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+* You should have received a copy of the GNU General Public License
+* along with this program; if not, write to the Free Software
+* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+**************************************************************************/
+
+#ifndef UEVENT_H
+#define UEVENT_H
+
+enum uevent_action {
+	UEVENT_UNKNOWN = 0x01,
+	UEVENT_ADD     = 0x02,
+	UEVENT_REMOVE  = 0x04,
+	UEVENT_CHANGE  = 0x08,
+};
+
+struct uevent_parameter {
+	char *key;
+	char *val;
+};
+
+struct uevent {
+	char *path;
+	enum uevent_action action;
+	int sequence;
+	char *subsystem;
+	GList *params;
+};
+
+struct uevent_notify {
+	int action; /* bitfield */
+	char *subsystem; /* NULL => any */
+	void *userdata;
+
+	void (*cb)(struct uevent *e, void *userdata);
+};
+
+#if ENABLE_UEVENT
+int uevent_init();
+void uevent_cleanup();
+void uevent_handler();
+
+void uevent_register_notifier(struct uevent_notify *nb);
+void uevent_unregister_notifier(struct uevent_notify *nb);
+#else
+static inline int uevent_init() {
+	return -1;
+}
+
+static inline void uevent_cleanup() { }
+static inline void uevent_handler() { }
+
+static inline void uevent_register_notifier(struct uevent_notify *nb) { }
+static inline void uevent_unregister_notifier(struct uevent_notify *nb) { }
+#endif
+
+#endif