srv, ibus: remove the endpoints on a signal too

A stopped daemon left its socket and IBus address file behind, since
plan9port ends a process on SIGTERM without running exit handlers. Both
files now go on a note as well as on exit, and only while they are still
the ones this daemon made, so a successor is never robbed of its own.

ibus.c

@@ -69,6 +69,15 @@ unlinkaddr(void)
 	addrino = 0;
 }
 
+static int
+addrnote(void *v, char *note)
+{
+	USED(v);
+	USED(note);
+	unlinkaddr();
+	return 0;
+}
+
 static void
 machineidfiles(char *buf, int sz, char **path, int npath)
 {
@@ -984,6 +993,7 @@ ibusinit(void)
 		goto fail;
 	}
 	cleanupregistered = 1;
+	threadnotify(addrnote, 1);
 	if(writeaddr(addrfile, full) < 0){
 		fprintf(stderr, "strans: ibus: cannot write %s\n", addrfile);
 		goto fail;

srv.c

@@ -5,8 +5,32 @@
 #include <sys/un.h>
 
 static char adir[256];
+static char sockpath[sizeof(((struct sockaddr_un*)0)->sun_path)];
+static dev_t sockdev;
+static ino_t sockino;
 static Channel *clientc;
 
+/* Removes the socket only while it is still the one we announced. */
+static void
+srvunlink(void)
+{
+	struct stat st;
+
+	if(sockpath[0] != '\0' && lstat(sockpath, &st) == 0 &&
+	   st.st_dev == sockdev && st.st_ino == sockino)
+		unlink(sockpath);
+	sockpath[0] = '\0';
+}
+
+static int
+srvnote(void *v, char *note)
+{
+	USED(v);
+	USED(note);
+	srvunlink();
+	return 0;
+}
+
 static int
 srvreadreq(int fd, Keyreq *kr, int *want)
 {
@@ -90,18 +114,23 @@ clientthread(void *arg)
 void
 srvinit(void)
 {
-	char *addr, path[sizeof(((struct sockaddr_un*)0)->sun_path)];
+	struct stat st;
+	char *addr;
 
-	if(ipcpath(path, sizeof path) < 0)
+	if(ipcpath(sockpath, sizeof sockpath) < 0)
 		die("IPC path is too long");
-	addr = smprint("unix!%s", path);
+	addr = smprint("unix!%s", sockpath);
 	if(addr == nil)
 		die("out of memory");
 	if(announce(addr, adir) < 0)
 		die("IPC endpoint is already in use: %r");
 	free(addr);
-	if(chmod(path, 0600) < 0)
+	if(chmod(sockpath, 0600) < 0 || lstat(sockpath, &st) < 0)
-		die("can't protect IPC endpoint: %s", path);
+		die("can't protect IPC endpoint: %s", sockpath);
+	sockdev = st.st_dev;
+	sockino = st.st_ino;
+	atexit(srvunlink);
+	threadnotify(srvnote, 1);
 }
 
 void

tests/ipc_live_test.c

@@ -334,6 +334,9 @@ main(int argc, char **argv)
 		showerrors(&daemon);
 	if(!stopdaemon(&daemon))
 		ok = 0;
+	/* SIGTERM must leave no socket behind. */
+	if(access(live.socket, F_OK) == 0)
+		ok = fail("socket %s survived the daemon", live.socket);
 	if(!closeerrors(&daemon))
 		ok = 0;
 	if(!liveclean(&live))