forward the events to a helper process via pipe

To reduce number of forks we pass over the events to a helper program
via a pipe. when there are no events for a certain time the helper
program can exit to save memory. Once new events arrives the nldev
application will respawn the helper.

1 files changed, 128 insertions, 0 deletions

diff --git a/nldev-handler.c b/nldev-handler.c
new file mode 100644
index 0000000..4fa6e2a
--- /dev/null
+++ b/nldev-handler.c
@@ -0,0 +1,128 @@
+
+#include <fcntl.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include "log.h"
+
+#define EVENT_TIMEOUT 2000
+
+void
+child(char *runpath)
+{
+	pid_t pid;
+
+	if (!(pid = fork())) {
+		dbg("running %s", runpath);
+		if (execlp(runpath, basename(runpath), NULL) < 0)
+			edie("execvp");
+		exit(0);
+	}
+	if (pid < 0)
+		edie("fork");
+
+	waitpid(pid, NULL, 0);
+}
+
+
+void
+usage(void)
+{
+	die("usage: %s [-d] [-r run]\n", argv0);
+}
+
+int main(int argc, char *argv[])
+{
+	struct pollfd fds;
+	int r;
+	static char buf[16384];
+	char *runpath = "/bin/mdev";
+	char *subsystem = NULL;
+
+	ARGBEGIN {
+	case 'd':
+		dodebug = 1;
+		break;
+	case 'r':
+		runpath = EARGF(usage());
+		break;
+	case 'f':
+		subsystem = EARGF(usage());
+		break;
+	default:
+		usage();
+	} ARGEND;
+
+	dbg("runpath=%s\n", runpath);
+
+	fds.fd = 0; /* stdin */
+	fds.events = POLLIN;
+	while ((r = poll(&fds, 1, EVENT_TIMEOUT)) > 0) {
+		size_t len;
+		int i, slen;
+		char *key, *value;
+
+		clearenv();
+		setenv("PATH", "/sbin:/bin", 1);
+
+		if (!(fds.revents & POLLIN))
+			continue;
+
+		len = read(fds.fd, buf, sizeof(buf)-1);
+		buf[len] = 0;
+		dbg("Got %u bytes", len);
+
+		slen = 0;
+		for (i = 0; i < len; i += slen + 1) {
+			key = buf + i;
+			value = strchr(key, '=');
+			slen = strlen(buf+i);
+
+			if (!slen || value == NULL)
+				continue;
+			if (subsystem && !strncmp(key, "SUBSYSTEM=", 10)
+					&& !strstr(key+10, subsystem)) {
+				dbg("subsystem filter '%s' applied.",
+						subsystem);
+				break;
+			}
+
+			value[0] = '\0';
+			value++;
+
+			/*
+			 * We generally trust the kernel. But there
+			 * might be some udev flaw. (It's >20k sloc!)
+			 */
+			if (strcmp(key, "PATH")) {
+				setenv(key, value, 1);
+				dbg("%s = \"%s\"", key, value);
+			}
+		}
+		if (getenv("ACTION") != NULL &&
+				getenv("DEVPATH") != NULL &&
+				getenv("SUBSYSTEM") != NULL &&
+				getenv("SEQNUM") != NULL) {
+			child(runpath);
+		}
+
+		if (fds.revents & POLLHUP) {
+			dbg("parent hung up\n");
+			return 0;
+		}
+	}
+	if (r == -1)
+		edie("poll");
+
+	if (r == 0)
+		dbg("exit due to timeout");
+
+	return 0;
+}
+
+