socketpair signal handling

2025-10-14 01:59:23 +08:00 · 2002-09-17 22:44:01 +00:00
parent ee3c1fb219
commit d5b915377b
9 changed files with 110 additions and 56 deletions
--- a/4
+++ b/4
@@ -1,9 +1,9 @@
-Moreton Bay DHCP Server
+udhcp server/client package
 -----------------------

+Russ Dill <Russ.Dill@asu.edu>
 Matthew Ramsay	<matthewr@moreton.com.au>
 Chris Trew <christ@moreton.com.au>
-Russ Dill <Russ.Dill@asu.edu>

 Other Credits:
 --------------
--- a/7
+++ b/7
@@ -1,4 +1,11 @@
 0.9.8 (pending)
+ updated client manpage (me)
+ both client and server now use sockets for signal handling,
+  hopefully, this will be the last needed change in signal
+  handling, I'm fairly certain all the possible races are now
+  closed. (me)
+ The server now restarts the auto_time timer when it receives
+  a SIGUSR1 (write out config file). (me)
 + Improve signal handling (David Poole)
 + Fix to config file parsing (Matt Kraai)
 + Fix load lease logic (me)
--- a/20
+++ b/20
@@ -16,17 +16,21 @@ udhcpd /etc/udhcpd.eth1.conf

 The udhcp server employs a number of simple config files:

-udhcpd.leased
+udhcpd.leases
 ------------

 The udhcpd.leases behavior is designed for an embedded system. The
 file is written either every auto_time seconds, or when a SIGUSR1
-is received. When the file is written, a script can be optionally
-called to commit the file to flash. Lease times are stored in the
-file by time remaining in lease (for systems without clock that works
-when there is no power), or by the absolute time that it expires in
-seconds from epoch. In the remainig format, expired leases are stored
-as zero. The file is of the format:
+is received (the auto_time timer restarts if a SIGUSR1 is received). 
+If you send a SIGTERM to udhcpd directly after a SIGUSR1, udhcpd will
+finish writing the leases file and wait for the aftermentioned script
+to be executed and finish before quiting, so you do not need to sleep
+between sending signals. When the file is written, a script can be
+optionally called to commit the file to flash. Lease times are stored
+in the file by time remaining in lease (for systems without clock
+that works when there is no power), or by the absolute time that it
+expires in seconds from epoch. In the remainig format, expired leases
+are stored as zero. The file is of the format:

 16 byte MAC
 4 byte ip address
@@ -147,7 +151,7 @@ udhcpc also responds to SIGUSR1 and SIGUSR2. SIGUSR1 will force a renew state,
 and SIGUSR2 will force a release of the current lease, and cause udhcpc to
 go into an inactive state (until it is killed, or receives a SIGUSR1). You do
 not need to sleep between sending signals, as signals received are processed
-in a logical order during the main loop (release, then renew, then term).
+sequencially in the order they are received.



--- a/dhcpc.c
+++ b/dhcpc.c
@@ -52,9 +52,7 @@ static unsigned long server_addr;
 static unsigned long timeout;
 static int packet_num; /* = 0 */
 static int fd;
-static int renew_requested; /* = 0 */
-static int release_requested; /* = 0 */
-static int term_received; /* = 0 */
+static int signal_pipe[2];

 #define LISTEN_NONE 0
 #define LISTEN_KERNEL 1
@@ -177,10 +175,9 @@ static void exit_client(int retval)
 /* Signal handler */
 static void signal_handler(int sig)
 {
-	switch (sig) {
-	case SIGUSR1: renew_requested = 1; break;
-	case SIGUSR2: release_requested = 1; break;
-	case SIGTERM: term_received = 1; break;
+	if (send(signal_pipe[1], &sig, sizeof(sig), MSG_DONTWAIT) < 0) {
+		LOG(LOG_ERR, "Could not send signal: %s",
+			strerror(errno));
 	}
 }

@@ -217,6 +214,8 @@ int main(int argc, char *argv[])
 	struct in_addr temp_addr;
 	int pid_fd;
 	time_t now;
+	int max_fd;
+	int sig;

 	static struct option options[] = {
 		{"clientid",	required_argument,	0, 'c'},
@@ -313,6 +312,7 @@ int main(int argc, char *argv[])
 	}

 	/* setup signal handlers */
+	socketpair(AF_UNIX, SOCK_STREAM, 0, signal_pipe);
 	signal(SIGUSR1, signal_handler);
 	signal(SIGUSR2, signal_handler);
 	signal(SIGTERM, signal_handler);
@@ -338,10 +338,12 @@ int main(int argc, char *argv[])
 			}
 		}
 		if (fd >= 0) FD_SET(fd, &rfds);
-		
+		FD_SET(signal_pipe[0], &rfds);		
+
 		if (tv.tv_sec > 0) {
 			DEBUG(LOG_INFO, "Waiting on select...\n");
-			retval = select(fd + 1, &rfds, NULL, NULL, &tv);
+			max_fd = signal_pipe[0] > fd ? signal_pipe[0] : fd;
+			retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
 		} else retval = 0; /* If we already timed out, fall through */

 		now = time(0);
@@ -524,21 +526,26 @@ int main(int argc, char *argv[])
 				}
 				break;
 			/* case BOUND, RELEASED: - ignore all packets */
-			}					
-		} else if (retval == -1 && errno == EINTR) {
-			/* a signal was caught */
-			if (release_requested) {
-				perform_release();
-				release_requested = 0;
+			}	
+		} else if (retval > 0 && FD_ISSET(signal_pipe[0], &rfds)) {
+			if (read(signal_pipe[0], &sig, sizeof(signal)) < 0) {
+				DEBUG(LOG_ERR, "Could not read signal: %s", 
+					strerror(errno));
+				continue; /* probably just EINTR */
 			}
-			if (renew_requested) {
+			switch (sig) {
+			case SIGUSR1: 
 				perform_renew();
-				renew_requested = 0;
-			}
-			if (term_received) {
+				break;
+			case SIGUSR2:
+				perform_release();
+				break;
+			case SIGTERM:
 				LOG(LOG_INFO, "Received SIGTERM");
 				exit_client(0);
-			}			
+			}
+		} else if (retval == -1 && errno == EINTR) {
+			/* a signal was caught */		
 		} else {
 			/* An error occured */
 			DEBUG(LOG_ERR, "Error on select");
--- a/dhcpd.c
+++ b/dhcpd.c
@@ -1,6 +1,6 @@
 /* dhcpd.c
 *
- * Moreton Bay DHCP Server
+ * udhcp Server
 * Copyright (C) 1999 Matthew Ramsay <matthewr@moreton.com.au>
 *			Chris Trew <ctrew@moreton.com.au>
 *
@@ -54,7 +54,7 @@
 /* globals */
 struct dhcpOfferedAddr *leases;
 struct server_config_t server_config;
-
+static int signal_pipe[2];

 /* Exit and cleanup */
 static void exit_server(int retval)
@@ -65,12 +65,13 @@ static void exit_server(int retval)
 }


-/* SIGTERM handler */
-static void udhcpd_killed(int sig)
+/* Signal handler */
+static void signal_handler(int sig)
 {
-	sig = 0;
-	LOG(LOG_INFO, "Received SIGTERM");
-	exit_server(0);
+	if (send(signal_pipe[1], &sig, sizeof(sig), MSG_DONTWAIT) < 0) {
+		LOG(LOG_ERR, "Could not send signal: %s", 
+			strerror(errno));
+	}
 }


@@ -92,6 +93,8 @@ int main(int argc, char *argv[])
 	struct option_set *option;
 	struct dhcpOfferedAddr *lease;
 	int pid_fd;
+	int max_sock;
+	int sig;
 	
 	OPEN_LOG("udhcpd");
 	LOG(LOG_INFO, "udhcp server (v%s) started", VERSION);
@@ -129,8 +132,9 @@ int main(int argc, char *argv[])
 #endif


-	signal(SIGUSR1, write_leases);
-	signal(SIGTERM, udhcpd_killed);
+	socketpair(AF_UNIX, SOCK_STREAM, 0, signal_pipe);
+	signal(SIGUSR1, signal_handler);
+	signal(SIGTERM, signal_handler);

 	timeout_end = time(0) + server_config.auto_time;
 	while(1) { /* loop until universe collapses */
@@ -143,26 +147,42 @@ int main(int argc, char *argv[])

 		FD_ZERO(&rfds);
 		FD_SET(server_socket, &rfds);
+		FD_SET(signal_pipe[0], &rfds);
 		if (server_config.auto_time) {
 			tv.tv_sec = timeout_end - time(0);
-			if (tv.tv_sec <= 0) {
-				tv.tv_sec = server_config.auto_time;
-				timeout_end = time(0) + server_config.auto_time;
-				write_leases(0);
-			}
 			tv.tv_usec = 0;
 		}
-		retval = select(server_socket + 1, &rfds, NULL, NULL, server_config.auto_time ? &tv : NULL);
+		if (!server_config.auto_time || tv.tv_sec > 0) {
+			max_sock = server_socket > signal_pipe[0] ? server_socket : signal_pipe[0];
+			retval = select(max_sock + 1, &rfds, NULL, NULL, 
+					server_config.auto_time ? &tv : NULL);
+		} else retval = 0; /* If we already timed out, fall through */

 		if (retval == 0) {
-			write_leases(0);
+			write_leases();
 			timeout_end = time(0) + server_config.auto_time;
 			continue;
-		} else if (retval < 0) {
+		} else if (retval < 0 && errno != EINTR) {
 			DEBUG(LOG_INFO, "error on select");
 			continue;
 		}
 		
+		if (FD_ISSET(signal_pipe[0], &rfds)) {
+			if (read(signal_pipe[0], &sig, sizeof(sig)) < 0)
+				continue; /* probably just EINTR */
+			switch (sig) {
+			case SIGUSR1:
+				LOG(LOG_INFO, "Received a SIGUSR1");
+				write_leases();
+				/* why not just reset the timeout, eh */
+				timeout_end = time(0) + server_config.auto_time;
+				continue;
+			case SIGTERM:
+				LOG(LOG_INFO, "Received a SIGTERM");
+				exit_server(0);
+			}
+		}
+
 		if ((bytes = get_packet(&packet, server_socket)) < 0) { /* this waits for a packet - idle */
 			if (bytes == -1 && errno != EINTR) {
 				DEBUG(LOG_INFO, "error on read, %s, reopening socket", strerror(errno));
--- a/files.c
+++ b/files.c
@@ -219,8 +219,7 @@ int read_config(char *file)
 }


-/* the dummy var is here so this can be a signal handler */
-void write_leases(int dummy)
+void write_leases(void)
 {
 	FILE *fp;
 	unsigned int i;
@@ -228,8 +227,6 @@ void write_leases(int dummy)
 	time_t curr = time(0);
 	unsigned long lease_time;
 	
-	dummy = 0;
-	
 	if (!(fp = fopen(server_config.lease_file, "w"))) {
 		LOG(LOG_ERR, "Unable to open %s for writing", server_config.lease_file);
 		return;
--- a/files.h
+++ b/files.h
@@ -11,7 +11,7 @@ struct config_keyword {


 int read_config(char *file);
-void write_leases(int dummy);
+void write_leases(void);
 void read_leases(char *file);

 #endif
--- a/socket.c
+++ b/socket.c
@@ -1,7 +1,7 @@
 /*
 * socket.c -- DHCP server client/server socket creation
 *
- * Moreton Bay DHCP Server
+ * udhcp client/server
 * Copyright (C) 1999 Matthew Ramsay <matthewr@moreton.com.au>
 *			Chris Trew <ctrew@moreton.com.au>
 *
@@ -153,6 +153,5 @@ int raw_socket(int ifindex)
 	}

 	return fd;
-
 }

--- a/udhcpc.8
+++ b/udhcpc.8
@@ -20,6 +20,10 @@ Do not fork after obtaining a lease.
 Send the client hostname
 .IR HOSTNAME .
 .TP
+.BI \-h\  HOSTNAME
+Alias for -H
+.IR HOSTNAME .
+.TP
 .BI \-i\  INTERFACE ,\ \-\-interface= INTERFACE
 Configure
 .IR INTERFACE .
@@ -47,7 +51,7 @@ Display version.
 .SH USAGE
 When an event occurs,
 .B udhcpc
-executes a script.  There are three possible arguments to this
+executes a script.  There are four possible arguments to this
 script:
 .TP
 .B deconfig
@@ -68,9 +72,22 @@ configure the interface and set any other relevant parameters
 .B renew
 .B renew
 is used when
-.B udhcpc when a lease is renewed.  The interface is already
+.B udhcpc
+when a lease is renewed.  The interface is already
 configured, so the IP address will not change.  Other parameters
 (e.g., default gateway, subnet mask, dns server) may.
+.TP
+.B nak
+.B nak
+is used when
+.B udhcpc
+receieves a NAK packet from the server. The
+enviromental variable
+.B $message
+will contain the reason for the
+NAK message if the server included one. Processing this message
+is optional, as the script will also be called with deconfig if
+need be.
 .PP
 Parameters are passed to the script via the following environment
 variables:
@@ -163,6 +180,9 @@ The DHCP message type (safely ignored).
 .B serverid
 The server IP address.
 .TP
+.B message
+Reason for a DHCPNAK.
+.TP
 .B tftp
 The TFTP server name.
 .TP