- Add -K keepalive flag for dropbear and dbclient

- Try to reduce the frequency of select() timeouts
- Add a max receive window size of 1MB

--HG--
extra : convert_revision : 9aa22036cb511cddb35fbc0e09ad05acb39b64d1

cli-runopts.c

@@ -63,11 +63,14 @@ static void printhelp() {
 #ifdef ENABLE_CLI_REMOTETCPFWD
 					"-R <listenport:remotehost:remoteport> Remote port forwarding\n"
 #endif
-					"-W <receive_window_buffer> (default %d, larger may be faster)\n"
+					"-W <receive_window_buffer> (default %d, larger may be faster, max 1MB)\n"
+					"-K <keepalive>  (0 is never, default %d)\n"
 #ifdef DEBUG_TRACE
 					"-v    verbose\n"
 #endif
-					,DROPBEAR_VERSION, cli_opts.progname, DEFAULT_RECV_WINDOW);
+					,DROPBEAR_VERSION, cli_opts.progname,
+					DEFAULT_RECV_WINDOW, DEFAULT_KEEPALIVE);
+					
 }
 
 void cli_getopts(int argc, char ** argv) {
@@ -112,6 +115,7 @@ void cli_getopts(int argc, char ** argv) {
 	*/
 	opts.recv_window = DEFAULT_RECV_WINDOW;
 	char* recv_window_arg = NULL;
+	char* keepalive_arg = NULL;
 
 	/* Iterate all the arguments */
 	for (i = 1; i < (unsigned int)argc; i++) {
@@ -207,6 +211,9 @@ void cli_getopts(int argc, char ** argv) {
 				case 'W':
 					next = &recv_window_arg;
 					break;
+				case 'K':
+					next = &keepalive_arg;
+					break;
 #ifdef DEBUG_TRACE
 				case 'v':
 					debug_trace = 1;
@@ -302,11 +309,19 @@ void cli_getopts(int argc, char ** argv) {
 	if (recv_window_arg)
 	{
 		opts.recv_window = atol(recv_window_arg);
-		if (opts.recv_window == 0)
+		if (opts.recv_window == 0 || opts.recv_window > MAX_RECV_WINDOW)
 		{
 			dropbear_exit("Bad recv window '%s'", recv_window_arg);
 		}
 	}
+	if (keepalive_arg) {
+		opts.keepalive_secs = strtoul(keepalive_arg, NULL, 10);
+		if (opts.keepalive_secs == 0 && errno == EINVAL)
+		{
+			dropbear_exit("Bad keepalive '%s'", keepalive_arg);
+		}
+	}
+	
 }
 
 #ifdef ENABLE_CLI_PUBKEY_AUTH

common-kex.c

@@ -188,8 +188,6 @@ void kexfirstinitialise() {
 /* Reset the kex state, ready for a new negotiation */
 static void kexinitialise() {
 
-	struct timeval tv;
-
 	TRACE(("kexinitialise()"))
 
 	/* sent/recv'd MSG_KEXINIT */
@@ -206,10 +204,7 @@ static void kexinitialise() {
 	ses.kexstate.datatrans = 0;
 	ses.kexstate.datarecv = 0;
 
-	if (gettimeofday(&tv, 0) < 0) {
+	ses.kexstate.lastkextime = time(NULL);
-		dropbear_exit("Error getting time");
-	}
-	ses.kexstate.lastkextime = tv.tv_sec;
 
 }
 

common-session.c

@@ -34,8 +34,10 @@
 #include "kex.h"
 #include "channel.h"
 #include "atomicio.h"
+#include "runopts.h"
 
 static void checktimeouts();
+static long select_timeout();
 static int ident_readln(int fd, char* buf, int count);
 
 struct sshsession ses; /* GLOBAL */
@@ -59,7 +61,8 @@ void common_session_init(int sock, char* remotehost) {
 	ses.sock = sock;
 	ses.maxfd = sock;
 
-	ses.connecttimeout = 0;
+	ses.connect_time = 0;
+	ses.last_packet_time = 0;
 	
 	if (pipe(ses.signal_pipe) < 0) {
 		dropbear_exit("signal pipe failed");
@@ -129,7 +132,7 @@ void session_loop(void(*loophandler)()) {
 	/* main loop, select()s for all sockets in use */
 	for(;;) {
 
-		timeout.tv_sec = SELECT_TIMEOUT;
+		timeout.tv_sec = select_timeout();
 		timeout.tv_usec = 0;
 		FD_ZERO(&writefd);
 		FD_ZERO(&readfd);
@@ -359,20 +362,22 @@ static int ident_readln(int fd, char* buf, int count) {
 	return pos+1;
 }
 
+void send_msg_ignore() {
+	CHECKCLEARTOWRITE();
+	buf_putbyte(ses.writepayload, SSH_MSG_IGNORE);
+	buf_putstring(ses.writepayload, "", 0);
+	encrypt_packet();
+}
+
 /* Check all timeouts which are required. Currently these are the time for
  * user authentication, and the automatic rekeying. */
 static void checktimeouts() {
 
-	struct timeval tv;
+	time_t now;
-	long secs;
 
-	if (gettimeofday(&tv, 0) < 0) {
+	now = time(NULL);
-		dropbear_exit("Error getting time");
-	}
-
-	secs = tv.tv_sec;
 	
-	if (ses.connecttimeout != 0 && secs > ses.connecttimeout) {
+	if (ses.connect_time != 0 && now - ses.connect_time >= AUTH_TIMEOUT) {
 			dropbear_close("Timeout before auth");
 	}
 
@@ -382,10 +387,27 @@ static void checktimeouts() {
 	}
 
 	if (!ses.kexstate.sentkexinit
-			&& (secs - ses.kexstate.lastkextime >= KEX_REKEY_TIMEOUT
+			&& (now - ses.kexstate.lastkextime >= KEX_REKEY_TIMEOUT
-			|| ses.kexstate.datarecv+ses.kexstate.datatrans >= KEX_REKEY_DATA)){
+			|| ses.kexstate.datarecv+ses.kexstate.datatrans >= KEX_REKEY_DATA)) {
 		TRACE(("rekeying after timeout or max data reached"))
 		send_msg_kexinit();
 	}
+	
+	if (opts.keepalive_secs > 0 
+		&& now - ses.last_packet_time >= opts.keepalive_secs) {
+		send_msg_ignore();
+	}
 }
 
+static long select_timeout() {
+	/* determine the minimum timeout that might be required, so
+	as to avoid waking when unneccessary */
+	long ret = LONG_MAX;
+	if (KEX_REKEY_TIMEOUT > 0)
+		ret = MIN(KEX_REKEY_TIMEOUT, ret);
+	if (AUTH_TIMEOUT > 0)
+		ret = MIN(AUTH_TIMEOUT, ret);
+	if (opts.keepalive_secs > 0)
+		ret = MIN(opts.keepalive_secs, ret);
+	return ret;
+}

dbclient.1

@@ -79,6 +79,13 @@ connection will abort as normal.
 Specify the per-channel receive window buffer size. Increasing this 
 may improve network performance at the expense of memory use. Use -h to see the
 default buffer size.
+.TP
+.B \-K \fItimeout_seconds
+Ensure that traffic is transmitted at a certain interval in seconds. This is
+useful for working around firewalls or routers that drop connections after
+a certain period of inactivity. The trade-off is that a session may be
+closed if there is a temporary lapse of network connectivity. A setting
+if 0 disables keepalives.
 .SH AUTHOR
 Matt Johnston (matt@ucc.asn.au).
 .br

dropbear.8

@@ -87,6 +87,13 @@ Allow remote hosts to connect to forwarded ports.
 Specify the per-channel receive window buffer size. Increasing this 
 may improve network performance at the expense of memory use. Use -h to see the
 default buffer size.
+.TP
+.B \-K \fItimeout_seconds
+Ensure that traffic is transmitted at a certain interval in seconds. This is
+useful for working around firewalls or routers that drop connections after
+a certain period of inactivity. The trade-off is that a session may be
+closed if there is a temporary lapse of network connectivity. A setting
+if 0 disables keepalives.
 .SH AUTHOR
 Matt Johnston (matt@ucc.asn.au).
 .br

includes.h

@@ -56,6 +56,7 @@
 #include <ctype.h>
 #include <stdarg.h>
 #include <dirent.h>
+#include <time.h>
 
 #ifdef HAVE_UTMP_H
 #include <utmp.h>

kex.h

@@ -53,7 +53,7 @@ struct KEXState {
 	unsigned donefirstkex : 1; /* Set to 1 after the first kex has completed,
 								  ie the transport layer has been set up */
 
-	long lastkextime; /* time of the last kex */
+	time_t lastkextime; /* time of the last kex */
 	unsigned int datatrans; /* data transmitted since last kex */
 	unsigned int datarecv; /* data received since last kex */
 

options.h

@@ -231,6 +231,9 @@ etc) slower (perhaps by 50%). Recommended for most small systems. */
    though increasing it may not make a significant difference. */
 #define TRANS_MAX_PAYLOAD_LEN 16384
 
+/* Ensure that data is transmitted every KEEPALIVE seconds. This can
+be overridden at runtime with -K. 0 disables keepalives */
+#define DEFAULT_KEEPALIVE 0
 
 /*******************************************************************
  * You shouldn't edit below here unless you know you need to.
@@ -287,9 +290,6 @@ etc) slower (perhaps by 50%). Recommended for most small systems. */
 
 #define _PATH_CP "/bin/cp"
 
-/* Timeouts in seconds */
-#define SELECT_TIMEOUT 20
-
 /* success/failure defines */
 #define DROPBEAR_SUCCESS 0
 #define DROPBEAR_FAILURE -1
@@ -343,6 +343,7 @@ etc) slower (perhaps by 50%). Recommended for most small systems. */
 
 #define RECV_WINDOWEXTEND (opts.recv_window / 3) /* We send a "window extend" every
 								RECV_WINDOWEXTEND bytes */
+#define MAX_RECV_WINDOW (1024*1024) /* 1 MB should be enough */
 
 #define MAX_CHANNELS 100 /* simple mem restriction, includes each tcp/x11
 							connection, so can't be _too_ small */

packet.c

@@ -71,6 +71,8 @@ void write_packet() {
 			dropbear_exit("error writing");
 		}
 	} 
+	
+	ses.last_packet_time = time(NULL);
 
 	if (written == 0) {
 		ses.remoteclosed();

process-packet.c

@@ -56,8 +56,8 @@ void process_packet() {
 	switch(type) {
 
 		case SSH_MSG_IGNORE:
+			goto out;
 		case SSH_MSG_DEBUG:
-			TRACE(("received SSH_MSG_IGNORE or SSH_MSG_DEBUG"))
 			goto out;
 
 		case SSH_MSG_UNIMPLEMENTED:

runopts.h

@@ -37,6 +37,7 @@ typedef struct runopts {
 	int listen_fwd_all;
 #endif
 	unsigned int recv_window;
+	time_t keepalive_secs;
 
 } runopts;
 

session.h

@@ -45,6 +45,7 @@ void common_session_init(int sock, char* remotehost);
 void session_loop(void(*loophandler)());
 void common_session_cleanup();
 void session_identification();
+void send_msg_ignore();
 
 
 /* Server */
@@ -92,8 +93,9 @@ struct sshsession {
 	/* Is it a client or server? */
 	unsigned char isserver;
 
-	long connecttimeout; /* time to disconnect if we have a timeout (for
+	time_t connect_time; /* time the connection was established
-							userauth etc), or 0 for no timeout */
+							(cleared after auth once we're not
+							respecting AUTH_TIMEOUT any more) */
 
 	int sock;
 
@@ -131,6 +133,9 @@ struct sshsession {
 	
     int signal_pipe[2]; /* stores endpoints of a self-pipe used for
 						   race-free signal handling */
+						
+	time_t last_packet_time; /* time of the last packet transmission, for
+							keepalive purposes */
 
 	/* KEX/encryption related */
 	struct KEXState kexstate;

svr-auth.c

@@ -357,7 +357,7 @@ void send_msg_userauth_success() {
 	encrypt_packet();
 
 	ses.authstate.authdone = 1;
-	ses.connecttimeout = 0;
+	ses.connect_time = 0;
 
 
 	if (ses.authstate.pw->pw_uid == 0) {

svr-main.c

@@ -111,7 +111,6 @@ static void main_inetd() {
 #ifdef NON_INETD_MODE
 void main_noinetd() {
 	fd_set fds;
-	struct timeval seltimeout;
 	unsigned int i, j;
 	int val;
 	int maxsock = -1;
@@ -175,9 +174,6 @@ void main_noinetd() {
 
 		FD_ZERO(&fds);
 		
-		seltimeout.tv_sec = 60;
-		seltimeout.tv_usec = 0;
-		
 		/* listening sockets */
 		for (i = 0; i < listensockcount; i++) {
 			FD_SET(listensocks[i], &fds);
@@ -191,7 +187,7 @@ void main_noinetd() {
 			}
 		}
 
-		val = select(maxsock+1, &fds, NULL, NULL, &seltimeout);
+		val = select(maxsock+1, &fds, NULL, NULL, NULL);
 
 		if (exitflag) {
 			unlink(svr_opts.pidfile);
@@ -199,7 +195,7 @@ void main_noinetd() {
 		}
 		
 		if (val == 0) {
-			/* timeout reached */
+			/* timeout reached - shouldn't happen. eh */
 			continue;
 		}
 

svr-runopts.c

@@ -80,7 +80,8 @@ static void printhelp(const char * progname) {
 #ifdef INETD_MODE
 					"-i		Start for inetd\n"
 #endif
-					"-W <receive_window_buffer> (default %d, larger may be faster)\n"
+					"-W <receive_window_buffer> (default %d, larger may be faster, max 1MB)\n"
+					"-K <keepalive>  (0 is never, default %d)\n"
 #ifdef DEBUG_TRACE
 					"-v		verbose\n"
 #endif
@@ -91,7 +92,8 @@ static void printhelp(const char * progname) {
 #ifdef DROPBEAR_RSA
 					RSA_PRIV_FILENAME,
 #endif
-					DROPBEAR_MAX_PORTS, DROPBEAR_DEFPORT, DROPBEAR_PIDFILE, DEFAULT_RECV_WINDOW);
+					DROPBEAR_MAX_PORTS, DROPBEAR_DEFPORT, DROPBEAR_PIDFILE,
+					DEFAULT_RECV_WINDOW, DEFAULT_KEEPALIVE);
 }
 
 void svr_getopts(int argc, char ** argv) {
@@ -99,6 +101,8 @@ void svr_getopts(int argc, char ** argv) {
 	unsigned int i;
 	char ** next = 0;
 	int nextisport = 0;
+	char* recv_window_arg = NULL;
+	char* keepalive_arg = NULL;
 
 	/* see printhelp() for options */
 	svr_opts.rsakeyfile = NULL;
@@ -130,7 +134,8 @@ void svr_getopts(int argc, char ** argv) {
 	svr_opts.usingsyslog = 1;
 #endif
 	opts.recv_window = DEFAULT_RECV_WINDOW;
-	char* recv_window_arg = NULL;
+	opts.keepalive_secs = DEFAULT_KEEPALIVE;	
+	
 #ifdef ENABLE_SVR_REMOTETCPFWD
 	opts.listen_fwd_all = 0;
 #endif
@@ -210,6 +215,9 @@ void svr_getopts(int argc, char ** argv) {
 				case 'W':
 					next = &recv_window_arg;
 					break;
+				case 'K':
+					next = &keepalive_arg;
+					break;
 #if defined(ENABLE_SVR_PASSWORD_AUTH) || defined(ENABLE_SVR_PAM_AUTH)
 				case 's':
 					svr_opts.noauthpass = 1;
@@ -274,14 +282,21 @@ void svr_getopts(int argc, char ** argv) {
 
 	}
 	
-	if (recv_window_arg)
+	if (recv_window_arg) {
-	{
 		opts.recv_window = atol(recv_window_arg);
-		if (opts.recv_window == 0)
+		if (opts.recv_window == 0 || opts.recv_window > MAX_RECV_WINDOW)
 		{
 			dropbear_exit("Bad recv window '%s'", recv_window_arg);
 		}
 	}
+	
+	if (keepalive_arg) {
+		opts.keepalive_secs = strtoul(keepalive_arg, NULL, 10);
+		if (opts.keepalive_secs == 0 && errno == EINVAL)
+		{
+			dropbear_exit("Bad keepalive '%s'", keepalive_arg);
+		}
+	}
 }
 
 static void addportandaddress(char* spec) {

svr-session.c

@@ -77,8 +77,6 @@ static const struct ChanType *svr_chantypes[] = {
 void svr_session(int sock, int childpipe, 
 		char* remotehost, char *addrstring) {
 
-	struct timeval timeout;
-
     reseedrandom();
 
 	crypto_init();
@@ -91,11 +89,7 @@ void svr_session(int sock, int childpipe,
 	chaninitialise(svr_chantypes);
 	svr_chansessinitialise();
 
-	if (gettimeofday(&timeout, 0) < 0) {
+	ses.connect_time = time(NULL);
-		dropbear_exit("Error getting time");
-	}
-
-	ses.connecttimeout = timeout.tv_sec + AUTH_TIMEOUT;
 
 	/* set up messages etc */
 	ses.remoteclosed = svr_remoteclosed;