Add -W <windowsize> argument and document it.

--HG--
extra : convert_revision : 98d4c0f15480bf749c451034cbc565d7e9d3b8dc

cli-chansession.c

@@ -350,7 +350,7 @@ static int cli_initchansess(struct Channel *channel) {
 	channel->errfd = STDERR_FILENO;
 	setnonblocking(STDERR_FILENO);
 
-	channel->extrabuf = cbuf_new(RECV_MAX_WINDOW);
+	channel->extrabuf = cbuf_new(opts.recv_window);
 
 	if (cli_opts.wantpty) {
 		send_chansess_pty_req(channel);

cli-runopts.c

@@ -63,10 +63,11 @@ 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"
 #ifdef DEBUG_TRACE
 					"-v    verbose\n"
 #endif
-					,DROPBEAR_VERSION, cli_opts.progname);
+					,DROPBEAR_VERSION, cli_opts.progname, DEFAULT_RECV_WINDOW);
 }
 
 void cli_getopts(int argc, char ** argv) {
@@ -109,6 +110,8 @@ void cli_getopts(int argc, char ** argv) {
 	opts.ipv4 = 1;
 	opts.ipv6 = 1;
 	*/
+	opts.recv_window = DEFAULT_RECV_WINDOW;
+	char* recv_window_arg = NULL;
 
 	/* Iterate all the arguments */
 	for (i = 1; i < (unsigned int)argc; i++) {
@@ -201,6 +204,9 @@ void cli_getopts(int argc, char ** argv) {
 				case 'u':
 					/* backwards compatibility with old urandom option */
 					break;
+				case 'W':
+					next = &recv_window_arg;
+					break;
 #ifdef DEBUG_TRACE
 				case 'v':
 					debug_trace = 1;
@@ -292,6 +298,15 @@ void cli_getopts(int argc, char ** argv) {
 			&& cli_opts.no_cmd == 0) {
 		dropbear_exit("command required for -f");
 	}
+	
+	if (recv_window_arg)
+	{
+		opts.recv_window = atol(recv_window_arg);
+		if (opts.recv_window == 0)
+		{
+			dropbear_exit("Bad recv window '%s'", recv_window_arg);
+		}
+	}
 }
 
 #ifdef ENABLE_CLI_PUBKEY_AUTH

common-channel.c

@@ -34,6 +34,7 @@
 #include "channel.h"
 #include "ssh.h"
 #include "listener.h"
+#include "runopts.h"
 
 static void send_msg_channel_open_failure(unsigned int remotechan, int reason,
 		const unsigned char *text, const unsigned char *lang);
@@ -150,9 +151,9 @@ struct Channel* newchannel(unsigned int remotechan,
 	newchan->await_open = 0;
 	newchan->flushing = 0;
 
-	newchan->writebuf = cbuf_new(RECV_MAX_WINDOW);
+	newchan->writebuf = cbuf_new(opts.recv_window);
 	newchan->extrabuf = NULL; /* The user code can set it up */
-	newchan->recvwindow = RECV_MAX_WINDOW;
+	newchan->recvwindow = opts.recv_window;
 	newchan->recvdonelen = 0;
 	newchan->recvmaxpacket = RECV_MAX_PAYLOAD_LEN;
 
@@ -421,7 +422,7 @@ static void writechannel(struct Channel* channel, int fd, circbuffer *cbuf) {
 		channel->recvdonelen = 0;
 	}
 
-	dropbear_assert(channel->recvwindow <= RECV_MAX_WINDOW);
+	dropbear_assert(channel->recvwindow <= opts.recv_window);
 	dropbear_assert(channel->recvwindow <= cbuf_getavail(channel->writebuf));
 	dropbear_assert(channel->extrabuf == NULL ||
 			channel->recvwindow <= cbuf_getavail(channel->extrabuf));
@@ -710,7 +711,7 @@ void common_recv_msg_channel_data(struct Channel *channel, int fd,
 
 	dropbear_assert(channel->recvwindow >= datalen);
 	channel->recvwindow -= datalen;
-	dropbear_assert(channel->recvwindow <= RECV_MAX_WINDOW);
+	dropbear_assert(channel->recvwindow <= opts.recv_window);
 
 	TRACE(("leave recv_msg_channel_data"))
 }
@@ -970,7 +971,7 @@ int send_msg_channel_open_init(int fd, const struct ChanType *type) {
 	buf_putbyte(ses.writepayload, SSH_MSG_CHANNEL_OPEN);
 	buf_putstring(ses.writepayload, type->name, strlen(type->name));
 	buf_putint(ses.writepayload, chan->index);
-	buf_putint(ses.writepayload, RECV_MAX_WINDOW);
+	buf_putint(ses.writepayload, opts.recv_window);
 	buf_putint(ses.writepayload, RECV_MAX_PAYLOAD_LEN);
 
 	TRACE(("leave send_msg_channel_open_init()"))

dbclient.1

@@ -74,6 +74,11 @@ by the ssh server.
 .B \-y
 Always accept hostkeys if they are unknown. If a hostkey mismatch occurs the
 connection will abort as normal.
+.TP
+.B \-W \fIwindowsize
+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.
 .SH AUTHOR
 Matt Johnston (matt@ucc.asn.au).
 .br

dropbear.8

@@ -82,6 +82,11 @@ default is /var/run/dropbear.pid
 .TP
 .B \-a
 Allow remote hosts to connect to forwarded ports.
+.TP
+.B \-W \fIwindowsize
+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.
 .SH AUTHOR
 Matt Johnston (matt@ucc.asn.au).
 .br

options.h

@@ -220,8 +220,10 @@ etc) slower (perhaps by 50%). Recommended for most small systems. */
    usage and network performance: */
 /* Size of the network receive window. This amount of memory is allocated
    as a per-channel receive buffer. Increasing this value can make a
-   significant difference to network performance. */
-#define RECV_MAX_WINDOW 8192
+   significant difference to network performance. 24kB was empirically
+   chosen for a 100mbit ethernet network. The value can be altered at
+   runtime with the -W argument. */
+#define DEFAULT_RECV_WINDOW 24576
 /* Maximum size of a received SSH data packet - this _MUST_ be >= 32768
    in order to interoperate with other implementations */
 #define RECV_MAX_PAYLOAD_LEN 32768
@@ -339,7 +341,7 @@ etc) slower (perhaps by 50%). Recommended for most small systems. */
 #define TRANS_MAX_WINDOW 500000000 /* 500MB is sufficient, stopping overflow */
 #define TRANS_MAX_WIN_INCR 500000000 /* overflow prevention */
 
-#define RECV_WINDOWEXTEND (RECV_MAX_WINDOW / 3) /* We send a "window extend" every
+#define RECV_WINDOWEXTEND (opts.recv_window / 3) /* We send a "window extend" every
 								RECV_WINDOWEXTEND bytes */
 
 #define MAX_CHANNELS 100 /* simple mem restriction, includes each tcp/x11

runopts.h

@@ -36,6 +36,7 @@ typedef struct runopts {
 #if defined(ENABLE_SVR_REMOTETCPFWD) || defined(ENABLE_CLI_LOCALTCPFWD)
 	int listen_fwd_all;
 #endif
+	unsigned int recv_window;
 
 } runopts;
 

svr-runopts.c

@@ -80,6 +80,7 @@ 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"
 #ifdef DEBUG_TRACE
 					"-v		verbose\n"
 #endif
@@ -90,7 +91,7 @@ static void printhelp(const char * progname) {
 #ifdef DROPBEAR_RSA
 					RSA_PRIV_FILENAME,
 #endif
-					DROPBEAR_MAX_PORTS, DROPBEAR_DEFPORT, DROPBEAR_PIDFILE);
+					DROPBEAR_MAX_PORTS, DROPBEAR_DEFPORT, DROPBEAR_PIDFILE, DEFAULT_RECV_WINDOW);
 }
 
 void svr_getopts(int argc, char ** argv) {
@@ -128,6 +129,8 @@ void svr_getopts(int argc, char ** argv) {
 #ifndef DISABLE_SYSLOG
 	svr_opts.usingsyslog = 1;
 #endif
+	opts.recv_window = DEFAULT_RECV_WINDOW;
+	char* recv_window_arg = NULL;
 #ifdef ENABLE_SVR_REMOTETCPFWD
 	opts.listen_fwd_all = 0;
 #endif
@@ -204,6 +207,9 @@ void svr_getopts(int argc, char ** argv) {
 				case 'w':
 					svr_opts.norootlogin = 1;
 					break;
+				case 'W':
+					next = &recv_window_arg;
+					break;
 #if defined(ENABLE_SVR_PASSWORD_AUTH) || defined(ENABLE_SVR_PAM_AUTH)
 				case 's':
 					svr_opts.noauthpass = 1;
@@ -265,8 +271,17 @@ void svr_getopts(int argc, char ** argv) {
 					svr_opts.bannerfile);
 		}
 		buf_setpos(svr_opts.banner, 0);
-	}
 
+	}
+	
+	if (recv_window_arg)
+	{
+		opts.recv_window = atol(recv_window_arg);
+		if (opts.recv_window == 0)
+		{
+			dropbear_exit("Bad recv window '%s'", recv_window_arg);
+		}
+	}
 }
 
 static void addportandaddress(char* spec) {