2 files changed, 38 insertions, 1 deletions

diff --git a/usr.bin/tftp/main.c b/usr.bin/tftp/main.c
index 5644132fe920..33546dc4ee23 100644
--- a/usr.bin/tftp/main.c
+++ b/usr.bin/tftp/main.c
@@ -114,6 +114,7 @@ static void	setblocksize2(int, char **);
 static void	setoptions(int, char **);
 static void	setrollover(int, char **);
 static void	setpacketdrop(int, char **);
+static void	setwindowsize(int, char **);
 
 static void command(bool, EditLine *, History *, HistEvent *) __dead2;
 static const char *command_prompt(void);
@@ -158,6 +159,7 @@ static struct cmd cmdtab[] = {
 	  "enable or disable RFC2347 style options" },
 	{ "help",	help,		"print help information"	},
 	{ "packetdrop",	setpacketdrop,	"artificial packetloss feature"	},
+	{ "windowsize",	setwindowsize,	"set windowsize[*]"		},
 	{ "?",		help,		"print help information"	},
 	{ NULL,		NULL,		NULL				}
 };
@@ -1069,3 +1071,27 @@ setpacketdrop(int argc, char *argv[])
 	printf("Randomly %d in 100 packets will be dropped\n",
 	    packetdroppercentage);
 }
+
+static void
+setwindowsize(int argc, char *argv[])
+{
+
+	if (!options_rfc_enabled)
+		printf("RFC2347 style options are not enabled "
+		    "(but proceeding anyway)\n");
+
+	if (argc != 1) {
+		int size = atoi(argv[1]);
+
+		if (size < WINDOWSIZE_MIN || size > WINDOWSIZE_MAX) {
+			printf("Windowsize should be between %d and %d "
+			    "blocks.\n", WINDOWSIZE_MIN, WINDOWSIZE_MAX);
+			return;
+		} else {
+			asprintf(&options[OPT_WINDOWSIZE].o_request, "%d",
+			    size);
+		}
+	}
+	printf("Windowsize is now %s blocks.\n",
+	    options[OPT_WINDOWSIZE].o_request);
+}
diff --git a/usr.bin/tftp/tftp.1 b/usr.bin/tftp/tftp.1
index 7ee892bc4c52..7f413e2b1035 100644
--- a/usr.bin/tftp/tftp.1
+++ b/usr.bin/tftp/tftp.1
@@ -28,7 +28,7 @@
 .\"     @(#)tftp.1	8.2 (Berkeley) 4/18/94
 .\" $FreeBSD$
 .\"
-.Dd Aug 22, 2018
+.Dd March 2, 2020
 .Dt TFTP 1
 .Os
 .Sh NAME
@@ -216,6 +216,14 @@ Toggle packet tracing.
 .Pp
 .It Cm verbose
 Toggle verbose mode.
+.Pp
+.It Cm windowsize Op Ar size
+Sets the TFTP windowsize option in TFTP Read Request or Write Request packets to
+.Op Ar size
+blocks as specified in RFC 7440.
+Valid values are between 1 and 65535.
+If no windowsize is specified,
+then the default windowsize of 1 block will be used.
 .El
 .Sh SEE ALSO
 .Xr tftpd 8
@@ -236,6 +244,9 @@ The following RFC's are supported:
 .Rs
 .%T RFC 3617: Uniform Resource Identifier (URI) Scheme and Applicability Statement for the Trivial File Transfer Protocol (TFTP)
 .Re
+.Rs
+.%T RFC 7440: TFTP Windowsize Option
+.Re
 .Pp
 The non-standard
 .Cm rollover