[U-Boot] [PATCH] TFTP: allow for adjustable retransmission timout

[Wolfgang Denk]

So far, TFTP negotiated a fixed retransmission timeout of 5 seconds.
In some cases (busy networks, slow TFTP servers) this caused very
slow transfers. Add new environment variable "tftptimeout" allows to
set this timeout. Lowering this value may make downloads succeed
faster in networks with high packet loss rates or with unreliable
TFTP servers.

Signed-off-by: Wolfgang Denk <wd at denx.de>
Cc: Ben Warren <biggerbadderben at gmail.com>
---
I submitted this patch for RFC in October, but never received any
feedback. Let's see if it goes in or gets rejected...

 README     |   19 ++++++++++++++++---
 net/tftp.c |   22 +++++++++++++++++-----
 2 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/README b/README
index 22e35c3..13bad41 100644
--- a/README
+++ b/README
@@ -2982,7 +2982,9 @@ environment. As long as you don't save the environment you are
 working with an in-memory copy. In case the Flash area containing the
 environment is erased by accident, a default environment is provided.
 
-Some configuration options can be set using Environment Variables:
+Some configuration options can be set using Environment Variables.
+
+List of environment variables (most likely not complete):
 
   baudrate	- see CONFIG_BAUDRATE
 
@@ -3094,7 +3096,7 @@ Some configuration options can be set using Environment Variables:
 		  available network interfaces.
 		  It just stays at the currently selected interface.
 
-   netretry	- When set to "no" each network operation will
+  netretry	- When set to "no" each network operation will
 		  either succeed or fail without retrying.
 		  When set to "once" the network operation will
 		  fail when all the available network interfaces
@@ -3110,7 +3112,18 @@ Some configuration options can be set using Environment Variables:
   tftpdstport	- If this is set, the value is used for TFTP's UDP
 		  destination port instead of the Well Know Port 69.
 
-   vlan		- When set to a value < 4095 the traffic over
+  tftpblocksize - Block size to use for TFTP transfers; if not set,
+		  we use the TFTP server's default block size
+
+  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
+		  seconds, minimum value is 1000 = 1 second). Defines
+		  when a packet is considered to be lost so it has to
+		  be retransmitted. The default is 5000 = 5 seconds.
+		  Lowering this value may make downloads succeed
+		  faster in networks with high packet loss rates or
+		  with unreliable TFTP servers.
+
+  vlan		- When set to a value < 4095 the traffic over
 		  Ethernet is encapsulated/received over 802.1q
 		  VLAN tagged frames.
 
diff --git a/net/tftp.c b/net/tftp.c
index a02463b..3f402d1 100644
--- a/net/tftp.c
+++ b/net/tftp.c
@@ -211,7 +211,7 @@ TftpSend (void)
 		pkt += 5 /*strlen("octet")*/ + 1;
 		strcpy ((char *)pkt, "timeout");
 		pkt += 7 /*strlen("timeout")*/ + 1;
-		sprintf((char *)pkt, "%lu", TIMEOUT / 1000);
+		sprintf((char *)pkt, "%lu", TftpTimeoutMSecs / 1000);
 		debug("send option \"timeout %s\"\n", (char *)pkt);
 		pkt += strlen((char *)pkt) + 1;
 #ifdef CONFIG_TFTP_TSIZE
@@ -413,7 +413,6 @@ TftpHandler (uchar * pkt, unsigned dest, unsigned src, unsigned len)
 		}
 
 		TftpLastBlock = TftpBlock;
-		TftpTimeoutMSecs = TIMEOUT;
 		TftpTimeoutCountMax = TIMEOUT_COUNT;
 		NetSetTimeout (TftpTimeoutMSecs, TftpTimeout);
 
@@ -528,10 +527,24 @@ TftpStart (void)
 {
 	char *ep;             /* Environment pointer */
 
-	/* Allow the user to choose tftpblocksize */
+	/*
+	 * Allow the user to choose TFTP blocksize and timeout.
+	 * TFTP protocol has a minimal timeout of 1 second.
+	 */
 	if ((ep = getenv("tftpblocksize")) != NULL)
 		TftpBlkSizeOption = simple_strtol(ep, NULL, 10);
-	debug("tftp block size is %i\n", TftpBlkSizeOption);
+
+	if ((ep = getenv("tftptimeout")) != NULL)
+		TftpTimeoutMSecs = simple_strtol(ep, NULL, 10);
+
+	if (TftpTimeoutMSecs < 1000) {
+		printf("TFTP timeout (%ld ms) too low, "
+			"set minimum = 1000 ms\n);
+		TftpTimeoutMSecs = 1000;
+	}
+
+	debug("TFTP blocksize = %i, timeout = %ld ms\n",
+		TftpBlkSizeOption, TftpTimeoutMSecs);
 
 	TftpServerIP = NetServerIP;
 	if (BootFile[0] == '\0') {
@@ -588,7 +601,6 @@ TftpStart (void)
 
 	puts ("Loading: *\b");
 
-	TftpTimeoutMSecs = TftpRRQTimeoutMSecs;
 	TftpTimeoutCountMax = TftpRRQTimeoutCountMax;
 
 	NetSetTimeout (TftpTimeoutMSecs, TftpTimeout);
-- 
1.6.2.5