[U-Boot-Users] PATCH: Force TFTP to use a fixed UDP port
Hi Wolfgang,
Attached is a patch to allow the user to set an environment variable "tftpourport" to force TFTP to use that value for "TftpOurPort" (our UDP port). As discussed yesterday on this list, this is helpful for "punching through" a firewall such as is installed with Windows XP SP2.
Making it an environment variable is cute but an overkill. If there is an outcry over the level of overkill, I would be willing to make the UDP port a simple #define of a compile time constant, in which case it would actually save a few bytes of ROM over the pseudo-random algorithm :-).
Thanks, gvb
CHANGELOG:
* Patch by Jerry Van Baren 05 Jan 2005 - Make the u-boot TFTP source port be configurable using the environment variable "tftpourport": * If set, use that port as the u-boot source port * If not set, use the current method of using a pseudo random port
- The additional code can be totally removed by setting the #define TFTP_PORT_FROM_ENV (in the net/tftp.c file) to zero.
- The purpose behind this change is that our customer will modify their TFTP server so that it blindly starts the TFTP transfer using the pre-configured target IP address and UDP port. This will have the effect of "punching through" the (Windows XP) firewall, allowing the remainder of the TFTP transfer to proceed normally.
Index: net/tftp.c =================================================================== RCS file: /cvsroot/u-boot/u-boot/net/tftp.c,v retrieving revision 1.9 diff -p -u -r1.9 tftp.c --- net/tftp.c 15 Apr 2004 21:48:55 -0000 1.9 +++ net/tftp.c 6 Jan 2005 03:20:41 -0000 @@ -24,6 +24,9 @@ /* (for checking the image size) */ #define HASHES_PER_LINE 65 /* Number of "loading" hashes per line */
+#define TFTP_PORT_FROM_ENV 1 /* define this to allow setting the */ + /* TFTP source port in the environment */ + /* variable "tftpourport" */ /* * TFTP operations. */ @@ -301,6 +304,8 @@ TftpTimeout (void) void TftpStart (void) { + char *ep; /* Environment pointer */ + if (BootFile[0] == '\0') { IPaddr_t OurIP = ntohl(NetOurIP);
@@ -354,7 +359,13 @@ TftpStart (void) TftpServerPort = WELL_KNOWN_PORT; TftpTimeoutCount = 0; TftpState = STATE_RRQ; + /* Use a pseudo-random port unless a specific port is set */ TftpOurPort = 1024 + (get_timer(0) % 3072); +#if TFTP_PORT_FROM_ENV + if ((ep = getenv("tftpourport")) != NULL) { + TftpOurPort= simple_strtol(ep, NULL, 10); + } +#endif TftpBlock = 0;
/* zero out server ether in case the server ip has changed */
In message 41DDB3DE.4010403@smiths-aerospace.com you wrote:
Attached is a patch to allow the user to set an environment variable
Please change a few things:
"tftpourport" to force TFTP to use that value for "TftpOurPort" (our UDP
Please use a more straightforward name, like "tftpport" or "tftp-port" or so.
Please document the variable in the README.
- The additional code can be totally removed by setting the #define TFTP_PORT_FROM_ENV (in the net/tftp.c file) to zero.
This is unacceptable. First, please make this a CONFIG_* name. Second, please make it such that you have to explicitely _enable_ this option when you want it, instead of making it the default. Finally, please use #ifdef instead of #if.
- The purpose behind this change is that our customer will modify their TFTP server so that it blindly starts the TFTP transfer using the pre-configured target IP address and UDP port. This will have the effect of "punching through" the (Windows XP) firewall, allowing the remainder of the TFTP transfer to proceed normally.
Such verbosity is inacceptable for the CHANGELOG. Move it to the README or a doc/ file.
Best regards,
Wolfgang Denk
I think you are doing something wrong with your Windows box. I have just tried 2 tftp servers (one running as service and another running as application) on Windows XP box and no such trickery that you prosed was needed.
You just have to tell Windows Firewall to unblock the application (or the executable for the service) and it works perfectly. What exactly is your configuration?
The only TFTP firewall issue I know is when client is behind a stateful firewall or NAT device, in which case the dynamic port chosen by the server for conducting the transfer (beyond 1st packet) gets blocked by the firewall. Source port of TFTP client is not an issue in that case. When server is behind a stateful firewall, this is not an issue!
I am having hard time understanding your issues. Can you describe the XP firewall issues a bit more in detail? I am feeling this patch is not really needed.
Best regards, Tolunay
Jerry Van Baren wrote:
Hi Wolfgang,
Attached is a patch to allow the user to set an environment variable "tftpourport" to force TFTP to use that value for "TftpOurPort" (our UDP port). As discussed yesterday on this list, this is helpful for "punching through" a firewall such as is installed with Windows XP SP2.
Making it an environment variable is cute but an overkill. If there is an outcry over the level of overkill, I would be willing to make the UDP port a simple #define of a compile time constant, in which case it would actually save a few bytes of ROM over the pseudo-random algorithm :-).
Thanks, gvb
CHANGELOG:
- Patch by Jerry Van Baren 05 Jan 2005
Make the u-boot TFTP source port be configurable using the environment variable "tftpourport":
- If set, use that port as the u-boot source port
- If not set, use the current method of using a pseudo random port
The additional code can be totally removed by setting the #define TFTP_PORT_FROM_ENV (in the net/tftp.c file) to zero.
The purpose behind this change is that our customer will modify their TFTP server so that it blindly starts the TFTP transfer using the pre-configured target IP address and UDP port. This will have the effect of "punching through" the (Windows XP) firewall, allowing the remainder of the TFTP transfer to proceed normally.
Index: net/tftp.c
RCS file: /cvsroot/u-boot/u-boot/net/tftp.c,v retrieving revision 1.9 diff -p -u -r1.9 tftp.c --- net/tftp.c 15 Apr 2004 21:48:55 -0000 1.9 +++ net/tftp.c 6 Jan 2005 03:20:41 -0000 @@ -24,6 +24,9 @@ /* (for checking the image size) */ #define HASHES_PER_LINE 65 /* Number of "loading" hashes per line */
+#define TFTP_PORT_FROM_ENV 1 /* define this to allow setting the */
/* TFTP source port in the environment *//* variable "tftpourport" *//*
- TFTP operations.
*/ @@ -301,6 +304,8 @@ TftpTimeout (void) void TftpStart (void) {
- char *ep; /* Environment pointer */
- if (BootFile[0] == '\0') { IPaddr_t OurIP = ntohl(NetOurIP);
@@ -354,7 +359,13 @@ TftpStart (void) TftpServerPort = WELL_KNOWN_PORT; TftpTimeoutCount = 0; TftpState = STATE_RRQ;
- /* Use a pseudo-random port unless a specific port is set */ TftpOurPort = 1024 + (get_timer(0) % 3072);
+#if TFTP_PORT_FROM_ENV
- if ((ep = getenv("tftpourport")) != NULL) {
TftpOurPort= simple_strtol(ep, NULL, 10);- }
+#endif TftpBlock = 0;
/* zero out server ether in case the server ip has changed */
Tolunay Orkun wrote:
I think you are doing something wrong with your Windows box. I have just tried 2 tftp servers (one running as service and another running as application) on Windows XP box and no such trickery that you prosed was needed.
You just have to tell Windows Firewall to unblock the application (or the executable for the service) and it works perfectly. What exactly is your configuration?
You understand it perfectly and it works perfectly as you describe. The problem isn't Windows XP firewall per se, it is stupid customers. They either don't understand the firewall (quite likely) and/or their machine is "locked down" by their IT staff so that they cannot unblock TFTP (a very serious problem). They expect to plug in our customer's software and have it "just work." When it doesn't, it is a major support headache for our customer and hurts their reputation.
The only TFTP firewall issue I know is when client is behind a stateful firewall or NAT device, in which case the dynamic port chosen by the server for conducting the transfer (beyond 1st packet) gets blocked by the firewall. Source port of TFTP client is not an issue in that case. When server is behind a stateful firewall, this is not an issue!
...and this patch won't help in that case.
I am having hard time understanding your issues. Can you describe the XP firewall issues a bit more in detail? I am feeling this patch is not really needed.
Agreed, it isn't a necessary patch, but it is one that would help our customer (who has to deal with stupid customers). I'll clean up the patch per Wolfgang's email and resubmit it. If it is accepted, maybe it will help someone else with stupid customers. If not, it will remain in _our_ build and will help _our_ customer with his stupid customers.
gvb P.S. The customer is always right (even if he is stupid ;-)
Best regards, Tolunay
Jerry Van Baren wrote:
Hi Wolfgang,
Attached is a patch to allow the user to set an environment variable "tftpourport" to force TFTP to use that value for "TftpOurPort" (our UDP port). As discussed yesterday on this list, this is helpful for "punching through" a firewall such as is installed with Windows XP SP2.
Making it an environment variable is cute but an overkill. If there is an outcry over the level of overkill, I would be willing to make the UDP port a simple #define of a compile time constant, in which case it would actually save a few bytes of ROM over the pseudo-random algorithm :-).
Thanks, gvb
participants (3)
-
Jerry Van Baren -
Tolunay Orkun -
Wolfgang Denk