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atftp exhibits the well known "Sorcerer's Apprentice Syndrome"(SAS) problem.
According to RFC 1350, the fix to SAS is quite simple: further copies of the
acknowledgment for a particular data block would be ignored.
Patch originally from OpenSUSE:
https://build.opensuse.org/package/view_file?file=atftp-0.7-sorcerers_apprentice.patch&package=atftp.539&project=openSUSE%3A12.1%3AUpdate&rev=84569792975e00573d7df597d2a6e895
Upstream-Status: Pending
Signed-off-by: Roy.Li <rongqing.li@windriver.com>
Index: atftp-0.7/tftp_file.c
===================================================================
--- atftp-0.7.orig/tftp_file.c 2011-11-22 15:12:53.792744083 +0100
+++ atftp-0.7/tftp_file.c 2011-11-22 15:13:51.706421893 +0100
@@ -605,6 +605,7 @@
int timeout_state = state; /* what state should we go on when timeout */
int result;
long block_number = 0;
+ long last_requested_block = -1;
long last_block = -1;
int data_size; /* size of data received */
int sockfd = data->sockfd; /* just to simplify calls */
@@ -765,6 +766,17 @@
connected = 1;
}
block_number = ntohs(tftphdr->th_block);
+
+ if (last_requested_block >= block_number)
+ {
+ if (data->trace)
+ fprintf(stderr, "received duplicated ACK <block: %ld >= %ld>\n",
+ last_requested_block, block_number);
+ break;
+ }
+ else
+ last_requested_block = block_number;
+
if (data->trace)
fprintf(stderr, "received ACK <block: %ld>\n",
block_number);
Index: atftp-0.7/tftpd_file.c
===================================================================
--- atftp-0.7.orig/tftpd_file.c 2011-11-22 15:12:53.793744112 +0100
+++ atftp-0.7/tftpd_file.c 2011-11-22 15:15:04.617534260 +0100
@@ -403,6 +403,7 @@
int timeout_state = state;
int result;
long block_number = 0;
+ long last_requested_block = -1;
long last_block = -1;
int block_loops = 0;
int data_size;
@@ -859,6 +860,32 @@
{
logger(LOG_DEBUG, "received ACK <block: %d>", block_number);
}
+
+ /* check whether the block request isn't already fulfilled */
+
+ /* multicast, block numbers could contain gaps */
+ if (multicast) {
+ if (last_requested_block >= block_number)
+ {
+ if (data->trace)
+ logger(LOG_DEBUG, "received duplicated ACK <block: %d >= %d>", last_requested_block, block_number);
+ break;
+ }
+ else
+ last_requested_block = block_number;
+ /* unicast, blocks should be requested one after another */
+ } else {
+ if (last_requested_block + 1 != block_number && last_requested_block != -1)
+ {
+ if (data->trace)
+ logger(LOG_DEBUG, "received out of order ACK <block: %d != %d>", last_requested_block + 1, block_number);
+ break;
+ }
+ else
+ last_requested_block = block_number;
+ }
+
+
if (ntohs(tftphdr->th_block) == 65535)
{
block_loops++;
@@ -958,6 +985,8 @@
/* nedd to send an oack to that client */
state = S_SEND_OACK;
fseek(fp, 0, SEEK_SET);
+ /* reset the last block received counter */
+ last_requested_block = -1;
}
else
{
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