| Patrick Williams | b48b7b4 | 2016-08-17 15:04:38 -0500 | [diff] [blame^] | 1 | atftp exhibits the well known "Sorcerer's Apprentice Syndrome"(SAS) problem. |
| 2 | According to RFC 1350, the fix to SAS is quite simple: further copies of the |
| 3 | acknowledgment for a particular data block would be ignored. |
| 4 | |
| 5 | Patch originally from OpenSUSE: |
| 6 | https://build.opensuse.org/package/view_file?file=atftp-0.7-sorcerers_apprentice.patch&package=atftp.539&project=openSUSE%3A12.1%3AUpdate&rev=84569792975e00573d7df597d2a6e895 |
| 7 | |
| 8 | Upstream-Status: Pending |
| 9 | |
| 10 | Signed-off-by: Roy.Li <rongqing.li@windriver.com> |
| 11 | Index: atftp-0.7/tftp_file.c |
| 12 | =================================================================== |
| 13 | --- atftp-0.7.orig/tftp_file.c 2011-11-22 15:12:53.792744083 +0100 |
| 14 | +++ atftp-0.7/tftp_file.c 2011-11-22 15:13:51.706421893 +0100 |
| 15 | @@ -605,6 +605,7 @@ |
| 16 | int timeout_state = state; /* what state should we go on when timeout */ |
| 17 | int result; |
| 18 | long block_number = 0; |
| 19 | + long last_requested_block = -1; |
| 20 | long last_block = -1; |
| 21 | int data_size; /* size of data received */ |
| 22 | int sockfd = data->sockfd; /* just to simplify calls */ |
| 23 | @@ -765,6 +766,17 @@ |
| 24 | connected = 1; |
| 25 | } |
| 26 | block_number = ntohs(tftphdr->th_block); |
| 27 | + |
| 28 | + if (last_requested_block >= block_number) |
| 29 | + { |
| 30 | + if (data->trace) |
| 31 | + fprintf(stderr, "received duplicated ACK <block: %ld >= %ld>\n", |
| 32 | + last_requested_block, block_number); |
| 33 | + break; |
| 34 | + } |
| 35 | + else |
| 36 | + last_requested_block = block_number; |
| 37 | + |
| 38 | if (data->trace) |
| 39 | fprintf(stderr, "received ACK <block: %ld>\n", |
| 40 | block_number); |
| 41 | Index: atftp-0.7/tftpd_file.c |
| 42 | =================================================================== |
| 43 | --- atftp-0.7.orig/tftpd_file.c 2011-11-22 15:12:53.793744112 +0100 |
| 44 | +++ atftp-0.7/tftpd_file.c 2011-11-22 15:15:04.617534260 +0100 |
| 45 | @@ -403,6 +403,7 @@ |
| 46 | int timeout_state = state; |
| 47 | int result; |
| 48 | long block_number = 0; |
| 49 | + long last_requested_block = -1; |
| 50 | long last_block = -1; |
| 51 | int block_loops = 0; |
| 52 | int data_size; |
| 53 | @@ -859,6 +860,32 @@ |
| 54 | { |
| 55 | logger(LOG_DEBUG, "received ACK <block: %d>", block_number); |
| 56 | } |
| 57 | + |
| 58 | + /* check whether the block request isn't already fulfilled */ |
| 59 | + |
| 60 | + /* multicast, block numbers could contain gaps */ |
| 61 | + if (multicast) { |
| 62 | + if (last_requested_block >= block_number) |
| 63 | + { |
| 64 | + if (data->trace) |
| 65 | + logger(LOG_DEBUG, "received duplicated ACK <block: %d >= %d>", last_requested_block, block_number); |
| 66 | + break; |
| 67 | + } |
| 68 | + else |
| 69 | + last_requested_block = block_number; |
| 70 | + /* unicast, blocks should be requested one after another */ |
| 71 | + } else { |
| 72 | + if (last_requested_block + 1 != block_number && last_requested_block != -1) |
| 73 | + { |
| 74 | + if (data->trace) |
| 75 | + logger(LOG_DEBUG, "received out of order ACK <block: %d != %d>", last_requested_block + 1, block_number); |
| 76 | + break; |
| 77 | + } |
| 78 | + else |
| 79 | + last_requested_block = block_number; |
| 80 | + } |
| 81 | + |
| 82 | + |
| 83 | if (ntohs(tftphdr->th_block) == 65535) |
| 84 | { |
| 85 | block_loops++; |
| 86 | @@ -958,6 +985,8 @@ |
| 87 | /* nedd to send an oack to that client */ |
| 88 | state = S_SEND_OACK; |
| 89 | fseek(fp, 0, SEEK_SET); |
| 90 | + /* reset the last block received counter */ |
| 91 | + last_requested_block = -1; |
| 92 | } |
| 93 | else |
| 94 | { |