CRC update failed. Firmware header not supported; firmware checksums may be incorrect.

```
What steps will reproduce the problem?
1.I extracted the firmware. ./extract-firmware.sh firmware.bin
2.Made a single change in the style folder.Changed the logo.(Web GUI)
3.Rebuild it using ./build-firmware.sh.
(I also tried ./build-firmware.sh -nopad and received the same results.)

What is the expected output? What do you see instead?

Expected Output:
This is my first attempt,so I am not really sure what the exact output looks
like. I guess it should say "Firmware appears extracted correctly!" without any
failures or warning.

What I got:
Firmware Mod Kit (build) 0.99, (c)2011-2013 Craig Heffner, Jeremy Collake

Preparing tools ...
Building new squashfs file system... (this may take several minutes!)
Squahfs block size is 128 Kb
Creating big endian 3.0 filesystem on /home/user.........., block size 131072.

Big endian filesystem, data block size 131072, compressed data, compressed
metadata, compressed fragments
Filesystem size 2821.46 Kbytes (2.76 Mbytes)
31.01% of uncompressed filesystem size (9099.18 Kbytes)
Inode table size 4727 bytes (4.62 Kbytes)
22.84% of uncompressed inode table size (20696 bytes)
Directory table size 5969 bytes (5.83 Kbytes)
57.42% of uncompressed directory table size (10395 bytes)
Number of duplicate files found 0
Number of inodes 670
Number of files 437
Number of fragments 29
Number of symbolic links 172
Number of device nodes 0
Number of fifo nodes 0
Number of socket nodes 0
Number of directories 61
Number of uids 1
root (0)
Number of gids 0
Remaining free bytes in firmware image: 57344
Processing 0 header(s) from /home/user/...new-firmware.bin...
CRC update failed.

Firmware header not supported; firmware checksums may be incorrect.
New firmware image has been saved to: /home/user.....new-firmware.bin

What version of the product are you using? On what operating system?
I'm using the latest version of the
kit(https://code.google.com/p/firmware-mod-kit/downloads/list) on Ubuntu 12.04.

Please provide any additional information below.
I thought this might have happened because I tried to modify the firmware, so i
tried rebuilding it,without making any changes,right after the extraction.
The firmware I used was ddwrt 23320 on TP Link WA901nd ver:2 router
link to firmware
ftp://ftp.dd-wrt.com/others/eko/BrainSlayer-V24-preSP2/2014/01-10-2014-r23320-fi
x/tplink_tl-wa901ndv2/tl-wa901ndv2-webflash.bin

Thanks for your help,
Amy

```

Original issue reported on code.google.com by `iamnotan...@gmail.com` on 29 Jan 2014 at 2:34

Reproduce the report with extract-firmware.sh and build-firmware.sh using the TP-Link WA901ND v2 firmware described, including the -nopad option. Start by tracing the build output around “Processing 0 header(s)” and “CRC update failed”; done means the rebuilt image handles the firmware header and checksum without that warning.

Written by the indexing model from the issue text.