openwrtv4/target/linux/ramips/base-files/lib/preinit/04_handle_checksumming

#!/bin/sh

# Netgear WNCE2001 has does a checksum check on boot and goes into recovery
# tftp mode when the check fails.  Initializing the JFFS2 partition triggers
# this, so we make sure to zero checksum and size to be checksummed before
# that happens, so this needs to run very early during boot.

do_checksumming_disable() {
	. /lib/ramips.sh

	local board=$(ramips_board_name)

	case "$board" in
	wnce2001)
		echo "Board is WNCE2001, updating checksum partition..."
		local zeroes=/dev/zero
		local tmpfile=/tmp/wnce2001_checksum
		local partname=checksum
		local mtd=$(find_mtd_part $partname)
		dd if=$mtd of=$tmpfile bs=80 count=1 2>/dev/null
		signature=$(dd if=$tmpfile bs=1 skip=24 count=20 2>/dev/null)
		checksum=$(dd if=$tmpfile bs=1 count=4 2>/dev/null | hexdump -v -n 4 -e '1/1 "%02x"')
		if [ "$signature" != "RT3052-AP-WNCE2001-3" ]; then
			echo "Signature of checksum partition is wrong, bailing."
			return 0
		fi
		if [ "$checksum" != "00000000" ]; then
			echo "Checksum is set, zeroing."
			# zero out checksum
			dd if=$zeroes of=$tmpfile conv=notrunc bs=1 seek=0 count=4 2>/dev/null
			# zero out bytecount to be checksummed
			dd if=$zeroes of=$tmpfile conv=notrunc bs=1 seek=60 count=4 2>/dev/null
			mtd write $tmpfile $partname
		else
			echo "Checksum is already zero, nothing to do."
		fi
	;;
	rt-n56u)
		echo "Board is ASUS RT-N56U, replacing uImage header..."
		local firmware_mtd=$(find_mtd_part firmware)
		local rootfs_mtd=$(find_mtd_part rootfs)
		local rootfs_data_mtd=$(find_mtd_part rootfs_data)
		local rootfs_len=$(grep \"rootfs\" /proc/mtd | awk -F' ' '{print "0x"$2}')
		local rootfs_data_len=$(grep \"rootfs_data\" /proc/mtd | awk -F' ' '{print "0x"$2}')
		local offset=$(echo "$rootfs_len $rootfs_data_len 0x40" | awk -F' ' '{printf "%i",$1-$2-$3}')
		local signature=$(dd if=$rootfs_mtd skip=$offset bs=1 count=4 2>/dev/null | hexdump -v -n 4 -e '1/1 "%02x"')
		if [ "$signature" = "27051956" ]; then
			dd conv=notrunc if=$rootfs_mtd skip=$offset of=$firmware_mtd bs=1 count=64 2>/dev/null
		fi
	;;
	esac

	return 0
}

boot_hook_add preinit_main do_checksumming_disable