kind of old thread, but there is more helpful content on other threads to these issues.
I am adding some cross-linking, in case someone just found this one thread:
same issue on D-Link, on slightly different device during discussion:
- DIR-2660 failing to flash
- [DIR-1960] Curl upload succeeds but no OpenWrt installation
outline: often issues when updating from a Linux PC via D-Link emergency room. Windows (but not all browsers) seems to be less of a hassle, when using the emergency room feature of D-Link.
There were some more threads for this topic. I remember there was yet another thread that explained something about headers and probably „http 100 continue“ not being properly implemented in D-Link recovery room partitions of some D-Link devices, but I cannot seem to find the thread right now.
The described fix might help as well here, yet the main cause of the issue on 2660 might be likely different. If it is the other cause, there are also alternative easier solutions available:
as far as I remember, newer 2660 A1 versions and all (?) of A2 have an additional problem. Their flashing via emergency room feature might not fail due to the previously mentioned http problem, but because their emergency room partition firmware version expects an additional crypto-signed header, which has not been present in openWRT images before v22. So flashing a v22 or later OpenWRT image can avoid running into this particular problem, if its due to the formerly missing headef. There are also some other threads regarding this issue. Maybe less and less relevant, once OpenWRT v22 or newer are commonly used.