cgminer log shows stratum header constructed as below
20000000da780ff935f3917ed99a7b616cb98ebb3104b3fa000b7acd0000000000000000854e4bd db4eeb7c1841b651ceb26f4d12116bfcc2c41ed18220fd701571914ba5a6fdbfa176c2146000000 00
Look at version, time, difficulty part. Shouldn't it be flipped as big endian ?
No, everything in Bitcoin is serialized as little endian. Actually, this is serialized as big endian, but in kind of a strange way. It seems like it is being printed out with each 4 byte chunk (32 bit integer length) in big endian, which also means that the merkle root and previous block hash fields are messed up. But this is not the actual block header it is hashing.
And at the calculation of midsate its flipping all 4 bytes.. meaning 00000020f90f78da7e91f335617b9ad9bb8eb96cfab30431cd7a0b000000000000000000dd4b4e8 5c1b7eeb41c651b84d1f426ebccbf162118ed412c01d70f22
This is the correct block header. Everything is in little endian as it should be. This is what the block header should look like.
When submitblock is called, what should be sent as block header ?
The second one.