Yes. I found this upload page is an encryption form. When I login the cookie is generated as

Set-Cookie: sysauth=ACA415DA69DD4170D34D2DDCE2B610F5; path=/cgi-bin/lu
+ci/;stok=44F89C9B8E1EB34F9D379B5162763EAF

Location: /cgi-bin/luci/;stok=44F89C9B8E1EB34F9D379B5162763EAF/enginee
+r
[download]

The URL changed when post the upload form. I used the upload file is around 15M with .ZIP form. I am still working on this, Thanks for your information