Range requests send an invalid response header #578
Description
$ curl -v -H 'Range: bytes=0-1023' 'https://nix-cache.internal.host:5000/nar/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.nar?hash=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'
[...]
> GET /nar/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.nar?hash=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx HTTP/2
> Host: nix-cache.internal.host:5000
> User-Agent: curl/8.14.1
> Accept: */*
> Range: bytes=0-1023
>
* Request completely sent off
< HTTP/2 200
< content-length: 1024
< accept-ranges: bytes
< content-encoding: identity
< content-type: application/x-nix-archive
< cache-control: max-age=31536000
< content-range: bytes 0-1023/2826744
< date: Mon, 04 Aug 2025 16:38:58 GMTcontent-encoding: identity is not a valid header.
Though identity is a valid value for the Accept-Encoding request header, it is not a valid value for the Content-Encoding response header.
Setting this header to this value causes Nix to fail the download when it attempts to resume after a disconnect:
warning: error: unable to download 'https://nix-cache.internal.host:5000/nar/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.nar?hash=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx': HTTP error 200 (curl error: Failure when receiving data from the peer); retrying from offset 222286391 in 342 ms
error: failed to get libarchive filter by name: No such filter 'identity'
error: some substitutes for the outputs of derivation '/nix/store/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx-my-derivation.drv' failed (usually happens due to networking issues); try '--fallback' to build derivation from source
error: Cannot build '/nix/store/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx-nix-shell-env.drv'.