Dear ghc-devs

Cabal can’t open a TCP connection from my Linux box.  It used to work fine.  Here’s what it says:

cabal -v3 update

Downloading the latest package list from hackage.haskell.org

Sending:

GET http://hackage.haskell.org/packages/archive/00-index.tar.gz HTTP/1.1

User-Agent: cabal-install/1.16.0.2

Host: hackage.haskell.org

proxy uri host: , port:

Creating new connection to

cabal: openTCPConnection: host lookup failure for ""

simonpj@cam-05-unx:~/code/HEAD$ cabal --version

cabal-install version 1.16.0.2

using version 1.16.0.3 of the Cabal library

simonpj@cam-05-unx:~/code/HEAD$

Can anyone help me work out what to do?  git works just fine, so the internet is connected all right.

Thanks

Simon