Only connection establishment was bounded by a timeout, so a substitute server
that accepted a connection but then stalled would block 'substitute --query'
and nar downloads indefinitely. Set a read timeout on substitute connections
so a stalled server is eventually abandoned and the next URL is tried.
* guix/scripts/substitute.scm (%fetch-read-timeout): New variable.
(open-connection-for-uri/cached): Add #:read-timeout defaulting to
%fetch-read-timeout; pass it to 'guix:open-connection-for-uri' and on the
recursive call.
self
4574af27f2
