The Collaborative International Dictionary of English v.0.48:

Upstream \Up*stream"\, adv.
   Toward the higher part of a stream; against the current.
   [1913 Webster]

WordNet (r) 3.0 (2006):

upstream
    adv 1: toward the source or against the current [syn: upriver,
           upstream] [ant: downriver, downstream]
    adj 1: in the direction against a stream's current [ant:
           downstream]

The Jargon File (version 4.4.7, 29 Dec 2003):

upstream
 adj.

    [common] Towards the original author(s) or maintainer(s) of a project. Used
    in connection with software that is distributed both in its original source
    form and in derived, adapted versions through a distribution (like the
    Debian version of Linux or one of the BSD ports) that has component
    maintainers for each of their parts. When a component maintainer receives a
    bug report or patch, he may choose to retain the patch as a porting tweak
    to the distribution's derivative of the project, or to pass it upstream to
    the project's maintainer. The antonym downstream is rare.


The Free On-line Dictionary of Computing (30 December 2018):

upstream
downstream

    Fewer network hops away from a backbone or
   hub.  For example, a small ISP that connects to the
   Internet through a larger ISP that has their own connection
   to the backbone is downstream from the larger ISP, and the
   larger ISP is upstream from the smaller ISP.

   (1999-08-05)