DC distribution grids are an option for future smart grids in order to directly connect distributed energy resources like photovoltaics, storage, electric vehicles and loads that already use dc internally. Due to the increased installed power capacity, voltage deviations and line congestion are likely to occur. Exact optimal power flow with locational marginal prices (LMP) is a way of tackling this problem.In this paper a fully distributed solution for the exact optimal power flow problem in dc distribution grids is presented. It uses the consensus and innovations approach and includes line losses as well as line current limits and over- and under-voltage bounds. Zero marginal cost and linear cost functions for generators and loads are possible in addition to quadratic cost functions. A simulation example shows initial results on a 4-node test network.