[HECnet] DECnet for Linux

To come back to the connection to MIM described below, it seems to be related to an unnecessary congestion issue. When connecting to a node, a configuration message contains the remote buffer size. MIM/RSX returns 2086. Accordingly, dnprogs' libdap/connection.cc:set_socket_buffer_size sets setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &blocksize, sizeof(blocksize)) and likewise for SO_SNDBUF, as per protocol. But this triggers "on/off" flow control in the kernel module; the overhead to have a packet in the decnet socket buffers is such that the above blocksize is too small, even when it is doubled by default by the kernel - especially with the low value of 2086. Increasing it with (in exchange_config()) set_blocksize(min(MAX_READ_SIZE, cm->get_bufsize()<<1)); (or perhaps just set_blocksize(MAX_READ_SIZE); ?) helps a lot. Note that the kernel module and VMS announce "no flow control" (apart from "on/off"), and RSX uses "Session Control Message" flow control, which the kernel module implements for outbound data, so having the buffers perhaps too large may not be too problematic. PS: For creating a decnet.conf the 'dncopynodes' utility may be used. On Wed, Jan 03, 2018 at 04:02:19PM +0100, Erik Olofsen wrote: